51
|
Knutsson L, Xu J, Ahlgren A, van Zijl P. CEST, ASL, and magnetization transfer contrast: How similar pulse sequences detect different phenomena. Magn Reson Med 2018; 80:1320-1340. [PMID: 29845640 PMCID: PMC6097930 DOI: 10.1002/mrm.27341] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 04/10/2018] [Accepted: 04/11/2018] [Indexed: 12/28/2022]
Abstract
Chemical exchange saturation transfer (CEST), arterial spin labeling (ASL), and magnetization transfer contrast (MTC) methods generate different contrasts for MRI. However, they share many similarities in terms of pulse sequences and mechanistic principles. They all use RF pulse preparation schemes to label the longitudinal magnetization of certain proton pools and follow the delivery and transfer of this magnetic label to a water proton pool in a tissue region of interest, where it accumulates and can be detected using any imaging sequence. Due to the versatility of MRI, differences in spectral, spatial or motional selectivity of these schemes can be exploited to achieve pool specificity, such as for arterial water protons in ASL, protons on solute molecules in CEST, and protons on semi-solid cell structures in MTC. Timing of these sequences can be used to optimize for the rate of a particular delivery and/or exchange transfer process, for instance, between different tissue compartments (ASL) or between tissue molecules (CEST/MTC). In this review, magnetic labeling strategies for ASL and the corresponding CEST and MTC pulse sequences are compared, including continuous labeling, single-pulse labeling, and multi-pulse labeling. Insight into the similarities and differences among these techniques is important not only to comprehend the mechanisms and confounds of the contrasts they generate, but also to stimulate the development of new MRI techniques to improve these contrasts or to reduce their interference. This, in turn, should benefit many possible applications in the fields of physiological and molecular imaging and spectroscopy.
Collapse
Affiliation(s)
- L Knutsson
- Department of Medical Radiation Physics, Lund University, Lund, Sweden
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - J Xu
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States
| | - A Ahlgren
- Department of Medical Radiation Physics, Lund University, Lund, Sweden
| | - P.C.M van Zijl
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States
| |
Collapse
|
52
|
Quevedo A, Luo G, Galhardo E, Price M, Nicolucci P, Gore JC, Zu Z. Polymer gel dosimetry by nuclear Overhauser enhancement (NOE) magnetic resonance imaging. Phys Med Biol 2018; 63:15NT03. [PMID: 29978838 DOI: 10.1088/1361-6560/aad1bd] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The response to radiation of polymer gel dosimeters has previously been measured by magnetic resonance imaging (MRI) in terms of changes in the water transverse relaxation rate (R 2w) or magnetization transfer (MT) parameters. Here we report a new MRI approach, based on detecting nuclear Overhauser enhancement (NOE) mediated saturation transfer effects, which can also be used to detect radiation and measure dose distributions in MAGIC-f (Methacrylic and Ascorbic Acid and Gelatin Initiated by Copper Solution with formaldehyde) polymer gels. Results show that the NOE effects produced by low powered radiofrequency (RF) irradiation at specific frequencies offset from water may be quantified by appropriate measurements and over a useful range depend linearly on the radiation dose. The NOE effect likely arises from the polymerization of methacrylic acid monomers which become less mobile, facilitating dipolar through-space cross-relaxation and/or relayed magnetization exchange between polymer and water protons. Our study suggests a potential new MRI method for polymer gel dosimetry.
Collapse
Affiliation(s)
- Ana Quevedo
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States of America. University of Sao Paulo, Faculty of Phylosophy Sciences and Letter at Ribeirao Preto, Sao Paulo, Brazil
| | | | | | | | | | | | | |
Collapse
|
53
|
Goerke S, Breitling J, Zaiss M, Windschuh J, Kunz P, Schuenke P, Paech D, Longo DL, Klika KD, Ladd ME, Bachert P. Dual-frequency irradiation CEST-MRI of endogenous bulk mobile proteins. NMR IN BIOMEDICINE 2018; 31:e3920. [PMID: 29672976 DOI: 10.1002/nbm.3920] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 02/09/2018] [Accepted: 02/20/2018] [Indexed: 06/08/2023]
Abstract
A novel MRI contrast is proposed which enables the selective detection of endogenous bulk mobile proteins in vivo. Such a non-invasive imaging technique may be of particular interest for many diseases associated with pathological alterations of protein expression, such as cancer and neurodegenerative disorders. Specificity to mobile proteins was achieved by the selective measurement of intramolecular spin diffusion and the removal of semi-solid macromolecular signal components by a correction procedure. For this purpose, the approach of chemical exchange saturation transfer (CEST) was extended to a radiofrequency (RF) irradiation scheme at two different frequency offsets (dualCEST). Using protein model solutions, it was demonstrated that the dualCEST technique allows the calculation of an image contrast which is exclusively sensitive to changes in concentration, molecular size and the folding state of mobile proteins. With respect to application in humans, dualCEST overcomes the selectivity limitations at relatively low magnetic field strengths, and thus enables examinations on clinical MR scanners. The feasibility of dualCEST examinations in humans was verified by a proof-of-principle examination of a brain tumor patient at 3 T. With its specificity for the mobile fraction of the proteome, its comparable sensitivity to conventional water proton MRI and its applicability to clinical MR scanners, this technique represents a further step towards the non-invasive imaging of proteomic changes in humans.
Collapse
Affiliation(s)
- Steffen Goerke
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Johannes Breitling
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Moritz Zaiss
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Department of High-field Magnetic Resonance, Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany
| | - Johannes Windschuh
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Patrick Kunz
- Division of Functional Genome Analysis, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Patrick Schuenke
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Daniel Paech
- Department of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Dario L Longo
- Institute of Biostructure and Bioimaging (IBB), National Research Council (CNR), Torino, Italy
| | - Karel D Klika
- Molecular Structure Analysis, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Mark E Ladd
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Department of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany
- Faculty of Medicine, University of Heidelberg, Heidelberg, Germany
| | - Peter Bachert
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Department of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany
| |
Collapse
|
54
|
Gochberg DF, Does MD, Zu Z, Lankford CL. Towards an analytic solution for pulsed CEST. NMR IN BIOMEDICINE 2018; 31:e3903. [PMID: 29460973 PMCID: PMC5935132 DOI: 10.1002/nbm.3903] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 12/26/2017] [Accepted: 01/05/2018] [Indexed: 05/10/2023]
Abstract
Chemical exchange saturation transfer (CEST) is an imaging method based on magnetization exchange between solutes and water. This exchange generates changes in the measured signal after off-resonance radiofrequency irradiation. Although the analytic solution for CEST with continuous wave (CW) irradiation has been determined, most studies are performed using pulsed irradiation. In this work, we derive an analytic solution for the CEST signal after pulsed irradiation that includes both short-time rotation effects and long-time saturation effects in a two-pool system corresponding to water and a low-concentration exchanging solute pool. Several approximations are made to balance the accuracy and simplicity of the resulting analytic form, which is tested against numerical solutions of the coupled Bloch equations and is found to be largely accurate for amides at high fields, but less accurate at the higher exchange rates, lower offsets and typically higher irradiation powers of amines.
Collapse
Affiliation(s)
- Daniel F Gochberg
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
| | - Mark D Does
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
- Department of Electrical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Christopher L Lankford
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
| |
Collapse
|
55
|
Zaiss M, Ehses P, Scheffler K. Snapshot-CEST: Optimizing spiral-centric-reordered gradient echo acquisition for fast and robust 3D CEST MRI at 9.4 T. NMR IN BIOMEDICINE 2018; 31:e3879. [PMID: 29372571 DOI: 10.1002/nbm.3879] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 11/13/2017] [Accepted: 11/14/2017] [Indexed: 06/07/2023]
Abstract
Gradient echo (GRE)-based acquisition provides a robust readout method for chemical exchange saturation transfer (CEST) at ultrahigh field (UHF). To develop a snapshot-CEST approach, the transient GRE signal and point spread function were investigated in detail, leading to optimized measurement parameters and reordering schemes for fast and robust volumetric CEST imaging. Simulation of the transient GRE signal was used to determine the optimal sequence parameters and the maximum feasible number of k-space lines. Point spread function analysis provided an insight into the induced k-space filtering and the performance of different rectangular reordering schemes in terms of blurring, signal-to-noise ratio (SNR) and relaxation dependence. Simulation results were confirmed in magnetic resonance imaging (MRI) measurements of healthy subjects. Minimal repetition time (TR) is beneficial for snapshot-GRE readout. At 9.4 T, for TR = 4 ms and optimal flip angle close to the Ernst angle, a maximum of 562 k-space lines can be acquired after a single presaturation, providing decent SNR with high image quality. For spiral-centric reordered k-space acquisition, the image quality can be further improved using a rectangular spiral reordering scheme adjusted to the field of view. Application of the derived snapshot-CEST sequence for fast imaging acquisition in the human brain at 9.4 T shows excellent image quality in amide and nuclear Overhauser enhancement (NOE), and enables guanidyl CEST detection. The proposed snapshot-CEST establishes a fast and robust volumetric CEST approach ready for the imaging of known and novel exchange-weighted contrasts at UHF.
