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Zhou IY, Ji Y, Zhao Y, Malvika V, Sun PZ, Zu Z. Specific and rapid guanidinium CEST imaging using double saturation power and QUASS analysis in a rodent model of global ischemia. Magn Reson Med 2024; 91:1512-1527. [PMID: 38098305 PMCID: PMC10872646 DOI: 10.1002/mrm.29960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 10/17/2023] [Accepted: 11/20/2023] [Indexed: 02/03/2024]
Abstract
PURPOSE Guanidinium CEST is sensitive to metabolic changes and pH variation in ischemia, and it can offer advantages over conventional pH-sensitive amide proton transfer (APT) imaging by providing hyperintense contrast in stroke lesions. However, quantifying guanidinium CEST is challenging due to multiple overlapping components and a close frequency offset from water. This study aims to evaluate the applicability of a new rapid and model-free CEST quantification method using double saturation power, termed DSP-CEST, for isolating the guanidinium CEST effect from confounding factors in ischemia. To further reduce acquisition time, the DSP-CEST was combined with a quasi-steady state (QUASS) CEST technique to process non-steady-state CEST signals. METHODS The specificity and accuracy of the DSP-CEST method in quantifying the guanidinium CEST effect were assessed by comparing simulated CEST signals with/without the contribution from confounding factors. The feasibility of this method for quantifying guanidinium CEST was evaluated in a rat model of global ischemia induced by cardiac arrest and compared to a conventional multiple-pool Lorentzian fit method. RESULTS The DSP-CEST method was successful in removing all confounding components and quantifying the guanidinium CEST signal increase in ischemia. This suggests that the DSP-CEST has the potential to provide hyperintense contrast in stroke lesions. Additionally, the DSP-CEST was shown to be a rapid method that does not require the acquisition of the entire or a portion of the CEST Z-spectrum that is required in conventional model-based fitting approaches. CONCLUSION This study highlights the potential of DSP-CEST as a valuable tool for rapid and specific detection of viable tissues.
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Affiliation(s)
- Iris Y. Zhou
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, US
| | - Yang Ji
- Wellcome Centre for Integrative Neuroimaging, FMRIB Division, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Yu Zhao
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
- Department of Radiology, West China Hospital of Sichuan University, Chengdu, China
| | - Viswanathan Malvika
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, US
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, US
- Primate Imaging Center, Emory National Primate Research Center, Emory University, Atlanta, GA
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
- Department of Biomedical Engineering, Vanderbilt University, Nashville, US
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Viswanathan M, Kurmi Y, Zu Z. A rapid method for phosphocreatine-weighted imaging in muscle using double saturation power-chemical exchange saturation transfer. NMR IN BIOMEDICINE 2024; 37:e5089. [PMID: 38114069 DOI: 10.1002/nbm.5089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 12/21/2023]
Abstract
Monitoring the variation in phosphocreatine (PCr) levels following exercise provides valuable insights into muscle function. Chemical exchange saturation transfer (CEST) has emerged as a sensitive method with which to measure PCr levels in muscle, surpassing conventional MR spectroscopy. However, existing approaches for quantifying PCr CEST signals rely on time-consuming fitting methods that require the acquisition of the entire or a section of the CEST Z-spectrum. Additionally, traditional fitting methods often necessitate clear CEST peaks, which may be challenging to obtain at low magnetic fields. This paper evaluated the application of a new model-free method using double saturation power (DSP), termed DSP-CEST, to estimate the PCr CEST signal in muscle. The DSP-CEST method requires the acquisition of only two or a few CEST signals at the PCr frequency offset with two different saturation powers, enabling rapid dynamic imaging. Additionally, the DSP-CEST approach inherently eliminates confounding signals, offering enhanced robustness compared with fitting methods. Furthermore, DSP-CEST does not demand clear CEST peaks, making it suitable for low-field applications. We evaluated the capability of DSP-CEST to enhance the specificity of PCr CEST imaging through simulations and experiments on muscle tissue phantoms at 4.7 T. Furthermore, we applied DSP-CEST to animal leg muscle both before and after euthanasia and observed successful reduction of confounding signals. The DSP-CEST signal still has contaminations from a residual magnetization transfer (MT) effect and an aromatic nuclear Overhauser enhancement effect, and thus only provides a PCr-weighted imaging. The residual MT effect can be reduced by a subtraction of DSP-CEST signals at 2.6 and 5 ppm. Results show that the residual MT-corrected DSP-CEST signal at 2.6 ppm has significant variation in postmortem tissues. By contrast, both the CEST signal at 2.6 ppm and a conventional Lorentzian difference analysis of CEST signal at 2.6 ppm demonstrate no significant variation in postmortem tissues.
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Affiliation(s)
- Malvika Viswanathan
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Yashwant Kurmi
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Shahid SS, Dzemidzic M, Butch ER, Jarvis EE, Snyder SE, Wu YC. Estimating the synaptic density deficit in Alzheimer's disease using multi-contrast CEST imaging. PLoS One 2024; 19:e0299961. [PMID: 38483851 PMCID: PMC10939256 DOI: 10.1371/journal.pone.0299961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 02/12/2024] [Indexed: 03/17/2024] Open
Abstract
In vivo noninvasive imaging of neurometabolites is crucial to improve our understanding of the underlying pathophysiological mechanism in neurodegenerative diseases. Abnormal changes in synaptic organization leading to synaptic degradation and neuronal loss is considered as one of the primary factors driving Alzheimer's disease pathology. Magnetic resonance based molecular imaging techniques such as chemical exchange saturation transfer (CEST) and magnetic resonance spectroscopy (MRS) can provide neurometabolite specific information which may relate to underlying pathological and compensatory mechanisms. In this study, CEST and short echo time single voxel MRS was performed to evaluate the sensitivity of cerebral metabolites to beta-amyloid (Aβ) induced synaptic deficit in the hippocampus of a mouse model of Alzheimer's disease. The CEST based spectra (Z-spectra) were acquired on a 9.4 Tesla small animal MR imaging system with two radiofrequency (RF) saturation amplitudes (1.47 μT and 5.9 μT) to obtain creatine-weighted and glutamate-weighted CEST contrasts, respectively. Multi-pool Lorentzian fitting and quantitative T1 longitudinal relaxation maps were used to obtain metabolic specific apparent exchange-dependent relaxation (AREX) maps. Short echo time (TE = 12 ms) single voxel MRS was acquired to quantify multiple neurometabolites from the right hippocampus region. AREX contrasts and MRS based metabolite concentration levels were examined in the ARTE10 animal model for Alzheimer's disease and their wild type (WT) littermate counterparts (age = 10 months). Using MRS voxel as a region of interest, group-wise analysis showed significant reduction in Glu-AREX and Cr-AREX in ARTE10, compared to WT animals. The MRS based results in the ARTE10 mice showed significant decrease in glutamate (Glu) and glutamate-total creatine (Glu/tCr) ratio, compared to WT animals. The MRS results also showed significant increase in total creatine (tCr), phosphocreatine (PCr) and glutathione (GSH) concentration levels in ARTE10, compared to WT animals. In the same ROI, Glu-AREX and Cr-AREX demonstrated positive associations with Glu/tCr ratio. These results indicate the involvement of neurotransmitter metabolites and energy metabolism in Aβ-mediated synaptic degradation in the hippocampus region. The study also highlights the feasibility of CEST and MRS to identify and track multiple competing and compensatory mechanisms involved in heterogeneous pathophysiology of Alzheimer's disease in vivo.
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Affiliation(s)
- Syed Salman Shahid
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, United States of America
| | - Mario Dzemidzic
- Department of Neurology, Indiana University School of Medicine, Indianapolis, IN, United States of America
| | - Elizabeth R. Butch
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, United States of America
| | - Erin E. Jarvis
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States of America
| | - Scott E. Snyder
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, United States of America
| | - Yu-Chien Wu
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Weldon School of Biomedical Engineering at Purdue University, West Lafayette, IN, United States of America
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Jin T, Chung JJ. Adjustment of rotation and saturation effects (AROSE) for CEST imaging. Magn Reson Med 2024; 91:1016-1029. [PMID: 38009992 PMCID: PMC10841829 DOI: 10.1002/mrm.29938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 10/09/2023] [Accepted: 11/06/2023] [Indexed: 11/29/2023]
Abstract
PURPOSE Endogenous CEST signal usually has low specificity due to contaminations from the magnetization transfer contrast (MTC) and other labile protons with overlapping or close Larmor frequencies. We propose to improve CEST signal specificity with adjustment of rotation and saturation effects (AROSE). METHODS The AROSE approach measures the difference between CEST signals acquired with the same average irradiation power but largely different duty cycles, for example, a continuous wave or a high duty cycle pulse train versus a low duty cycle pulse train with a flip angle φ. Simulation, phantom, and in vivo rodent studies were performed to evaluate the characteristics of the AROSEφ signal. RESULTS Simulation and experimental results show that AROSE2π is a low-pass filter that can suppress fast exchanging processes (e.g., >3000 s-1 ), whereas AROSEπ is a band-pass filter suppressing both fast and slow exchange (e.g., <30 s-1 ) rates. For other φ angles, the sensitivity and the exchange-rate filtering effect of AROSEφ falls between AROSEπ and AROSE2π . AROSE can also minimize MTC and improve the Larmor frequency selectivity of the CEST signal. The linewidth of the AROSE1.5π spectrum is about 60% to 65% when compared to the CEST spectrum measured by continuous wave. Depending on the needs of an application, the sensitivity, exchange-rate filtering, and Larmor frequency selectivity can be adjusted by varying the flip angle, duty cycle, and average irradiation power. CONCLUSION Compared to conventional CEST signals, AROSE can minimize MTC and improve exchange rate filtering and Larmor frequency specificity.
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Affiliation(s)
- Tao Jin
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Julius Juhyun Chung
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Chung J, Sun D, Hitchens TK, Modo M, Bandos A, Mettenburg J, Wang P, Jin T. Dual contrast CEST MRI for pH-weighted imaging in stroke. Magn Reson Med 2024; 91:357-367. [PMID: 37798945 PMCID: PMC10872804 DOI: 10.1002/mrm.29842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 07/30/2023] [Accepted: 08/05/2023] [Indexed: 10/07/2023]
Abstract
PURPOSE pH enhanced (pHenh ) CEST imaging combines the pH sensitivity from amide and guanidino signals, but the saturation parameters have not been optimized. We propose pHdual as a variant of pHenh that suppresses background signal variations, while enhancing pH sensitivity and potential for imaging ischemic brain injury of stroke. METHODS Simulation and in vivo rodent stroke experiments of pHenh MRI were performed with varied RF saturation powers for both amide and guanidino protons to optimize the contrast between lesion/normal tissues, while simultaneously minimizing signal variations across different types of normal tissues. In acute stroke, contrast and volume ratio measured by pHdual imaging were compared with an amide-CEST approach, and perfusion and diffusion MRI. RESULTS Simulation experiments indicated that amide and guanidino CEST signals exhibit unique sensitivities across different pH ranges, with pHenh producing greater sensitivity over a broader pH regime. The pHenh data of rodent stroke brain demonstrated that the lesion/normal tissue contrast was maximized for an RF saturation power pair of 0.5 μT at 2.0 ppm and 1.0 μT at 3.6 ppm, whereas an optimal contrast-to-variation ratio (CVR) was obtained with a 0.7 μT saturation at 2.0 ppm and 0.8 μT at 3.6 ppm. In acute stroke, CVR optimized pHenh (i.e., pHdual ) achieved a higher sensitivity than the three-point amide-CEST approach, and distinct patterns of lesion tissue compared to diffusion and perfusion MRI. CONCLUSION pHdual MRI improves the sensitivity of pH-weighted imaging and will be a valuable tool for assessing tissue viability in stroke.
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Affiliation(s)
- Julius Chung
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - T. Kevin Hitchens
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Michel Modo
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Andriy Bandos
- Department of Biostatistics, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Joseph Mettenburg
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Ping Wang
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Tao Jin
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
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Sun C, Zhao Y, Zu Z. Validation of the presence of fast exchanging amine CEST effect at low saturation powers and its influence on the quantification of APT. Magn Reson Med 2023; 90:1502-1517. [PMID: 37317709 PMCID: PMC10614282 DOI: 10.1002/mrm.29742] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 05/16/2023] [Accepted: 05/17/2023] [Indexed: 06/16/2023]
Abstract
PURPOSE Accurately quantifying the amide proton transfer (APT) effect and the underlying exchange parameters is crucial for its applications, but previous studies have reported conflicting results. In these quantifications, the CEST effect from the fast exchange amine was always ignored because it was considered weak with low saturation powers. This paper aims to evaluate the influence of the fast exchange amine CEST on the quantification of APT at low saturation powers. METHODS A quantification method with low and high saturation powers was used to distinguish APT from the fast exchange amine CEST effect. Simulations were conducted to assess the method's capability to separate APT from the fast exchange amine CEST effect. Animal experiments were performed to assess the relative contributions from the fast exchange amine and amide to CEST signals at 3.5 ppm. Three APT quantification methods, each with varying degrees of contamination from the fast exchange amine, were employed to process the animal data to assess the influence of the amine on the quantification of APT effect and the exchange parameters. RESULTS The relative size of the fast exchange amine CEST effect to APT effect gradually increases with increasing saturation power. At 9.4 T, it increases from approximately 20% to 40% of APT effect with a saturation power increase from 0.25 to 1 μT. CONCLUSION The fast exchange amine CEST effect leads overestimation of APT effect, fitted amide concentration, and amide-water exchange rate, potentially contributing to the conflicting results reported in previous studies.
