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Chung JJ, Kim H, Ji Y, Lu D, Zhou IY, Sun PZ. Improving standardization and accuracy of in vivo omega plot exchange parameter determination using rotating-frame model-based fitting of quasi-steady-state Z-spectra. Magn Reson Med 2025; 93:151-165. [PMID: 39221563 PMCID: PMC11518644 DOI: 10.1002/mrm.30259] [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: 05/02/2024] [Revised: 07/31/2024] [Accepted: 08/01/2024] [Indexed: 09/04/2024]
Abstract
PURPOSE Although Ω-plot-driven quantification of in vivo amide exchange properties has been demonstrated, differences in scan parameters may complicate the fidelity of determination. This work systematically evaluated the use of quasi-steady-state (QUASS) Z-spectra reconstruction to standardize in vivo amide exchange quantification across acquisition conditions and further determined it in vivo. METHODS Simulation and in vivo rodent brain chemical exchange saturation transfer (CEST) data at 4.7 T were fit with and without QUASS reconstruction using both multi-Lorentzian and model-based fitting approaches. pH modulation was accomplished both in simulation and in vivo by inducing global ischemia via cardiac arrest. Amide parameters were determined via Ω-plots and compared across methods. RESULTS Simulation showed that Ω-plots using multi-Lorentzian fitting could underestimate the exchange rate, with error increasing as conditions diverged from the steady state. In comparison, model-based fitting using QUASS estimated the same exchange rate within 2%. These results aligned with in vivo findings where multi-Lorentzian fitting of native Z-spectra resulted in an exchange rate of 64 ± 13 s-1 (38 ± 16 s-1 after cardiac arrest), whereas model-based fitting of QUASS Z-spectra yielded an exchange rate of 126 ± 25 s-1 (49 ± 13 s-1). CONCLUSION The model-based fitting of QUASS CEST Z-spectra enables consistent and accurate quantification of exchange parameters through Ω-plot construction by reducing error due to signal overlap and nonequilibrium CEST effects.
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Affiliation(s)
- Julius Juhyun Chung
- Primate Imaging Center, Emory National Primate Research Center, Emory University, Atlanta, GA
| | - Hahnsung Kim
- 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
| | - Yang Ji
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA
| | - Dongshuang Lu
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA
| | - Iris Y. Zhou
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA
| | - Phillip Zhe Sun
- 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
- Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA
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Viswanathan M, Yin L, Kurmi Y, Afzal A, Zu Z. Enhancing amide proton transfer imaging in ischemic stroke using a machine learning approach with partially synthetic data. NMR IN BIOMEDICINE 2024:e5277. [PMID: 39434444 DOI: 10.1002/nbm.5277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 09/21/2024] [Accepted: 10/07/2024] [Indexed: 10/23/2024]
Abstract
Amide proton transfer (APT) imaging, a technique sensitive to tissue pH, holds promise in the diagnosis of ischemic stroke. Achieving accurate and rapid APT imaging is crucial for this application. However, conventional APT quantification methods either lack accuracy or are time-consuming. Machine learning (ML) has recently been recognized as a potential solution to improve APT quantification. In this paper, we applied an ML model trained on a new type of partially synthetic data, along with an optimization approach utilizing recursive feature elimination, to predict APT imaging in an animal stroke model. This partially synthetic datum is not a simple blend of measured and simulated chemical exchange saturation transfer (CEST) signals. Rather, it integrates the underlying components including all CEST, direct water saturation, and magnetization transfer effects partly derived from measurements and simulations to reconstruct the CEST signals using an inverse summation relationship. Training with partially synthetic data requires less in vivo data compared to training entirely with fully synthetic or in vivo data, making it a more practical approach. Since this type of data closely resembles real tissue, it leads to more accurate predictions than ML models trained on fully synthetic data. Results indicate that an ML model trained on this partially synthetic data can successfully predict the APT effect with enhanced accuracy, providing significant contrast between stroke lesions and normal tissues, thus clearly delineating lesions. In contrast, conventional quantification methods such as the asymmetric analysis method, three-point method, and multiple-pool model Lorentzian fit showed inadequate accuracy in quantifying the APT effect. Moreover, ML methods trained using in vivo data and fully synthetic data exhibited poor predictive performance due to insufficient training data and inaccurate simulation pool settings or parameter ranges, respectively. Following optimization, only 13 frequency offsets were selected from the initial 69, resulting in significantly reduced scan time.
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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
| | - Leqi Yin
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- School of 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
| | - Aqeela Afzal
- Department of Neurological Surgery, 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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Tokunaga C, Wada T, Togao O, Kobayashi K, Kato T. Amide proton transfer-weighted imaging with a short acquisition time based on a self B0 correction using the turbo spin echo-Dixon method: A phantom study. Magn Reson Imaging 2024; 110:69-77. [PMID: 38614223 DOI: 10.1016/j.mri.2024.04.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 04/06/2024] [Accepted: 04/07/2024] [Indexed: 04/15/2024]
Abstract
PURPOSE Conventional amide proton transfer (APT)-weighted imaging requires a chemical exchange saturation transfer (CEST) sequence with multiple saturation frequency offsets and a B0 correction sequence, plus a long acquisition time that can be reduced by applying the conventional method using CEST images with seven radiation pulses (i.e., the seven-points method). For a further reduction of acquisition times, we propose fast two-dimensional (2D) APT-weighted imaging based on a self B0 correction using the turbo spin echo (TSE)-Dixon method. We conducted a phantom study to investigate the accuracy of TSE-Dixon APT-weighted imaging. METHODS We prepared two types of phantoms with six samples for a concentrationdependent evaluation and a pH-dependent evaluation. APT-weighted images were acquired by the conventional, seven-points, and TSE-Dixon methods. Linear regression analyses assessed the dependence between each method's APT signal intensities (SIs) and the concentration or pH. We performed a one-way analysis of variance with Tukey's honestly significant difference post hoc test to compare the APT SIs among the three methods. The agreement of the APT SIs between the conventional and seven-points or TSE-Dixon methods was assessed by a Bland- Altman plot analysis. RESULTS The APT SIs of all three acquisition methods showed positive concentration dependence and pH dependence. No significant differences were observed in the APT SIs between the conventional and TSE-Dixon methods at each concentration. The Bland-Altman plot analyses showed that the APT SIs measured with the seven-points method resulted in 0.42% bias and narrow 95% limits of agreement (LOA) (0.93%-0.09%) compared to the conventional method. The APT SIs measured using the TSE-Dixon method showed 0.14% bias and similar 95% LOA (-0.33% to 0.61%) compared with the seven-points method. The APT SIs of all three methods showed positive pH dependence. At each pH, no significant differences in the APT SIs were observed among the methods. Bland-Altman plot analyses showed that the APT SIs measured with the seven-points method resulted in low bias (0.03%) and narrow 95% LOA (-0.30% to 0.36%) compared to the conventional method. The APT SIs measured by the TSE-Dixon method showed slightly larger bias (0.29%) and similar 95% LOA (from -0.15% to 0.72%) compared to those measured by the seven-points method. CONCLUSION These results demonstrated that our proposed method has the same concentration dependence and pH dependence as the conventional method and the seven-points method. We thus expect that APT-weighted imaging with less influence of motion can be obtained in clinical examinations.
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Affiliation(s)
- Chiaki Tokunaga
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
| | - Tatsuhiro Wada
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Osamu Togao
- Department of Molecular Imaging and Diagnosis, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Kouji Kobayashi
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Toyoyuki Kato
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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Yamasaki T, Mori W, Ohkubo T, Hiraishi A, Zhang Y, Kurihara Y, Nengaki N, Tashima H, Fujinaga M, Zhang MR. Potential for in vivo visualization of intracellular pH gradient in the brain using PET imaging. Brain Commun 2024; 6:fcae172. [PMID: 38863573 PMCID: PMC11166174 DOI: 10.1093/braincomms/fcae172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 04/16/2024] [Accepted: 05/22/2024] [Indexed: 06/13/2024] Open
Abstract
Intracellular pH is a valuable index for predicting neuronal damage and injury. However, no PET probe is currently available for monitoring intracellular pH in vivo. In this study, we developed a new approach for visualizing the hydrolysis rate of monoacylglycerol lipase, which is widely distributed in neurons and astrocytes throughout the brain. This approach uses PET with the new radioprobe [11C]QST-0837 (1,1,1,3,3,3-hexafluoropropan-2-yl-3-(1-phenyl-1H-pyrazol-3-yl)azetidine-1-[11C]carboxylate), a covalent inhibitor containing an azetidine carbamate skeleton for monoacylglycerol lipase. The uptake and residence of this new radioprobe depends on the intracellular pH gradient, and we evaluated this with in silico, in vitro and in vivo assessments. Molecular dynamics simulations predicted that because the azetidine carbamate moiety is close to that of water molecules, the compound containing azetidine carbamate would be more easily hydrolyzed following binding to monoacylglycerol lipase than would its analogue containing a piperidine carbamate skeleton. Interestingly, it was difficult for monoacylglycerol lipase to hydrolyze the azetidine carbamate compound under weakly acidic (pH 6) conditions because of a change in the interactions with water molecules on the carbamate moiety of their complex. Subsequently, an in vitro assessment using rat brain homogenate to confirm the molecular dynamics simulation-predicted behaviour of the azetidine carbamate compound showed that [11C]QST-0837 reacted with monoacylglycerol lipase to yield an [11C]complex, which was hydrolyzed to liberate 11CO2 as a final product. Additionally, the 11CO2 liberation rate was slower at lower pH. Finally, to indicate the feasibility of estimating how the hydrolysis rate depends on intracellular pH in vivo, we performed a PET study with [11C]QST-0837 using ischaemic rats. In our proposed in vivo compartment model, the clearance rate of radioactivity from the brain reflected the rate of [11C]QST-0837 hydrolysis (clearance through the production of 11CO2) in the brain, which was lower in a remarkably hypoxic area than in the contralateral region. In conclusion, we indicated the potential for visualization of the intracellular pH gradient in the brain using PET imaging, although some limitations remain. This approach should permit further elucidation of the pathological mechanisms involved under acidic conditions in multiple CNS disorders.
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Affiliation(s)
- Tomoteru Yamasaki
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
| | - Wakana Mori
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
| | - Takayuki Ohkubo
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
- SHI Accelerator Service Co. Ltd., Tokyo 141-0031, Japan
| | - Atsuto Hiraishi
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
| | - Yiding Zhang
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
| | - Yusuke Kurihara
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
- SHI Accelerator Service Co. Ltd., Tokyo 141-0031, Japan
| | - Nobuki Nengaki
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
- SHI Accelerator Service Co. Ltd., Tokyo 141-0031, Japan
| | - Hideaki Tashima
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
| | - Masayuki Fujinaga
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
| | - Ming-Rong Zhang
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan
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Zhang Q, Huang S, Liu X, Wang W, Zhu Z, Chen L. Innovations in Breaking Barriers: Liposomes as Near-Perfect Drug Carriers in Ischemic Stroke Therapy. Int J Nanomedicine 2024; 19:3715-3735. [PMID: 38681090 PMCID: PMC11046314 DOI: 10.2147/ijn.s462194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 04/13/2024] [Indexed: 05/01/2024] Open
Abstract
Liposomes, noted for their tunable particle size, surface customization, and varied drug delivery capacities, are increasingly acknowledged in therapeutic applications. These vesicles exhibit surface flexibility, enabling the incorporation of targeting moieties or peptides to achieve specific targeting and avoid lysosomal entrapment. Internally, their adaptable architecture permits the inclusion of a broad spectrum of drugs, contingent on their solubility characteristics. This study thoroughly reviews liposome fabrication, surface modifications, and drug release mechanisms post-systemic administration, with a particular emphasis on drugs crossing the blood-brain barrier (BBB) to address lesions. Additionally, the review delves into recent developments in the use of liposomes in ischemic stroke models, offering a comparative evaluation with other nanocarriers like exosomes and nano-micelles, thereby facilitating their clinical advancement.
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Affiliation(s)
- Qiankun Zhang
- Department of Neurosurgery, Southern Medical University Hospital of Integrated Traditional Chinese and Western Medicine, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China
| | - Songze Huang
- Department of Neurosurgery, Southern Medical University Hospital of Integrated Traditional Chinese and Western Medicine, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China
| | - Xiaowen Liu
- Department of Neurosurgery, Southern Medical University Hospital of Integrated Traditional Chinese and Western Medicine, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China
| | - Wei Wang
- Department of Neurosurgery, Southern Medical University Hospital of Integrated Traditional Chinese and Western Medicine, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China
| | - Zhihan Zhu
- Department of Neurosurgery, Southern Medical University Hospital of Integrated Traditional Chinese and Western Medicine, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China
| | - Lukui Chen
- Department of Neurosurgery, Southern Medical University Hospital of Integrated Traditional Chinese and Western Medicine, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China
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6
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Shen L, Lu X, Wang H, Wu G, Guo Y, Zheng S, Ren L, Zhang H, Huang L, Ren B, Zhu J, Xia S. Impaired T1 mapping and Tmax during the first 7 days after ischemic stroke. A retrospective observational study. J Stroke Cerebrovasc Dis 2023; 32:107383. [PMID: 37844455 DOI: 10.1016/j.jstrokecerebrovasdis.2023.107383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 09/14/2023] [Accepted: 09/19/2023] [Indexed: 10/18/2023] Open
Abstract
OBJECTIVE To measure the relative T1 (rT1) value in different hypo-perfused regions after ischemic stroke using T1 mapping derived by Strategically Acquired Gradient Echo (STAGE) and assess its relationship with onset time and severity of ischemia. MATERIALS AND METHODS Sixty-three patients with acute anterior circulation ischemic stroke from 2017 to 2022 who underwent STAGE, diffusion weighted imaging (DWI) and dynamic susceptibility contrast perfusion weighted imaging (DSC-PWI) within 7 days were retrospectively enrolled. The areas with reduced diffusion and hypo-perfusion were segmented based on apparent diffusion coefficient (ADC) value < 0.62 × 10-3mm2/s and time-to-maximum (Tmax) thresholds (4, 6, 8, and 10 seconds). We measured the T1 value in the diffusion reduced and every 2 s Tmax strata regions and calculated rT1 (T1ipsi/T1contra) to explore the relationship between rT1 value, Tmax, and onset time. RESULTS rT1 value was increased in diffusion reduced (1.42) and hypo-perfused regions (1.02, 1.06, 1.12, 1.27, Tmax 4-6 s, 6-8 s, 8-10 s, > 10 s, respectively; all different from 1, P < 0.001). rT1 value was positively correlated with Tmax (rs = 0.61, P < 0.001) and onset time in area with reduced diffusion (rs = 0.39, P = 0.014). CONCLUSIONS Increased rT1 value in different hypo-perfused brain regions using T1 mapping derived by STAGE may reflect the edema; it was associated with the severity of Tmax and showed a weak correlation with the onset time in diffusion reduced areas.