Collapse
Affiliation(s)
- Moritz Zaiss
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Philipp Ehses
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Klaus Scheffler
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Department of Biomedical Magnetic Resonance, Eberhard-Karls University Tübingen, Tübingen, Germany
| |
Collapse
|
56
|
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.
Collapse
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
| |
Collapse
|
57
|
Chen L, Xu X, Zeng H, Chan KWY, Yadav N, Cai S, Schunke KJ, Faraday N, van Zijl PCM, Xu J. Separating fast and slow exchange transfer and magnetization transfer using off-resonance variable-delay multiple-pulse (VDMP) MRI. Magn Reson Med 2018; 80:1568-1576. [PMID: 29405374 DOI: 10.1002/mrm.27111] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 01/03/2018] [Accepted: 01/08/2018] [Indexed: 12/12/2022]
Abstract
PURPOSE To develop a method that can separate and quantify the fast (>1 kHz) and slow exchange transfer and magnetization transfer components in Z-spectra. METHODS Z-spectra were recorded as a function of mixing time using a train of selective pulses providing variable-delay multipulse build-up curves. Fast and slow transfer components in the Z-spectra were separated and quantified on a voxel-by-voxel basis by fitting the mixing time-dependent CEST signal using a 3-pool model. RESULTS Phantom studies of glutamate solution, bovine serum albumin solution, and hair conditioner showed the capability of the proposed method to separate fast and slow transfer components. In vivo mouse brain studies showed a strong contrast between white matter and gray matter in the slow-transferring map, corresponding to an asymmetric component of the conventional semisolid magnetization transfer contrast. In addition, a fast-transferring proton map was found that was homogeneous across the brain and attributed to the total contributions of the fast-exchanging protons from proteins, metabolites, and a symmetric magnetization transfer contrast component. CONCLUSIONS This new method provides a simple way to extract fast and slow transfer components from the Z-spectrum, leading to novel MRI contrasts, and providing insight into the different magnetization transfer contrast contributions.
Collapse
Affiliation(s)
- Lin Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China.,Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Xiang Xu
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Haifeng Zeng
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Kannie W Y Chan
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA.,Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Nirbhay Yadav
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Kathryn J Schunke
- Department of Anesthesiology/Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Nauder Faraday
- Department of Anesthesiology/Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Peter C M van Zijl
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Jiadi Xu
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| |
Collapse
|
58
|
Discriminating MGMT promoter methylation status in patients with glioblastoma employing amide proton transfer-weighted MRI metrics. Eur Radiol 2017; 28:2115-2123. [PMID: 29234914 DOI: 10.1007/s00330-017-5182-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 10/30/2017] [Accepted: 11/06/2017] [Indexed: 02/07/2023]
Abstract
OBJECTIVES To explore the feasibility of using amide proton transfer-weighted (APTw) MRI metrics as surrogate biomarkers to identify the O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status in glioblastoma (GBM). METHODS Eighteen newly diagnosed GBM patients, who were previously scanned at 3T and had a confirmed MGMT methylation status, were retrospectively analysed. For each case, a histogram analysis in the tumour mass was performed to evaluate several quantitative APTw MRI metrics. The Mann-Whitney test was used to evaluate the difference in APTw parameters between MGMT methylated and unmethylated GBMs, and the receiver-operator-characteristic analysis was further used to assess diagnostic performance. RESULTS Ten GBMs were found to harbour a methylated MGMT promoter, and eight GBMs were unmethylated. The mean, variance, 50th percentile, 90th percentile and Width10-90 APTw values were significantly higher in the MGMT unmethylated GBMs than in the MGMT methylated GBMs, with areas under the receiver-operator-characteristic curves of 0.825, 0.837, 0.850, 0856 and 0.763, respectively, for the discrimination of MGMT promoter methylation status. CONCLUSIONS APTw signal metrics have the potential to serve as valuable imaging biomarkers for identifying MGMT methylation status in the GBM population. KEY POINTS • APTw-MRI is applied to predict MGMT promoter methylation status in GBMs. • GBMs with unmethylated MGMT promoter present higher APTw-MRI than methylated GBMs. • Multiple APTw histogram metrics can identify MGMT methylation status. • Mean APTw values showed the highest diagnostic accuracy (AUC = 0.825).
Collapse
|
59
|
Chen L, Zeng H, Xu X, Yadav NN, Cai S, Puts NA, Barker PB, Li T, Weiss RG, van Zijl PCM, Xu J. Investigation of the contribution of total creatine to the CEST Z-spectrum of brain using a knockout mouse model. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3834. [PMID: 28961344 PMCID: PMC5685917 DOI: 10.1002/nbm.3834] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 08/25/2017] [Accepted: 08/26/2017] [Indexed: 05/08/2023]
Abstract
The current study aims to assign and estimate the total creatine (tCr) signal contribution to the Z-spectrum in mouse brain at 11.7 T. Creatine (Cr), phosphocreatine (PCr) and protein phantoms were used to confirm the presence of a guanidinium resonance at this field strength. Wild-type (WT) and knockout mice with guanidinoacetate N-methyltransferase deficiency (GAMT-/-), which have low Cr and PCr concentrations in the brain, were used to assign the tCr contribution to the Z-spectrum. To estimate the total guanidinium concentrations, two pools for the Z-spectrum around 2 ppm were assumed: (i) a Lorentzian function representing the guanidinium chemical exchange saturation transfer (CEST) at 1.95 ppm in the 11.7-T Z-spectrum; and (ii) a background signal that can be fitted by a polynomial function. Comparison between the WT and GAMT-/- mice provided strong evidence for three types of contribution to the peak in the Z-spectrum at 1.95 ppm, namely proteins, Cr and PCr, the latter fitted as tCr. A ratio of 20 ± 7% (protein) and 80 ± 7% tCr was found in brain at 2 μT and 2 s saturation. Based on phantom experiments, the tCr peak was estimated to consist of about 83 ± 5% Cr and 17 ± 5% PCr. Maps for tCr of mouse brain were generated based on the peak at 1.95 ppm after concentration calibration with in vivo magnetic resonance spectroscopy.
Collapse
Affiliation(s)
- Lin Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
| | - Haifeng Zeng
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
| | - Xiang Xu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
| | - Nirbhay N. Yadav
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Nicolaas A. Puts
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
| | - Peter B. Barker
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
| | - Tong Li
- Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Robert G. Weiss
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Peter C. M. van Zijl
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
| | - Jiadi Xu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA
- Corresponding Author: Jiadi Xu, Ph.D. Kennedy Krieger Institute, Johns Hopkins University School of Medicine, 707 N. Broadway, Baltimore, MD, 21205, , Tel: 443-923-9572, Fax: 443-923-9505
| |
Collapse
|
60
|
Zu Z, Louie EA, Lin EC, Jiang X, Does MD, Gore JC, Gochberg DF. Chemical exchange rotation transfer imaging of intermediate-exchanging amines at 2 ppm. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3756. [PMID: 28590070 PMCID: PMC5597471 DOI: 10.1002/nbm.3756] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/10/2017] [Accepted: 05/11/2017] [Indexed: 05/08/2023]
Abstract
Chemical exchange saturation transfer (CEST) imaging of amine protons exchanging at intermediate rates and whose chemical shift is around 2 ppm may provide a means of mapping creatine. However, the quantification of this effect may be compromised by the influence of overlapping CEST signals from fast-exchanging amines and hydroxyls. We aimed to investigate the exchange rate filtering effect of a variation of CEST, named chemical exchange rotation transfer (CERT), as a means of isolating creatine contributions at around 2 ppm from other overlapping signals. Simulations were performed to study the filtering effects of CERT for the selection of transfer effects from protons of specific exchange rates. Control samples containing the main metabolites in brain, bovine serum albumin (BSA) and egg white albumen (EWA) at their physiological concentrations and pH were used to study the ability of CERT to isolate molecules with amines at 2 ppm that exchange at intermediate rates, and corresponding methods were used for in vivo rat brain imaging. Simulations showed that exchange rate filtering can be combined with conventional filtering based on chemical shift. Studies on samples showed that signal contributions from creatine can be separated from those of other metabolites using this combined filter, but contributions from protein amines may still be significant. This exchange filtering can also be used for in vivo imaging. CERT provides more specific quantification of amines at 2 ppm that exchange at intermediate rates compared with conventional CEST imaging.