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Affiliation(s)
- Casey Sun
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, US
- Department of Chemistry, University of Florida, Gainesville, US
| | - Yu Zhao
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
- Department of Biomedical Engineering, Vanderbilt University, Nashville, US
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Zhao Y, Sun C, Zu Z. Isolation of amide proton transfer effect and relayed nuclear Overhauser enhancement effect at -3.5ppm using CEST with double saturation powers. Magn Reson Med 2023; 90:1025-1040. [PMID: 37154382 PMCID: PMC10646838 DOI: 10.1002/mrm.29691] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Revised: 03/18/2023] [Accepted: 04/16/2023] [Indexed: 05/10/2023]
Abstract
PURPOSE Quantifications of amide proton transfer (APT) and nuclear Overhauser enhancement (rNOE(-3.5)) mediated saturation transfer with high specificity are challenging because their signals measured in a Z-spectrum are overlapped with confounding signals from direct water saturation (DS), semi-solid magnetization transfer (MT), and CEST of fast-exchange pools. In this study, based on two canonical CEST acquisitions with double saturation powers (DSP), a new data-postprocessing method is proposed to specifically quantify the effects of APT and rNOE. METHODS For CEST imaging with relatively low saturation powers (ω 1 2 $$ {\upomega}_1^2 $$ ), both the fast-exchange CEST effect and the semi-solid MT effect roughly depend onω 1 2 $$ {\upomega}_1^2 $$ , whereas the slow-exchange APT/rNOE(-3.5) effect do not, which is exploited to isolate a part of the APT and rNOE effects from the confounding signals in this study. After a mathematical derivation for the establishment of the proposed method, numerical simulations based on Bloch equations are then performed to demonstrate its specificity to detections of the APT and rNOE effects. Finally, an in vivo validation of the proposed method is conducted using an animal tumor model at a 4.7 T MRI scanner. RESULTS The simulations show that DSP-CEST can quantify the effects of APT and rNOE and substantially eliminate the confounding signals. The in vivo experiments demonstrate that the proposed DSP-CEST method is feasible for the imaging of tumors. CONCLUSION The data-postprocessing method proposed in this study can quantify the APT and rNOE effects with considerably increased specificities and a reduced cost of imaging time.
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Affiliation(s)
- Yu Zhao
- Vanderbilt University Institute of Imaging Science, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
- Department of Radiology, West China Hospital of Sichuan University, Chengdu, China
| | - Casey Sun
- Vanderbilt University Institute of Imaging Science, Nashville, US
- Department of Chemistry, University of Florida, Gainesville, US
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
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Cui J, Zhao Y, Sun C, Xu J, Zu Z. Evaluation of contributors to amide proton transfer-weighted imaging and nuclear Overhauser enhancement-weighted imaging contrast in tumors at a high magnetic field. Magn Reson Med 2023; 90:596-614. [PMID: 37093984 PMCID: PMC10616782 DOI: 10.1002/mrm.29675] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 03/31/2023] [Accepted: 03/31/2023] [Indexed: 04/26/2023]
Abstract
PURPOSE The purpose is to evaluate the relative contribution from confounding factors (T1 weighting and magnetization transfer) to the CEST ratio (CESTR)-quantified amide proton transfer (APT) and nuclear Overhauser enhancement (NOE) (-3.5) in tumors as well as whether the CESTR can reflect the distribution of the solute concentration (fs ). METHODS We first provided a signal model that shows the separate dependence of CESTR on these confounding factors and the clean CEST/NOE effects quantified by an apparent exchange-dependent relaxation (AREX) method. We then measured the change in these effects in the 9-L tumor model in rats, through which we calculated the relative contribution of each confounding factor. fs was also fitted, and its correlations with the CESTR and AREX were assessed to evaluate their capabilities to reflect fs . RESULTS The CESTR-quantified APT shows "positive" contrast in tumors, which arises primarily from R1w at low powers and both R1w and magnetization transfer at high powers. CESTR-quantified NOE (-3.5) shows no or weak contrast in tumors, which is due to the cancelation of R1w and NOE (-3.5), which have opposite contributions. CESTR-quantified APT has a stronger correlation with APT fs than AREX-quantified APT. CESTR-quantified NOE (-3.5) has a weaker correlation with NOE (-3.5) fs than AREX-quantified NOE (-3.5). CONCLUSION CESTR reflects a combined effect of T1 weighting and CEST/NOE. Both factors depend on fs , which contributes positively to the dependence of CESTR on fs in APT imaging and enhances its correlation with fs . In contrast, these factors have opposite contributions to its dependence on fs in NOE (-3.5) imaging, thereby weakening the correlation.
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Affiliation(s)
- Jing Cui
- Vanderbilt University Institute of Imaging Science, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
| | - Yu Zhao
- Vanderbilt University Institute of Imaging Science, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
| | - Casey Sun
- Vanderbilt University Institute of Imaging Science, Nashville, US
- Department of Chemistry, University of Florida, Gainesville, US
| | - Junzhong Xu
- Vanderbilt University Institute of Imaging Science, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
- Department of Biomedical Engineering, Vanderbilt University, Nashville, US
- Department of Physics and Astronomy, Vanderbilt University, Nashville, US
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
- Department of Biomedical Engineering, Vanderbilt University, Nashville, US
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Chen M, Zhou X, Cai H, Li D, Song C, You H, Ma R, Dong Z, Peng Z, Feng ST. Evaluation of Hypoxia in Hepatocellular Carcinoma Using Quantitative MRI: Significances, Challenges, and Advances. J Magn Reson Imaging 2023; 58:12-25. [PMID: 36971442 DOI: 10.1002/jmri.28694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 03/09/2023] [Accepted: 03/10/2023] [Indexed: 03/29/2023] Open
Abstract
This review aimed to perform a scoping review of promising MRI methods in assessing tumor hypoxia in hepatocellular carcinoma (HCC). The hypoxic microenvironment and upregulated hypoxic metabolism in HCC are determining factors of poor prognosis, increased metastatic potential, and resistance to chemotherapy and radiotherapy. Assessing hypoxia in HCC is essential for personalized therapy and predicting prognoses. Oxygen electrodes, protein markers, optical imaging, and positron emission tomography can evaluate tumor hypoxia. These methods lack clinical applicability because of invasiveness, tissue depth, and radiation exposure. MRI methods, including blood oxygenation level-dependent, dynamic contrast-enhanced MRI, diffusion-weighted imaging, MRI spectroscopy, chemical exchange saturation transfer MRI, and multinuclear MRI, are promising noninvasive methods that evaluate the hypoxic microenvironment by observing biochemical processes in vivo, which may inform on therapeutic options. This review summarizes the recent challenges and advances in MRI techniques for assessing hypoxia in HCC and highlights the potential of MRI methods for examining the hypoxic microenvironment via specific metabolic substrates and pathways. Although the utilization of MRI methods for evaluating hypoxia in patients with HCC is increasing, rigorous validation is needed in order to translate these MRI methods into clinical use. Due to the limited sensitivity and specificity of current quantitative MRI methods, their acquisition and analysis protocols require further improvement. EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 4.
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Affiliation(s)
- Meicheng Chen
- Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
| | - Xiaoqi Zhou
- Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
| | - Huasong Cai
- Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
| | - Di Li
- Department of Medical Ultrasonics, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
| | - Chenyu Song
- Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
| | - Huayu You
- Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
| | - Ruixia Ma
- Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
| | - Zhi Dong
- Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
| | - Zhenpeng Peng
- Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
| | - Shi-Ting Feng
- Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Province Guangdong, People's Republic of China
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Zhang Y, Zu T, Liu R, Zhou J. Acquisition sequences and reconstruction methods for fast chemical exchange saturation transfer imaging. NMR IN BIOMEDICINE 2023; 36:e4699. [PMID: 35067987 DOI: 10.1002/nbm.4699] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 01/02/2022] [Accepted: 01/17/2022] [Indexed: 05/23/2023]
Abstract
Chemical exchange saturation transfer (CEST) imaging is an emerging molecular magnetic resonance imaging (MRI) technique that has been developed and employed in numerous diseases. Based on the unique saturation transfer principle, a family of CEST-detectable biomolecules in vivo have been found capable of providing valuable diagnostic information. However, CEST MRI needs a relatively long scan time due to the common long saturation labeling module and typical acquisition of multiple frequency offsets and signal averages, limiting its widespread clinical applications. So far, a plethora of imaging schemes and techniques has been developed to accelerate CEST MRI. In this review, the key acquisition and reconstruction methods for fast CEST imaging are summarized from a practical and systematic point of view. The first acquisition sequence section describes the major development of saturation schemes, readout patterns, ultrafast z-spectroscopy, and saturation-editing techniques for rapid CEST imaging. The second reconstruction method section lists the important advances of parallel imaging, compressed sensing, sparsity in the z-spectrum, and algorithms beyond the Fourier transform for speeding up CEST MRI.
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Affiliation(s)
- Yi Zhang
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
- Cancer Center, Zhejiang University, Hangzhou, Zhejiang, China
| | - Tao Zu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Ruibin Liu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jinyuan Zhou
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
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Jiang S, Wen Z, Ahn SS, Cai K, Paech D, Eberhart CG, Zhou J. Applications of chemical exchange saturation transfer magnetic resonance imaging in identifying genetic markers in gliomas. NMR IN BIOMEDICINE 2023; 36:e4731. [PMID: 35297117 PMCID: PMC10557022 DOI: 10.1002/nbm.4731] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 03/07/2022] [Accepted: 03/14/2022] [Indexed: 05/23/2023]
Abstract
Chemical exchange saturation transfer (CEST) imaging is an important molecular magnetic resonance imaging technique that can image numerous low-concentration biomolecules with water-exchangeable protons (such as cellular proteins) and tissue pH. CEST, or more specially amide proton transfer-weighted imaging, has been widely used for the detection, diagnosis, and response assessment of brain tumors, and its feasibility in identifying molecular markers in gliomas has also been explored in recent years. In this paper, after briefing on the basic principles and quantification methods of CEST imaging, we review its early applications in identifying isocitrate dehydrogenase mutation status, MGMT methylation status, 1p/19q deletion status, and H3K27M mutation status in gliomas. Finally, we discuss the limitations or weaknesses in these studies.
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Affiliation(s)
- Shanshan Jiang
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
| | - Zhibo Wen
- Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Sung Soo Ahn
- Department of Radiology and Research Institute of Radiological Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Kejia Cai
- Department of Radiology, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Daniel Paech
- Department of Radiology, German Cancer Research Center, Heidelberg, Germany
- Clinic for Neuroradiology, University Hospital Bonn, Bonn, Germany
| | | | - Jinyuan Zhou
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
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Bie C, van Zijl P, Xu J, Song X, Yadav NN. Radiofrequency labeling strategies in chemical exchange saturation transfer MRI. NMR IN BIOMEDICINE 2023; 36:e4944. [PMID: 37002814 PMCID: PMC10312378 DOI: 10.1002/nbm.4944] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 03/19/2023] [Accepted: 03/27/2023] [Indexed: 05/23/2023]
Abstract
Chemical exchange saturation transfer (CEST) MRI has generated great interest for molecular imaging applications because it can image low-concentration solute molecules in vivo with enhanced sensitivity. CEST effects are detected indirectly through a reduction in the bulk water signal after repeated perturbation of the solute proton magnetization using one or more radiofrequency (RF) irradiation pulses. The parameters used for these RF pulses-frequency offset, duration, shape, strength, phase, and interpulse spacing-determine molecular specificity and detection sensitivity, thus their judicious selection is critical for successful CEST MRI scans. This review article describes the effects of applying RF pulses on spin systems and compares conventional saturation-based RF labeling with more recent excitation-based approaches that provide spectral editing capabilities for selectively detecting molecules of interest and obtaining maximal contrast.
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Affiliation(s)
- Chongxue Bie
- Department of Information Science and Technology, Northwest University, No.1 Xuefu Avenue, Xi’an, Shaanxi 710127 (China)
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, 707 N. Broadway, Baltimore MD 21205 (USA)
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 720 Rutland Ave, Baltimore, MD 21205 (USA)
| | - Peter van Zijl
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, 707 N. Broadway, Baltimore MD 21205 (USA)
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 720 Rutland Ave, Baltimore, MD 21205 (USA)
| | - Jiadi Xu
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, 707 N. Broadway, Baltimore MD 21205 (USA)
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 720 Rutland Ave, Baltimore, MD 21205 (USA)
| | - Xiaolei Song
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Haidian District, Beijing 100084 (China)
| | - Nirbhay N. Yadav
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, 707 N. Broadway, Baltimore MD 21205 (USA)
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 720 Rutland Ave, Baltimore, MD 21205 (USA)
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Liu Y, Gauthier GC, Gendelman HE, Bade AN. Dual-Peak Lorentzian CEST MRI for antiretroviral drug brain distribution. NEUROIMMUNE PHARMACOLOGY AND THERAPEUTICS 2023; 2:63-69. [PMID: 37027345 PMCID: PMC10070014 DOI: 10.1515/nipt-2022-0012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Accepted: 08/24/2022] [Indexed: 11/15/2022]
Abstract
Objectives Spatial-temporal biodistribution of antiretroviral drugs (ARVs) can now be achieved using MRI by utilizing chemical exchange saturation transfer (CEST) contrasts. However, the presence of biomolecules in tissue limits the specificity of current CEST methods. To overcome this limitation, a Lorentzian line-shape fitting algorithm was developed that simultaneously fits CEST peaks of ARV protons on its Z-spectrum. Case presentation This algorithm was tested on the common first line ARV, lamivudine (3TC), that has two peaks resulting from amino (-NH2) and hydroxyl (-OH) protons in 3TC. The developed dual-peak Lorentzian function fitted these two peaks simultaneously, and used the ratio of -NH2 and -OH CEST contrasts as a constraint parameter to measure 3TC presence in brains of drug-treated mice. 3TC biodistribution calculated using the new algorithm was compared against actual drug levels measured using UPLC-MS/MS. In comparison to the method that employs the -NH2 CEST peak only, the dual-peak Lorentzian fitting algorithm showed stronger correlation with brain tissue 3TC levels, signifying estimation of actual drug levels. Conclusions We concluded that 3TC levels can be extracted from confounding CEST effects of tissue biomolecules resulting in improved specificity for drug mapping. This algorithm can be expanded to measure a variety of ARVs using CEST MRI.