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Affiliation(s)
- Lianfang Shen
- Department of Radiology, The First Central Clinical School, Tianjin Medical University, Tianjin, China
| | - Xiudi Lu
- Department of Radiology, First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Huiying Wang
- The School of Medicine, Nankai University, Tianjin, China
| | - Gemuer Wu
- Department of Radiology, Affiliated Hospital of Inner Mongolia Medical University, Hohhot, China
| | - Yu Guo
- Department of Radiology, Medical Imaging Institute of Tianjin, Tianjin First Central Hospital, School of Medicine, Nankai University, Tianjin, China
| | - Shaowei Zheng
- Department of Radiology, The First Affiliated Hospital of Dalian Medical University, Dalian, Liaoning, China
| | - Lei Ren
- Department of Radiology, First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Huanlei Zhang
- Department of Radiology, Yidu Central Hospital of Weifang, Qingzhou City, Shandong, China
| | - Lixiang Huang
- Department of Radiology, Medical Imaging Institute of Tianjin, Tianjin First Central Hospital, School of Medicine, Nankai University, Tianjin, China
| | - Bo Ren
- College of Computer Science, Nankai University, Tianjin, China
| | - Jinxia Zhu
- MR Collaboration, Siemens Healthcare Ltd, Beijing, China
| | - Shuang Xia
- Department of Radiology, Medical Imaging Institute of Tianjin, Tianjin First Central Hospital, School of Medicine, Nankai University, Tianjin, China.
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Igarashi T, Kim H, Sun PZ. Detection of tissue pH with quantitative chemical exchange saturation transfer magnetic resonance imaging. NMR IN BIOMEDICINE 2023; 36:e4711. [PMID: 35141979 PMCID: PMC10249910 DOI: 10.1002/nbm.4711] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 02/03/2022] [Accepted: 02/05/2022] [Indexed: 05/12/2023]
Abstract
Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) has emerged as a novel means for sensitive detection of dilute labile protons and chemical exchange rates. By sensitizing to pH-dependent chemical exchange, CEST MRI has shown promising results in monitoring tissue statuses such as pH changes in disorders like acute stroke, tumor, and acute kidney injury. This article briefly reviews the basic principles for CEST imaging and quantitative measures, from the simplistic asymmetry analysis to multipool Lorentzian decoupling and quasi-steady-state reconstruction. In particular, the advantages and limitations of commonly used quantitative approaches for CEST applications are discussed.
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Affiliation(s)
- Takahiro Igarashi
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA
| | - Hahnsung Kim
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA
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Discrimination between progressive penumbra and benign oligemia of the diffusion-perfusion mismatch region by amide proton transfer-weighted imaging. Magn Reson Imaging 2023; 99:123-129. [PMID: 36822450 DOI: 10.1016/j.mri.2023.02.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Revised: 02/15/2023] [Accepted: 02/19/2023] [Indexed: 02/25/2023]
Abstract
PURPOSE Amide proton transfer-weighted (APTw) imaging was an effective tool to reveal the tissue acidosis of acute ischemic stroke. This study aimed to evaluate the ability of APTw MRI to distinguish progressive penumbra and benign oligemia in the diffusion-perfusion mismatch region. MATERIALS AND METHODS 38 acute cerebral infarction patients who underwent a comprehensive MRI examination, including diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI), APT imaging, and a follow-up scan in one week were recruited. There were 12 DWI/PWI match cases. The DWI/PWI mismatch patients were divided into 10 progressive cases and 16 stable cases according to the lesion size on the follow-up DWI image compared to the admission scan. Three ROIs: infarction lesion, peripheral, and contralateral normal regions were measured on each subject's MTRasym map. The Friedman test was used to compare the changes of MTRasym among three different regions within each group. The Kruskal-Wallis ANOVA test was used to compare them among the same region of different groups. The correlation between the MTRasym of the peripheral region and the lesion enlargement was analyzed by the Spearman test. RESULTS The MTRasym at the infarction lesion of all three groups showed significant decrease to the contralateral normal tissue. In the progressive mismatch group, the MTRasym at the peripheral region within the DWI/PWI mismatch showed a significant difference with the contralateral normal region and no difference with the infarct core. Whereas both the MTRasym at the peripheral region of the stable mismatch and match groups had no significant difference with the contralateral side, but the differences were significant from those of the central core. When comparing the peripheral region of three groups, the MTRasym of the progressive mismatch group showed a significant decrease to that of the stable mismatch and match groups. The MTRasym of the peripheral region showed a negative correlation with lesion enlargement. CONCLUSION APTw imaging is promising to stratify the heterogeneous PWI/DWI mismatch region and benefit the clinical treatment.
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Ji Y, Lu D, Sun PZ, Zhou IY. In vivo pH mapping with omega plot-based quantitative chemical exchange saturation transfer MRI. Magn Reson Med 2023; 89:299-307. [PMID: 36089834 PMCID: PMC9617761 DOI: 10.1002/mrm.29444] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 08/05/2022] [Accepted: 08/15/2022] [Indexed: 02/01/2023]
Abstract
PURPOSE Chemical exchange saturation transfer (CEST) MRI is promising for detecting dilute metabolites and microenvironment properties, which has been increasingly adopted in imaging disorders such as acute stroke and cancer. However, in vivo CEST MRI quantification remains challenging because routine asymmetry analysis (MTRasym ) or Lorentzian decoupling measures a combined effect of the labile proton concentration and its exchange rate. Therefore, our study aimed to quantify amide proton concentration and exchange rate independently in a cardiac arrest-induced global ischemia rat model. METHODS The amide proton CEST (APT) effect was decoupled from tissue water, macromolecular magnetization transfer, nuclear Overhauser enhancement, guanidinium, and amine protons using the image downsampling expedited adaptive least-squares (IDEAL) fitting algorithm on Z-spectra obtained under multiple RF saturation power levels, before and after global ischemia. Omega plot analysis was applied to determine amide proton concentration and exchange rate simultaneously. RESULTS Global ischemia induces a significant APT signal drop from intact tissue. Using the modified omega plot analysis, we found that the amide proton exchange rate decreased from 29.6 ± 5.6 to 12.1 ± 1.3 s-1 (P < 0.001), whereas the amide proton concentration showed little change (0.241 ± 0.035% vs. 0.202 ± 0.034%, P = 0.074) following global ischemia. CONCLUSION Our study determined the labile proton concentration and exchange rate underlying the in vivo APT MRI. The significant change in the exchange rate, but not the concentration of amide proton demonstrated that the pH effect dominates the APT contrast during tissue ischemia.
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Affiliation(s)
- Yang Ji
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
- Wellcome Centre for Integrative Neuroimaging, FMRIB Division, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Dongshuang Lu
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
- Emory Primate Imaging Center, Emory Primate Research Center, Emory University, Atlanta, GA, USA
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA
| | - Iris Y. Zhou
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
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10
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Larkin JR, Foo LS, Sutherland BA, Khrapitchev A, Tee YK. Magnetic Resonance pH Imaging in Stroke – Combining the Old With the New. Front Physiol 2022; 12:793741. [PMID: 35185600 PMCID: PMC8852727 DOI: 10.3389/fphys.2021.793741] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 12/22/2021] [Indexed: 11/24/2022] Open
Abstract
The study of stroke has historically made use of traditional spectroscopy techniques to provide the ground truth for parameters like pH. However, techniques like 31P spectroscopy have limitations, in particular poor temporal and spatial resolution, coupled with a need for a high field strength and specialized coils. More modern magnetic resonance spectroscopy (MRS)-based imaging techniques like chemical exchange saturation transfer (CEST) have been developed to counter some of these limitations but lack the definitive gold standard for pH that 31P spectroscopy provides. In this perspective, both the traditional (31P spectroscopy) and emerging (CEST) techniques in the measurement of pH for ischemic imaging will be discussed. Although each has its own advantages and limitations, it is likely that CEST may be preferable simply due to the hardware, acquisition time and image resolution advantages. However, more experiments on CEST are needed to determine the specificity of endogenous CEST to absolute pH, and 31P MRS can be used to calibrate CEST for pH measurement in the preclinical model to enhance our understanding of the relationship between CEST and pH. Combining the two imaging techniques, one old and one new, we may be able to obtain new insights into stroke physiology that would not be possible otherwise with either alone.
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Affiliation(s)
- James R. Larkin
- Department of Oncology, Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
- *Correspondence: James R. Larkin,
| | - Lee Sze Foo
- Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kajang, Malaysia
| | - Brad A. Sutherland
- Tasmanian School of Medicine, College of Health and Medicine, University of Tasmania, Hobart, TAS, Australia
| | - Alexandre Khrapitchev
- Department of Oncology, Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Yee Kai Tee
- Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kajang, Malaysia
- Yee Kai Tee,
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11
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Sun PZ. Consistent depiction of the acidic ischemic lesion with APT MRI-Dual RF power evaluation of pH-sensitive image in acute stroke. Magn Reson Med 2022; 87:850-858. [PMID: 34590730 PMCID: PMC8627494 DOI: 10.1002/mrm.29029] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/31/2021] [Accepted: 09/09/2021] [Indexed: 02/03/2023]
Abstract
PURPOSE Amide proton transfer-weighted (APTw) MRI provides a non-invasive pH-sensitive image, complementing perfusion and diffusion imaging for refined stratification of ischemic tissue. Although the commonly used magnetization transfer (MT) asymmetry (MTRasym ) calculation reasonably corrects the direct RF saturation effect, it is susceptible to the concomitant semisolid macromolecular MT contribution. Therefore, this study aimed to compare the performance of MTRasym and magnetization transfer and relaxation-normalized APT (MRAPT) analyses under 2 representative experimental conditions. METHODS Multiparametric MRI scans were performed in a rodent model of acute stroke, including relaxation, diffusion, and Z spectral images under 2 representative RF levels of 0.75 and 1.5 µT. Both MTRasym and MRAPT values in the ischemic diffusion lesion and the contralateral normal areas were compared using correlation and Bland-Altman tests. In addition, the acidic lesion volumes were compared. RESULTS MRAPT measurements from the diffusion lesion under the 2 conditions were highly correlated (R2 = 0.97) versus MTRasym measures (R2 = 0.58). The pH lesion sizes determined from MRAPT analysis were in good agreement (178 ± 43 mm3 vs. 186 ± 55 mm3 for B1 of 0.75 and 1.5 µT, respectively). CONCLUSIONS The study demonstrated that MRAPT analysis could be generalized to moderately different RF amplitudes, providing a more consistent depiction of acidic lesions than the MTRasym analysis.
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Affiliation(s)
- Phillip Zhe Sun
- Athinoula A Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA,Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta GA,Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta GA,Corresponding Author: Phillip Zhe Sun, Ph.D., Department of Radiology and Imaging Sciences, Emory University School of Medicine, 954 Gatewood Road NE, Atlanta, GA 30329, Phone: (404) 727-7786; (404) 712-1667,
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12
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Chen W, Jiang L, Hu Y, Fang G, Yang B, Li J, Liang N, Wu L, Hussain Z. Nanomedicines, an emerging therapeutic regimen for treatment of ischemic cerebral stroke: A review. J Control Release 2021; 340:342-360. [PMID: 34695522 DOI: 10.1016/j.jconrel.2021.10.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 10/14/2021] [Accepted: 10/15/2021] [Indexed: 12/18/2022]
Abstract
Owing to its intricate pathophysiology, cerebral stroke is a serious medical condition caused by interruption or obstruction of blood supply (blockage of vasculature) to the brain tissues which results in diminished supply of essential nutrients and oxygen (hypoxia) and ultimate necrosis of neuronal tissues. A prompt risks assessment and immediate rational therapeutic plan with proficient neuroprotection play critically important role in the effective management of this neuronal emergency. Various conventional medications are being used for treatment of acute ischemic cerebral stroke but fibrinolytic agents, alone or in combination with other agents are considered the mainstay. These clot-busting agents effectively restore blood supply (reperfusion) to ischemic regions of the brain; however, their clinical significance is hampered due to various factors such as short plasma half-life, limited distribution to brain tissues due to the presence of highly efficient physiological barrier, blood brain barrier (BBB), and lacking of target-specific delivery to the ischemic brain regions. To alleviate these issues, various types of nanomedicines such as polymeric nanoparticles (NPs), liposomes, nanoemulsion, micelles and dendrimers have been designed and evaluated. The implication of these newer therapies (nanomedicines) have revolutionized the therapeutic outcomes by improving the plasma half-life, permeation across BBB, efficient distribution to ischemic cerebral tissues and neuroprotection. Furthermore, the adaptation of some diverse techniques including PEGylation, tethering of targeting ligands on the surfaces of nanomedicines, and pH responsive features have also been pondered. The implication of these emerging adaptations have shown remarkable potential in maximizing the targeting efficiency of drugs to ischemic brain tissues, simultaneous delivery of drugs and imaging agents (for early prognosis as well as monitoring of therapy), and therapeutic outcomes such as long-term neuroprotection.