Collapse
Affiliation(s)
- Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Elizabeth A. Louie
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Eugene C. Lin
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Xiaoyu Jiang
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Mark D. Does
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
| | - John C. Gore
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
| | - Daniel F. Gochberg
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, TN
| |
Collapse
|
61
|
Jones KM, Pollard AC, Pagel MD. Clinical applications of chemical exchange saturation transfer (CEST) MRI. J Magn Reson Imaging 2017; 47:11-27. [PMID: 28792646 DOI: 10.1002/jmri.25838] [Citation(s) in RCA: 184] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2017] [Accepted: 05/30/2017] [Indexed: 02/06/2023] Open
Abstract
Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) has been developed and employed in multiple clinical imaging research centers worldwide. Selective radiofrequency (RF) saturation pulses with standard 2D and 3D MRI acquisition schemes are now routinely performed, and CEST MRI can produce semiquantitative results using magnetization transfer ratio asymmetry (MTRasym ) analysis while accounting for B0 inhomogeneity. Faster clinical CEST MRI acquisition methods and more quantitative acquisition and analysis routines are under development. Endogenous biomolecules with amide, amine, and hydroxyl groups have been detected during clinical CEST MRI studies, and exogenous CEST agents have also been administered to patients. These CEST MRI tools show promise for contributing to assessments of cerebral ischemia, neurological disorders, lymphedema, osteoarthritis, muscle physiology, and solid tumors. This review summarizes the salient features of clinical CEST MRI protocols and critically evaluates the utility of CEST MRI for these clinical imaging applications. LEVEL OF EVIDENCE 5 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:11-27.
Collapse
Affiliation(s)
- Kyle M Jones
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona, USA
| | | | - Mark D Pagel
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona, USA.,Department of Chemistry, Rice University, Houston, Texas, USA.,Department of Cancer Systems Imaging, MD Anderson Cancer Center, Houston, Texas, USA
| |
Collapse
|
62
|
Jiang S, Zou T, Eberhart CG, Villalobos MAV, Heo HY, Zhang Y, Wang Y, Wang X, Yu H, Du Y, van Zijl PCM, Wen Z, Zhou J. Predicting IDH mutation status in grade II gliomas using amide proton transfer-weighted (APTw) MRI. Magn Reson Med 2017; 78:1100-1109. [PMID: 28714279 DOI: 10.1002/mrm.26820] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 05/31/2017] [Accepted: 06/11/2017] [Indexed: 12/24/2022]
Abstract
PURPOSE To assess the amide proton transfer-weighted (APTw) MRI features of isocitrate dehydrogenase (IDH)-wildtype and IDH-mutant grade II gliomas and to test the hypothesis that the APTw signal is a surrogate imaging marker for identifying IDH mutation status preoperatively. METHODS Twenty-seven patients with pathologically confirmed low-grade glioma, who were previously scanned at 3T, were retrospectively analyzed. The Mann-Whitney test was used to evaluate relationships between APTw intensities for IDH-mutant and IDH-wildtype groups, and receiver operator characteristic (ROC) analysis was used to assess the diagnostic performance of APTw. RESULTS Based on histopathology and molecular analysis, seven cases were diagnosed as IDH-wildtype grade II gliomas and 20 cases as IDH-mutant grade II gliomas. The maximum and minimum APTw values, based on multiple regions of interest, as well as the whole-tumor histogram-based mean and 50th percentile APTw values, were significantly higher in the IDH-wildtype gliomas than in the IDH-mutant groups. This corresponded to the areas under the ROC curves of 0.89, 0.76, 0.75, and 0.75, respectively, for the prediction of the IDH mutation status. CONCLUSION IDH-wildtype lesions typically were associated with relatively high APTw signal intensities as compared with IDH-mutant lesions. The APTw signal could be a valuable imaging biomarker by which to identify IDH1 mutation status in grade II gliomas. Magn Reson Med 78:1100-1109, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
Collapse
Affiliation(s)
- Shanshan Jiang
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China.,Department of Radiology, Futian Traditional Chinese Medicine Hospital, Shenzhen, Guangdong, China
| | - Tianyu Zou
- Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Charles G Eberhart
- Department of Pathology, Johns Hopkins University, Baltimore, Maryland, USA
| | | | - Hye-Young Heo
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Yi Zhang
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Yu Wang
- Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Xianlong Wang
- Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Hao Yu
- Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Yongxing Du
- Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - 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
| | - Zhibo Wen
- Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - 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
| |
Collapse
|
63
|
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.
Collapse
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.
| |
Collapse
|
64
|
Zhang XY, Wang F, Li H, Xu J, Gochberg DF, Gore JC, Zu Z. Accuracy in the quantification of chemical exchange saturation transfer (CEST) and relayed nuclear Overhauser enhancement (rNOE) saturation transfer effects. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3716. [PMID: 28272761 PMCID: PMC5490367 DOI: 10.1002/nbm.3716] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 01/26/2017] [Accepted: 02/01/2017] [Indexed: 05/08/2023]
Abstract
Accurate quantification of chemical exchange saturation transfer (CEST) effects, including dipole-dipole mediated relayed nuclear Overhauser enhancement (rNOE) saturation transfer, is important for applications and studies of molecular concentration and transfer rate (and thereby pH or temperature). Although several quantification methods, such as Lorentzian difference (LD) analysis, multiple-pool Lorentzian fits, and the three-point method, have been extensively used in several preclinical and clinical applications, the accuracy of these methods has not been evaluated. Here we simulated multiple-pool Z spectra containing the pools that contribute to the main CEST and rNOE saturation transfer signals in the brain, numerically fit them using the different methods, and then compared their derived CEST metrics with the known solute concentrations and exchange rates. Our results show that the LD analysis overestimates contributions from amide proton transfer (APT) and intermediate exchanging amine protons; the three-point method significantly underestimates both APT and rNOE saturation transfer at -3.5 ppm (NOE(-3.5)). The multiple-pool Lorentzian fit is more accurate than the other two methods, but only at lower irradiation powers (≤1 μT at 9.4 T) within the range of our simulations. At higher irradiation powers, this method is also inaccurate because of the presence of a fast exchanging CEST signal that has a non-Lorentzian lineshape. Quantitative parameters derived from in vivo images of rodent brain tumor obtained using an irradiation power of 1 μT were also compared. Our results demonstrate that all three quantification methods show similar contrasts between tumor and contralateral normal tissue for both APT and the NOE(-3.5). However, the quantified values of the three methods are significantly different. Our work provides insight into the fitting accuracy obtainable in a complex tissue model and provides guidelines for evaluating other newly developed quantification methods.
Collapse
Affiliation(s)
- Xiao-Yong Zhang
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Feng Wang
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, 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
| | - Junzhong Xu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Daniel F. Gochberg
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biomedical Engineering, 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
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|
65
|
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.