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Affiliation(s)
- Yutong Liu
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
- Department of Radiology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Gabriel C. Gauthier
- Department of Radiology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Howard E. Gendelman
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
| | - Aditya N. Bade
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
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14
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Cui J, Sun C, Zu Z. NOE-weighted imaging in tumors using low-duty-cycle 2π-CEST. Magn Reson Med 2023; 89:636-651. [PMID: 36198015 PMCID: PMC9792266 DOI: 10.1002/mrm.29475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 08/19/2022] [Accepted: 09/12/2022] [Indexed: 02/03/2023]
Abstract
PURPOSE Nuclear Overhauser enhancement (NOE)-mediated CEST imaging at -3.5 ppm has shown clinical interest in diagnosing tumors. Multiple-pool Lorentzian fit has been used to quantify NOE, which, however, requires a long scan time. Asymmetric analysis of CEST signals could be a simple and fast method to quantify this NOE, but it has contamination from the amide proton transfer (APT) at 3.5 ppm. This work proposes a new method using an asymmetric analysis of a low-duty-cycle pulsed-CEST sequence with a flip angle of 360°, termed 2π-CEST, to reduce the contribution from APT. METHODS Simulations were used to evaluate the capability of the 2π-CEST to reduce APT. Experiments on animal tumor models were performed to show its advantages compared with the conventional asymmetric analysis. Samples of reconstituted phospholipids and proteins were used to evaluate the molecular origin of this NOE. RESULTS The 2π-CEST has reduced contribution from APT. In tumors where we show that the NOE is comparable to the APT effect, reducing the contamination from APT is crucial. The results show that the NOE signal obtained with 2π-CEST in tumor regions appears more homogeneous than that obtained with the conventional method. The phantom study showed that both phospholipids and proteins contribute to the NOE at -3.5 ppm. CONCLUSION The NOE at -3.5 ppm has a different contrast mechanism from APT and other CEST/NOE effects. The proposed 2π-CEST is more accurate than the conventional asymmetric analysis in detecting NOE, and requires much less scan time than the multiple-pool Lorentzian fit.
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Affiliation(s)
- Jing Cui
- Vanderbilt University Institute of Imaging Science, Nashville, US,Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
| | - Casey Sun
- Vanderbilt University Institute of Imaging Science, Nashville, US,Department of Chemistry, University of Florida, Gainesville, US
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Nashville, US,Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
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15
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Jabehdar Maralani P, Chan RW, Lam WW, Oakden W, Oglesby R, Lau A, Mehrabian H, Heyn C, Chan AK, Soliman H, Sahgal A, Stanisz GJ. Chemical Exchange Saturation Transfer MRI: What Neuro-Oncology Clinicians Need To Know. Technol Cancer Res Treat 2023; 22:15330338231208613. [PMID: 37872686 PMCID: PMC10594966 DOI: 10.1177/15330338231208613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 09/19/2023] [Accepted: 09/28/2023] [Indexed: 10/25/2023] Open
Abstract
Chemical exchange saturation transfer (CEST) is a relatively novel magnetic resonance imaging (MRI) technique with an image contrast designed for in vivo measurement of certain endogenous molecules with protons that are exchangeable with water protons, such as amide proton transfer commonly used for neuro-oncology applications. Recent technological advances have made it feasible to implement CEST on clinical grade scanners within practical acquisition times, creating new opportunities to integrate CEST in clinical workflow. In addition, the majority of CEST applications used in neuro-oncology are performed without the use gadolinium-based contrast agents which are another appealing feature of this technique. This review is written for clinicians involved in neuro-oncologic care (nonphysicists) as the target audience explaining what they need to know as CEST makes its way into practice. The purpose of this article is to (1) review the basic physics and technical principles of CEST MRI, and (2) review the practical applications of CEST in neuro-oncology.
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Affiliation(s)
- Pejman Jabehdar Maralani
- Department of Medical Imaging, University of Toronto, Toronto, ON, Canada
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Rachel W. Chan
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Wilfred W. Lam
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Wendy Oakden
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Ryan Oglesby
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Angus Lau
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Hatef Mehrabian
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Chris Heyn
- Department of Medical Imaging, University of Toronto, Toronto, ON, Canada
| | - Aimee K.M. Chan
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Hany Soliman
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Arjun Sahgal
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Greg J. Stanisz
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
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16
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Zaiss M, Jin T, Kim SG, Gochberg DF. Theory of chemical exchange saturation transfer MRI in the context of different magnetic fields. NMR IN BIOMEDICINE 2022; 35:e4789. [PMID: 35704180 DOI: 10.1002/nbm.4789] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2021] [Revised: 05/31/2022] [Accepted: 06/10/2022] [Indexed: 06/15/2023]
Abstract
Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) is a versatile MRI method that provides contrast based on the level of molecular and metabolic activity. This contrast arises from indirect measurement of protons in low concentration molecules that are exchanging with the abundant water proton pool. The indirect measurement is based on magnetization transfer of radio frequency (rf)-prepared magnetization from the small pool to the water pool. The signal can be modeled by the Bloch-McConnell equations combining standard magnetization dynamics and chemical exchange processes. In this article, we review analytical solutions of the Bloch-McConnell equations and especially the derived CEST signal equations and their implications. The analytical solutions give direct insight into the dependency of measurable CEST effects on underlying parameters such as the exchange rate and concentration of the solute pools, but also on the system parameters such as the rf irradiation field B1 , as well as the static magnetic field B0 . These theoretical field-strength dependencies and their influence on sequence design are highlighted herein. In vivo results of different groups making use of these field-strength benefits/dependencies are reviewed and discussed.
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Affiliation(s)
- Moritz Zaiss
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Tao Jin
- NeuroImaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Seong-Gi Kim
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea
- Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, South Korea
| | - Daniel F Gochberg
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, USA
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17
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Glang F, Mueller S, Herz K, Loktyushin A, Scheffler K, Zaiss M. MR-double-zero - Proof-of-concept for a framework to autonomously discover MRI contrasts. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 341:107237. [PMID: 35714389 DOI: 10.1016/j.jmr.2022.107237] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 04/02/2022] [Accepted: 05/10/2022] [Indexed: 06/15/2023]
Abstract
PURPOSE A framework for supervised design of MR sequences for any given target contrast is proposed, based on fully automatic acquisition and reconstruction of MR data on a real MR scanner. The proposed method does not require any modeling of MR physics and thus allows even unknown contrast mechanisms to be addressed. METHODS A derivative-free optimization algorithm is set up to repeatedly update and execute a parametrized sequence on the MR scanner to acquire data. In each iteration, the acquired data are mapped to a given target contrast by linear regression. RESULTS It is shown that with the proposed framework it is possible to find an MR sequence that yields a predefined target contrast. In the present case, as a proof-of principle, a sequence mapping absolute creatine concentration, which cannot be extracted from T1 or T2-weighted scans directly, is discovered. The sequence was designed in a comparatively short time and with no human interaction. CONCLUSIONS New MR contrasts for mapping a given target can be discovered by derivative-free optimization of parametrized sequences that are directly executed on a real MRI scanner. This is demonstrated by 're-discovery' of a chemical exchange weighted sequence. The proposed method is considered to be a paradigm shift towards autonomous, model-free and target-driven sequence design.
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Affiliation(s)
- Felix Glang
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | - Sebastian Mueller
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany; Department of Biomedical Magnetic Resonance, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Kai Herz
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany; Department of Biomedical Magnetic Resonance, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Alexander Loktyushin
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | - Klaus Scheffler
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany; Department of Biomedical Magnetic Resonance, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Moritz Zaiss
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany; Institute of Neuroradiology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
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18
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Jin T, Chung JJ. Average saturation efficiency filter (ASEF) for CEST imaging. Magn Reson Med 2022; 88:254-265. [PMID: 35344594 PMCID: PMC9172934 DOI: 10.1002/mrm.29211] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 01/06/2022] [Accepted: 02/08/2022] [Indexed: 12/21/2022]
Abstract
PURPOSE Endogenous CEST signal usually has low specificity due to contamination from the magnetization transfer effect and from fast exchanging labile protons with close Larmor frequencies. We propose to improve CEST signal specificity with an average saturation efficiency filter (ASEF). METHODS ASEF measures the difference between CEST signals acquired with similar average irradiation power but largely different duty cycles (DC), for example, a continuous wave or a high DC pulse train versus a low DC one. Simulation and Cr phantom studies were performed to evaluate the characteristics of ASEF for CEST. RESULTS Theoretical and simulation studies show that ASEF can suppress fast exchanging processes, with only a small loss of chemical exchange contrast for slow-to-intermediate exchange rates if the difference in DC is large. In the RF offset range of 2 to 5 ppm with an averaged saturation power of 0.8 and 1.6 microteslas, there is a mismatch of ∼0.1% to 2% in the magnetization transfer signal between saturation by continuous wave and a pulse train with DC = 15% and pulse duration of 24 ms, respectively. This mismatch can be minimized by careful selection of saturation power, pulse duration, and DC differences or by applying a small fudge factor between the 2 irradiation powers. Phantom studies of Cr confirmed that ASEF can minimize the magnetization transfer effect and reduce sensitivity to fast exchange processes. CONCLUSION ASEF can improve the specificity of slow-to-intermediate exchanging CEST signal with a relatively small loss of sensitivity.
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Affiliation(s)
- Tao Jin
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Julius Juhyun Chung
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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19
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Zhao Y, Zu Z, Xu J, Gore JC, Does MD, Li J, Gochberg DF. Mapping pH using stimulated echoes formed via chemical exchange. Magn Reson Imaging 2022; 92:100-107. [PMID: 35764217 DOI: 10.1016/j.mri.2022.06.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 06/10/2022] [Accepted: 06/22/2022] [Indexed: 12/09/2022]
Abstract
PURPOSE RACETE (refocused acquisition of chemical exchange transferred excitations) is a recently developed approach to imaging solute exchange with water. However, it lacks biophysical specificity, as it is sensitive to exchange rates, relaxation rates, solute concentration, and macromolecular content. We modified this sequence and developed a protocol and corresponding metric with specific sensitivity to the solute exchange rate and hence a means for mapping pH. THEORY AND METHODS RACETE splits the two gradients traditionally used in a stimulated-echo sequence into one applied after exciting solutes and one applied after exciting water, hence requiring exchange for echo formation. In this work, we leverage the dependence of the stimulated-echo signal on the exchange process. By preserving the total irradiation power and using a ratio metric, the other signal dependencies cancel, leaving a specific measure of exchange rate. Additionally, artifacts due to off-resonance excitation of water are addressed using a phase cancelling approach; and a gradient-echo imaging sequence with a variable flip angle excitation is tailored for a fast read-out of RECETE prepared signals. This method is validated using numerical simulations and salicylic acid phantom experiments at 9.4 T. RESULTS Numerical simulations and phantom experiments demonstrate that the ratio-metric is a single-variable function of exchange rate with extremely low dependence on confounding factors. Additionally, artifacts due to direct water excitation are removed and robustness to B0 and B1 inhomogeneities is demonstrated. CONCLUSION The proposed method can be used for fast pH mapping with robustness against the confounding effects that widely exist in other methods.
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Affiliation(s)
- Yu Zhao
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai, China
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Junzhong Xu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - John C Gore
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Mark D Does
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jianqi Li
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai, China
| | - Daniel F Gochberg
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA.
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20
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Wu QX, Liu HQ, Wang YJ, Chen TC, Wei ZY, Chang JH, Chen TH, Seema J, Lin EC. Chemical Exchange Saturation Transfer (CEST) Signal at −1.6 ppm and Its Application for Imaging a C6 Glioma Model. Biomedicines 2022; 10:biomedicines10061220. [PMID: 35740241 PMCID: PMC9219881 DOI: 10.3390/biomedicines10061220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 05/17/2022] [Accepted: 05/21/2022] [Indexed: 02/01/2023] Open
Abstract
The chemical exchange saturation transfer (CEST) signal at −1.6 ppm is attributed to the choline methyl on phosphatidylcholines and results from the relayed nuclear Overhauser effect (rNOE), that is, rNOE(−1.6). The formation of rNOE(−1.6) involving the cholesterol hydroxyl is shown in liposome models. We aimed to confirm the correlation between cholesterol content and rNOE(−1.6) in cell cultures, tissues, and animals. C57BL/6 mice (N = 9) bearing the C6 glioma tumor were imaged in a 7 T MRI scanner, and their rNOE(−1.6) images were cross-validated through cholesterol staining with filipin. Cholesterol quantification was obtained using an 18.8-T NMR spectrometer from the lipid extracts of the brain tissues from another group of mice (N = 3). The cholesterol content in the cultured cells was manipulated using methyl-β-cyclodextrin and a complex of cholesterol and methyl-β-cyclodextrin. The rNOE(−1.6) of the cell homogenates and their cholesterol levels were measured using a 9.4-T NMR spectrometer. The rNOE(−1.6) signal is hypointense in the C6 tumors of mice, which matches the filipin staining results, suggesting that their tumor region is cholesterol deficient. The tissue extracts also indicate less cholesterol and phosphatidylcholine contents in tumors than in normal brain tissues. The amplitude of rNOE(−1.6) is positively correlated with the cholesterol concentration in the cholesterol-manipulated cell cultures. Our results indicate that the cholesterol dependence of rNOE(−1.6) occurs in cell cultures and solid tumors of C6 glioma. Furthermore, when the concentration of phosphatidylcholine is carefully considered, rNOE(−1.6) can be developed as a cholesterol-weighted imaging technique.
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Affiliation(s)
- Qi-Xuan Wu
- Department of Chemistry and Biochemistry, National Chung Cheng University, Chiayi 62102, Taiwan; (Q.-X.W.); (H.-Q.L.); (Y.-J.W.); (Z.-Y.W.); (J.-H.C.); (T.-H.C.)
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan; (T.-C.C.); (J.S.)
| | - Hong-Qing Liu
- Department of Chemistry and Biochemistry, National Chung Cheng University, Chiayi 62102, Taiwan; (Q.-X.W.); (H.-Q.L.); (Y.-J.W.); (Z.-Y.W.); (J.-H.C.); (T.-H.C.)