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Affiliation(s)
- Wei Chen
- Department of Neurology, The First Affiliated Hospital of Guangxi, University of Chinese Medicine, Nanning, Guangxi 530023, China; Graduate School, Jiangxi University of Chinese Medicine, Nanchang, Jiangxi 330004, China
| | - Lingfei Jiang
- Graduate College, Guangxi University of Chinese Medicine, Nanning, Guangxi 530200, China
| | - Yueqiang Hu
- Department of Neurology, The First Affiliated Hospital of Guangxi, University of Chinese Medicine, Nanning, Guangxi 530023, China; Guangxi Key Laboratory of Chinese Medicine Foundation Research, Guangxi University of Chinese Medicine, Nanning, Guangxi 530200, China.
| | - Gang Fang
- Guangxi Zhuang and Yao Medicine Engineering Technology Research Center, Guangxi University of Chinese Medicine, Nanning, Guangxi 530200, China
| | - Bilin Yang
- Graduate College, Guangxi University of Chinese Medicine, Nanning, Guangxi 530200, China
| | - Junhong Li
- Department of Neurology, The First Affiliated Hospital of Guangxi, University of Chinese Medicine, Nanning, Guangxi 530023, China
| | - Ni Liang
- Department of Neurology, The First Affiliated Hospital of Guangxi, University of Chinese Medicine, Nanning, Guangxi 530023, China
| | - Lin Wu
- Department of Neurology, The First Affiliated Hospital of Guangxi, University of Chinese Medicine, Nanning, Guangxi 530023, China; Guangxi Key Laboratory of Chinese Medicine Foundation Research, Guangxi University of Chinese Medicine, Nanning, Guangxi 530200, China.
| | - Zahid Hussain
- Department of Pharmaceutics and Pharmaceutical Technology, College of Pharmacy, University of Sharjah, Sharjah 27272, United Arab Emirates; Research Institute for Medical & Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates.
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13
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Cheung J, Doerr M, Hu R, Sun PZ. Refined Ischemic Penumbra Imaging with Tissue pH and Diffusion Kurtosis Magnetic Resonance Imaging. Transl Stroke Res 2021; 12:742-753. [PMID: 33159656 PMCID: PMC8102648 DOI: 10.1007/s12975-020-00868-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 10/14/2020] [Accepted: 10/18/2020] [Indexed: 12/19/2022]
Abstract
Imaging has played a vital role in our mechanistic understanding of acute ischemia and the management of acute stroke patients. The most recent DAWN and DEFUSE-3 trials showed that endovascular therapy could be extended to a selected group of late-presenting stroke patients with the aid of imaging. Although perfusion and diffusion MRI have been commonly used in stroke imaging, the approximation of their mismatch as the penumbra is oversimplified, particularly in the era of endovascular therapy. Briefly, the hypoperfusion lesion includes the benign oligemia that does not proceed to infarction. Also, with prompt and effective reperfusion therapy, a portion of the diffusion lesion is potentially reversible. Therefore, advanced imaging that provides improved ischemic tissue characterization may enable new experimental stroke therapeutics and eventually further individualize stroke treatment upon translation to the clinical setting. Specifically, pH imaging captures tissue of altered metabolic state that demarcates the hypoperfused lesion into ischemic penumbra and benign oligemia, which remains promising to define the ischemic penumbra's outer boundary. On the other hand, diffusion kurtosis imaging (DKI) differentiates the most severely damaged and irreversibly injured diffusion lesion from the portion of diffusion lesion that is potentially reversible, refining the inner boundary of the penumbra. Altogether, the development of advanced imaging has the potential to not only transform the experimental stroke research but also aid clinical translation and patient management.
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Affiliation(s)
- Jesse Cheung
- Emory College of Arts and Sciences, Emory University, Atlanta, GA, 30329, USA
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30329, USA
| | - Madeline Doerr
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30329, USA
- Dartmouth College, Hanover, NH, 03755, USA
| | - Ranliang Hu
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1364 Clifton RD NE, Atlanta, GA, 30322, USA
| | - Phillip Zhe Sun
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30329, USA.
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1364 Clifton RD NE, Atlanta, GA, 30322, USA.
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14
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Foo LS, Harston G, Mehndiratta A, Yap WS, Hum YC, Lai KW, Mohamed Mukari SA, Mohd Zaki F, Tee YK. Clinical translation of amide proton transfer (APT) MRI for ischemic stroke: a systematic review (2003-2020). Quant Imaging Med Surg 2021; 11:3797-3811. [PMID: 34341751 DOI: 10.21037/qims-20-1339] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Accepted: 03/22/2021] [Indexed: 12/15/2022]
Abstract
Amide proton transfer (APT) magnetic resonance imaging (MRI) is a pH-sensitive imaging technique that can potentially complement existing clinical imaging protocol for the assessment of ischemic stroke. This review aims to summarize the developments in the clinical research of APT imaging of ischemic stroke after 17 years of progress since its first preclinical study in 2003. Three electronic databases: PubMed, Scopus, and Cochrane Library were systematically searched for articles reporting clinical studies on APT imaging of ischemic stroke. Only articles in English published between 2003 to 2020 that involved patients presenting ischemic stroke-like symptoms that underwent APT MRI were included. Of 1,093 articles screened, 14 articles met the inclusion criteria with a total of 282 patients that had been scanned using APT imaging. Generally, the clinical studies agreed APT effect to be hypointense in ischemic tissue compared to healthy tissue, allowing for the detection of ischemic stroke. Other uses of APT imaging have also been investigated in the studies, including penumbra identification, predicting long term clinical outcome, and serving as a biomarker for supportive treatment monitoring. The published results demonstrated the potential of APT imaging in these applications, but further investigations and larger trials are needed for conclusive evidence. Future studies are recommended to report the result of asymmetry analysis at 3.5 ppm along with the findings of the study to reduce this contribution to the heterogeneity of experimental methods observed and to facilitate effective comparison of results between studies and centers. In addition, it is important to focus on the development of fast 3D imaging for full volumetric ischemic tissue assessment for clinical translation.
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Affiliation(s)
- Lee Sze Foo
- Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kajang, Malaysia
| | | | - Amit Mehndiratta
- Centre for Biomedical Engineering, Indian Institute of Technology Delhi, New Delhi, India.,Department of Biomedical Engineering, All India Institute of Medical Sciences, New Delhi, India
| | - Wun-She Yap
- Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kajang, Malaysia
| | - Yan Chai Hum
- Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kajang, Malaysia
| | - Khin Wee Lai
- Faculty of Engineering, Department of Biomedical Engineering, University of Malaya, Kuala Lumpur, Malaysia
| | | | - Faizah Mohd Zaki
- Department of Radiology, Universiti Kebangsaan Malaysia Medical Center (UKMMC), Kuala Lumpur, Malaysia
| | - Yee Kai Tee
- Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kajang, Malaysia
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15
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Quantitative Analysis of Mobile Proteins in Normal Brain Tissue by Amide Proton Transfer Imaging: Age Dependence and Sex Differences. J Comput Assist Tomogr 2021; 45:277-284. [PMID: 33661152 DOI: 10.1097/rct.0000000000001141] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE The aims of this study were to evaluate the relationship between age change and amide proton transfer (APT) signal in each region of the whole brain and to derive the standard value of APT signal in each brain region of normal adults. MATERIALS AND METHODS Using the mDIXON 3-dimensional-APT sequence of the fast spin echo method, an APT image was obtained. In total, 60 patients (mean age, 49.8 ± 16.9 years) with no abnormal findings on magnetic resonance imaging data were included. For image analysis, registration parameters were created using the FMRIB Software Library 5.0.11, and then a region of interest was set in the Montreal Neurological Institute structural atlas for analysis. Statistical analyses were performed using the age-dependent and sex differences in APT signals from each brain region. RESULTS No significant correlation was seen between APT signal and age and sex in all brain regions. CONCLUSION Under the APT imaging parameter conditions used in this study, local brain APT signals in healthy adults are independent of age and sex.
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16
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Shaul D, Azar A, Sapir G, Uppala S, Nardi-Schreiber A, Gamliel A, Sosna J, Gomori JM, Katz-Brull R. Correlation between lactate dehydrogenase/pyruvate dehydrogenase activities ratio and tissue pH in the perfused mouse heart: A potential noninvasive indicator of cardiac pH provided by hyperpolarized magnetic resonance. NMR IN BIOMEDICINE 2021; 34:e4444. [PMID: 33258527 DOI: 10.1002/nbm.4444] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 10/05/2020] [Accepted: 10/24/2020] [Indexed: 06/12/2023]
Abstract
Cardiovascular diseases account for more than 30% of all deaths worldwide and many could be ameliorated with early diagnosis. Current cardiac imaging modalities can assess blood flow, heart anatomy and mechanical function. However, for early diagnosis and improved treatment, further functional biomarkers are needed. One such functional biomarker could be the myocardium pH. Although tissue pH is already determinable via MR techniques, and has been since the early 1990s, it remains elusive to use practically. The objective of this study was to explore the possibility to evaluate cardiac pH noninvasively, using in-cell enzymatic rates of hyperpolarized [1-13 C]pyruvate metabolism (ie, moles of product produced per unit time) determined directly in real time using magnetic resonance spectroscopy in a perfused mouse heart model. As a gold standard for tissue pH we used 31 P spectroscopy and the chemical shift of the inorganic phosphate (Pi) signal. The nonhomogenous pH distribution of the perfused heart was analyzed using a multi-parametric analysis of this signal, thus taking into account the heterogeneous nature of this characteristic. As opposed to the signal ratio of hyperpolarized [13 C]bicarbonate to [13 CO2 ], which has shown correlation to pH in other studies, we investigated here the ratio of two intracellular enzymatic rates: lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH), by way of determining the production rates of [1-13 C]lactate and [13 C]bicarbonate, respectively. The enzyme activities determined here are intracellular, while the pH determined using the Pi signal may contain an extracellular component, which could not be ruled out. Nevertheless, we report a strong correlation between the tissue pH and the LDH/PDH activities ratio. This work may pave the way for using the LDH/PDH activities ratio as an indicator of cardiac intracellular pH in vivo, in an MRI examination.
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Affiliation(s)
- David Shaul
- Department of Radiology, Hadassah Medical Center, Hebrew University of Jerusalem, The Faculty of Medicine, Jerusalem, Israel
| | - Assad Azar
- Department of Radiology, Hadassah Medical Center, Hebrew University of Jerusalem, The Faculty of Medicine, Jerusalem, Israel
| | - Gal Sapir
- Department of Radiology, Hadassah Medical Center, Hebrew University of Jerusalem, The Faculty of Medicine, Jerusalem, Israel
| | - Sivaranjan Uppala
- Department of Radiology, Hadassah Medical Center, Hebrew University of Jerusalem, The Faculty of Medicine, Jerusalem, Israel
| | - Atara Nardi-Schreiber
- Department of Radiology, Hadassah Medical Center, Hebrew University of Jerusalem, The Faculty of Medicine, Jerusalem, Israel
| | - Ayelet Gamliel
- Department of Radiology, Hadassah Medical Center, Hebrew University of Jerusalem, The Faculty of Medicine, Jerusalem, Israel
| | - Jacob Sosna
- Department of Radiology, Hadassah Medical Center, Hebrew University of Jerusalem, The Faculty of Medicine, Jerusalem, Israel
| | - J Moshe Gomori
- Department of Radiology, Hadassah Medical Center, Hebrew University of Jerusalem, The Faculty of Medicine, Jerusalem, Israel
| | - Rachel Katz-Brull
- Department of Radiology, Hadassah Medical Center, Hebrew University of Jerusalem, The Faculty of Medicine, Jerusalem, Israel
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17
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Sun PZ. Quasi-steady state chemical exchange saturation transfer (QUASS CEST) analysis-correction of the finite relaxation delay and saturation time for robust CEST measurement. Magn Reson Med 2021; 85:3281-3289. [PMID: 33486816 DOI: 10.1002/mrm.28653] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 11/28/2020] [Accepted: 11/30/2020] [Indexed: 12/11/2022]
Abstract
PURPOSE CEST provides a MR contrast mechanism sensitizing to the exchange between dilute labile and bulk water protons. However, the CEST effect depends on the RF saturation duration and relaxation delay, which need to be long to reach its steady state. Our study aims to estimate the QUAsi-Steady State (QUASS) CEST signal from experiments with shorter saturation and relaxation delay times. METHODS The evolution of the CEST signal was modeled as a function of the bulk water longitudinal relaxation rate during the relaxation delay (Td) and spin-lock relaxation rate during the RF saturation (Ts), from which the QUASS CEST effect is solved. Numeric simulations were programmed to compare the apparent CEST and QUASS CEST effects as a function of Ts and Td times. We also performed CEST MRI experiments from a creatine-gel pH phantom under serially varied Ts and Td times. RESULTS The numeric simulation showed that although the apparent CEST effect depends on Td and Ts, the QUASS CEST solution has little dependence. Phantom results showed that the routine CEST pH contrast could be described by a nonlinear regression model (ie, Δ C E S T R = Δ C E S T R eq app 1 - e - R 1 ρ app · t ). We had Δ C E S T R eq app = 3.90 ± 0.03 % (P < 5e-8) and R 1 ρ app = 0.62 ± 0.02 s - 1 (P < 5e-6). For the QUASS CEST analysis, we modeled the pH contrast as Δ C E S T R = Δ C E S T R eq QUASS + s · t , using a linear regression model. We had Δ C E S T R eq QUASS = 3.63 ± 0.01 % (P < 5e-9) and s = - 0.02 ± 0.00 % / s (P < 0.01), the slope of which is minimal. CONCLUSIONS The QUASS CEST algorithm provides a post-processing solution that facilitates robust CEST measurement.