Collapse
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
| |
Collapse
|
66
|
Zu Z, Li H, Xu J, Zhang XY, Zaiss M, Li K, Does MD, Gore JC, Gochberg DF. Measurement of APT using a combined CERT-AREX approach with varying duty cycles. Magn Reson Imaging 2017; 42:22-31. [PMID: 28526431 DOI: 10.1016/j.mri.2017.05.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Revised: 05/12/2017] [Accepted: 05/16/2017] [Indexed: 12/14/2022]
Abstract
The goal is to develop an imaging method where contrast reflects amide-water magnetization exchange, with minimal signal contributions from other sources. Conventional chemical exchange saturation transfer (CEST) imaging of amides (often called amide proton transfer, or APT, and quantified by the metric MTRasym) is confounded by several factors unrelated to amides, such as aliphatic protons, water relaxation, and macromolecular magnetization transfer. In this work, we examined the effects of combining our previous chemical exchange rotation (CERT) approach with the non-linear AREX method while using different duty cycles (DC) for the label and reference scans. The dependencies of this approach, named AREXdouble,vdc, on tissue parameters, including T1, T2, semi-solid component concentration (fm), relayed nuclear Overhauser enhancement (rNOE), and nearby amines, were studied through numerical simulations and control sample experiments at 9.4T and 1μT irradiation. Simulations and experiments show that AREXdouble,vdc is sensitive to amide-water exchange effects, but is relatively insensitive to T1, T2, fm, nearby amine, and distant aliphatic protons, while the conventional metric MTRasym, as well as several other APT imaging methods, are significantly affected by at least some of these confounding factors.
Collapse
Affiliation(s)
- Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States.
| | - Hua Li
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States
| | - Junzhong Xu
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States
| | - Xiao-Yong Zhang
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States
| | - Moritz Zaiss
- Department of Medical Physics in Radiology, German Cancer Research Center, Germany
| | - Ke Li
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States
| | - Mark D Does
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States
| | - John C Gore
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States; Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, United States
| | - Daniel F Gochberg
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States
| |
Collapse
|
67
|
Khlebnikov V, Windschuh J, Siero JC, Zaiss M, Luijten PR, Klomp DW, Hoogduin H. On the transmit field inhomogeneity correction of relaxation-compensated amide and NOE CEST effects at 7 T. NMR IN BIOMEDICINE 2017; 30:e3687. [PMID: 28111824 PMCID: PMC5412922 DOI: 10.1002/nbm.3687] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 11/22/2016] [Accepted: 11/22/2016] [Indexed: 05/08/2023]
Abstract
High field MRI is beneficial for chemical exchange saturation transfer (CEST) in terms of high SNR, CNR, and chemical shift dispersion. These advantages may, however, be counter-balanced by the increased transmit field inhomogeneity normally associated with high field MRI. The relatively high sensitivity of the CEST contrast to B1 inhomogeneity necessitates the development of correction methods, which is essential for the clinical translation of CEST. In this work, two B1 correction algorithms for the most studied CEST effects, amide-CEST and nuclear Overhauser enhancement (NOE), were analyzed. Both methods rely on fitting the multi-pool Bloch-McConnell equations to the densely sampled CEST spectra. In the first method, the correction is achieved by using a linear B1 correction of the calculated amide and NOE CEST effects. The second method uses the Bloch-McConnell fit parameters and the desired B1 amplitude to recalculate the CEST spectra, followed by the calculation of B1 -corrected amide and NOE CEST effects. Both algorithms were systematically studied in Bloch-McConnell equations and in human data, and compared with the earlier proposed ideal interpolation-based B1 correction method. In the low B1 regime of 0.15-0.50 μT (average power), a simple linear model was sufficient to mitigate B1 inhomogeneity effects on a par with the interpolation B1 correction, as demonstrated by a reduced correlation of the CEST contrast with B1 in both the simulations and the experiments.
Collapse
Affiliation(s)
- Vitaliy Khlebnikov
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Johannes Windschuh
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center]HeidelbergGermany
| | - Jeroen C.W. Siero
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
- Spinoza Centre for NeuroimagingAmsterdamThe Netherlands
| | - Moritz Zaiss
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center]HeidelbergGermany
| | - Peter R. Luijten
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Dennis W.J. Klomp
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Hans Hoogduin
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| |
Collapse
|
68
|
van Zijl PCM, Lam WW, Xu J, Knutsson L, Stanisz GJ. Magnetization Transfer Contrast and Chemical Exchange Saturation Transfer MRI. Features and analysis of the field-dependent saturation spectrum. Neuroimage 2017; 168:222-241. [PMID: 28435103 DOI: 10.1016/j.neuroimage.2017.04.045] [Citation(s) in RCA: 206] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 04/18/2017] [Accepted: 04/19/2017] [Indexed: 11/30/2022] Open
Abstract
Magnetization Transfer Contrast (MTC) and Chemical Exchange Saturation Transfer (CEST) experiments measure the transfer of magnetization from molecular protons to the solvent water protons, an effect that becomes apparent as an MRI signal loss ("saturation"). This allows molecular information to be accessed with the enhanced sensitivity of MRI. In analogy to Magnetic Resonance Spectroscopy (MRS), these saturation data are presented as a function of the chemical shift of participating proton groups, e.g. OH, NH, NH2, which is called a Z-spectrum. In tissue, these Z-spectra contain the convolution of multiple saturation transfer effects, including nuclear Overhauser enhancements (NOEs) and chemical exchange contributions from protons in semi-solid and mobile macromolecules or tissue metabolites. As a consequence, their appearance depends on the magnetic field strength (B0) and pulse sequence parameters such as B1 strength, pulse shape and length, and interpulse delay, which presents a major problem for quantification and reproducibility of MTC and CEST effects. The use of higher B0 can bring several advantages. In addition to higher detection sensitivity (signal-to-noise ratio, SNR), both MTC and CEST studies benefit from longer water T1 allowing the saturation transferred to water to be retained longer. While MTC studies are non-specific at any field strength, CEST specificity is expected to increase at higher field because of a larger chemical shift dispersion of the resonances of interest (similar to MRS). In addition, shifting to a slower exchange regime at higher B0 facilitates improved detection of the guanidinium protons of creatine and the inherently broad resonances of the amine protons in glutamate and the hydroxyl protons in myoinositol, glycogen, and glucosaminoglycans. Finally, due to the higher mobility of the contributing protons in CEST versus MTC, many new pulse sequences can be designed to more specifically edit for CEST signals and to remove MTC contributions.
Collapse
Affiliation(s)
- Peter C M van Zijl
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.
| | - Wilfred W Lam
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Jiadi Xu
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Linda Knutsson
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Medical Radiation Physics, Lund University, Lund, Sweden
| | - Greg J Stanisz
- Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada; Department of Neurosurgery and Pediatric Neurosurgery, Medical University of Lublin, Lublin, Poland.