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan; (T.-C.C.); (J.S.)
| | - Yi-Jiun Wang
- Department of Chemistry and Biochemistry, National Chung Cheng University, Chiayi 62102, Taiwan; (Q.-X.W.); (H.-Q.L.); (Y.-J.W.); (Z.-Y.W.); (J.-H.C.); (T.-H.C.)
| | - Tsai-Chen Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan; (T.-C.C.); (J.S.)
| | - Zi-Ying Wei
- Department of Chemistry and Biochemistry, National Chung Cheng University, Chiayi 62102, Taiwan; (Q.-X.W.); (H.-Q.L.); (Y.-J.W.); (Z.-Y.W.); (J.-H.C.); (T.-H.C.)
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan; (T.-C.C.); (J.S.)
| | - Jung-Hsuan Chang
- Department of Chemistry and Biochemistry, National Chung Cheng University, Chiayi 62102, Taiwan; (Q.-X.W.); (H.-Q.L.); (Y.-J.W.); (Z.-Y.W.); (J.-H.C.); (T.-H.C.)
| | - Ting-Hao Chen
- Department of Chemistry and Biochemistry, National Chung Cheng University, Chiayi 62102, Taiwan; (Q.-X.W.); (H.-Q.L.); (Y.-J.W.); (Z.-Y.W.); (J.-H.C.); (T.-H.C.)
| | - Jaya Seema
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan; (T.-C.C.); (J.S.)
| | - Eugene C. Lin
- Department of Chemistry and Biochemistry, National Chung Cheng University, Chiayi 62102, Taiwan; (Q.-X.W.); (H.-Q.L.); (Y.-J.W.); (Z.-Y.W.); (J.-H.C.); (T.-H.C.)
- Center for Nano Bio-Detection, National Chung Cheng University, Chiayi 62102, Taiwan
- Correspondence: ; Tel.: +886-5-272-0411 (ext. 66418); Fax: +886-5-272-1040
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21
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Sawaya R, Kuribayashi S, Ueda J, Saito S. Evaluating the Cisplatin Dose Dependence of Testicular Dysfunction using Creatine Chemical Exchange Saturation Transfer Imaging. Diagnostics (Basel) 2022; 12:diagnostics12051046. [PMID: 35626202 PMCID: PMC9139560 DOI: 10.3390/diagnostics12051046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 04/18/2022] [Accepted: 04/19/2022] [Indexed: 11/16/2022] Open
Abstract
Chemical exchange saturation transfer (CEST) imaging is a non-invasive molecular imaging technique for indirectly measuring low-concentration endogenous metabolites. Conventional CEST has low specificity, owing to the effects of spillover, magnetization transfer (MT), and T1 relaxation, thus necessitating an inverse Z-spectrum analysis. We aimed to investigate the usefulness of inverse Z-spectrum analysis in creatine (Cr)-CEST in mice, by conducting preclinical 7T-magnetic resonance imaging (MRI) and comparing the conventional analysis metric magnetization transfer ratio (MTRconv) with the novel metric apparent exchange-dependent relaxation (AREX). We performed Cr-CEST imaging using 7T-MRI on mouse testes, using C57BL/6 mice as the control and a cisplatin-treated model. We prepared different doses of cisplatin to observe its dose dependence effect on testicular function. CEST imaging was obtained using an MT pulse with varying saturation frequencies, ranging from −4.8 ppm to +4.8 ppm. The application of control mouse testes improved the specificity of the CEST effect and image contrast between the testes and testicular epithelium. The cisplatin-treated model revealed impaired testicular function, and the Cr-CEST imaging displayed decreased Cr levels in the testes. There was a significant difference between the low- and high-dose models. The MTR values of Cr-CEST reflected the cisplatin dose dependence of testicular dysfunction.
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Affiliation(s)
- Reika Sawaya
- Department of Medical Physics and Engineering, Area of Medical Imaging Technology and Science, Division of Health Sciences, Osaka University Graduate School of Medicine, Suita 565-0871, Osaka, Japan; (R.S.); (J.U.)
- Department of Medical Technology, Osaka University Hospital, Suita 565-0871, Osaka, Japan
| | - Sohei Kuribayashi
- Department of Urology, Osaka University Graduate School of Medicine, Suita 565-0871, Osaka, Japan;
| | - Junpei Ueda
- Department of Medical Physics and Engineering, Area of Medical Imaging Technology and Science, Division of Health Sciences, Osaka University Graduate School of Medicine, Suita 565-0871, Osaka, Japan; (R.S.); (J.U.)
| | - Shigeyoshi Saito
- Department of Medical Physics and Engineering, Area of Medical Imaging Technology and Science, Division of Health Sciences, Osaka University Graduate School of Medicine, Suita 565-0871, Osaka, Japan; (R.S.); (J.U.)
- Department of Advanced Medical Technologies, National Cerebral and Cardiovascular Center Research Institute, Suita 564-8565, Osaka, Japan
- Correspondence: ; Tel.: +81-6-6879-2619
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22
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Lankford CL, Louie EA, Zu Z, Does MD, Gochberg DF. A hybrid numeric-analytic solution for pulsed CEST. NMR IN BIOMEDICINE 2022; 35:e4610. [PMID: 34636458 PMCID: PMC9045009 DOI: 10.1002/nbm.4610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 07/23/2021] [Accepted: 08/12/2021] [Indexed: 05/08/2023]
Abstract
Chemical exchange saturation transfer (CEST) methods measure the effect of magnetization exchange between solutes and water. While CEST methods are often implemented using a train of off-resonant shaped RF pulses, they are typically analyzed as if the irradiation were continuous. This approximation does not account for exchange of rotated magnetization, unique to pulsed irradiation and exploited by chemical exchange rotation transfer methods. In this work, we derive and test an analytic solution for the steady-state water signal under pulsed irradiation by extending a previous work to include the effects of pulse shape. The solution is largely accurate at all offsets, but this accuracy diminishes at higher exchange rates and when applying pulse shapes with large root-mean-squared to mean ratios (such as multi-lobe sinc pulses).
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Affiliation(s)
- Christopher L. Lankford
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
| | - Elizabeth A. Louie
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Mark D. Does
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
- Department of Electrical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Daniel F. Gochberg
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
- Corresponding author. Vanderbilt University Institute of Imaging Science, 1161 21 Ave. S, MCN AAA–3112, Nashville, TN 37232–2310, USA.
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23
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Huang J, Lai JHC, Tse KH, Cheng GWY, Liu Y, Chen Z, Han X, Chen L, Xu J, Chan KWY. Deep neural network based CEST and AREX processing: Application in imaging a model of Alzheimer's disease at 3 T. Magn Reson Med 2021; 87:1529-1545. [PMID: 34657318 DOI: 10.1002/mrm.29044] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 08/26/2021] [Accepted: 09/22/2021] [Indexed: 02/06/2023]
Abstract
PURPOSE To optimize and apply deep neural network based CEST (deepCEST) and apparent exchange dependent-relaxation (deepAREX) for imaging the mouse brain with Alzheimer's disease (AD) at 3T MRI. METHODS CEST and T1 data of central and anterior brain slices of 10 AD mice and 10 age-matched wild type (WT) mice were acquired at a 3T animal MRI scanner. The networks of deepCEST/deepAREX were optimized and trained on the WT data. The CEST/AREX contrasts of AD and WT mice predicted by the networks were analyzed and further validated by immunohistochemistry. RESULTS After optimization and training on CEST data of WT mice, deepCEST/deepAREX could rapidly (~1 s) generate precise CEST and AREX results for unseen CEST data of AD mice, indicating the accuracy and generalization of the networks. Significant lower amide weighted (3.5 ppm) signal related to amyloid β-peptide (Aβ) plaque depositions, which was validated by immunohistochemistry results, was detected in both central and anterior brain slices of AD mice compared to WT mice. Decreased magnetization transfer (MT) signal was also found in AD mice especially in the anterior slice. CONCLUSION DeepCEST/deepAREX could rapidly generate accurate CEST/AREX contrasts in animal study. The well-optimized deepCEST/deepAREX have potential for AD differentiation at 3T MRI.
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Affiliation(s)
- Jianpan Huang
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Joseph H C Lai
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Kai-Hei Tse
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, China
| | - Gerald W Y Cheng
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, China
| | - Yang Liu
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China.,Hong Kong Centre for Cerebro-Cardiovascular Health Engineering (COCHE), Hong Kong, China
| | - Zilin Chen
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Xiongqi Han
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Lin Chen
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA.,Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Jiadi Xu
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA.,Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Kannie W Y Chan
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China.,Hong Kong Centre for Cerebro-Cardiovascular Health Engineering (COCHE), Hong Kong, China.,Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,City University of Hong Kong Shenzhen Research Institute, Shenzhen, China
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24
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Chung JJ, Jin T. Low duty cycle pulse trains for exchange rate insensitive chemical exchange saturation transfer MRI. Magn Reson Med 2021; 86:2542-2551. [PMID: 34196028 DOI: 10.1002/mrm.28896] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 04/29/2021] [Accepted: 06/02/2021] [Indexed: 12/22/2022]
Abstract
PURPOSE To introduce and validate a pulse scheme that uses low duty cycle trains of π-pulses to achieve saturation that is relatively insensitive to exchange rate yet linearly dependent on labile proton concentration. METHODS Simulations were performed to explore the exchange rate sensitivity of π-pulse trains and continuous wave chemical exchange saturation transfer (CEST) signals. Creatine phantoms with varying pH and varying concentrations were imaged to demonstrate pH insensitivity and concentration dependence of low duty cycle π-pulse saturation. RESULTS Simulations show decreasing the duty cycle of π-pulse saturation decreases peak sensitivity to exchange rate, and this range of insensitivity can be tuned to different exchange rates through average B1 power. The range of insensitivity is unaffected by changes in relaxation and magnetization transfer, while the sensitivity of CEST signal maintains linear dependence on labile proton concentration. Under B1, avg = 0.48 μT, 30 mM creatine with pHs ranging between 6.36 and 8.21 exhibited CEST contrast ranging between ~6 and 11% under continuous wave and ~4% across all pHs using 10% duty cycle π-pulses. Imaging these phantoms using duty cycles of 5, 10, 25, and 50% showed decreasing pH sensitivity with decreased duty cycle. Creatine phantoms with varied concentrations and pHs reveal that π-pulse train saturation exhibited stricter correlation to concentration at lower DCs. CONCLUSION Low DC π-pulse train is an easy-to-implement way of providing labile proton concentration-dependent CEST MRI signal that is insensitive to exchange rate. This approach can be useful in studies where a change of chemical exchange rate may interfere with accurate assessments of physiology or pathology.
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Affiliation(s)
- Julius Juhyun Chung
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Tao Jin
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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25
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Zu Z, Lin EC, Louie EA, Jiang X, Lankford CL, Damon B, Does MD, Gore JC, Gochberg DF. Chemical exchange rotation transfer imaging of phosphocreatine in muscle. NMR IN BIOMEDICINE 2021; 34:e4437. [PMID: 33283945 PMCID: PMC7902410 DOI: 10.1002/nbm.4437] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 10/09/2020] [Accepted: 10/12/2020] [Indexed: 05/22/2023]
Abstract
In chemical exchange saturation transfer (CEST) imaging, the signal at 2.6 ppm from the water resonance in muscle has been assigned to phosphocreatine (PCr). However, this signal has limited specificity for PCr since the signal is also sensitive to exchange with protein and macromolecular protons when using some conventional quantification methods, and will vary with changes in the water longitudinal relaxation rate. Correcting for these effects while maintaining reasonable acquisition times is challenging. As an alternative approach to overcome these problems, here we evaluate chemical exchange rotation transfer (CERT) imaging of PCr in muscle at 9.4 T. Specifically, the CERT metric, AREXdouble,cpw at 2.6 ppm, was measured in solutions containing the main muscle metabolites, in tissue homogenates with controlled PCr content, and in vivo in rat leg muscles. PCr dominates CERT metrics around 2.6 ppm (although with nontrivial confounding baseline contributions), indicating that CERT is well-suited to PCr specific imaging, and has the added benefit of requiring a relatively small number of acquisitions.
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Affiliation(s)
- Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Eugene C. Lin
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Elizabeth A. Louie
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Xiaoyu Jiang
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Christopher L. Lankford
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Bruce Damon
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
| | - Mark D. Does
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
| | - John C. Gore
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
| | - Daniel F. Gochberg
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, TN
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26
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Kim H, Krishnamurthy LC, Sun PZ. Brain pH Imaging and its Applications. Neuroscience 2021; 474:51-62. [PMID: 33493621 DOI: 10.1016/j.neuroscience.2021.01.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 01/12/2021] [Accepted: 01/13/2021] [Indexed: 12/14/2022]
Abstract
Acid-base homeostasis and pH regulation are critical for normal tissue metabolism and physiology, and brain tissue pH alters in many diseased states. Several noninvasive tissue pH Magnetic Resonance (MR) techniques have been developed over the past few decades to shed light on pH change during tissue function and dysfunction. Nevertheless, there are still challenges for mapping brain pH noninvasively at high spatiotemporal resolution. To address this unmet biomedical need, chemical exchange saturation transfer (CEST) MR techniques have been developed as a sensitive means for non-invasive pH mapping. This article briefly reviews the basic principles of different pH measurement techniques with a focus on CEST imaging of pH. Emerging pH imaging applications in the tumor are provided as examples throughout the narrative, and CEST pH imaging in acute stroke is discussed in the final section.
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Affiliation(s)
- Hahnsung Kim
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, United States; Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States
| | - Lisa C Krishnamurthy
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA, Decatur, GA, United States; Department of Physics & Astronomy, Georgia State University, Atlanta, GA, United States
| | - Phillip Zhe Sun
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, United States; Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States.