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Affiliation(s)
- Phillip Zhe Sun
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA.,Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia, USA
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18
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Kim H, Wu Y, Villano D, Longo DL, McMahon MT, Sun PZ. Analysis Protocol for the Quantification of Renal pH Using Chemical Exchange Saturation Transfer (CEST) MRI. Methods Mol Biol 2021; 2216:667-688. [PMID: 33476030 PMCID: PMC9703203 DOI: 10.1007/978-1-0716-0978-1_40] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
The kidney plays a major role in maintaining body pH homeostasis. Renal pH, in particular, changes immediately following injuries such as intoxication and ischemia, making pH an early biomarker for kidney injury before the symptom onset and complementary to well-established laboratory tests. Because of this, it is imperative to develop minimally invasive renal pH imaging exams and test pH as a new diagnostic biomarker in animal models of kidney injury before clinical translation. Briefly, iodinated contrast agents approved by the US Food and Drug Administration (FDA) for computed tomography (CT) have demonstrated promise as novel chemical exchange saturation transfer (CEST) MRI agents for pH-sensitive imaging. The generalized ratiometric iopamidol CEST MRI analysis enables concentration-independent pH measurement, which simplifies in vivo renal pH mapping. This chapter describes quantitative CEST MRI analysis for preclinical renal pH mapping, and their application in rodents, including normal conditions and acute kidney injury.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This analysis protocol chapter is complemented by two separate chapters describing the basic concepts and experimental procedure.
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Affiliation(s)
- Hahnsung Kim
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA
| | - Yin Wu
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Daisy Villano
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Dario Livio Longo
- Institute of Biostructures and Bioimaging (IBB), Italian National Research Council (CNR), Torino, Italy
| | - Michael T McMahon
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Phillip Zhe Sun
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA.
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA.
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA.
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19
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Almalki WH, Alghamdi S, Alzahrani A, Zhang W. Emerging paradigms in treating cerebral infarction with nanotheranostics: opportunities and clinical challenges. Drug Discov Today 2020; 26:826-835. [PMID: 33383212 DOI: 10.1016/j.drudis.2020.12.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 10/10/2020] [Accepted: 12/21/2020] [Indexed: 12/28/2022]
Abstract
Interest is increasing in the use of nanotheranostics as diagnosis, imaging and therapeutic tools for stroke management, but movement to the clinic remains challenging.
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Affiliation(s)
- Waleed H Almalki
- Department of Pharmacology and Toxicology, College of Pharmacy, Umm al-qura University, Saudi Arabia.
| | - Saad Alghamdi
- Laboratory Medicine Department, Faculty of Applied Medical Sciences, Umm Al-qura University, Makkah, Saudi Arabia
| | - Abdulaziz Alzahrani
- Department of Pharmacology, College of Clinical Pharmacy, Albaha University, Saudi Arabia
| | - Wenzhi Zhang
- Senior Research Scientist, Inn Research Sdn. Bhd., Subang Jaya, Selangor, Malaysia
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20
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Wu L, Jiang L, Sun PZ. Investigating the origin of pH-sensitive magnetization transfer ratio asymmetry MRI contrast during the acute stroke: Correction of T 1 change reveals the dominant amide proton transfer MRI signal. Magn Reson Med 2020; 84:2702-2712. [PMID: 32416012 PMCID: PMC7402019 DOI: 10.1002/mrm.28313] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 03/22/2020] [Accepted: 04/17/2020] [Indexed: 12/12/2022]
Abstract
PURPOSE Amide proton transfer (APT) MRI is promising to serve as a surrogate metabolic imaging biomarker of acute stroke. Although the magnetization transfer ratio asymmetry (MTRasym ) has been used commonly, the origin of pH-weighted MRI effect remains an area of investigation, including contributions from APT, semisolid MT contrast asymmetry, and nuclear Overhauser enhancement effects. Our study aimed to determine the origin of pH-weighted MTRasym contrast following acute stroke. METHODS Multiparametric MRI, including T1 , T2 , diffusion and Z-spectrum, were performed in rats after middle cerebral artery occlusion. We analyzed the conventional Z-spectrum I Δ ω I 0 and the apparent exchange spectrum R ex Δ ω , being the difference between the relaxation-scaled inverse Z-spectrum and the intrinsic spinlock relaxation rate R 1 · cos 2 θ · I 0 I Δ ω - R 1 ρ Δ ω . The ischemia-induced change was calculated as the spectral difference between the diffusion lesion and the contralateral normal area. RESULTS The conventional Z-spectrum signal change at -3.5 ppm dominates that at +3.5 ppm (-1.16 ± 0.39% vs. 0.76 ± 0.26%, P < .01) following acute stroke. In comparison, the magnitude of ΔRex change at 3.5 ppm becomes significantly larger than that at -3.5 ppm (-2.80 ± 0.40% vs. -0.94 ± 0.80%, P < .001), with their SNR being 7.0 and 1.2, respectively. We extended the magnetization transfer and relaxation normalized APT concept to the apparent exchange-dependent relaxation image, documenting an enhanced pH contrast between the ischemic lesion and the intact tissue, over that of MTRasym . CONCLUSION Our study shows that after the relaxation-effect correction, the APT effect is the dominant contributing factor to pH-weighted MTRasym following acute stroke.
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Affiliation(s)
- Limin Wu
- Neuroscience Center and Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolCharlestownMassachusettsUSA
| | - Liang Jiang
- Department of Otolaryngology, Head and Neck SurgeryAffiliated Hospital of Southwestern Medical UniversityLuzhouSichuanChina
- Yerkes Imaging CenterYerkes National Primate Research CenterEmory UniversityAtlantaGeorgiaUSA
| | - Phillip Zhe Sun
- Yerkes Imaging CenterYerkes National Primate Research CenterEmory UniversityAtlantaGeorgiaUSA
- Department of Radiology and Imaging SciencesEmory University School of MedicineAtlantaGeorgiaUSA
- Athinoula A. Martinos Center for Biomedical ImagingDepartment of RadiologyMassachusetts General Hospital and Harvard Medical SchoolCharlestownMassachusettsUSA
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21
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Mukherjee S, Sikdar SK. Intracellular activation of full-length human TREK-1 channel by hypoxia, high lactate, and low pH denotes polymodal integration by ischemic factors. Pflugers Arch 2020; 473:167-183. [PMID: 33025137 DOI: 10.1007/s00424-020-02471-5] [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: 09/01/2020] [Revised: 09/18/2020] [Accepted: 09/30/2020] [Indexed: 10/23/2022]
Abstract
TREK-1, a two-pore domain potassium channel, responds to ischemic levels of intracellular lactate and acidic pH to provide neuroprotection. There are two splice variants of hTREK1: the shorter splice variant having a shorter N-terminus compared with the full-length hTREK1 with similar C-terminus sequence that is widely expressed in the brain. The shorter variant was reported to be irresponsive to hypoxia-a condition attributed to ischemia, which has put the neuroprotective role of hTREK-1 channel into question. Since interaction between N- and C-terminus of different ion channels shapes their gating, we re-examined the sensitivity of the full-length as well as the shorter hTREK-1 channel to intracellular hypoxia along with lactate. Single-channel data obtained from the excised inside-out patches of the full-length channel expressed in HEK293 cells indicated an increase in activity as opposed to a decrease in activity in the shorter isoform. However, both the isoforms showed an increase in activity under combined hypoxia, 20mM lactate, and low pH 6 condition, albeit with subtle differences in their individual actions, confirming the neuroprotective role played by hTREK-1 irrespective of the differences in the N-terminus among the splice variants. Furthermore, E321A mutant that disrupts the interaction of the C-terminus with the membrane showed a decrease in activity with hypoxia indicating the importance of the C-terminus in the hypoxic response of the full-length hTREK-1. We propose an increase in activity of both the splice variants of hTREK-1 in combined hypoxia, high lactate, and low pH conditions typically associated with ischemia provides neuroprotection.
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Affiliation(s)
- Sourajit Mukherjee
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, 560012, India
| | - Sujit Kumar Sikdar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, 560012, India.
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Lee H, Choi SH, Sohn CH, Kim SG, Lee J, Park J. Rapid three-dimensional steady-state chemical exchange saturation transfer magnetic resonance imaging. Magn Reson Med 2020; 85:1209-1221. [PMID: 32851659 DOI: 10.1002/mrm.28487] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Revised: 07/11/2020] [Accepted: 07/30/2020] [Indexed: 02/05/2023]
Abstract
PURPOSE To make clinically feasible whole-brain chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) by enhancing imaging efficiency. METHODS A novel, whole-brain three-dimensional (3D) steady-state CEST MRI method was introduced by utilizing a time-efficient, fat-suppressed excitation followed by rapid, segmented 3D echo-planar-imaging with incoherent undersampling in k-ω space. Missing signals and CEST-specific spectral images were then jointly estimated directly from incomplete measurements using model-based reconstruction and robust spectral analysis. In vivo studies were performed at 3T both retrospectively (using a fully sampled reference) and prospectively to validate the effectiveness of the proposed method in patients with brain cancer. RESULTS In retrospective studies, the proposed method exhibits superior accuracies to existing methods in estimating images, z-spectra, and APTw relative to the reference. In prospective patient studies, compared with existing methods, the proposed method is statistically significantly different in contrast-to-noise ratio of the APTw contrast between tumor and normal appearing white matter (NAWM) and amide proton transfer weighted contrast (p < 0.05) while not being significantly different in signal-to-noise ratio in an NAWM region. CONCLUSIONS We successfully demonstrated that it is feasible to perform whole-brain CEST MRI roughly within 4 minutes for patients with brain cancer. It is expected that the proposed method widens clinical utilities of CEST MRI.
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Affiliation(s)
- Hoonjae Lee
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.,Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea
| | - Seung Hong Choi
- Department of Radiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Chul-Ho Sohn
- Department of Radiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Seong-Gi Kim
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.,Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea
| | - Joonyeol Lee
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.,Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea
| | - Jaeseok Park
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.,Biomedical Institute for Convergence, Sungkyunkwan University, Suwon, Republic of Korea
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23
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Momosaka D, Togao O, Kikuchi K, Kikuchi Y, Wakisaka Y, Hiwatashi A. Correlations of amide proton transfer-weighted MRI of cerebral infarction with clinico-radiological findings. PLoS One 2020; 15:e0237358. [PMID: 32790705 PMCID: PMC7425944 DOI: 10.1371/journal.pone.0237358] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 07/23/2020] [Indexed: 01/01/2023] Open
Abstract
Objective To clarify the relationship between amide proton transfer-weighted (APTW) signal, which reflects intracellular pH, and clinico-radiological findings in patients with hyperacute to subacute cerebral infarction. Materials and methods Twenty-nine patients (median age, 70 years [IQR, 54 to 74]; 15 men) were retrospectively examined. The 10th, 25th, 50th, 75th, and 90th percentiles of APTW signal (APT10, APT25, APT50, APT75 and APT90, respectively) were measured within the infarction region-of-interest (ROI), and compared between poor prognosis and good prognosis groups (modified Rankin Scale [mRS] score ≥2 and mRS score <2, respectively). Correlations between APTW signal and time after onset, lesion size, National Institutes of Health Stroke Scale (NIHSS) score, mRS score, and mean apparent diffusion coefficient (ADC) were evaluated. Results The poor prognosis group had lower APT50, APT75, and APT90 than the good prognosis group (–0.66 [–1.19 to –0.27] vs. –0.09 [–0.62 to –0.21]; –0.27 [–0.63 to –0.01] vs. 0.31 [–0.15 to 1.06]; 0.06 [–0.21 to 0.34] vs. 0.93 [0.36 to 1.50] %; p <0.05, respectively). APT50 was positively correlated with time after onset (r = 0.37, p = 0.0471) and negatively with lesion size (r = –0.39, p = 0.0388). APT75 and APT90 were negatively correlated with NIHSS (r = –0.41 and –0.43; p <0.05, respectively). APT50, APT75 and APT90 were negatively correlated with mRS (r = –0.37, –0.52 and –0.57; p <0.05, respectively). APT10 and APT25 were positively correlated with mean ADC (r = 0.37 and 0.38; p <0.05, respectively). Conclusion We demonstrated correlations between APTW signals of infarctions and clinico-radiological findings in patients with hyperacute to subacute infarctions. The poor prognosis group had a lower APTW signal than the good prognosis group. APTW signal was reduced in large infarctions, infarctions with low ADC, and in patients with high NIHSS and mRS scores.