| |
Collapse
|
69
|
Wang Y, Zhang Y, Zhao X, Wu B, Gao JH. Perturbation of longitudinal relaxation rate in rotating frame (PLRF) analysis for quantification of chemical exchange saturation transfer signal in a transient state. Magn Reson Med 2016; 78:1711-1723. [PMID: 27888530 DOI: 10.1002/mrm.26559] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 10/03/2016] [Accepted: 10/29/2016] [Indexed: 11/06/2022]
Abstract
PURPOSE To develop a novel analytical method for quantification of chemical exchange saturation transfer (CEST) in the transient state. The proposed method aims to reduce the effects of non-chemical-exchange (non-CE) parameters on the CEST signal, emphasizing the effect of chemical exchange. METHODS The difference in the longitudinal relaxation rate in the rotating frame ( ΔR1ρ) was calculated based on perturbation of the Z-value by R1ρ, and a saturation-pulse-amplitude-compensated exchange-dependent relaxation rate (SPACER) was determined with a high-exchange-rate approximation. In both phantom and human subject experiments, MTRasym (representative of the traditional CEST index), ΔR1ρ, and SPACER were measured, evaluated, and compared by altering the non-CE parameters in a transient-state continuous-wave CEST sequence. RESULTS In line with the theoretical expectation, our experimental data demonstrate that the effects of the non-CE parameters can be more effectively reduced using the proposed indices ( ΔR1ρ and SPACER) than using the traditional CEST index ( MTRasym). CONCLUSION The proposed method allows for the chemical exchange weight to be better emphasized in the transient-state CEST signal, which is beneficial, in practice, for quantifying the CEST signal. Magn Reson Med 78:1711-1723, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
Collapse
Affiliation(s)
- Yi Wang
- Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.,Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Yaoyu Zhang
- Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.,Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Xuna Zhao
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Bing Wu
- GE Healthcare China, Beijing, China
| | - Jia-Hong Gao
- Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.,Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.,McGovern Institute for Brain Research, Peking University, Beijing, China
| |
Collapse
|
70
|
Zhang H, Kang H, Zhao X, Jiang S, Zhang Y, Zhou J, Peng Y. Amide Proton Transfer (APT) MR imaging and Magnetization Transfer (MT) MR imaging of pediatric brain development. Eur Radiol 2016; 26:3368-76. [PMID: 26762941 PMCID: PMC5747245 DOI: 10.1007/s00330-015-4188-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 12/03/2015] [Accepted: 12/21/2015] [Indexed: 10/22/2022]
Abstract
OBJECTIVES To quantify the brain maturation process during childhood using combined amide proton transfer (APT) and conventional magnetization transfer (MT) imaging at 3 Tesla. METHODS Eighty-two neurodevelopmentally normal children (44 males and 38 females; age range, 2-190 months) were imaged using an APT/MT imaging protocol with multiple saturation frequency offsets. The APT-weighted (APTW) and MT ratio (MTR) signals were quantitatively analyzed in multiple brain areas. Age-related changes in MTR and APTW were evaluated with a non-linear regression analysis. RESULTS The APTW signals followed a decreasing exponential curve with age in all brain regions measured (R(2) = 0.7-0.8 for the corpus callosum, frontal and occipital white matter, and centrum semiovale). The most significant changes appeared within the first year. At maturation, larger decreases in APTW and lower APTW values were found in the white matter. On the contrary, the MTR signals followed an increasing exponential curve with age in the same brain regions measured, with the most significant changes appearing within the initial 2 years. There was an inverse correlation between the MTR and APTW signal intensities during brain maturation. CONCLUSIONS Together with MT imaging, protein-based APT imaging can provide additional information in assessing brain myelination in the paediatric population. KEY POINTS • APTW signals followed a decreasing exponential curve with age. • The most significant APTW changes appeared within the first year • At maturation, larger APTW decreases and lower APTW appeared in white matter • MTR signals followed an increasing exponential curve with age.
Collapse
Affiliation(s)
- Hong Zhang
- Imaging Center, Department of Radiology, Beijing Children's Hospital, Capital Medical University, Beijing, China
| | - Huiying Kang
- Imaging Center, Department of Radiology, Beijing Children's Hospital, Capital Medical University, Beijing, China
| | | | - Shanshan Jiang
- Division of MR Research, Department of Radiology, Johns Hopkins University, 600 N. Wolfe Street, Park 336, Baltimore, MD, 21287, USA
| | - Yi Zhang
- Division of MR Research, Department of Radiology, Johns Hopkins University, 600 N. Wolfe Street, Park 336, Baltimore, MD, 21287, USA
| | - Jinyuan Zhou
- Division of MR Research, Department of Radiology, Johns Hopkins University, 600 N. Wolfe Street, Park 336, Baltimore, MD, 21287, USA.
| | - Yun Peng
- Imaging Center, Department of Radiology, Beijing Children's Hospital, Capital Medical University, Beijing, China.
| |
Collapse
|
71
|
Zaiss M, Windschuh J, Goerke S, Paech D, Meissner J, Burth S, Kickingereder P, Wick W, Bendszus M, Schlemmer H, Ladd ME, Bachert P, Radbruch A. Downfield‐NOE‐suppressed amide‐CEST‐MRI at 7 Tesla provides a unique contrast in human glioblastoma. Magn Reson Med 2016; 77:196-208. [DOI: 10.1002/mrm.26100] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 12/04/2015] [Accepted: 12/06/2015] [Indexed: 01/12/2023]
Affiliation(s)
- Moritz Zaiss
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
| | - Johannes Windschuh
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
| | - Steffen Goerke
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
| | - Daniel Paech
- Department of NeuroradiologyUniversity of Heidelberg Medical CenterHeidelberg Germany
- Department of RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
| | - Jan‐Eric Meissner
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
- Department of RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
| | - Sina Burth
- Department of NeuroradiologyUniversity of Heidelberg Medical CenterHeidelberg Germany
- Department of RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
| | - Philipp Kickingereder
- Department of NeuroradiologyUniversity of Heidelberg Medical CenterHeidelberg Germany
| | - Wolfgang Wick
- University of Heidelberg Neurology ClinicHeidelberg Germany
- Clinical Cooperation Unit Neuro‐oncologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg
| | - Martin Bendszus
- Department of NeuroradiologyUniversity of Heidelberg Medical CenterHeidelberg Germany
| | | | - Mark E. Ladd
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
| | - Peter Bachert
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
| | - Alexander Radbruch
- Department of NeuroradiologyUniversity of Heidelberg Medical CenterHeidelberg Germany
- Department of RadiologyDeutsches Krebsforschungszentrum (DKFZ)Heidelberg Germany
| |
Collapse
|
72
|
Ma B, Blakeley JO, Hong X, Zhang H, Jiang S, Blair L, Zhang Y, Heo HY, Zhang M, van Zijl PCM, Zhou J. Applying amide proton transfer-weighted MRI to distinguish pseudoprogression from true progression in malignant gliomas. J Magn Reson Imaging 2016; 44:456-62. [PMID: 26788865 DOI: 10.1002/jmri.25159] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Accepted: 01/04/2016] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To assess amide proton transfer-weighted (APTW) imaging features in patients with malignant gliomas after chemoradiation and the diagnostic performance of APT imaging for distinguishing true progression from pseudoprogression. MATERIALS AND METHODS After approval by the Institutional Review Board, 32 patients with clinically suspected tumor progression in the first 3 months after chemoradiation were enrolled and scanned at 3T. Longitudinal routine magnetic resonance imaging (MRI) changes and medical records were assessed to confirm true progression versus pseudoprogression. True progression was defined as lesions progressing on serial imaging over 6 months, and pseudoprogression was defined as lesions stabilizing or regressing without intervention. The APTWmean and APTWmax signals were obtained from three to five regions of interests for each patient and compared between the true progression and pseudoprogression groups. The diagnostic performance was assessed with receiver operating characteristic curve analysis. RESULTS The true progression was associated with APTW hyperintensity (APTWmean = 2.75% ± 0.42%), while pseudoprogression was associated with APTW isointensity to mild hyperintensity (APTWmean = 1.56% ± 0.42%). The APTW signal intensities were significantly higher in the true progression group (n = 20) than in the pseudoprogression group (P < 0.001; n = 12). The cutoff APTWmean and APTWmax intensity values to distinguish between true progression and pseudoprogression were 2.42% (with a sensitivity of 85.0% and a specificity of 100%) and 2.54% (with a sensitivity of 95.0% and a specificity of 91.7%), respectively. CONCLUSION The APTW-MRI signal is a valuable imaging biomarker for distinguishing pseudoprogression from true progression in glioma patients. J. Magn. Reson. Imaging 2016;44:456-462.
Collapse
Affiliation(s)
- Bo Ma
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,Department of Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, PR China.,Department of Radiology, Henan Provincial People's Hospital, Zhengzhou, Henan, PR China
| | - Jaishri O Blakeley
- Department of Neurology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Xiaohua Hong
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Hongyan Zhang
- Department of Pathology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Shanshan Jiang
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Lindsay Blair
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,Department of Neurology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Yi Zhang
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Hye-Young Heo
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Mingzhi Zhang
- Department of Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, PR China
| | - Peter C M van Zijl
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| | - Jinyuan Zhou
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| |
Collapse
|
73
|
Prevost VH, Girard OM, Varma G, Alsop DC, Duhamel G. Minimizing the effects of magnetization transfer asymmetry on inhomogeneous magnetization transfer (ihMT) at ultra-high magnetic field (11.75 T). MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2016; 29:699-709. [PMID: 26762244 DOI: 10.1007/s10334-015-0523-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 12/29/2015] [Accepted: 12/30/2015] [Indexed: 11/30/2022]
Abstract
OBJECTIVES The recently reported inhomogeneous magnetization transfer technique (ihMT) has been proposed for specific imaging of inhomogeneously broadened lines, and has shown great promise for characterizing myelinated tissues. The ihMT contrast is obtained by subtracting magnetization transfer images obtained with simultaneous saturation at positive and negative frequency offsets (dual frequency saturation experiment, MT (+/-)) from those obtained with single frequency saturation (MT (+)) at the same total power. Hence, ihMT may be biased by MT-asymmetry, especially at ultra-high magnetic field. Use of the average of single positive and negative frequency offset saturation MT images, i.e., (MT (+)+MT (-)) has been proposed to correct the ihMT signal from MT-asymmetry signal. MATERIALS AND METHODS The efficiency of this correction method was experimentally assessed in this study, performed at 11.75 T on mice. Quantitative corrected ihMT and MT-asymmetry ratios (ihMTR and MTRasym) were measured in mouse brain structures for several MT-asymmetry magnitudes and different saturation parameter sets. RESULTS Our results indicated a "safe" range of magnitudes (/MTRasym/<4 %) for which MT-asymmetry signal did not bias the corrected ihMT signal. Moreover, experimental evidence of the different natures of both MT-asymmetry and inhomogeneous MT contrasts were provided. In particular, non-zero ihMT ratios were obtained at zero MTRasym values. CONCLUSION MTRasym is not a confounding factor for ihMT quantification, even at ultra-high field, as long as MTRasym is restricted to ±4 %.