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27
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Tang X, Zhang H, Zhou J, Kang H, Yang S, Cui H, Peng Y. Brain development in children with developmental delay using amide proton transfer-weighted imaging and magnetization transfer imaging. Pediatr Investig 2020; 4:250-256. [PMID: 33376952 PMCID: PMC7768295 DOI: 10.1002/ped4.12237] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 06/02/2020] [Indexed: 11/09/2022] Open
Abstract
IMPORTANCE The process of brain development in children with developmental delay is not well known. Amide proton transfer-weighted (APTw) imaging is a novel molecular magnetic resonance imaging (MRI) technique that can noninvasively detect cytosolic endogenous mobile proteins and peptides involved in the myelination process, and may be useful for providing insights into brain development. OBJECTIVE To assess the contribution of amide proton transfer-weighted (APTw) imaging and magnetization transfer (MT) imaging to the evaluation of children with developmental delay (DD). METHODS Fifty-one patients with DD were recruited to this study. The patients were divided into two groups according to the state of myelination assessed on conventional magnetic resonance imaging (MRI). Thirty patients (10 girls, 20 boys; age range: 1-8 months; median age: 4 months) in group A showed delayed myelination on MRI, while 21 patients (3 girls, 18 boys; age range: 12-36months; median age: 25months) in group B showed normal myelination on MRI. Fifty-one age- and sex-matched children with normal developmental quotient (DQ) and normal MRI appearance were recruited as normal controls. Three-slice APTw/MT axial imaging was performed at the level of the centrum semiovale, the basal ganglia and the pons. Quantitative data of the MT ratio (MTR) and APTw were analyzed for multiple brain regions. Independent-sample t-tests were used to compare differences in APTw and MTR signals between the two DD groups and normal controls. Analysis of Covariance was conducted to correct the statistical results. The level of statistical significance was set to P < 0.05. RESULTS For group A, the MTR values were lower in all regions (P = 0.004-0.033) compared with the normal controls, while the APTw values were higher in the pons, middle cerebellar peduncle, corpus callosum, frontal white matter, occipital white matter and centrum semiovale (P = 0.004-0.040 ). For Group B, the MTR values were slightly reduced, and the APTw values were slightly increased compared with the normal controls, but the differences were not statistically significant (P > 0.05). INTERPRETATION For DD patients showing signs of delayed myelination on MRI, MTR and APTw imaging can help to diagnose myelination delay by quantifying semi-solid macromolecules and cytosolic endogenous mobile proteins and peptides at a molecular level, providing a new method for comprehensive evaluation of DD. For DD patients with normal myelination on MRI, the clinical values of MTR and APTw imaging remain to be explored.
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Affiliation(s)
- Xiaolu Tang
- Imaging CenterBeijing Children's HospitalCapital Medical UniversityNational Center for Children's HealthBeijingChina
| | - Hong Zhang
- Imaging CenterBeijing Children's HospitalCapital Medical UniversityNational Center for Children's HealthBeijingChina
| | - Jinyuan Zhou
- Division of MR ResearchDepartment of RadiologyJohns Hopkins UniversityBaltimoreMDUSA
| | - Huiying Kang
- Imaging CenterBeijing Children's HospitalCapital Medical UniversityNational Center for Children's HealthBeijingChina
| | - Shuangfeng Yang
- Imaging CenterBeijing Children's HospitalCapital Medical UniversityNational Center for Children's HealthBeijingChina
| | - Haijing Cui
- Rehabilitation DepartmentBeijing Children's HospitalCapital Medical UniversityNational Center for Children's HealthBeijingChina
| | - Yun Peng
- Imaging CenterBeijing Children's HospitalCapital Medical UniversityNational Center for Children's HealthBeijingChina
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28
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Demetriou E, Kujawa A, Golay X. Pulse sequences for measuring exchange rates between proton species: From unlocalised NMR spectroscopy to chemical exchange saturation transfer imaging. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2020; 120-121:25-71. [PMID: 33198968 DOI: 10.1016/j.pnmrs.2020.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 06/27/2020] [Accepted: 06/30/2020] [Indexed: 06/11/2023]
Abstract
Within the field of NMR spectroscopy, the study of chemical exchange processes through saturation transfer techniques has a long history. In the context of MRI, chemical exchange techniques have been adapted to increase the sensitivity of imaging to small fractions of exchangeable protons, including the labile protons of amines, amides and hydroxyls. The MR contrast is generated by frequency-selective irradiation of the labile protons, which results in a reduction of the water signal associated with transfer of the labile protons' saturated magnetization to the protons of the surrounding free water. The signal intensity depends on the rate of chemical exchange and the concentration of labile protons as well as on the properties of the irradiation field. This methodology is referred to as CEST (chemical exchange saturation transfer) imaging. Applications of CEST include imaging of molecules with short transverse relaxation times and mapping of physiological parameters such as pH, temperature, buffer concentration and chemical composition due to the dependency of this chemical exchange effect on all these parameters. This article aims to describe these effects both theoretically and experimentally. In depth analysis and mathematical modelling are provided for all pulse sequences designed to date to measure the chemical exchange rate. Importantly, it has become clear that the background signal from semi-solid protons and the presence of the Nuclear Overhauser Effect (NOE), either through direct dipole-dipole mechanisms or through exchange-relayed signals, complicates the analysis of CEST effects. Therefore, advanced methods to suppress these confounding factors have been developed, and these are also reviewed. Finally, the experimental work conducted both in vitro and in vivo is discussed and the progress of CEST imaging towards clinical practice is presented.
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Affiliation(s)
- Eleni Demetriou
- Brain Repair & Rehabilitation, Institute of Neurology, University College London, United Kingdom.
| | - Aaron Kujawa
- Brain Repair & Rehabilitation, Institute of Neurology, University College London, United Kingdom.
| | - Xavier Golay
- Brain Repair & Rehabilitation, Institute of Neurology, University College London, United Kingdom.
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29
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Zu Z, Lin EC, Louie EA, Xu J, Li H, Xie J, Lankford CL, Chekmenev EY, Swanson SD, Does MD, Gore JC, Gochberg DF. Relayed nuclear Overhauser enhancement sensitivity to membrane Cho phospholipids. Magn Reson Med 2020; 84:1961-1976. [PMID: 32243662 PMCID: PMC8238412 DOI: 10.1002/mrm.28258] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 02/17/2020] [Accepted: 02/26/2020] [Indexed: 12/20/2022]
Abstract
PURPOSE Phospholipids are key constituents of cell membranes and serve vital functions in the regulation of cellular processes; thus, a method for in vivo detection and characterization could be valuable for detecting changes in cell membranes that are consequences of either normal or pathological processes. Here, we describe a new method to map the distribution of partially restricted phospholipids in tissues. METHODS The phospholipids were measured by signal changes caused by relayed nuclear Overhauser enhancement-mediated CEST between the phospholipid Cho headgroup methyl protons and water at around -1.6 ppm from the water resonance. The biophysical basis of this effect was examined by controlled manipulation of head group, chain length, temperature, degree of saturation, and presence of cholesterol. Additional experiments were performed on animal tumor models to evaluate potential applications of this novel signal while correcting for confounding contributions. RESULTS Negative relayed nuclear Overhauser dips in Z-spectra were measured from reconstituted Cho phospholipids with cholesterol but not for other Cho-containing metabolites or proteins. Significant contrast was found between tumor and contralateral normal tissue signals in animals when comparing both the measured saturation transfer signal and a more specific imaging metric. CONCLUSION We demonstrated specific relayed nuclear Overhauser effects in partially restricted phospholipid phantoms and similar effects in solid brain tumors after correcting for confounding signal contributions, suggesting possible translational applications of this novel molecular imaging method, which we name restricted phospholipid transfer.
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Affiliation(s)
- Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Eugene C. Lin
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Elizabeth A. Louie
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Junzhong Xu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee
| | - Hua Li
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee
| | - Jingping Xie
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
| | - Christopher L. Lankford
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
| | - Eduard Y. Chekmenev
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee
| | - Scott D. Swanson
- Department of Radiology, University of Michigan, Ann Arbor, Michigan
| | - Mark D. Does
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee
- Department of Electrical Engineering, Vanderbilt University, Nashville, Tennessee
| | - John C. Gore
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Daniel F. Gochberg
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee
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30
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Liu R, Zhang H, Qian Y, Hsu YC, Fu C, Sun Y, Wu D, Zhang Y. Frequency-stabilized chemical exchange saturation transfer imaging with real-time free-induction-decay readout. Magn Reson Med 2020; 85:1322-1334. [PMID: 32970882 DOI: 10.1002/mrm.28513] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 08/17/2020] [Accepted: 08/17/2020] [Indexed: 01/19/2023]
Abstract
PURPOSE To correct the temporal B0 drift in chemical exchange saturation transfer (CEST) imaging in real-time with extra free-induction-decay (FID) readout. THEORY AND METHODS The frequency stabilization module of the recently proposed frequency-stabilized CEST (FS-CEST) sequence was further simplified by replacing the original three k-space lines of gradient-echo (GRE) readout with a single k-space line of FID readout. The B0 drift was quantified using the phase difference between the odd and even parts of the FID signal in the frequency stabilization module and then used to update the B0 frequency in the succeeding modules. The proposed FS-CEST sequence with FID readout (FID FS-CEST) was validated in phantoms and 16 human subjects on cross-vendor scanners. RESULTS In the Siemens experiments, the FID FS-CEST sequence successfully corrected the user-induced B0 drift, generating consistent amide proton transfer-weighted (APTw) images and magnetization transfer ratio asymmetry (MTRasym ) spectra with those from the non-frequency-stabilized CEST (NFS-CEST) sequence without B0 drift. In the Philips experiments, the FID FS-CEST sequence produced more stable APTw images and MTRasym spectra than the NFS-CEST sequence in the presence of practical B0 drift. Quantitatively, the SD of the APTw signal values in the deep gray matter from 15 subjects was 0.26% for the FID FS-CEST sequence compared to 1.03% for the NFS-CEST sequences, with the fluctuations reduced by nearly three-quarters. CONCLUSIONS The proposed FS-CEST sequence with FID readout can effectively correct the temporal B0 drift on cross-vendor scanners.
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Affiliation(s)
- Ruibin Liu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Hongxi Zhang
- Department of Radiology, Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yue Qian
- Department of Radiology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yi-Cheng Hsu
- MR Collaboration, Siemens Healthcare Ltd., Shanghai, China
| | - Caixia Fu
- Siemens Shenzhen Magnetic Resonance Ltd., Shenzhen, China
| | - Yi Sun
- MR Collaboration, Siemens Healthcare Ltd., Shanghai, China
| | - Dan Wu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yi Zhang
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
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Huang J, Han X, Chen L, Xu X, Xu J, Chan KWY. Relayed nuclear Overhauser enhancement imaging with magnetization transfer contrast suppression at 3 T. Magn Reson Med 2020; 85:254-267. [PMID: 32738080 DOI: 10.1002/mrm.28433] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Revised: 06/10/2020] [Accepted: 06/24/2020] [Indexed: 12/11/2022]
Abstract
PURPOSE To develop a pulsed CEST magnetization-transfer method for rapidly acquiring relayed nuclear Overhauser enhancement (rNOE)-weighted images with magnetic transfer contrast (MTC) suppression at clinical field strength (3 T). METHODS Using a pulsed CEST magnetization-transfer method with low saturation powers (B1 ) and long mixing time (tmix ) to suppress contributions due to strong MTC from solid-like macromolecules, a low B1 also minimized direct water saturation. These MTC contributions were further reduced by subtracting the Z-spectral signals at two or three offsets by assuming that the residual MTC is a linear function between -3.5 ppm and -12.5 ppm. RESULTS Phantom studies of a lactic acid (Lac) solution mixed with cross-linked bovine serum albumin show that strong MTC interference has a significant impact on the optimum B1 for detecting rNOEs, due to lactate binding. The MTC could be effectively suppressed using a pulse train with a B1 of 0.8 μT, a pulse duration (tp ) of 40 ms, a tmix of 60 ms, and a pulse number (N) of 30, while rNOE signal was well maintained. As a proof of concept, we applied the method in mouse brain with injected hydrogel and a cell-hydrogel phantom. Results showed that rNOE-weighted images could provide good contrast between brain/cell and hydrogel. CONCLUSION The developed pulsed CEST magnetization-transfer method can achieve MTC suppression while preserving most of the rNOE signal at 3 T, which indicates the potential for translation of this technique to clinical applications related to mobile proteins/lipids change.
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Affiliation(s)
- Jianpan Huang
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Xiongqi Han
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Lin Chen
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA.,Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Xiang Xu
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA.,Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jiadi Xu
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA.,Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Kannie W Y Chan
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China.,Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,City University of Hong Kong Shenzhen Research Institute, Shenzhen, China
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32
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Amide Proton Transfer-Weighted (APTw) Imaging of Intracranial Infection in Children: Initial Experience and Comparison with Gadolinium-Enhanced T1-Weighted Imaging. BIOMED RESEARCH INTERNATIONAL 2020; 2020:6418343. [PMID: 32509865 PMCID: PMC7251435 DOI: 10.1155/2020/6418343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 03/21/2020] [Accepted: 04/25/2020] [Indexed: 12/05/2022]
Abstract
Purpose To evaluate the performance of amide proton transfer-weighted (APTw) imaging against the reference standard of gadolinium-enhanced T1-weighted imaging (Gd-T1w) in children with intracranial infection. Materials and Methods Twenty-eight pediatric patients (15 males and 13 females; age range 1-163 months) with intracranial infection were recruited in this study. 2D APTw imaging and conventional MR sequences were conducted using a 3 T MRI scanner. Kappa (κ) statistics and the McNemar test were performed to determine whether the hyperintensity on APTw was related to the enhancement on Gd-T1w. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of APTw imaging to predict lesion enhancement were calculated. Result In twelve patients with brain abscesses, the enhancing rim of the abscesses on the Gd-T1w images was consistently hyperintense on the APTw images. In eight patients with viral encephalitis, three showed slight spotted gadolinium enhancement, while the APTw image also showed a slight spotted high signal. Five of these patients showed no enhancement on Gd-T1w and isointensity on the APTw image. In eleven patients with meningitis, increased APTw signal intensities were clearly visible in gadolinium-enhancing meninges. Sixty infectious lesions (71%) showed enhancement on Gd-T1w images. The sensitivity and specificity of APTw were 93.3% (56/60) and 91.7% (22/24). APTw demonstrated excellent agreement (κ = 0.83) with Gd-T1w, with no significant difference (P = 0.69) in detection of infectious lesions. Conclusions These initial data show that APTw MRI is a noninvasive technique for the detection and characterization of intracranial infectious lesions. APTw MRI enabled similar detection of infectious lesions to Gd-T1w and may provide an injection-free means of evaluation of intracranial infection.