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Affiliation(s)
- Daichi Momosaka
- Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Osamu Togao
- Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
- * E-mail:
| | - Kazufumi Kikuchi
- Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshitomo Kikuchi
- Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshinobu Wakisaka
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Akio Hiwatashi
- Department of Molecular Imaging & Diagnosis, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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24
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Sun PZ. Demonstration of magnetization transfer and relaxation normalized pH-specific pulse-amide proton transfer imaging in an animal model of acute stroke. Magn Reson Med 2020; 84:1526-1533. [PMID: 32080897 DOI: 10.1002/mrm.28223] [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: 09/26/2019] [Revised: 01/12/2020] [Accepted: 01/29/2020] [Indexed: 12/14/2022]
Abstract
PURPOSE pH-weighted amide proton transfer (APT) MRI is promising to serve as a new surrogate metabolic imaging biomarker for refined ischemic tissue demarcation. APT MRI with pulse-RF irradiation (pulse-APT) is an alternative to the routine continuous wave (CW-) APT MRI that overcomes the RF duty cycle limit. Our study aimed to generalize the recently developed pH-specific magnetization transfer and relaxation-normalized APT (MRAPT) analysis to pulse-APT MRI in acute stroke imaging. METHODS Multiparametric MRI, including CW- and pulse-APT MRI scans, were performed following middle cerebral artery occlusion in rats. We calculated pH-sensitive MTRasym and pH-specific MRAPT contrast between the ipsilateral diffusion lesion and contralateral normal area. RESULTS An inversion pulse of 10 to 15 ms maximizes the pH-sensitive MRI contrast for pulse-APT MRI. The contrast-to-noise ratio of pH-specific MRAPT effect between the contralateral normal area and ischemic lesion from both methods are comparable (3.25 ± 0.65 vs. 3.59 ± 0.40, P > .05). pH determined from both methods were in good agreement, with their difference within 0.1. CONCLUSIONS Pulse-APT MRI provides highly pH-specific mapping for acute stroke imaging.
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Affiliation(s)
- Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.,Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA.,Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA
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25
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Lee H, Chung JJ, Lee J, Kim SG, Han JH, Park J. Model-Based Chemical Exchange Saturation Transfer MRI for Robust z-Spectrum Analysis. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:283-293. [PMID: 30762539 DOI: 10.1109/tmi.2019.2898672] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
This paper introduces a novel, model-based chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI), in which asymmetric spectra of interest are directly estimated from complete or incomplete measurements by incorporating subspace-based spectral signal decomposition into the measurement model of CEST MRI for a robust z-spectrum analysis. Spectral signals are decomposed into symmetric and asymmetric components. The symmetric component, which varies smoothly, is delineated by the linear superposition of a finite set of vectors in a basis trained from the simulated (Lorentzian) signal vectors augmented with data-driven signal vectors, while the asymmetric component is to be inherently lower than or equal to zero due to saturation transfer phenomena. Spectral decomposition is performed directly on the measured spectral data by solving a constrained optimization problem that employs the linearized spectral decomposition model for the symmetric component and the weighted Frobenius norm regularization for the asymmetric component while utilizing additional spatial sparsity and low-rank priors. The simulations and in vivo experiments were performed to demonstrate the feasibility of the proposed method as a reliable molecular MRI.
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26
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Sun PZ. Development of intravoxel inhomogeneity correction for chemical exchange saturation transfer spectral imaging: a high-resolution field map-based deconvolution algorithm for magnetic field inhomogeneity correction. Magn Reson Med 2019; 83:1348-1355. [PMID: 31628765 DOI: 10.1002/mrm.28015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Revised: 09/04/2019] [Accepted: 09/05/2019] [Indexed: 12/12/2022]
Abstract
PURPOSE CEST MRI is sensitive to dilute proteins/peptides and microenvironmental properties yet susceptible to magnetic field inhomogeneity. We aimed to develop a high-resolution field map-based CEST intravoxel inhomogeneity correction (CIVIC) algorithm for CEST Z-spectral imaging. METHODS The proposed CIVIC approach treats the intravoxel inhomogeneity as a point spread function and applies the deconvolution algorithm to reconstruct the original Z-spectrum. We simulated the effect of B0 field inhomogeneity on CEST measurement and tested the efficacy of the proposed CIVIC algorithm. We also performed CEST MRI on a dual-pH Creatine-gel phantom under varied field homogeneity conditions and compared the CEST MRI contrast-to-noise ratio from the raw Z-spectrum, water saturation shift referencing, and the proposed CIVIC methods. RESULTS The numerical simulation showed that the CIVIC algorithm remains effective even in the case of symmetric field dispersion with a 0 mean shift. The experimental results confirmed that the proposed CIVIC method substantially improves the CEST MRI contrast-to-noise ratio under different field homogeneity conditions. CONCLUSION Our study established a new intravoxel B0 inhomogeneity correction algorithm, promising to facilitate CEST spectral imaging in challenging experimental conditions.
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Affiliation(s)
- Phillip Zhe Sun
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia.,Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia
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27
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Chen S, Liu X, Mei Y, Li C, Ren D, Zhong M, Xu Y. Early identification of neonatal mild hypoxic-ischemic encephalopathy by amide proton transfer magnetic resonance imaging: A pilot study. Eur J Radiol 2019; 119:108620. [PMID: 31422164 DOI: 10.1016/j.ejrad.2019.07.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 07/13/2019] [Accepted: 07/16/2019] [Indexed: 11/18/2022]
Abstract
PURPOSE This study aimed to evaluate the amide proton transfer (APT) values in neonates with mild hypoxic-ischemic encephalopathy (HIE) using APT imaging. METHOD A total of 30 full-term neonates with mild HIE (16 males and 14 females; mean postnatal age 4.2 days, age range 2-7 days) and 12 normal neonates (six males and six females; mean postnatal age 3.3 days, age range 2-5 days) underwent conventional magnetic resonance imaging and APT imaging. APT measurements were performed in multiple regions of interest (ROIs) in the brain. APT values were statistically analyzed to assess for significant differences between the mild HIE and normal neonates in different regions of the brain, and correlation with neonatal gestational age. RESULTS In 30 neonates with mild HIE, 10% (3/30) of the HIE patients had normal conventional MRI. There were significant differences in APT values of the HIE group in bilateral caudate, bilateral thalamus, bilateral centrum semiovale and left globus pallidus/putamen (p < 0.05), and no statistical difference was observed in right globus pallidus/putamen (p = 0.051) and brainstem (p = 0.073) between the two groups. Furthermore, APT values in bilateral caudate, bilateral globus pallidus/putamen, bilateral thalamus, and brainstem regions (p < 0.05) exhibited positive linear correlations with gestational age in the control group, except for bilateral centrum semiovale (right: Pearson's r = 0.554, p = 0.062; left: Pearson's r = 0.561, p = 0.058). In the mild HIE groups, no significant correlation with gestational age was found in all regions. CONCLUSIONS APT imaging is a feasible and useful technique with diagnostic capability for neonatal HIE.
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Affiliation(s)
- Sijin Chen
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China; Department of Obstetrics and Gynecology, Nanfang Hospital, Southern Medical University Guangzhou 510515, China
| | - Xilong Liu
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China
| | - Yingjie Mei
- Philips Healthcare, Guangzhou, Guangdong 510055, China
| | - Caixia Li
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China
| | - Daokun Ren
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China
| | - Mei Zhong
- Department of Obstetrics and Gynecology, Nanfang Hospital, Southern Medical University Guangzhou 510515, China
| | - Yikai Xu
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China.
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28
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Kaviarasi S, Yuba E, Harada A, Krishnan UM. Emerging paradigms in nanotechnology for imaging and treatment of cerebral ischemia. J Control Release 2019; 300:22-45. [DOI: 10.1016/j.jconrel.2019.02.031] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 02/20/2019] [Accepted: 02/21/2019] [Indexed: 02/07/2023]
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29
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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: 15] [Impact Index Per Article: 3.0] [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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30
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Wang E, Wu Y, Cheung JS, Igarashi T, Wu L, Zhang X, Sun PZ. Mapping tissue pH in an experimental model of acute stroke - Determination of graded regional tissue pH changes with non-invasive quantitative amide proton transfer MRI. Neuroimage 2019; 191:610-617. [PMID: 30753926 DOI: 10.1016/j.neuroimage.2019.02.022] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 02/05/2019] [Accepted: 02/08/2019] [Indexed: 12/20/2022] Open
Abstract
pH-weighted amide proton transfer (APT) MRI is sensitive to tissue pH change during acute ischemia, complementing conventional perfusion and diffusion stroke imaging. However, the currently used pH-weighted magnetization transfer (MT) ratio asymmetry (MTRasym) analysis is of limited pH specificity. To overcome this, MT and relaxation normalized APT (MRAPT) analysis has been developed that to homogenize the background signal, thus providing highly pH conspicuous measurement. Our study aimed to calibrate MRAPT MRI toward absolute tissue pH mapping and determine regional pH changes during acute stroke. Using middle cerebral artery occlusion (MCAO) rats, we performed lactate MR spectroscopy and multi-parametric MRI. MRAPT MRI was calibrated against a region of interest (ROI)-based pH spectroscopy measurement (R2 = 0.70, P < 0.001), showing noticeably higher correlation coefficient than the simplistic MTRasym index. Capitalizing on this, we mapped brain tissue pH and semi-automatically segmented pH lesion, in addition to routine perfusion and diffusion lesions. Tissue pH from regions of the contralateral normal, perfusion/diffusion lesion mismatch and diffusion lesion was found to be 7.03 ± 0.04, 6.84 ± 0.10, 6.52 ± 0.19, respectively. Most importantly, we delineated the heterogeneous perfusion/diffusion lesion mismatch into perfusion/pH and pH/diffusion lesion mismatches, with their pH being 7.01 ± 0.04 and 6.71 ± 0.12, respectively (P < 0.05). To summarize, our study calibrated pH-sensitive MRAPT MRI toward absolute tissue pH mapping, semi-automatically segmented and determined graded tissue pH changes in ischemic tissue and demonstrated its feasibility for refined demarcation of heterogeneous metabolic disruption following acute stroke.
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Affiliation(s)
- Enfeng Wang
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA; Department of Radiology, 3rd Affiliated Hospital, Zhengzhou University, Henan, China
| | - Yin Wu
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA; Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Jerry S Cheung
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Takahiro Igarashi
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Limin Wu
- Neuroscience Center and Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Xiaoan Zhang
- Department of Radiology, 3rd Affiliated Hospital, Zhengzhou University, Henan, China
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA.
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31
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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: 228] [Impact Index Per Article: 45.6] [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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32
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Devaux JBL, Hedges CP, Birch N, Herbert N, Renshaw GMC, Hickey AJR. Acidosis Maintains the Function of Brain Mitochondria in Hypoxia-Tolerant Triplefin Fish: A Strategy to Survive Acute Hypoxic Exposure? Front Physiol 2019; 9:1941. [PMID: 30713504 PMCID: PMC6346031 DOI: 10.3389/fphys.2018.01941] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 12/22/2018] [Indexed: 11/13/2022] Open
Abstract
The vertebrate brain is generally very sensitive to acidosis, so a hypoxia-induced decrease in pH is likely to have an effect on brain mitochondria (mt). Mitochondrial respiration (JO2) is required to generate an electrical gradient (ΔΨm) and a pH gradient to power ATP synthesis, yet the impact of pH modulation on brain mt function remains largely unexplored. As intertidal fishes within rock pools routinely experience hypoxia and reoxygenation, they would most likely experience changes in cellular pH. We hence compared four New Zealand triplefin fish species ranging from intertidal hypoxia-tolerant species (HTS) to subtidal hypoxia-sensitive species (HSS). We predicted that HTS would tolerate acidosis better than HSS in terms of sustaining mt structure and function. Using respirometers coupled to fluorimeters and pH electrodes, we titrated lactic-acid to decrease the pH of the media, and simultaneously recorded JO2, ΔΨm, and H+ buffering capacities within permeabilized brain and swelling of mt isolated from non-permeabilized brains. We then measured ATP synthesis rates in the most HTS (Bellapiscus medius) and the HSS (Forsterygion varium) at pH 7.25 and 6.65. Mitochondria from HTS brain did have greater H+ buffering capacities than HSS mt (∼10 mU pH.mgprotein -1). HTS mt swelled by 40% when exposed to a decrease of 1.5 pH units, and JO2 was depressed by up to 15% in HTS. However, HTS were able to maintain ΔΨm near -120 mV. Estimates of work, in terms of charges moved across the mt inner-membrane, suggested that with acidosis, HTS mt may in part harness extra-mt H+ to maintain ΔΨm, and could therefore support ATP production. This was confirmed with elevated ATP synthesis rates and enhanced P:O ratios at pH 6.65 relative to pH 7.25. In contrast, mt volumes and ΔΨm decreased downward pH 6.9 in HSS mt and paradoxically, JO2 increased (∼25%) but ATP synthesis and P:O ratios were depressed at pH 6.65. This indicates a loss of coupling in the HSS with acidosis. Overall, the mt of these intertidal fish have adaptations that enhance ATP synthesis efficiency under acidic conditions such as those that occur in hypoxic or reoxygenated brain.