Collapse
Affiliation(s)
- Valentin H Prevost
- Centre de Résonance Magnétique Biologique et Médicale, CRMBM-CEMEREM, UMR 7339, CNRS, Faculté de Médecine, Aix-Marseille Université (AMU), 27 Boulevard Jean Moulin, 13005, Marseille, France
| | - Olivier M Girard
- Centre de Résonance Magnétique Biologique et Médicale, CRMBM-CEMEREM, UMR 7339, CNRS, Faculté de Médecine, Aix-Marseille Université (AMU), 27 Boulevard Jean Moulin, 13005, Marseille, France
| | - Gopal Varma
- Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - David C Alsop
- Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Guillaume Duhamel
- Centre de Résonance Magnétique Biologique et Médicale, CRMBM-CEMEREM, UMR 7339, CNRS, Faculté de Médecine, Aix-Marseille Université (AMU), 27 Boulevard Jean Moulin, 13005, Marseille, France.
| |
Collapse
|
74
|
Li H, Li K, Zhang XY, Jiang X, Zu Z, Zaiss M, Gochberg DF, Gore JC, Xu J. R1 correction in amide proton transfer imaging: indication of the influence of transcytolemmal water exchange on CEST measurements. NMR IN BIOMEDICINE 2015; 28:1655-62. [PMID: 26466161 PMCID: PMC4715641 DOI: 10.1002/nbm.3428] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 08/26/2015] [Accepted: 09/11/2015] [Indexed: 05/08/2023]
Abstract
Amide proton transfer (APT) imaging may potentially detect mobile proteins/peptides non-invasively in vivo, but its specificity may be reduced by contamination from other confounding effects such as asymmetry of non-specific magnetization transfer (MT) effects and spin-lattice relaxation with rate R1 (=1/T1). Previously reported spillover, MT and R1 correction methods were based on a two-pool model, in which the existence of multiple water compartments with heterogeneous relaxation properties in real tissues was ignored. Such simple models may not adequately represent real tissues, and thus such corrections may be unreliable. The current study investigated the effectiveness and accuracy of correcting for R1 in APT imaging via simulations and in vivo experiments using tumor-bearing rats subjected to serial injections of Gd-DTPA that produced different tissue R1 values in regions of blood-brain-barrier breakdown. The results suggest that conventional measurements of APT contrast (such as APT* and MTRasym ) may be significantly contaminated by R1 variations, while the R1 -corrected metric AREX* was found to be relatively unaffected by R1 changes over a broad range (0.4-1 Hz). Our results confirm the importance of correcting for spin-lattice relaxation effects in quantitative APT imaging, and demonstrate the reliability of using the observed tissue R1 for corrections to obtain more specific and accurate measurements of APT contrast in vivo. The results also indicate that, due to relatively fast transcytolemmal water exchange, the influence of intra- and extracellular water compartments on CEST measurements with seconds long saturation time may be ignored in tumors.
Collapse
Affiliation(s)
- Hua Li
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
| | - Ke Li
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Xiao-Yong Zhang
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Xiaoyu Jiang
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Zhongliang Zu
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Moritz Zaiss
- Department of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ, German Cancer Research Center), Heidelberg, Germany
| | - Daniel F. Gochberg
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | - John C. Gore
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Junzhong Xu
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
- Correspondence to: Junzhong Xu, PhD, Vanderbilt University Institute of Imaging Science, 1161 21st Avenue South, AA 1105 MCN, Nashville, TN 37232-2310.
| |
Collapse
|
75
|
Rerich E, Zaiss M, Korzowski A, Ladd ME, Bachert P. Relaxation-compensated CEST-MRI at 7 T for mapping of creatine content and pH--preliminary application in human muscle tissue in vivo. NMR IN BIOMEDICINE 2015; 28:1402-1412. [PMID: 26374674 DOI: 10.1002/nbm.3367] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 06/19/2015] [Accepted: 06/30/2015] [Indexed: 06/05/2023]
Abstract
The small biomolecule creatine is involved in energy metabolism. Mapping of the total creatine (mostly PCr and Cr) in vivo has been done with chemical shift imaging. Chemical exchange saturation transfer (CEST) allows an alternative detection of creatine via water MRI. Living tissue exhibits CEST effects from different small metabolites, including creatine, with four exchanging protons of its guanidinium group resonating about 2 ppm from the water peak and hence contributing to the amine proton CEST peak. The intermediate exchange rate (≈ 1000 Hz) of the guanidinium protons requires high RF saturation amplitude B1. However, strong B1 fields also label semi-solid magnetization transfer (MT) effects originating from immobile protons with broad linewidths (~kHz) in the tissue. Recently, it was shown that endogenous CEST contrasts are strongly affected by the MT background as well as by T1 relaxation of the water protons. We show that this influence can be corrected in the acquired CEST data by an inverse metric that yields the apparent exchange-dependent relaxation (AREX). AREX has some useful linearity features that enable preparation of both concentration, and--by using the AREX-ratio of two RF irradiation amplitudes B1--purely exchange-rate-weighted CEST contrasts. These two methods could be verified in phantom experiments with different concentration and pH values, but also varying water relaxation properties. Finally, results from a preliminary application to in vivo CEST imaging data of the human calf muscle before and after exercise are presented. The creatine concentration increases during exercise as expected and as confirmed by (31)P NMR spectroscopic imaging. However, the estimated concentrations obtained by our method were higher than the literature values: cCr,rest=24.5±3.74mM to cCr,ex=38.32±13.05mM. The CEST-based pH method shows a pH decrease during exercise, whereas a slight increase was observed by (31)P NMR spectroscopy.
Collapse
Affiliation(s)
- Eugenia Rerich
- Deutsches Krebsforschungszentrum (DKFZ), Heidelberg, Germany
| | - Moritz Zaiss
- Deutsches Krebsforschungszentrum (DKFZ), Heidelberg, Germany
| | | | - Mark E Ladd
- Deutsches Krebsforschungszentrum (DKFZ), Heidelberg, Germany
| | - Peter Bachert
- Deutsches Krebsforschungszentrum (DKFZ), Heidelberg, Germany
| |
Collapse
|
76
|
Xu X, Yadav NN, Zeng H, Jones CK, Zhou J, van Zijl PCM, Xu J. Magnetization transfer contrast-suppressed imaging of amide proton transfer and relayed nuclear overhauser enhancement chemical exchange saturation transfer effects in the human brain at 7T. Magn Reson Med 2015; 75:88-96. [PMID: 26445350 DOI: 10.1002/mrm.25990] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 08/18/2015] [Accepted: 08/24/2015] [Indexed: 01/15/2023]
Abstract
PURPOSE To use the variable delay multipulse (VDMP) chemical exchange saturation transfer (CEST) approach to obtain clean amide proton transfer (APT) and relayed Nuclear Overhauser enhancement (rNOE) CEST images in the human brain by suppressing the conventional magnetization transfer contrast (MTC) and reducing the direct water saturation contribution. METHODS The VDMP CEST scheme consists of a train of RF pulses with a specific mixing time. The CEST signal with respect to the mixing time shows distinguishable characteristics for protons with different exchange rates. Exchange rate filtered CEST images are generated by subtracting images acquired at two mixing times at which the MTC signals are equal, while the APT and rNOE-CEST signals differ. Because the subtraction is performed at the same frequency offset for each voxel and the CEST signals are broad, no B0 correction is needed. RESULTS MTC-suppressed APT and rNOE-CEST images of human brain were obtained using the VDMP method. The APT-CEST data show hyperintensity in gray matter versus white matter, whereas the rNOE-CEST images show negligible contrast between gray and white matter. CONCLUSION The VDMP approach provides a simple and rapid way of recording MTC-suppressed APT-CEST and rNOE-CEST images without the need for B0 field correction.