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Zhang Z, Zhang C, Yao J, Gao F, Gong T, Jiang S, Chen W, Zhou J, Wang G. Amide proton transfer-weighted magnetic resonance imaging of human brain aging at 3 Tesla. Quant Imaging Med Surg 2020; 10:727-742. [PMID: 32269932 DOI: 10.21037/qims.2020.02.22] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Background Amide proton transfer-weighted (APTw) imaging has been revealed to hold great potential in the diagnosis of several brain diseases. The purpose of this proof-of-concept study was to evaluate the feasibility and value of APTw magnetic resonance imaging (MRI) in characterizing normal brain aging. Methods A total of 106 healthy subjects were recruited and scanned at 3.0 Tesla, with APTw and conventional magnetization transfer (MT) sequences. Quantitative image analyses were performed in 12 regions of interest (ROIs) for each subject. The APTw or MT ratio (MTR) signal differences among five age groups (young, mature, middle-aged, young-old, and middle-old) were assessed using the one-way analysis of variance, with the Benjamini-Hochberg correction for multiple comparisons. The relationship between APTw and MTR signals and the age dependencies of APTw and MTR signals were assessed using the Pearson correlation and non-linear regression. Results There were no significant differences between the APTw or MTR values for males and females in any of the 12 ROIs analyzed. Among the five age groups, there were significant differences in the three white matter regions in the temporal, occipital, and frontal lobes. Overall, the mean APTw values in the older group were higher than those in the younger group. Positive correlations were observed in relation to age in most brain regions, including four with significant positive correlations (r=0.2065-0.4182) and five with increasing trends. As a comparison, the mean MTR values did not appear to be significantly different among the five age groups. In addition, the mean APTw and MTR values revealed significant positive correlations in 10 ROIs (r=0.2214-0.7269) and a significant negative correlation in one ROI (entorhinal cortex, r=-0.2141). Conclusions Our early results show that the APTw signal can be used as a promising and complementary imaging biomarker with which normal brain aging can be evaluated at the molecular level.
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Affiliation(s)
- Zewen Zhang
- Department of MR, Shandong Medical Imaging Research Institute, Shandong University, Jinan 250021, China.,Division of MR Research, Department of Radiology, Johns Hopkins University, Maryland, USA
| | - Caiqing Zhang
- Department of Respiratory Medicine, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan 250014, China
| | - Jian Yao
- Department of MR, Shandong Medical Imaging Research Institute, Shandong University, Jinan 250021, China
| | - Fei Gao
- Department of MR, Shandong Medical Imaging Research Institute, Shandong University, Jinan 250021, China
| | - Tao Gong
- Department of MR, Shandong Medical Imaging Research Institute, Shandong University, Jinan 250021, China
| | - Shanshan Jiang
- Division of MR Research, Department of Radiology, Johns Hopkins University, Maryland, USA
| | - Weibo Chen
- Philips Healthcare, Shanghai 200072, China
| | - Jinyuan Zhou
- Division of MR Research, Department of Radiology, Johns Hopkins University, Maryland, USA
| | - Guangbin Wang
- Department of MR, Shandong Medical Imaging Research Institute, Shandong University, Jinan 250021, China
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Protein-based amide proton transfer-weighted MR imaging of amnestic mild cognitive impairment. NEUROIMAGE-CLINICAL 2019; 25:102153. [PMID: 31901792 PMCID: PMC6948365 DOI: 10.1016/j.nicl.2019.102153] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 12/07/2019] [Accepted: 12/26/2019] [Indexed: 02/06/2023]
Abstract
Amide proton transfer-weighted (APTw) MRI is a novel molecular imaging technique that can noninvasively detect endogenous cellular proteins and peptides in tissue. Here, we demonstrate the feasibility of protein-based APTw MRI in characterizing amnestic mild cognitive impairment (aMCI). Eighteen patients with confirmed aMCI and 18 matched normal controls were scanned at 3 Tesla. The APTw, as well as conventional magnetization transfer ratio (MTR), signal differences between aMCI and normal groups were assessed by the independent samples t-test, and the receiver-operator-characteristic analysis was used to assess the diagnostic performance of APTw. When comparing the normal control group, aMCI brains typically had relatively higher APTw signals. Quantitatively, APTw intensity values were significantly higher in nine of 12 regions of interest in aMCI patients than in normal controls. The largest areas under the receiver-operator-characteristic curves were 0.88 (gray matter in occipital lobe) and 0.82 (gray matter in temporal lobe, white matter in occipital lobe) in diagnosing aMCI patients. On the contrary, MTR intensity values were significantly higher in only three of 12 regions of interest in the aMCI group. Additionally, the age dependency analyses revealed that these cross-sectional APTw/MTR signals had an increasing trend with age in most brain regions for normal controls, but a decreasing trend with age in most brain regions for aMCI patients. Our early results show the potential of the APTw signal as a new imaging biomarker for the noninvasive molecular diagnosis of aMCI.
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35
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Chen L, Wei Z, Cai S, Li Y, Liu G, Lu H, Weiss RG, van Zijl PCM, Xu J. High-resolution creatine mapping of mouse brain at 11.7 T using non-steady-state chemical exchange saturation transfer. NMR IN BIOMEDICINE 2019; 32:e4168. [PMID: 31461196 DOI: 10.1002/nbm.4168] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 07/27/2019] [Accepted: 07/31/2019] [Indexed: 06/10/2023]
Abstract
The current study aims to optimize the acquisition scheme for the creatine chemical exchange saturation transfer weighted (CrCESTw) signal on mouse brain at 11.7 T, in which a strong magnetization transfer contrast (MTC) is present, and to further develop the polynomial and Lorentzian line-shape fitting (PLOF) method for quantifying CrCESTw signal with a non-steady-state (NSS) acquisition scheme. Studies on a Cr phantom with cross-linked bovine serum albumin (BSA) as well as on mouse brain demonstrated that the maximum CrCESTw signal was reached with a short saturation time determined by the rotating frame relaxation time of the MTC pool instead of the steady-state saturation. The saturation power for the maximal signal was around 1-1.5 μT for Cr with 20% cross-linked BSA and in vivo applications, but 2 μT was found to be most practical for signal stability. For the CrCEST acquisition with strong MTC interference, the optimal saturation power and length are completely different from those on Cr solution alone. This observation could be explained well using R1ρ theory by incorporating the strong MTC pool. Finally, a high-resolution Cr map was obtained on mouse brain using the PLOF method with the NSS CEST acquisition and a cryogenic coil. The Cr map obtained by CEST showed homogenous intensity across the mouse brain except for regions with cerebrospinal fluid.
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Affiliation(s)
- Lin Chen
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Zhiliang Wei
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Yuguo Li
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Guanshu Liu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Hanzhang Lu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Robert G Weiss
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Peter C M van Zijl
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Jiadi Xu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
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Rivlin M, Navon G. Molecular imaging of tumors by chemical exchange saturation transfer MRI of glucose analogs. Quant Imaging Med Surg 2019; 9:1731-1746. [PMID: 31728315 DOI: 10.21037/qims.2019.09.12] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Early detection of the cancerous process would benefit greatly from imaging at the cellular and molecular level. Increased glucose demand has been recognized as one of the hallmarks of cancerous cells (the "Warburg effect"), hence glucose and its analogs are commonly used for cancer imaging. One example is FDG-PET technique, that led to the use of chemical exchange saturation transfer (CEST) MRI of glucose ("glucoCEST") for tumor imaging. This technique combines high-resolution MRI obtained by conventional imaging with simultaneous molecular information obtained from the exploitation of agents with exchangeable protons from amine, amide or hydroxyl residues with the water signal. In the case of glucoCEST, these agents are based on glucose or its analogs. Recently, preclinical glucoCEST studies demonstrated the ability to increase the sensitivity of MRI to the level of metabolic activity, enabling identification of tumor staging, biologic potential, treatment planning, therapy response and local recurrence, in addition to guiding target biopsy for clinically suspected cancer. However, natural glucose limits this method because of its rapid conversion to lactic acid, leading to reduced CEST effect and short signal duration. For that reason, a variety of glucose analogs have been tested as alternatives to the original glucoCEST. This review discusses the merits of these analogs, including new data on glucose analogs heretofore not reported in the literature. This summarized preclinical data may help strengthen the translation of CEST MRI of glucose analogs into the clinic, improving cancer imaging to enable early intervention without the need for invasive techniques. The data should also broaden our knowledge of fundamental biological processes.
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Affiliation(s)
- Michal Rivlin
- School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Gil Navon
- School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
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37
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Lin Y, Luo X, Yu L, Zhang Y, Zhou J, Jiang Y, Zhang C, Zhang J, Li C, Chen M. Amide proton transfer-weighted MRI for predicting histological grade of hepatocellular carcinoma: comparison with diffusion-weighted imaging. Quant Imaging Med Surg 2019; 9:1641-1651. [PMID: 31728308 DOI: 10.21037/qims.2019.08.07] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Background Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver, preoperative grading of HCC is of great clinical significance. Amide proton transfer-weighted (APTw) imaging, as a novel contrast mechanism in the field of molecular imaging, provided new diagnostic ideas for the grading of HCC. Methods Between May 2017 and April 2018, 32 consecutive patients with pathologically confirmed HCC were enrolled, including 19 high-grade HCCs and 13 low-grade HCCs. DWI and APTw scanning was performed on a 3T MRI scanner. Two observers drew regions of interest independently by referring to the axial T2-weighted imaging, and APTw and apparent diffusion coefficient (ADC) values were obtained. Inter- and intra-observer agreements were assessed with the intraclass correlation coefficients (ICCs). The independent sample t test was used to compare the APTw and ADC values between the high- and low-grade HCC tumor parenchyma. The receiver operating characteristic curve was used to analyze the diagnostic efficacy of high- from low-grade HCC tumors. Spearman correlation analysis was used to assess the relationship between APTw and ADC values and HCC histological grades. Results There were significant differences between the APTw or ADC values for the high- and low-grade HCCs (P=0.034 and 0.010). Both APTw and DWI had good diagnostic performance in differentiating the high- from the low-grade HCCs, with areas under the curves of 0.814 and 0.745, respectively. Moderate correlations existed between APTw values and histological grades (r=0.534; P=0.002), as well as ADC values and histological grades (r=-0.417; P=0.018). Conclusions The APTw imaging is a useful imaging biomarker that complements DWI for the more accurate and comprehensive HCC characterization.
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Affiliation(s)
- Yue Lin
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, China.,Graduate School of Peking Union Medical College, Beijing 100730, China
| | - Xiaojie Luo
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, China
| | - Lu Yu
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, China.,Graduate School of Peking Union Medical College, Beijing 100730, China
| | - Yi Zhang
- Center for Brain Imaging Science and Technology, Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou 310058, China
| | - Jinyuan Zhou
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
| | - Yuwei Jiang
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, China
| | - Chen Zhang
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, China
| | - Jintao Zhang
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, China
| | - Chunmei Li
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, China
| | - Min Chen
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, China.,Graduate School of Peking Union Medical College, Beijing 100730, China
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Liu J, Li C, Chen Y, Lv X, Lv Y, Zhou J, Xi S, Dou W, Qian L, Zheng H, Wu Y, Chen Z. Diagnostic performance of multiparametric MRI in the evaluation of treatment response in glioma patients at 3T. J Magn Reson Imaging 2019; 51:1154-1161. [DOI: 10.1002/jmri.26900] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 07/30/2019] [Accepted: 08/01/2019] [Indexed: 01/07/2023] Open
Affiliation(s)
- Jie Liu
- Paul C. Lauterbur Research Center for Biomedical ImagingShenzhen Institutes of Advanced Technology, Chinese Academy of Sciences Shenzhen Guangdong China
| | - Cong Li
- Department of NeurosurgerySun Yat‐Sen University Cancer Center Guangzhou Guangdong China
| | - Yinsheng Chen
- Department of NeurosurgerySun Yat‐Sen University Cancer Center Guangzhou Guangdong China
| | - Xiaofei Lv
- Department of Medical ImagingSun Yat‐Sen University Cancer Center Guangzhou Guangdong China
| | - Yanchun Lv
- Department of Medical ImagingSun Yat‐Sen University Cancer Center Guangzhou Guangdong China
| | - Jian Zhou
- Department of Medical ImagingSun Yat‐Sen University Cancer Center Guangzhou Guangdong China
| | - Shaoyan Xi
- Department of PathologySun Yat‐Sen University Cancer Center Guangzhou Guangdong China
| | | | | | - Hairong Zheng
- Paul C. Lauterbur Research Center for Biomedical ImagingShenzhen Institutes of Advanced Technology, Chinese Academy of Sciences Shenzhen Guangdong China
| | - Yin Wu
- Paul C. Lauterbur Research Center for Biomedical ImagingShenzhen Institutes of Advanced Technology, Chinese Academy of Sciences Shenzhen Guangdong China
| | - Zhongping Chen
- Department of NeurosurgerySun Yat‐Sen University Cancer Center Guangzhou Guangdong China
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Zhang X, Yuan Y, Li S, Zeng Q, Guo Q, Liu N, Yang M, Yang Y, Liu M, McMahon MT, Zhou X. Free-base porphyrins as CEST MRI contrast agents with highly upfield shifted labile protons. Magn Reson Med 2019; 82:577-585. [PMID: 30968442 PMCID: PMC7294594 DOI: 10.1002/mrm.27753] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Revised: 02/26/2019] [Accepted: 03/06/2019] [Indexed: 12/29/2022]
Abstract
PURPOSE CEST has become a preeminent technology for the rapid detection and grading of tumors, securing its widespread use in both laboratory and clinical research. However, many existing CEST MRI agents exhibit a sensitivity limitation due to small chemical shifts between their exchangeable protons and water. We propose a new group of CEST MRI agents, free-base porphyrins and chlorin, with large exchangeable proton chemical shifts from water for enhanced detection. METHODS To test these newly identified CEST agents, we acquired a series of Z-spectra at multiple pH values and saturation field strengths to determine their CEST properties. The data were analyzed using the quantifying exchange using saturation power method to quantify exchange rates. After identifying several promising candidates, a porphyrin solution was injected into tumor-bearing mice, and MR images were acquired to assess detection feasibility in vivo. RESULTS Based on the Z-spectra, the inner nitrogen protons in free-base porphyrins and chlorin resonate from -8 to -13.5 ppm from water, far shifted from the majority of endogenous metabolites (0-4 ppm) and Nuclear Overhauser enhancements (-1 to -3.5 ppm) and far removed from the salicylates, imidazoles, and anthranillates (5-12 ppm). The exchange rates are sufficiently slow to intermediate (500-9000 s-1 ) to allow robust detection and were sensitive to substituents on the porphyrin ring. CONCLUSION These results highlight the capabilities of free-base porphyrins and chlorin as highly upfield CEST MRI agents and provide a new scaffold that can be integrated into a variety of diagnostic or theranostic agents for biomedical applications.