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Affiliation(s)
- Jules B L Devaux
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Christopher P Hedges
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Nigel Birch
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Neill Herbert
- Institute of Marine Science, The University Auckland, Auckland, New Zealand
| | - Gillian M C Renshaw
- School of Allied Health Sciences, Griffith University, Gold Coast, QLD, Australia
| | - Anthony J R Hickey
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
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33
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Zhou IY, Lu D, Ji Y, Wu L, Wang E, Cheung JS, Zhang XA, Sun PZ. Determination of multipool contributions to endogenous amide proton transfer effects in global ischemia with high spectral resolution in vivo chemical exchange saturation transfer MRI. Magn Reson Med 2019; 81:645-652. [PMID: 30058148 PMCID: PMC6258351 DOI: 10.1002/mrm.27385] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 04/26/2018] [Accepted: 05/08/2018] [Indexed: 12/31/2022]
Abstract
PURPOSE Chemical exchange saturation transfer (CEST) MRI has been used for quantitative assessment of dilute metabolites and/or pH in disorders such as acute stroke and tumor. However, routine asymmetry analysis (MTRasym ) may be confounded by concomitant effects such as semisolid macromolecular magnetization transfer (MT) and nuclear Overhauser enhancement. Resolving multiple contributions is essential for elucidating the origins of in vivo CEST contrast. METHODS Here we used a newly proposed image downsampling expedited adaptive least-squares fitting on densely sampled Z-spectrum to quantify multipool contribution from water, nuclear Overhauser enhancement, MT, guanidinium, amine, and amide protons in adult male Wistar rats before and after global ischemia. RESULTS Our results revealed the major contributors to in vivo T1 -normalized MTRasym (3.5 ppm) contrast between white and gray matter (WM/GM) in normal brain (-1.96%/second) are pH-insensitive macromolecular MT (-0.89%/second) and nuclear Overhauser enhancement (-1.04%/second). Additionally, global ischemia resulted in significant changes of MTRasym , being -2.05%/second and -1.56%/second in WM and GM, which are dominated by changes in amide (-1.05%/second, -1.14%/second) and MT (-0.88%/second, -0.62%/second). Notably, the pH-sensitive amine and amide effects account for nearly 60% and 80% of the MTRasym changes seen in WM and GM, respectively, after global ischemia, indicating that MTRasym is predominantly pH-sensitive. CONCLUSION Combined amide and amine effects dominated the MTRasym changes after global ischemia, indicating that MTRasym is predominantly pH-sensitive and suitable for detecting tissue acidosis following acute stroke.
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Affiliation(s)
- Iris Yuwen Zhou
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Dongshuang Lu
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Yang Ji
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Limin Wu
- Neuroscience Center and Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Enfeng Wang
- Department of Radiology, 3rd Affiliated Hospital, Zhengzhou University, Henan China
| | - Jerry S. Cheung
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Xiao-An Zhang
- Department of Radiology, 3rd Affiliated Hospital, Zhengzhou University, Henan China
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
- Department of Radiology, Emory University School of Medicine, Atlanta, GA, USA
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Lin G, Zhuang C, Shen Z, Xiao G, Chen Y, Shen Y, Zong X, Wu R. APT Weighted MRI as an Effective Imaging Protocol to Predict Clinical Outcome After Acute Ischemic Stroke. Front Neurol 2018; 9:901. [PMID: 30405523 PMCID: PMC6205981 DOI: 10.3389/fneur.2018.00901] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 10/05/2018] [Indexed: 11/13/2022] Open
Abstract
To explore the capability of the amide-proton-transfer weighted (APTW) magnetic resonance imaging (MRI) in the evaluation of clinical neurological deficit at the time of hospitalization and assessment of long-term daily functional outcome for patients with acute ischemic stroke (AIS). We recruited 55 AIS patients with brain MRI acquired within 24-48 h of symptom onset and followed up with their 90-day modified Rankin Scale (mRS) score. APT weighted MRI was performed for all the study subjects to measure APTW signal quantitatively in the acute ischemic area (APTWipsi) and the contralateral side (APTWcont). Change of the APT signal between the acute ischemic region and the contralateral side (ΔAPTW) was calculated. Maximum APTW signal (APTWmax) and minimal APTW signal (APTWmin) were also acquired to demonstrate APTW signals heterogeneity (APTWmax-min). In addition, all the patients were divided into 2 groups according to their 90-day mRS score (good prognosis group with mRS score <2 and poor prognosis group with mRS score ≥2). In the meantime, ΔAPTW of these groups was compared. We found that ΔAPTW was in good correlation with National Institutes of Health Stroke Scale (NIHSS) score (R 2 = 0.578, p < 0.001) and 90-day mRS score (R 2 = 0.55, p < 0.001). There was significant difference of ΔAPTW between patients with good prognosis and patients with poor prognosis. Plus, APTWmax-min was significantly different between two groups. These results suggested that APT weighted MRI could be used as an effective tool to assess the stroke severity and prognosis for patients with AIS, with APTW signal heterogeneity as a possible biomarker.
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Affiliation(s)
- Guisen Lin
- Department of Medical Imaging, The Second Affiliated Hospital, Medical College of Shantou University, Shantou, China
| | - Caiyu Zhuang
- Department of Medical Imaging, The Second Affiliated Hospital, Medical College of Shantou University, Shantou, China
| | - Zhiwei Shen
- Department of Medical Imaging, The Second Affiliated Hospital, Medical College of Shantou University, Shantou, China
| | - Gang Xiao
- Department of Mathematics and Statistics, Hanshan Normal University, Chaozhou, China
| | - Yanzi Chen
- Department of Medical Imaging, The Second Affiliated Hospital, Medical College of Shantou University, Shantou, China
| | - Yuanyu Shen
- Department of Medical Imaging, The Second Affiliated Hospital, Medical College of Shantou University, Shantou, China
| | - Xiaodan Zong
- Department of Medical Imaging, The Second Affiliated Hospital, Medical College of Shantou University, Shantou, China
| | - Renhua Wu
- Department of Medical Imaging, The Second Affiliated Hospital, Medical College of Shantou University, Shantou, China.,Provincial Key Laboratory of Medical Molecular Imaging, Shantou, China
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35
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Zu Z. Towards the complex dependence of MTR asym on T 1w in amide proton transfer (APT) imaging. NMR IN BIOMEDICINE 2018; 31:e3934. [PMID: 29806717 PMCID: PMC6089235 DOI: 10.1002/nbm.3934] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 03/05/2018] [Accepted: 03/23/2018] [Indexed: 05/08/2023]
Abstract
Amide proton transfer (APT) imaging is a variation of chemical exchange saturation transfer MRI that has shown promise in diagnosing tumors, ischemic stroke, multiple sclerosis, traumatic brain injury, etc. Specific quantification of the APT effect is crucial for the interpretation of APT contrast in pathologies. Conventionally, magnetization transfer ratio with asymmetric analysis (MTRasym ) has been used to quantify the APT effect. However, some studies indicate that MTRasym is contaminated by water longitudinal relaxation time (T1w ), and thus it is necessary to normalize T1w in MTRasym to obtain specific quantification of the APT effect. So far, whether to use MTRasym or the T1w -normalized MTRasym is still under debate in the field. In this paper, the influence of T1w on the quantification of APT was evaluated through theoretical analysis, numerical simulations, and phantom studies for different experimental conditions. Results indicate that there are two types of T1w effect (T1w recovery and T1w -related saturation), which have inverse influences on the steady-state MTRasym . In situations with no or weak direct water saturation (DS) effect, there is only the T1w recovery effect, and MTRasym linearly depends on T1w . In contrast, in situations with significant DS effects, the dependence of MTRasym on T1w is complex, and is dictated by the competition of these two T1w effects. Therefore, by choosing appropriate irradiation powers, MTRasym could be roughly insensitive to T1w . Moreover, in non-steady-state acquisitions with very short irradiation time, MTRasym is also roughly insensitive to T1w . Therefore, for steady-state APT imaging at high fields or with very low irradiation powers, where there are no significant DS effects, it is necessary to normalize T1w to improve the specificity of MTRasym . However, in clinical MRI systems (usually low fields or non-steady-state acquisitions), T1w normalization may not be necessary when appropriate sequence parameters are chosen.
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Affiliation(s)
- Zhongliang Zu
- Vanderbilt University Institute of Imaging Science
- Department of Radiology and Radiological Sciences
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36
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Zheng Y, Wang X. The Applicability of Amide Proton Transfer Imaging in the Nervous System: Focus on Hypoxic-Ischemic Encephalopathy in the Neonate. Cell Mol Neurobiol 2018; 38:797-807. [PMID: 28942555 DOI: 10.1007/s10571-017-0552-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Accepted: 09/16/2017] [Indexed: 12/29/2022]
Abstract
In recent years, magnetic resonance imaging (MRI) has become more widely used in neonatal hypoxic-ischemic encephalopathy (HIE), involving, for example, evaluation of cerebral edema, white matter fiber bundle tracking, cerebral perfusion status, and assessment of brain metabolites. MRI has many imaging modalities. However, its application for assessing changes in the internal environment at the tissue and cellular level after hypoxia-ischemia remains a challenge and is currently the focus of intense research. Based on the exchange between amide protons of proteins and polypeptides and free water protons, amide proton transfer (APT) imaging can display changes in pH and protein concentrations in vivo. This paper is a review of the principles of APT imaging, with a focus on the potential application of APT imaging for neonatal HIE.
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Affiliation(s)
- Yang Zheng
- Department of Radiology, Shengjing Hospital of China Medical University, No. 36, Sanhao Street, Heping District, Shenyang, 110004, People's Republic of China
| | - Xiaoming Wang
- Department of Radiology, Shengjing Hospital of China Medical University, No. 36, Sanhao Street, Heping District, Shenyang, 110004, People's Republic of China.
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37
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Zu Z, Afzal A, Li H, Xie J, Gore JC. Spin-lock imaging of early tissue pH changes in ischemic rat brain. NMR IN BIOMEDICINE 2018; 31:e3893. [PMID: 29424463 PMCID: PMC5854549 DOI: 10.1002/nbm.3893] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 11/23/2017] [Accepted: 12/07/2017] [Indexed: 05/03/2023]
Abstract
We have previously reported that the dispersion of spin-lattice relaxation rates in the rotating frame (R1ρ ) of tissue water protons at high field can be dominated by chemical exchange contributions. Ischemia in brain causes changes in tissue pH, which in turn may affect proton exchange rates. Amide proton transfer (APT, a form of chemical exchange saturation transfer) has been shown to be sensitive to chemical exchange rates and able to detect pH changes non-invasively following ischemic stroke. However, the specificity of APT to pH changes is decreased because of the influence of several other factors that affect magnetization transfer. R1ρ is less influenced by such confounding factors and thus may be more specific for detecting variations in pH. Here, we applied a spin-locking sequence to detect ischemic stroke in animal models. Although R1ρ images acquired with a single spin-locking amplitude (ω1 ) have previously been used to assess stroke, here we use ΔR1ρ , which is the difference in R1ρ values acquired with two different locking fields to emphasize selectively the contribution of chemical exchange effects. Numerical simulations with different exchange rates and measurements of tissue homogenates with different pH were performed to evaluate the specificity of ΔR1ρ to detect tissue acidosis. Spin-lock and APT data were acquired on five rat brains after ischemic strokes induced via middle cerebral artery occlusions. Correlations between these data were analyzed at different time points after the onset of stroke. The results show that ΔR1ρ (but not R1ρ acquired with a single ω1 ) was significantly correlated with APT metrics consistent with ΔR1ρ varying with pH.
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Affiliation(s)
- Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Aqeela Afzal
- Department of Neurological Surgery, Vanderbilt University, Nashville, Tennessee, USA
| | - Hua Li
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Jingping Xie
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - John C. Gore
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
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Tan Y, Xu J, Chen R, Chen B, Xu J, Ren D, Chan Q, Mei Y, Wu Y, Xu Y. Use of T 1 relaxation time in rotating frame (T 1 ρ) and apparent diffusion coefficient to estimate cerebral stroke evolution. J Magn Reson Imaging 2018; 48:1247-1254. [PMID: 29446510 DOI: 10.1002/jmri.25971] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 01/26/2018] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The major factor for the appropriate treatment strategies for ischemia patients is its onset timing. PURPOSE/HYPOTHESIS To study to evaluate the diagnostic accuracy of T1 relaxation time in a rotating frame (T1 ρ) and apparent diffusion coefficient (ADC) from MRI to estimate ischemia stages. STUDY TYPE Prospective. POPULATION/SUBJECTS/PHANTOM/SPECIMEN/ANIMAL MODEL In all, 73 patients (49 males, aged 29-78 years and 24 females, aged 22-94 years) with ischemia were prospectively imaged with T1 ρ and diffusion MRI during the postischemic period. FIELD STRENGTH/SEQUENCE 3T/T1 ρ and diffusion-weighted imaging (DWI). ASSESSMENT Ischemic parenchyma included tissue with elevated signal areas on DWI and correlative hypointense areas on ADC maps. STATISTICAL TESTS The sensitivity of variables to ischemia time was quantified by analyzing the respective correlations of these values with onset time. RESULTS ΔT1 ρ (ipsilateral-contralateral differences in T1 ρ) (R2 = 0.956) and T1 ρipsi (ipsilateral ischemia T1 ρ values) (R2 = 0.941) were elevated in all ischemic lesions; these values increased linearly as a function of time, unlike ΔADC (ipsilateral-contralateral differences in ADC) (R2 = -0.410) and ADCipsi (ipsilateral ischemia ADC values) (R2 = 0.550). ΔT1 ρ and T1 ρipsi were significantly different between all stages (P < 0.01), except the acute and hyperacute stages (P = 0.589 for ΔT1 ρ, P = 0.290 for T1 ρipsi , respectively), but ΔADC and ADCipsi only between the late subacute and early subacute stages (P < 0.01) and the late subacute and chronic stages (P < 0.01). DATA CONCLUSION These data suggest that T1 ρ can provide estimates for the ischemic time in patients. T1 ρ has the potential to outperform diffusion for single-timepoint examination because the T1 ρ change during strokes is positive and linear. If patients with suspected stroke are scanned by MRI within the appropriate timeframe, T1 ρ may provide tools for evaluating stroke onset, potentially aiding in treatment strategies. LEVEL OF EVIDENCE 4 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1247-1254.