Collapse
Affiliation(s)
- Xiang Xu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Nirbhay N Yadav
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Haifeng Zeng
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Craig K Jones
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Jinyuan Zhou
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Peter C M van Zijl
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - Jiadi Xu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| |
Collapse
|
77
|
Meissner JE, Goerke S, Rerich E, Klika KD, Radbruch A, Ladd ME, Bachert P, Zaiss M. Quantitative pulsed CEST-MRI using Ω-plots. NMR IN BIOMEDICINE 2015; 28:1196-208. [PMID: 26278686 DOI: 10.1002/nbm.3362] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 06/18/2015] [Accepted: 06/19/2015] [Indexed: 05/24/2023]
Abstract
Chemical exchange saturation transfer (CEST) allows the indirect detection of dilute metabolites in living tissue via MRI of the tissue water signal. Selective radio frequency (RF) with amplitude B1 is used to saturate the magnetization of protons of exchanging groups, which transfer the saturation to the abundant water pool. In a clinical setup, the saturation scheme is limited to a series of short pulses to follow regulation of the specific absorption rate (SAR). Pulsed saturation is difficult to describe theoretically, thus rendering quantitative CEST a challenging task. In this study, we propose a new analytical treatment of pulsed CEST by extending a former interleaved saturation-relaxation approach. Analytical integration of the continuous wave (cw) eigenvalue as a function of the RF pulse shape leads to a formula for pulsed CEST that has the same structure as that for cw CEST, but incorporates two form factors that are determined by the pulse shape. This enables analytical Z-spectrum calculations and permits deeper insight into pulsed CEST. Furthermore, it extends Dixon's Ω-plot method to the case of pulsed saturation, yielding separately, and independently, the exchange rate and the relative proton concentration. Consequently, knowledge of the form factors allows a direct comparison of the effect of the strength and B1 dispersion of pulsed CEST experiments with the ideal case of cw saturation. The extended pulsed CEST quantification approach was verified using creatine phantoms measured on a 7 T whole-body MR tomograph, and its range of validity was assessed by simulations.
Collapse
Affiliation(s)
- Jan-Eric Meissner
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany
- Division of Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany
| | - Steffen Goerke
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany
| | - Eugenia Rerich
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany
| | - Karel D Klika
- Molecular Structure Analysis, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany
| | - Alexander Radbruch
- Division of Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany
- Department of Neuroradiology, Medical Faculty, University of Heidelberg, Heidelberg, Germany
| | - Mark E Ladd
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany
| | - Peter Bachert
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany
| | - Moritz Zaiss
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany
| |
Collapse
|
78
|
Goerke S, Zaiss M, Kunz P, Klika KD, Windschuh JD, Mogk A, Bukau B, Ladd ME, Bachert P. Signature of protein unfolding in chemical exchange saturation transfer imaging. NMR IN BIOMEDICINE 2015; 28:906-13. [PMID: 26010522 DOI: 10.1002/nbm.3317] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/11/2015] [Accepted: 04/07/2015] [Indexed: 05/24/2023]
Abstract
Chemical exchange saturation transfer (CEST) allows the detection of metabolites of low concentration in tissue with nearly the sensitivity of MRI with water protons. With this spectroscopic imaging approach, several tissue-specific CEST effects have been observed in vivo. Some of these originate from exchanging sites of proteins, such as backbone amide protons, or from aliphatic protons within the hydrophobic protein core. In this work, we employed CEST experiments to detect global protein unfolding. Spectral evaluation revealed exchange- and NOE-mediated CEST effects that varied in a highly characteristic manner with protein unfolding tracked by fluorescence spectroscopy. We suggest the use of this comprehensive spectral signature for the detection of protein unfolding by CEST, as it relies on several spectral hallmarks. As proof of principle, we demonstrate that the presented signature is readily detectable using a whole-body MR tomograph (B0 = 7 T), not only in denatured aqueous protein solutions, but also in heat-shocked yeast cells. A CEST imaging contrast with the potential to detect global protein unfolding would be of particular interest regarding protein unfolding as a marker for stress, ageing, and disease.
Collapse
Affiliation(s)
- Steffen Goerke
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Heidelberg, Baden-Württemberg, Germany
| | - Moritz Zaiss
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Heidelberg, Baden-Württemberg, Germany
| | - Patrick Kunz
- Division of Functional Genome Analysis, Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Heidelberg, Baden-Württemberg, Germany
| | - Karel D Klika
- Molecular Structure Analysis, Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Heidelberg, Baden-Württemberg, Germany
| | - Johannes D Windschuh
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Heidelberg, Baden-Württemberg, Germany
| | - Axel Mogk
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz, Heidelberg, Baden-Württemberg, Germany
- Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Heidelberg, Baden-Württemberg, Germany
| | - Bernd Bukau
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz, Heidelberg, Baden-Württemberg, Germany
- Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Heidelberg, Baden-Württemberg, Germany
| | - Mark E Ladd
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Heidelberg, Baden-Württemberg, Germany
| | - Peter Bachert
- Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Heidelberg, Baden-Württemberg, Germany
| |
Collapse
|
79
|
Xiao G, Sun PZ, Wu R. Fast simulation and optimization of pulse-train chemical exchange saturation transfer (CEST) imaging. Phys Med Biol 2015; 60:4719-30. [PMID: 26020414 DOI: 10.1088/0031-9155/60/12/4719] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Chemical exchange saturation transfer (CEST) MRI has been increasingly applied to detect dilute solutes and physicochemical properties, with promising in vivo applications. Whereas CEST imaging has been implemented with continuous wave (CW) radio-frequency irradiation on preclinical scanners, pulse-train irradiation is often chosen on clinical systems. Therefore, it is necessary to optimize pulse-train CEST imaging, particularly important for translational studies. Because conventional Bloch-McConnell formulas are not in the form of homogeneous differential equations, the routine simulation approach simulates the evolving magnetization step by step, which is time consuming. Herein we developed a computationally efficient numerical solution using matrix iterative analysis of homogeneous Bloch-McConnell equations. The proposed algorithm requires simulation of pulse-train CEST MRI magnetization within one irradiation repeat, with 99% computation time reduction from that of conventional approach under typical experimental conditions. The proposed solution enables determination of labile proton ratio and exchange rate from pulse-train CEST MRI experiment, within 5% from those determined from quantitative CW-CEST MRI. In addition, the structural similarity index analysis shows that the dependence of CEST contrast on saturation pulse flip angle and duration between simulation and experiment was 0.98 ± 0.01, indicating that the proposed simulation algorithm permits fast optimization and quantification of pulse-train CEST MRI.
Collapse
Affiliation(s)
- Gang Xiao
- Department of Mathematics and Statistics, Hanshan Normal University, Guangdong, People's Republic of China
| | | | | |
Collapse
|
80
|
Windschuh J, Zaiss M, Meissner JE, Paech D, Radbruch A, Ladd ME, Bachert P. Correction of B1-inhomogeneities for relaxation-compensated CEST imaging at 7 T. NMR IN BIOMEDICINE 2015; 28:529-37. [PMID: 25788155 DOI: 10.1002/nbm.3283] [Citation(s) in RCA: 158] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 01/20/2015] [Accepted: 02/05/2015] [Indexed: 05/17/2023]
Abstract
Chemical exchange saturation transfer (CEST) imaging of endogenous agents in vivo is influenced by direct water proton saturation (spillover) and semi-solid macromolecular magnetization transfer (MT). Lorentzian fit isolation and application of the inverse metric yields the pure CEST contrast AREX, which is less affected by these processes, but still depends on the measurement technique, in particular on the irradiation amplitude B1 of the saturation pulses. This study focuses on two well-known CEST effects in the slow exchange regime originating from amide and aliphatic protons resonating at 3.5 ppm or -3.5 ppm from water protons, respectively. A B1-correction of CEST contrasts is crucial for the evaluation of data obtained in clinical studies at high field strengths with strong B1-inhomogeneities. Herein two approaches for B1-inhomogeneity correction, based on either CEST contrasts or Z-spectra, are investigated. Both rely on multiple acquisitions with different B1-values. One volunteer was examined with eight different B1-values to optimize the saturation field strength and the correction algorithm. Histogram evaluation allowed quantification of the quality of the B1-correction. Finally, the correction was applied to CEST images of a patient with oligodendroglioma WHO grade 2, and showed improvement of the image quality compared with the non-corrected CEST images, especially in the tumor region.