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Affiliation(s)
- Xiaoxiao Zhang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
| | - Yaping Yuan
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Sha Li
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Qingbin Zeng
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Qianni Guo
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Na Liu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Minghui Yang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Yunhuang Yang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Maili Liu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Michael T. McMahon
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
| | - Xin Zhou
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
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40
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Zhao Y, Yan X, Zhang Z, Zhao W, Liu Z, Li J. Self-adapting multi-peak water-fat reconstruction for the removal of lipid artifacts in chemical exchange saturation transfer (CEST) imaging. Magn Reson Med 2019; 82:1700-1712. [PMID: 31241219 DOI: 10.1002/mrm.27859] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 04/23/2019] [Accepted: 05/21/2019] [Indexed: 12/26/2022]
Abstract
PURPOSE Artifacts caused by strong lipid signals pose challenges in body chemical exchange saturation transfer (CEST) imaging. This study aimed to develop an accurate water-fat reconstruction method based on the multi-echo Dixon technique to remove lipid artifacts in CEST imaging. THEORY AND METHODS It is well known that fat has multiple spectral peaks. Furthermore, RF pulses in CEST preparation saturate each fat peak at different levels, complicating fat modeling. Therefore, a self-adapting multi-peak model (SMPM) is proposed to update relative amplitudes of fat peaks using numerical calculation. With the SMPM-based updating, nonlinear least-squares fitting combined with IDEAL (Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation) algorithms was used for water-fat reconstruction and B0 mapping. The proposed method was compared with the reported 3-point Dixon method and the fixed multi-peak model in a phantom study using a fat-free Z-spectrum obtained from MR spectroscopy acquisition as the ground truth. This method was also validated by in vivo experiments on human breast. RESULTS In the phantom experiments, the Z-spectrum from the SMPM-based method agreed well with the fat-free Z-spectrum from CEST-PRESS (point-resolved spectroscopy), validating the effective removal of lipid artifacts, while a decrease or a rise that appeared at -3.5 ppm was observed in the Z-spectrum from the 3-point method and the FMPM-based method, respectively. In the in vivo experiments, no lipid artifacts were observed in the Z-spectrum or the amide CEST map from the SMPM-based method in the fibro-glandular region of the breast with high fat fractions. CONCLUSION The SMPM-based method successfully removes lipid artifacts and significantly improves the accuracy of CEST contrast.
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Affiliation(s)
- Yu Zhao
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai, China
| | - Xu Yan
- MR Collaboration NE Asia, Siemens Healthcare, Shanghai, China
| | | | - Weiwei Zhao
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai, China
| | - Zhenzhi Liu
- Molecular Imaging Program at Stanford, Department of Radiology, Stanford University, Stanford, California
| | - Jianqi Li
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai, China
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Heo HY, Xu X, Jiang S, Zhao Y, Keupp J, Redmond KJ, Laterra J, van Zijl PCM, Zhou J. Prospective acceleration of parallel RF transmission-based 3D chemical exchange saturation transfer imaging with compressed sensing. Magn Reson Med 2019; 82:1812-1821. [PMID: 31209938 DOI: 10.1002/mrm.27875] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/07/2019] [Accepted: 05/30/2019] [Indexed: 12/26/2022]
Abstract
PURPOSE To develop prospectively accelerated 3D CEST imaging using compressed sensing (CS), combined with a saturation scheme based on time-interleaved parallel transmission. METHODS A variable density pseudo-random sampling pattern with a centric elliptical k-space ordering was used for CS acceleration in 3D. Retrospective CS studies were performed with CEST phantoms to test the reconstruction scheme. Prospectively CS-accelerated 3D-CEST images were acquired in 10 healthy volunteers and 6 brain tumor patients with an acceleration factor (RCS ) of 4 and compared with conventional SENSE reconstructed images. Amide proton transfer weighted (APTw) signals under varied RF saturation powers were compared with varied acceleration factors. RESULTS The APTw signals obtained from the CS with acceleration factor of 4 were well-preserved as compared with the reference image (SENSE R = 2) both in retrospective phantom and prospective healthy volunteer studies. In the patient study, the APTw signals were significantly higher in the tumor region (gadolinium [Gd]-enhancing tumor core) than in the normal tissue (p < .001). There was no significant APTw difference between the CS-accelerated images and the reference image. The scan time of CS-accelerated 3D APTw imaging was dramatically reduced to 2:10 minutes (in-plane spatial resolution of 1.8 × 1.8 mm2 ; 15 slices with 4-mm slice thickness) as compared with SENSE (4:07 minutes). CONCLUSION Compressed sensing acceleration was successfully extended to 3D-CEST imaging without compromising CEST image quality and quantification. The CS-based CEST imaging can easily be integrated into clinical protocols and would be beneficial for a wide range of applications.
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Affiliation(s)
- Hye-Young Heo
- Divison of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
| | - Xiang Xu
- Divison of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
| | - Shanshan Jiang
- Divison of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | | | | | - Kristin J Redmond
- Department of Radiation Oncology and Molecular Radiation Science, Johns Hopkins University, Baltimore, Maryland
| | - John Laterra
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland.,Department of Neurology, Johns Hopkins University, Baltimore, Maryland
| | - Peter C M van Zijl
- Divison of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
| | - Jinyuan Zhou
- Divison of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
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42
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Kujawa A, Kim M, Demetriou E, Anemone A, Livio Longo D, Zaiss M, Golay X. Assessment of a clinically feasible Bayesian fitting algorithm using a simplified description of Chemical Exchange Saturation Transfer (CEST) imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 300:120-134. [PMID: 30739012 DOI: 10.1016/j.jmr.2019.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 01/13/2019] [Accepted: 01/15/2019] [Indexed: 06/09/2023]
Abstract
Fitting a model based on the Bloch-McConnell (BM) equations to Chemical Exchange Saturation Transfer (CEST) spectra allows for the quantification of metabolite concentration and exchange rate as well as simultaneous correction of field inhomogeneity, direct water saturation and magnetization transfer. Employing a Bayesian fitting approach permits the integration of prior information into the analysis to incorporate expected parameter distributions and to prevent over-fitting. However, the analysis can be time consuming if a general numerical solution of the BM equations is applied. In this study, we combined a Bayesian fitting algorithm with approximate analytical solutions of the BM equations to achieve feasible computational times. To evaluate the accuracy and speed of the suggested approach, phantoms including Iodipamide, Taurine and Creatine were tested in addition to simulated data with continuous-wave (CW) and pulsed saturation with Gaussian pulses. A significant reduction of computational time was achieved when fitting CW data (about 50-fold) and pulsed saturation data (more than 100-fold) with the analytical model while the estimated parameters were largely consistent with the parameters from the general numerical solution. The increased speed of the algorithm facilitates the Bayesian analysis of CEST data within clinically feasible processing times. Other analytical models valid for different parameter regimes may be employed to extend the applicability to a wider range of CEST agents.
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Affiliation(s)
- Aaron Kujawa
- Brain Repair and Rehabilitation, University College London, 8-11 Queen Square, London WC1N 3AR, United Kingdom.
| | - Mina Kim
- Brain Repair and Rehabilitation, University College London, 8-11 Queen Square, London WC1N 3AR, United Kingdom
| | - Eleni Demetriou
- Brain Repair and Rehabilitation, University College London, 8-11 Queen Square, London WC1N 3AR, United Kingdom
| | - Annasofia Anemone
- Molecular Biotechnology and Health Sciences, University of Torino, Via Nizza 52, 10126 Turin, Italy
| | - Dario Livio Longo
- Institute of Biostructures and Bioimaging (IBB), National Research Council of Italy (CNR), Via Nizza 52, 10126 Torino, Italy
| | - Moritz Zaiss
- Magnetic Resonance Center, Max-Planck Institute for Biological Cybernetics, Max-Planck-Ring 8-14, 72076 Tübingen, Germany
| | - Xavier Golay
- Brain Repair and Rehabilitation, University College London, 8-11 Queen Square, London WC1N 3AR, United Kingdom
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Yu L, Chen Y, Chen M, Luo X, Jiang S, Zhang Y, Chen H, Gong T, Zhou J, Li C. Amide Proton Transfer MRI Signal as a Surrogate Biomarker of Ischemic Stroke Recovery in Patients With Supportive Treatment. Front Neurol 2019; 10:104. [PMID: 30853932 PMCID: PMC6395437 DOI: 10.3389/fneur.2019.00104] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Accepted: 01/25/2019] [Indexed: 12/11/2022] Open
Abstract
Background: Amide proton transfer (APT) MR imaging has shown great potential in the evaluation of stroke severity because of its sensitivity to acid environments. However, this promising MRI technique has not been used to assess treatment efficacy with regard to stroke recovery. Purpose: To assess the therapeutic effect of supportive treatment in ischemic stroke patients using the pH-sensitive APT MRI technique. Material and Methods: Forty-three ischemic stroke patients at an early stage were recruited and scanned with conventional and APT MRI sequences at 3T before treatment. After treatment, 26 patients underwent a follow-up MRI scan (one to three times on different days). The magnetization-transfer-ratio asymmetry at 3.5 ppm, usually called the APT-weighted (APTW) signal, was measured. The APTW signal changes following treatment were analyzed. Results: Baseline APTW signal intensities in the infarcted lesions inversely correlated with baseline stroke severity. Lesion APTW values gradually increased with time in 24 cases (92.3%) with a follow-up MRI scan, showing clinical symptom improvements. Two cases (7.7%) showed further decreased APTW signal in the follow-up scan, accompanied by clinical symptom aggravation. Compared to the baseline, significant APTW signal increases were found for all post-treatment patients (efficacious), whether based on post-treatment or on stroke onset times. The increase in APTW signal in the ischemic stroke lesion after treatment was associated with an improvement in clinical symptoms. Conclusion: The APTW signal would be a useful imaging biomarker by which to assess the therapeutic efficacy of ischemic stroke treatment.
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Affiliation(s)
- Lu Yu
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing, China.,Graduate School of Peking Union Medical College, Beijing, China
| | - Yuhui Chen
- Department of Neurology, Beijing Hospital, National Center of Gerontology, Beijing, China
| | - Min Chen
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing, China
| | - Xiaojie Luo
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing, China
| | - Shanshan Jiang
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, MD, United States
| | - Yi Zhang
- Key Laboratory for Biomedical Engineering of Ministry of Education, Center for Brain Imaging Science and Technology, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
| | - Haibo Chen
- Department of Neurology, Beijing Hospital, National Center of Gerontology, Beijing, China
| | - Tao Gong
- Department of Neurology, Beijing Hospital, National Center of Gerontology, Beijing, China
| | - Jinyuan Zhou
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, MD, United States
| | - Chunmei Li
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing, China
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44
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Liu R, Zhang H, Niu W, Lai C, Ding Q, Chen W, Liang S, Zhou J, Wu D, Zhang Y. Improved chemical exchange saturation transfer imaging with real-time frequency drift correction. Magn Reson Med 2019; 81:2915-2923. [PMID: 30697813 DOI: 10.1002/mrm.27663] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 12/10/2018] [Accepted: 12/28/2018] [Indexed: 01/24/2023]
Abstract
PURPOSE To investigate the effects of frequency drift on chemical exchange saturation transfer (CEST) imaging at 3T, and to propose a new sequence for correcting artifacts attributed to B0 drift in real time. THEORY AND METHODS A frequency-stabilized CEST (FS-CEST) imaging sequence was proposed by adding a frequency stabilization module to the conventional non-frequency-stabilized CEST (NFS-CEST) sequence, which consisted of a small tip angle radiofrequency excitation pulse and readout of three non-phase-encoded k-space lines. Experiments were performed on an egg white phantom and 26 human subjects on a heavy-duty clinical scanner, in order to compare the difference of FS-CEST and NFS-CEST sequences for generating the z-spectrum, magnetization transfer ratio asymmetry (MTRasym ) spectrum, and amide proton transfer weighted (APTw) image. RESULTS The B0 drift in CEST imaging, if not corrected, would cause APTw images and MTRasym spectra from both the phantom and volunteers to be either significantly higher or lower than the true values, depending on the status of the scanner. The FS-CEST sequence generated substantially more stable MTRasym spectra and APTw images than the conventional NFS-CEST sequence. Quantitatively, the compartmental-average APTw signals (mean ± standard deviation) from frontal white matter regions of all 26 human subjects were -0.32% ± 2.32% for the NFS-CEST sequence and -0.14% ± 0.37% for the FS-CEST sequence. CONCLUSIONS The proposed FS-CEST sequence provides an effective approach for B0 drift correction without additional scan time and should be adopted on heavy-duty MRI scanners.