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Affiliation(s)
- Yuefa Tan
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Jun Xu
- Department of Hematology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Ruiying Chen
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Bin Chen
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Juan Xu
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Daokun Ren
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | | | | | - Yuankui Wu
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Yikai Xu
- Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou, China
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Systematic Evaluation of Amide Proton Chemical Exchange Saturation Transfer at 3 T: Effects of Protein Concentration, pH, and Acquisition Parameters. Invest Radiol 2017; 51:635-46. [PMID: 27272542 DOI: 10.1097/rli.0000000000000292] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVE The goal of this work was to systematically evaluate the reproducibility of amide proton transfer chemical exchange saturation transfer (APT-CEST) at 3 T and its signal dependence on pH, protein concentration, and acquisition parameters. An in vitro system based on bovine serum albumin (BSA) was used, and its limitations were tested by comparing it to in vivo measurements. The contribution of small endogenous metabolites on the APT-CEST signal at 3 T was also investigated. In addition, the reliability of different z-spectrum interpolations as well as the use of only a few frequency offset data points instead of a whole z-spectrum were tested. MATERIALS AND METHODS We created both a BSA phantom at different concentrations and pH values and a metabolite phantom with different small molecules. Chemical exchange saturation transfer data were acquired using a 2-dimensional fast spoiled gradient-echo sequence with pulsed CEST preparation at different saturation durations and power levels. Healthy volunteer measurements were taken for comparison. Z-spectra were interpolated using a 24th-order polynomial (Poly), an eighth-order Fourier series (Fourier), and a smoothing Spline (sSpline) algorithm. To evaluate reduced data sets, only 6 to 14 frequency offsets of the z-spectrum were used and interpolated via a cubic Spline. Region of interest (ROI) evaluations were used to investigate the reproducibility of amide magnetization transfer ratio asymmetry [MTRasym(3.5 ppm)] and to analyze the MTRasym and z-spectra. RESULTS Interscan standard deviations of MTRasym(3.5 ppm) were always below 0.3%. MTRasym(3.5 ppm) increased when the BSA concentrations increased and decreased when the pH increased. The amine MTRasym signal of small molecules was very small compared with BSA and was only detectable using short saturation times and higher power levels. The MTRasym(3.5 ppm) between BSA concentration steps and between nearly all pH steps was significantly different for all 3 fitting methods. The Fourier and sSpline methods showed no statistically significant differences; however, the results for the Poly method were significantly higher at some concentrations and pH values. Using only few frequency offsets resulted in less significant differences compared with fitting the complete z-spectrum. In general, MTRasym(3.5 ppm) of gray matter, white matter, and ventricle ROIs from volunteer scans increased with an increase in saturation power and partially decreased with an increase in saturation duration. Intra-ROI covariances of MTRasym(3.5 ppm) revealed the highest variations for Poly, whereas using reduced spectral data resulted in an increased signal variation. CONCLUSIONS Amide proton transfer-CEST imaging is a highly reproducible method in which absolute signal differences of approximately 0.5% are detectable in principle. For in vivo applications, Fourier or sSpline interpolations of z-spectra are preferable. Using reduced data sets delivers similar results but with increased variation and therefore decreased (pH/concentration) differentiation capability. Differentiation capability increases with increases in the saturation duration and power level. The results from the in vitro BSA system cannot be directly transferred to the in vivo situation due to different chemical environments resulting in, for example, higher asymmetric macromolecular cMT effects in vivo. Amine signals from small molecules are unlikely to contribute to APT-CEST at 3 T (except for creatine); however, signals can be enhanced by using short saturation times and higher power levels.
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40
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Wang E, Wu Y, Cheung JS, Zhou IY, Igarashi T, Zhang X, Sun PZ. pH imaging reveals worsened tissue acidification in diffusion kurtosis lesion than the kurtosis/diffusion lesion mismatch in an animal model of acute stroke. J Cereb Blood Flow Metab 2017; 37:3325-3333. [PMID: 28752790 PMCID: PMC5624397 DOI: 10.1177/0271678x17721431] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Diffusion weighted imaging (DWI) has been commonly used in acute stroke examination, yet a portion of DWI lesion may be salvageable. Recently, it has been shown that diffusion kurtosis imaging (DKI) defines the most severely damaged DWI lesion that does not renormalize following early reperfusion. We postulated that the diffusion and kurtosis lesion mismatch experience heterogeneous hemodynamic and/or metabolic injury. We investigated tissue perfusion, pH, diffusion, kurtosis and relaxation from regions of the contralateral normal area, diffusion lesion, kurtosis lesion and their mismatch in an animal model of acute stroke. Our study revealed significant kurtosis and diffusion lesion volume mismatch (19.7 ± 10.7%, P < 0.01). Although there was no significant difference in perfusion and diffusion between the kurtosis lesion and kurtosis/diffusion lesion mismatch, we showed lower pH in the kurtosis lesion (pH = 6.64 ± 0.12) from that of the kurtosis/diffusion lesion mismatch (6.84 ± 0.11, P < 0.05). Moreover, pH in the kurtosis lesion and kurtosis/diffusion mismatch agreed well with literature values for regions of ischemic core and penumbra, respectively. Our work documented initial evidence that DKI may reveal the heterogeneous metabolic derangement within the commonly used DWI lesion.
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Affiliation(s)
- Enfeng Wang
- 1 Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, USA.,2 Department of Radiology, Third Affiliated Hospital, Zhengzhou University, Zhengzhou, China
| | - Yin Wu
- 1 Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, USA.,3 Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Jerry S Cheung
- 1 Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, USA
| | - Iris Yuwen Zhou
- 1 Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, USA
| | - Takahiro Igarashi
- 1 Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, USA
| | - XiaoAn Zhang
- 2 Department of Radiology, Third Affiliated Hospital, Zhengzhou University, Zhengzhou, China
| | - Phillip Zhe Sun
- 1 Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, USA
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Wu Y, Zhou IY, Lu D, Manderville E, Lo EH, Zheng H, Sun PZ. pH-sensitive amide proton transfer effect dominates the magnetization transfer asymmetry contrast during acute ischemia-quantification of multipool contribution to in vivo CEST MRI. Magn Reson Med 2017; 79:1602-1608. [PMID: 28733991 DOI: 10.1002/mrm.26829] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/12/2017] [Accepted: 06/18/2017] [Indexed: 12/30/2022]
Abstract
PURPOSE To determine the origins of in vivo magnetization transfer asymmetry contrast during acute ischemic stroke, particularly in the diffusion lesion, perfusion lesion, and their mismatch using a middle cerebral artery occlusion rat model of acute stroke. METHODS Adult male Wistar rats underwent multiparametric MRI of diffusion, perfusion, T1 , and amide proton transfer (APT) imaging at 4.7 T following a middle cerebral artery occlusion procedure. A multipool Lorentzian model, including the nuclear Overhauser effect, magnetization transfer, direct water saturation, amine and amide chemical exchange saturation transfer effects, was applied for Z-spectrum fitting to determine the sources of in vivo magnetization transfer asymmetry following acute stroke. RESULTS We showed that changes in amine chemical exchange saturation transfer (2 ppm) and APT (3.5 ppm) effects, particularly the APT MRI effect, dominate the commonly used magnetization transfer asymmetry analysis and hence confer pH sensitivity to APT imaging of acute stroke. Also, the nuclear Overhauser effect and magnetization transfer show small changes that counteracted each other, contributing less than 0.3% to magnetization transfer asymmetry at 3.5 ppm. Moreover, we showed that diffusion lesion had worsened acidosis from perfusion/diffusion lesion mismatch (P < 0.05). CONCLUSIONS The study complements recent in vivo quantitative chemical exchange saturation transfer work to shed light on the sensitivity and specificity of endogenous APT MRI to tissue acidosis. Magn Reson Med 79:1602-1608, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Yin Wu
- Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Key Laboratory for MRI, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China.,Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA
| | - Iris Yuwen Zhou
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA
| | - Dongshuang Lu
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA
| | - Emiri Manderville
- Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
| | - Eng H Lo
- Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
| | - Hairong Zheng
- Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Key Laboratory for MRI, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA.,Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
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42
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Jiang S, Eberhart CG, Zhang Y, Heo HY, Wen Z, Blair L, Qin H, Lim M, Quinones-Hinojosa A, Weingart JD, Barker PB, Pomper MG, Laterra J, van Zijl PCM, Blakeley JO, Zhou J. Amide proton transfer-weighted magnetic resonance image-guided stereotactic biopsy in patients with newly diagnosed gliomas. Eur J Cancer 2017; 83:9-18. [PMID: 28704644 DOI: 10.1016/j.ejca.2017.06.009] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Revised: 05/31/2017] [Accepted: 06/11/2017] [Indexed: 01/03/2023]
Abstract
PURPOSE Pathological assessment using World Health Organization (WHO) criteria is the gold standard for diagnosis of gliomas. However, the accuracy of diagnosis is limited by tissue sampling, particularly for infiltrating, heterogeneous tumours. We assessed the accuracy of amide proton transfer-weighted (APTw) magnetic resonance imaging (MRI)-guided tissue sampling to identify regions of high-grade glioma via radiographic-histopathologic correlation in patients with newly suspected glioma. PATIENTS AND METHODS Twenty-four patients with previously undiagnosed gliomas underwent a volumetric APTw MRI prior to their first neurosurgical procedure. A total of 70 specimens were collected via APTw image-directed stereotactic biopsy. Cellularity, necrosis, proliferation and glioma WHO grade were analysed for all specimens and correlated with corresponding APTw signal intensities. RESULTS Thirty-three specimens displayed grade-II pathology, 14 grade-III, 15 grade-IV, and eight specimens revealed only peritumoural oedema. Multiple glioma grades were found within a single lesion in six patients. APTw signal intensities of the biopsied sites and the maximum APTw values across all biopsied sites in each patient were significantly higher for high-grade versus low-grade specimens. APTw signal intensities were significantly positively correlated with cellularity (R = 0.757) and proliferation (R = 0.538). Multiple linear regression analysis showed that tumour cellularity and proliferation index were the best predictors of APTw signal intensities. CONCLUSION APTw imaging identified tumour areas of higher cellularity and proliferation, allowing identification of high-grade regions within heterogeneous gliomas. APTw imaging can be readily translated for more widespread use and can assist diagnostic neurosurgical procedures by increasing the accuracy of tumour sampling in patients with infiltrating gliomas.
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Affiliation(s)
- Shanshan Jiang
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA; Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | | | - Yi Zhang
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
| | - Hye-Young Heo
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
| | - Zhibo Wen
- Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Lindsay Blair
- Department of Neurology, Johns Hopkins University, Baltimore, MD, USA
| | - Huamin Qin
- Department of Pathology, Johns Hopkins University, Baltimore, MD, USA
| | - Michael Lim
- Department of Neurosurgery, Johns Hopkins University, Baltimore, MD, USA
| | | | - Jon D Weingart
- Department of Neurosurgery, Johns Hopkins University, Baltimore, MD, USA
| | - Peter B Barker
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
| | - Martin G Pomper
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
| | - John Laterra
- Department of Neurology, Johns Hopkins University, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Peter C M van Zijl
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | | | - Jinyuan Zhou
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.
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43
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Jin T, Wang P, Hitchens TK, Kim SG. Enhancing sensitivity of pH-weighted MRI with combination of amide and guanidyl CEST. Neuroimage 2017; 157:341-350. [PMID: 28602944 DOI: 10.1016/j.neuroimage.2017.06.007] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 05/26/2017] [Accepted: 06/01/2017] [Indexed: 11/17/2022] Open
Abstract
Amide-proton-transfer weighted (APTw) MRI has emerged as a non-invasive pH-weighted imaging technique for studies of several diseases such as ischemic stroke. However, its pH-sensitivity is relatively low, limiting its capability to detect small pH changes. In this work, computer simulations, protamine phantom experiments, and in vivo gas challenge and experimental stroke in rats showed that, with judicious selection of the saturation pulse power, the amide-CEST at 3.6ppm and guanidyl-CEST signals at 2.0ppm changed in opposite directions with decreased pH. Thus, the difference between amide-CEST and guanidyl-CEST can enhance the pH measurement sensitivity, and is dubbed as pHenh. Acidification induced a negative contrast in APTw, but a positive contrast in pHenh. In vivo experiments showed that pHenh can detect hypercapnia-induced acidosis with about 3-times higher sensitivity than APTw. Also, pHenh slightly reduced gray and white matter contrast compared to APTw. In stroke animals, the CEST contrast between the ipsilateral ischemic core and contralateral normal tissue was -1.85 ± 0.42% for APTw and 3.04 ± 0.61% (n = 5) for pHenh, and the contrast to noise was 2.9 times higher for pHenh than APTw. Our results suggest that pHenh can be a useful tool for non-invasive pH-weighted imaging.
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Affiliation(s)
- Tao Jin
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States.
| | - Ping Wang
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States
| | - T Kevin Hitchens
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, United States
| | - 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
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44
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Kanazawa Y, Fushimi Y, Sakashita N, Okada T, Arakawa Y, Miyazaki M. B 1 Power Optimization for Chemical Exchange Saturation Transfer Imaging: A Phantom Study Using Egg White for Amide Proton Transfer Imaging Applications in the Human Brain. Magn Reson Med Sci 2017; 17:86-94. [PMID: 28566586 PMCID: PMC5760238 DOI: 10.2463/mrms.tn.2016-0069] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The chemical exchange saturation transfer (CEST) effect on an egg white (EW) suspension was investigated for optimization of magnetization transfer (MT) power (B1,rms) and pH dependency with the addition of lactic acid. Applying a higher MT pulse, B1,rms, Z-spectrum shows higher asymmetry and the magnetisation transfer ratio (MTR)asym signal increases to around 1–3.5 ppm, indicating a higher CEST effect. Amide proton transfer (APT) at 3.5 ppm shows a signal elevation in MTRasym with the application of higher B1,rms power and high pH. In addition, the hydroxyl proton signal in MTRasym increases as pH is reduced by lactic acid. In Z-spectrum of B1,rms at 1.0 μT and 2.0 μT, the dependence on CEST effect of amide proton and hydroxyl proton could be observed by using an EW suspension phantom. The CEST MT power was optimized on the EW suspension phantom with pH dependency and further confirmed on volunteers. In addition, APT imaging at 3.5 ppm using B1,rms at 1.0 μT performed on two human brains with different pathophysiological conditions indicated appropriate ATP effect.