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Affiliation(s)
- Ruibin Liu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Hongxi Zhang
- Department of Radiology, Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Weiming Niu
- Department of Radiology, Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Can Lai
- Department of Radiology, Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Qiuping Ding
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | | | - Sayuan Liang
- Clinical Research Board, Philips Research China, Shanghai, China
| | - Jinyuan Zhou
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Dan Wu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China.,Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Yi Zhang
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China.,Department of Radiology, Johns Hopkins University, Baltimore, Maryland
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Zhou J, Heo HY, Knutsson L, van Zijl PCM, Jiang S. APT-weighted MRI: Techniques, current neuro applications, and challenging issues. J Magn Reson Imaging 2019; 50:347-364. [PMID: 30663162 DOI: 10.1002/jmri.26645] [Citation(s) in RCA: 199] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 12/26/2018] [Accepted: 12/27/2018] [Indexed: 02/06/2023] Open
Abstract
Amide proton transfer-weighted (APTw) imaging is a molecular MRI technique that generates image contrast based predominantly on the amide protons in mobile cellular proteins and peptides that are endogenous in tissue. This technique, the most studied type of chemical exchange saturation transfer imaging, has been used successfully for imaging of protein content and pH, the latter being possible due to the strong dependence of the amide proton exchange rate on pH. In this article we briefly review the basic principles and recent technical advances of APTw imaging, which is showing promise clinically, especially for characterizing brain tumors and distinguishing recurrent tumor from treatment effects. Early applications of this approach to stroke, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and traumatic brain injury are also illustrated. Finally, we outline the technical challenges for clinical APT-based imaging and discuss several controversies regarding the origin of APTw imaging signals in vivo. Level of Evidence: 3 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2019;50:347-364.
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Affiliation(s)
- Jinyuan Zhou
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| | - Hye-Young Heo
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| | - Linda Knutsson
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,Department of Medical Radiation Physics, Lund University, Lund, Sweden
| | - Peter C M van Zijl
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| | - Shanshan Jiang
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
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46
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Chen L, Barker PB, Weiss RG, van Zijl PCM, Xu J. Creatine and phosphocreatine mapping of mouse skeletal muscle by a polynomial and Lorentzian line-shape fitting CEST method. Magn Reson Med 2019; 81:69-78. [PMID: 30246265 PMCID: PMC6258268 DOI: 10.1002/mrm.27514] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/19/2018] [Accepted: 08/10/2018] [Indexed: 01/01/2023]
Abstract
PURPOSE To obtain high-resolution Cr and PCr maps of mouse skeletal muscle using a polynomial and Lorentzian line-shape fitting (PLOF) CEST method. METHODS Wild-type mice and guanidinoacetate N-methyltransferase-deficient (GAMT-/-) mice that have low Cr and PCr concentrations in muscle were used to assign the Cr and PCr peaks in the Z-spectrum at 11.7 T. A PLOF method was proposed to simultaneously extract and quantify the Cr and PCr by assuming a polynomial function for the background and 2 Lorentzian functions for the CEST peaks at 1.95 ppm and 2.5 ppm. RESULTS The Z-spectra of phantoms revealed that PCr has 2 CEST peaks (2 ppm and 2.5 ppm), whereas Cr only showed 1 peak at 2 ppm. Comparison of the Z-spectra of wild-type and GAMT-/- mice indicated that, contrary to brain, there was no visible protein guanidinium peak in the skeletal-muscle Z-spectrum, which allowed us to extract clean PCr and Cr CEST signals. High-resolution PCr and Cr concentration maps of mouse skeletal muscle were obtained by the PLOF CEST method after calibration with in vivo MRS. CONCLUSIONS The PLOF method provides an efficient way to map Cr and PCr concentrations simultaneously in the skeletal muscle at high MRI field.
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Affiliation(s)
- Lin Chen
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Peter B. Barker
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Robert G. Weiss
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Peter C. M. van Zijl
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jiadi Xu
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Zu Z. Toward more reliable measurements of NOE effects in CEST spectra at around -1.6 ppm (NOE (-1.6)) in rat brain. Magn Reson Med 2019; 81:208-219. [PMID: 30058128 PMCID: PMC6258343 DOI: 10.1002/mrm.27370] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 04/24/2018] [Accepted: 04/29/2018] [Indexed: 01/17/2023]
Abstract
PURPOSE Recently, a new relayed nuclear Overhauser enhancement (NOE) saturation transfer effect at around -1.6 parts per million, termed NOE(-1.6), and its potential applications in tumor and stroke were reported by several institutes. However, there is a concern of the reproducibility of NOE(-1.6) measurements because it is not reported by many other publications. This paper aims to study the influence of typically overlooked experimental settings on the NOE(-1.6) signal and to build a framework for more reliable measurements of NOE(-1.6) at 9.4T. METHODS Z-spectra were obtained in rat brains. A fitting approach was performed to quantify all known saturation transfer effects except NOE(-1.6). Residual signals were obtained by removing these confounding effects from Z-spectra and were then used to quantify NOE(-1.6). Multislice imaging was performed to study the NOE(-1.6) dependence on brain regions. The influences of euthanasia, anesthesia, breathing gases, and RF irradiation power were also evaluated. RESULTS Results demonstrate that the NOE(-1.6) signal contributions are often not clearly observable in raw Z-spectra at relatively high irradiation powers due to, for example, the direct water saturation effect, but they can be visualized after removing other nonspecific effects. In addition, the NOE(-1.6) effect depends on brain region, decreases postmortem, shifts after long-duration anesthesia, and may be enhanced by increasing O2 and N2 O breathing air concentrations. CONCLUSION Because the NOE(-1.6) effect is more susceptible to the direct water saturation effect and more sensitive to physiological conditions than are other CEST effects, incorporating known sensitivities into the experimental design and data analysis is necessary to ensure more reliable NOE(-1.6) results.
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Affiliation(s)
- Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
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48
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Lin EC, Li H, Zu Z, Louie EA, Lankford CL, Dortch RD, Does MD, Gore JC, Gochberg DF. Chemical exchange rotation transfer (CERT) on human brain at 3 Tesla. Magn Reson Med 2018; 80:2609-2617. [PMID: 29802641 PMCID: PMC6252284 DOI: 10.1002/mrm.27365] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 03/23/2018] [Accepted: 04/24/2018] [Indexed: 12/14/2022]
Abstract
PURPOSE To test the ability of a novel pulse sequence applied in vivo at 3 Tesla to separate the contributions to the water signal from amide proton transfer (APT) and relayed nuclear Overhauser enhancement (rNOE) from background direct water saturation and semisolid magnetization transfer (MT). The lack of such signal source isolation has confounded conventional chemical exchange saturation transfer (CEST) imaging. METHODS We quantified APT and rNOE signals using a chemical exchange rotation transfer (CERT) metric, MTRdouble . A range of duty cycles and average irradiation powers were applied, and results were compared with conventional CEST analyses using asymmetry (MTRasym ) and extrapolated magnetization transfer (EMR). RESULTS Our results indicate that MTRdouble is more specific than MTRasym and, because it requires as few as 3 data points, is more rapid than methods requiring a complete Z-spectrum, such as EMR. In white matter, APT (1.5 ± 0.5%) and rNOE (2.1 ± 0.7%) were quantified by using MTRdouble with a 30% duty cycle and a 0.5-µT average power. In addition, our results suggest that MTRdouble is insensitive to B0 inhomogeneity, further magnifying its speed advantage over CEST metrics that require a separate B0 measurement. However, MTRdouble still has nontrivial sensitivity to B1 inhomogeneities. CONCLUSION We demonstrated that MTRdouble is an alternative metric to evaluate APT and rNOE, which is fast, robust to B0 inhomogeneity, and easy to process.
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Affiliation(s)
- Eugene C. Lin
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Hua Li
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Elizabeth A. Louie
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Chris L. Lankford
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Richard D. Dortch
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
| | - Mark D. Does
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
| | - John C. Gore
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, TN
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Daniel F. Gochberg
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, TN
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49
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Zu Z. Ratiometric NOE(-1.6) contrast in brain tumors. NMR IN BIOMEDICINE 2018; 31:e4017. [PMID: 30334295 DOI: 10.1002/nbm.4017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 08/06/2018] [Accepted: 08/24/2018] [Indexed: 06/08/2023]
Abstract
Recently, a new nuclear Overhauser enhancement (NOE)-mediated saturation transfer effect at around -1.6 ppm from water, termed NOE(-1.6), was reported to show hypointense signals in brain tumors. Similar to chemical exchange saturation transfer or magnetization transfer (MT) effects, which depend on the solute pool concentration, the exchange/coupling rate, the solute transverse relaxation rate, etc., the NOE(-1.6) effect should also depend on these factors. Since the exchange rate is relevant to tissue pH, and the coupling rate and the solute transverse relaxation rate are relevant to the motional property of the coupled molecules, further studies to quantify the contribution from only the exchange/coupling rate and the solute transverse relaxation rate are always interesting. The purpose of this paper is to apply a ratiometric approach to the NOE(-1.6) effect to obtain a metric that is more specific to the NOE coupling rate and the solute transverse relaxation rate than the NOE(-1.6) signal amplitude. Simulations indicate that the ratiometric approach allows us to rule out nearly all of the non-specific factors including the solute pool concentration, solute and water longitudinal relaxation rates, direct water saturation, and semi-solid MT effects, and provides a more specific NOE coupling rate- and solute transverse relaxation rate-weighted signal. Animal studies show that the ratiometric NOE(-1.6) decreases dramatically in brain tumors, which suggests that the change in the NOE(-1.6) coupling rate and/or the solute transverse relaxation rate are major contributors to the previously observed hypointense NOE(-1.6) signal in tumors.
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Affiliation(s)
- Zhongliang Zu
- Department of Radiology and Radiological Sciences, Vanderbilt University Institute of Imaging Science, Nashville, TN, USA
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Harris RJ, Yao J, Chakhoyan A, Raymond C, Leu K, Liau LM, Nghiemphu PL, Lai A, Salamon N, Pope WB, Cloughesy TF, Ellingson BM. Simultaneous pH-sensitive and oxygen-sensitive MRI of human gliomas at 3 T using multi-echo amine proton chemical exchange saturation transfer spin-and-gradient echo echo-planar imaging (CEST-SAGE-EPI). Magn Reson Med 2018; 80:1962-1978. [PMID: 29626359 PMCID: PMC6107417 DOI: 10.1002/mrm.27204] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 03/05/2018] [Accepted: 03/11/2018] [Indexed: 01/09/2023]
Abstract
PURPOSE To introduce a new pH-sensitive and oxygen-sensitive MRI technique using amine proton CEST echo spin-and-gradient echo (SAGE) EPI (CEST-SAGE-EPI). METHODS pH-weighting was obtained using CEST estimations of magnetization transfer ratio asymmetry (MTRasym ) at 3 ppm, and oxygen-weighting was obtained using R2' measurements. Glutamine concentration, pH, and relaxation rates were varied in phantoms to validate simulations and estimate relaxation rates. The values of MTRasym and R2' in normal-appearing white matter, T2 hyperintensity, contrast enhancement, and macroscopic necrosis were measured in 47 gliomas. RESULTS Simulation and phantom results confirmed an increase in MTRasym with decreasing pH. The CEST-SAGE-EPI estimates of R2 , R2*, and R2' varied linearly with gadolinium diethylenetriamine penta-acetic acid concentration (R2 = 6.2 mM-1 ·sec-1 and R2* = 6.9 mM-1 ·sec-1 ). The CEST-SAGE-EPI and Carr-Purcell-Meiboom-Gill estimates of R2 (R2 = 0.9943) and multi-echo gradient-echo estimates of R2* (R2 = 0.9727) were highly correlated. T2 lesions had lower R2' and higher MTRasym compared with normal-appearing white matter, suggesting lower hypoxia and high acidity, whereas contrast-enhancement tumor regions had elevated R2' and MTRasym , indicating high hypoxia and acidity. CONCLUSION The CEST-SAGE-EPI technique provides simultaneous pH-sensitive and oxygen-sensitive image contrasts for evaluation of the brain tumor microenvironment. Advantages include fast whole-brain acquisition, in-line B0 correction, and simultaneous estimation of CEST effects, R2 , R2*, and R2' at 3 T.
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Affiliation(s)
- Robert J. Harris
- UCLA Brain Tumor Imaging Laboratory (BTIL), Center for Computer Vision and Imaging Biomarkers, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Dept. of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Physics and Biology in Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Jingwen Yao
- UCLA Brain Tumor Imaging Laboratory (BTIL), Center for Computer Vision and Imaging Biomarkers, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Dept. of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Dept. of Bioengineering, Henry Samueli School of Engineering and Applied Science, University of California Los Angeles, Los Angeles, CA
| | - Ararat Chakhoyan
- UCLA Brain Tumor Imaging Laboratory (BTIL), Center for Computer Vision and Imaging Biomarkers, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Dept. of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Catalina Raymond
- UCLA Brain Tumor Imaging Laboratory (BTIL), Center for Computer Vision and Imaging Biomarkers, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Dept. of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Kevin Leu
- UCLA Brain Tumor Imaging Laboratory (BTIL), Center for Computer Vision and Imaging Biomarkers, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Dept. of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Physics and Biology in Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Linda M. Liau
- UCLA Brain Research Institute (BRI), David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Dept. of Neurosurgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Phioanh L. Nghiemphu
- Dept. of Neurology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Albert Lai
- Dept. of Neurology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- UCLA Brain Research Institute (BRI), David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Noriko Salamon
- Dept. of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Whitney B. Pope
- Dept. of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Timothy F. Cloughesy
- Dept. of Neurology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Benjamin M. Ellingson
- UCLA Brain Tumor Imaging Laboratory (BTIL), Center for Computer Vision and Imaging Biomarkers, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Dept. of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Physics and Biology in Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- Dept. of Bioengineering, Henry Samueli School of Engineering and Applied Science, University of California Los Angeles, Los Angeles, CA
- Dept. of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
- UCLA Brain Research Institute (BRI), David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
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