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Affiliation(s)
- Yuki Kanazawa
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University.,Institute of Biomedical Sciences, Tokushima University Graduate School
| | - Yasutaka Fushimi
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University
| | | | - Tomohisa Okada
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University
| | - Yoshiki Arakawa
- Department of Neurosurgery, Kyoto University Graduate School of Medicine, Kyoto University
| | - Mitsue Miyazaki
- Toshiba Medical Systems Corporation.,Toshiba Medical Research Institute, 706 Deerpath Dr. Vernon Hills
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45
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Zheng Y, Wang XM. Measurement of Lactate Content and Amide Proton Transfer Values in the Basal Ganglia of a Neonatal Piglet Hypoxic-Ischemic Brain Injury Model Using MRI. AJNR Am J Neuroradiol 2017; 38:827-834. [PMID: 28154122 DOI: 10.3174/ajnr.a5066] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 11/06/2016] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE As amide proton transfer imaging is sensitive to protein content and intracellular pH, it has been widely used in the nervous system, including brain tumors and stroke. This work aimed to measure the lactate content and amide proton transfer values in the basal ganglia of a neonatal piglet hypoxic-ischemic brain injury model by using MR spectroscopy and amide proton transfer imaging. MATERIALS AND METHODS From 58 healthy neonatal piglets (3-5 days after birth; weight, 1-1.5 kg) selected initially, 9 piglets remained in the control group and 43 piglets, in the hypoxic-ischemic brain injury group. Single-section amide proton transfer imaging was performed at the coronal level of the basal ganglia. Amide proton transfer values of the bilateral basal ganglia were measured in all piglets. The ROI of MR spectroscopy imaging was the right basal ganglia, and the postprocessing was completed with LCModel software. RESULTS After hypoxic-ischemic insult, the amide proton transfer values immediately decreased, and at 0-2 hours, they remained at their lowest level. Thereafter, they gradually increased and finally exceeded those of the control group at 48-72 hours. After hypoxic-ischemic insult, the lactate content increased immediately, was maximal at 2-6 hours, and then gradually decreased to the level of the control group. The amide proton transfer values were negatively correlated with lactate content (r = -0.79, P < .05). CONCLUSIONS This observation suggests that after hypoxic-ischemic insult, the recovery of pH was faster than that of lactate homeostasis.
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Affiliation(s)
- Y Zheng
- From the Department of Radiology, Shengjing Hospital of China Medical University, Shenyang, PR China
| | - X-M Wang
- From the Department of Radiology, Shengjing Hospital of China Medical University, Shenyang, PR China.
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46
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Song G, Li C, Luo X, Zhao X, Zhang S, Zhang Y, Jiang S, Wang X, Chen Y, Chen H, Gong T, Zhou J, Chen M. Evolution of Cerebral Ischemia Assessed by Amide Proton Transfer-Weighted MRI. Front Neurol 2017; 8:67. [PMID: 28303115 PMCID: PMC5332413 DOI: 10.3389/fneur.2017.00067] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Accepted: 02/15/2017] [Indexed: 12/25/2022] Open
Abstract
Amide proton transfer-weighted (APTW) magnetic resonance imaging (MRI) has recently become a potentially important tool for evaluating acidosis in ischemic stroke. The purpose of this study was to evaluate the dynamic pH-related changes in the lesions in patients with ischemia. Thirty-nine patients with ischemic stroke (symptom onset to imaging time ranging 2 h–7 days) were examined with a 3.0-T MRI system. Patients were divided into four groups: at the hyperacute stage (onset time ≤ 6 h), at the acute stage (6 h < onset time ≤ 48 h), at the early subacute stage (48 h < onset time ≤ 96 h), and at the late subacute stage (96 h < onset time ≤ 168 h). The APTW signal intensities were quantitatively measured in multiple ischemic regions for each patient. Compared with the contralateral normal white matter, APTW signals were significantly lower in ischemic tissue for all four stages (P < 0.05). The APTW signal intensities (APTWave and APTWmin) increased consistently with onset time (R2 = 0.11, P = 0.040; R2 = 0.13, P = 0.022, respectively). APTWmax–min showed a continued reduction with onset time (R2 = 0.44, P < 0.001). Our results suggest that persistent tissue acidification could occur after ischemia, and as the time from stroke onset increases, the acidotic environment would alleviate. APTW signal intensities could reflect pH-weighted properties in ischemic tissue at different stages and time points.
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Affiliation(s)
- Guodong Song
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing, China; Graduate School of Peking Union Medical College, Beijing, China
| | - Chunmei Li
- Department of Radiology, Beijing Hospital, National Center of Gerontology , Beijing , China
| | - Xiaojie Luo
- Department of Radiology, Beijing Hospital, National Center of Gerontology , Beijing , China
| | - Xuna Zhao
- Department of Radiology, Johns Hopkins University , Baltimore, MD , USA
| | - Shuai Zhang
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing, China; Graduate School of Peking Union Medical College, Beijing, China
| | - Yi Zhang
- Department of Radiology, Johns Hopkins University , Baltimore, MD , USA
| | - Shanshan Jiang
- Department of Radiology, Johns Hopkins University , Baltimore, MD , USA
| | - Xianlong Wang
- Department of Radiology, Zhujiang Hospital of Southern Medical University , Guangzhou , China
| | - Yuhui Chen
- Department of Neurology, Beijing Hospital, National Center of Gerontology , Beijing , 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
- Department of Radiology, Johns Hopkins University , Baltimore, MD , USA
| | - Min Chen
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Beijing, China; Graduate School of Peking Union Medical College, Beijing, China
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47
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Khlebnikov V, Geades N, Klomp DWJ, Hoogduin H, Gowland P, Mougin O. Comparison of pulsed three-dimensional CEST acquisition schemes at 7 tesla: steady state versus pseudosteady state. Magn Reson Med 2016; 77:2280-2287. [PMID: 27455028 PMCID: PMC5484355 DOI: 10.1002/mrm.26323] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 05/31/2016] [Accepted: 06/05/2016] [Indexed: 01/15/2023]
Abstract
PURPOSE To compare two pulsed, volumetric chemical exchange saturation transfer (CEST) acquisition schemes: steady state (SS) and pseudosteady state (PS) for the same brain coverage, spatial/spectral resolution and scan time. METHODS Both schemes were optimized for maximum sensitivity to amide proton transfer (APT) and nuclear Overhauser enhancement (NOE) effects through Bloch-McConnell simulations, and compared in terms of sensitivity to APT and NOE effects, and to transmit field inhomogeneity. Five consented healthy volunteers were scanned on a 7 Tesla Philips MR-system using the optimized protocols at three nominal B1 amplitudes: 1 μT, 2 μT, and 3 μT. RESULTS Region of interest based analysis revealed that PS is more sensitive (P < 0.05) to APT and NOE effects compared with SS at low B1 amplitudes (0.7-1.0 μT). Also, both sequences have similar dependence on the transmit field inhomogeneity. For the optimum CEST presaturation parameters (1 μT and 2 μT for APT and NOE, respectively), NOE is less sensitive to the inhomogeneity effects (15% signal to noise ratio [SNR] change for a B1 dropout of 40%) compared with APT (35% SNR change for a B1 dropout of 40%). CONCLUSION For the same brain coverage, spatial/spectral resolution and scan time, at low power levels PS is more sensitive to the slow chemical exchange-mediated processes compared with SS. Magn Reson Med 77:2280-2287, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
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Affiliation(s)
- Vitaliy Khlebnikov
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Nicolas Geades
- Sir Peter Mansfield Imaging Center, School of Physics and Astronomy, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom
| | - Dennis W J Klomp
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Hans Hoogduin
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Penny Gowland
- Sir Peter Mansfield Imaging Center, School of Physics and Astronomy, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom
| | - Olivier Mougin
- Sir Peter Mansfield Imaging Center, School of Physics and Astronomy, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom
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48
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Guo Y, Zhou IY, Chan ST, Wang Y, Mandeville ET, Igarashi T, Lo EH, Ji X, Sun PZ. pH-sensitive MRI demarcates graded tissue acidification during acute stroke - pH specificity enhancement with magnetization transfer and relaxation-normalized amide proton transfer (APT) MRI. Neuroimage 2016; 141:242-249. [PMID: 27444569 DOI: 10.1016/j.neuroimage.2016.07.025] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 07/06/2016] [Accepted: 07/11/2016] [Indexed: 11/26/2022] Open
Abstract
pH-sensitive amide proton transfer (APT) MRI provides a surrogate metabolic biomarker that complements the widely-used perfusion and diffusion imaging. However, the endogenous APT MRI is often calculated using the asymmetry analysis (MTRasym), which is susceptible to an inhomogeneous shift due to concomitant semisolid magnetization transfer (MT) and nuclear overhauser (NOE) effects. Although the intact brain tissue has little pH variation, white and gray matter appears distinct in the MTRasym image. Herein we showed that the heterogeneous MTRasym shift not related to pH highly correlates with MT ratio (MTR) and longitudinal relaxation rate (R1w), which can be reasonably corrected using the multiple regression analysis. Because there are relatively small MT and R1w changes during acute stroke, we postulate that magnetization transfer and relaxation-normalized APT (MRAPT) analysis increases MRI specificity to acidosis over the routine MTRasym image, hence facilitates ischemic lesion segmentation. We found significant differences in perfusion, pH and diffusion lesion volumes (P<0.001, ANOVA). Furthermore, MRAPT MRI depicted graded ischemic acidosis, with the most severe acidosis in the diffusion lesion (-1.05±0.29%/s), moderate acidification within the pH/diffusion mismatch (i.e., metabolic penumbra, -0.67±0.27%/s) and little pH change in the perfusion/pH mismatch (i.e., benign oligemia, -0.04±0.14%/s), providing refined stratification of ischemic tissue injury.
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Affiliation(s)
- Yingkun Guo
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Iris Yuwen Zhou
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Suk-Tak Chan
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Yu Wang
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA; China-America Joint Neuroscience Institute, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Emiri T Mandeville
- Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Takahiro Igarashi
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Eng H Lo
- Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Xunming Ji
- China-America Joint Neuroscience Institute, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA; China-America Joint Neuroscience Institute, Xuanwu Hospital, Capital Medical University, Beijing, China; Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA.
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49
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Huang J, Zhang M, Lu J, Cai C, Chen L, Cai S. A fast chemical exchange saturation transfer imaging scheme based on single-shot spatiotemporal encoding. Magn Reson Med 2016; 77:1786-1796. [PMID: 27120691 DOI: 10.1002/mrm.26258] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 03/30/2016] [Accepted: 04/01/2016] [Indexed: 01/31/2023]
Abstract
PURPOSE To design a new approach that can not only keep the spatial and temporal resolution but also have better built-in immunity to magnetic field inhomogeneity and chemical shift effects than the single-shot echo planar imaging (EPI) for chemical exchange saturation transfer (CEST) MRI. METHOD The single-shot spatiotemporally encoded (SPEN) MRI sequence was combined with a continuous wave saturation pulse for fast CEST MRI (CEST-SPEN MRI). The resulting images were super-resolved reconstructed by a hybrid method that solves the l1 norm minimization together with total variation (TV) regularization. Partial Lorentzian fitting was used to analyze the subsequent Z-spectra. RESULTS Experimental results of a creatine phantom and in vivo tumor rat brains show that CEST-SPEN MRI has good capability in providing CEST-based and NOE-based contrast images. CONCLUSIONS Compared with CEST-EPI, CEST-SPEN MRI has better immunity to magnetic field inhomogeneity and provides better contrast images within identical acquisition time, especially under an identical inhomogeneous field. Magn Reson Med 77:1786-1796, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Jianpan Huang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Miao Zhang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Jianhua Lu
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China.,Meizhouwan Vocational Technology College, Putian, China
| | - Congbo Cai
- Department of Communication Engineering, Xiamen University, Xiamen, China
| | - Lin Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
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50
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Khlebnikov V, Polders D, Hendrikse J, Robe PA, Voormolen EH, Luijten PR, Klomp DWJ, Hoogduin H. Amide proton transfer (APT) imaging of brain tumors at 7 T: The role of tissue water T1-Relaxation properties. Magn Reson Med 2016; 77:1525-1532. [DOI: 10.1002/mrm.26232] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 12/12/2022]
Affiliation(s)
- Vitaliy Khlebnikov
- Department of Radiology, Image Sciences Institute; University Medical Center Utrecht; Utrecht the Netherlands
| | | | - Jeroen Hendrikse
- Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus; University Medical Center Utrecht; Utrecht The Netherlands
| | - Pierre A. Robe
- Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus; University Medical Center Utrecht; Utrecht The Netherlands
| | - Eduard H. Voormolen
- Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus; University Medical Center Utrecht; Utrecht The Netherlands
| | - Peter R. Luijten
- Department of Radiology, Image Sciences Institute; University Medical Center Utrecht; Utrecht the Netherlands
| | - Dennis W. J. Klomp
- Department of Radiology, Image Sciences Institute; University Medical Center Utrecht; Utrecht the Netherlands
| | - Hans Hoogduin
- Department of Radiology, Image Sciences Institute; University Medical Center Utrecht; Utrecht the Netherlands
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