Collapse
Affiliation(s)
- Johannes Windschuh
- Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Division of Medical Physics in Radiology, Heidelberg, Germany
| | | | | | | | | | | | | |
Collapse
|
81
|
Kim J, Wu Y, Guo Y, Zheng H, Sun PZ. A review of optimization and quantification techniques for chemical exchange saturation transfer MRI toward sensitive in vivo imaging. CONTRAST MEDIA & MOLECULAR IMAGING 2015; 10:163-178. [PMID: 25641791 DOI: 10.1002/cmmi.1628] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 08/26/2014] [Accepted: 09/10/2014] [Indexed: 01/10/2023]
Abstract
Chemical exchange saturation transfer (CEST) MRI is a versatile imaging method that probes the chemical exchange between bulk water and exchangeable protons. CEST imaging indirectly detects dilute labile protons via bulk water signal changes following selective saturation of exchangeable protons, which offers substantial sensitivity enhancement and has sparked numerous biomedical applications. Over the past decade, CEST imaging techniques have rapidly evolved owing to contributions from multiple domains, including the development of CEST mathematical models, innovative contrast agent designs, sensitive data acquisition schemes, efficient field inhomogeneity correction algorithms, and quantitative CEST (qCEST) analysis. The CEST system that underlies the apparent CEST-weighted effect, however, is complex. The experimentally measurable CEST effect depends not only on parameters such as CEST agent concentration, pH and temperature, but also on relaxation rate, magnetic field strength and more importantly, experimental parameters including repetition time, RF irradiation amplitude and scheme, and image readout. Thorough understanding of the underlying CEST system using qCEST analysis may augment the diagnostic capability of conventional imaging. In this review, we provide a concise explanation of CEST acquisition methods and processing algorithms, including their advantages and limitations, for optimization and quantification of CEST MRI experiments.
Collapse
Affiliation(s)
- Jinsuh Kim
- Department of Radiology, University of Iowa, Iowa City, IA, USA
| | - Yin Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Key Laboratory for MRI, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China.,Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Yingkun Guo
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Hairong Zheng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Key Laboratory for MRI, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| |
Collapse
|
82
|
Jin T, Kim SG. Advantages of chemical exchange-sensitive spin-lock (CESL) over chemical exchange saturation transfer (CEST) for hydroxyl- and amine-water proton exchange studies. NMR IN BIOMEDICINE 2014; 27:1313-24. [PMID: 25199631 PMCID: PMC4201909 DOI: 10.1002/nbm.3191] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Revised: 07/16/2014] [Accepted: 07/24/2014] [Indexed: 05/03/2023]
Abstract
The chemical exchange (CE) rate of endogenous hydroxyl and amine protons with water is often comparable to the difference in their chemical shifts. These intermediate exchange processes have been imaged by the CE saturation transfer (CEST) approach with low-power and long-duration irradiation. However, the sensitivity is not optimal and, more importantly, the signal is contaminated by slow magnetization transfer processes. Here, the properties of CEST signals are compared with those of a CE-sensitive spin-lock (CESL) technique irradiating at the labile proton frequency. First, using a higher power and shorter irradiation in CE-MRI, we obtain: (i) an increased selectivity to faster CE rates via a higher sensitivity to faster CEs and a lower sensitivity to slower CEs and magnetization transfer processes; and (ii) a decreased in vivo asymmetric magnetization transfer contrast measured at ±15 ppm. The sensitivity gain of CESL over CEST is higher for a higher power and shorter irradiation. Unlike CESL, CEST signals oscillate at a very high power and short irradiation. Second, time-dependent CEST and CESL signals are well modeled by analytical solutions of CE-MRI with an asymmetric population approximation, which can be used for quantitative CE-MRI and validated by simulations of Bloch-McConnell equations and phantom experiments. Finally, the in vivo amine-water proton exchange contrast measured at 2.5 ppm with ω1 = 500 Hz is 18% higher in sensitivity for CESL than CEST at 9.4 T. Overall, CESL provides better exchange rate selectivity and sensitivity than CEST; therefore, CESL is more suitable for CE-MRI of intermediate exchange protons.
Collapse
Affiliation(s)
- Tao Jin
- Neuroimaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Seong-Gi Kim
- Neuroimaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Korea
- Departments of Global Biomedical Engineering and Biological Sciences, Sungkyunkwan University, Suwon, Korea
| |
Collapse
|
83
|
Scheidegger R, Wong ET, Alsop DC. Contributors to contrast between glioma and brain tissue in chemical exchange saturation transfer sensitive imaging at 3 Tesla. Neuroimage 2014; 99:256-68. [PMID: 24857712 DOI: 10.1016/j.neuroimage.2014.05.036] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 04/30/2014] [Accepted: 05/14/2014] [Indexed: 11/26/2022] Open
Abstract
Off-resonance saturation transfer images have shown intriguing differences in intensity in glioma compared to normal brain tissues. Interpretation of these differences is complicated, however, by the presence of multiple sources of exchanging magnetization including amide, amine, and hydroxyl protons, asymmetric magnetization transfer contrast (MTC) from macromolecules, and various protons with resonances in the aliphatic spectral region. We report a study targeted at separating these components and identifying their relative contributions to contrast in glioma. Off-resonance z-spectra at several saturation powers and durations were obtained from 6 healthy controls and 8 patients with high grade glioma. Results indicate that broad macromolecular MTC in normal brain tissue is responsible for the majority of contrast with glioma. Amide exchange could be detected with lower saturation power than has previously been reported in glioma, but it was a weak signal source with no detectable contrast from normal brain tissue. At higher saturation powers, amine proton exchange was a major contributor to the observed signal but showed no significant difference from normal brain. Robust acquisition strategies that effectively isolate the contributions of broad macromolecular MTC asymmetry from amine exchange were demonstrated that may provide improved contrast between glioma and normal tissue.
Collapse
Affiliation(s)
- Rachel Scheidegger
- Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Ave E25, Cambridge, MA 02139, USA; Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston, MA 02215, USA.
| | - Eric T Wong
- Brain Tumor Center and Neuro-Oncology Unit, Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston, MA 02215, USA; Neurology, Harvard Medical School, Boston, MA 02115, USA.
| | - David C Alsop
- Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston, MA 02215, USA; Radiology, Harvard Medical School, Boston, MA 02115, USA.
| |
Collapse
|
84
|
Goerke S, Zaiss M, Bachert P. Characterization of creatine guanidinium proton exchange by water-exchange (WEX) spectroscopy for absolute-pH CEST imaging in vitro. NMR IN BIOMEDICINE 2014; 27:507-18. [PMID: 24535718 DOI: 10.1002/nbm.3086] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 01/09/2014] [Accepted: 01/09/2014] [Indexed: 05/17/2023]
Abstract
Chemical exchange saturation transfer (CEST) enables indirect detection of small metabolites in tissue by MR imaging. To optimize and interpret creatine-CEST imaging we characterized the dependence of the exchange-rate constant k(sw) of creatine guanidinium protons in aqueous creatine solutions as a function of pH and temperature T in vitro. Model solutions in the low pH range (pH = 5-6.4) were measured by means of water-exchange (WEX)-filtered ¹H NMR spectroscopy on a 3 T whole-body MR tomograph. An extension of the Arrhenius equation with effective base-catalyzed Arrhenius parameters yielded a general expression for k(sw) (pH, T). The defining parameters were identified as the effective base-catalyzed rate constant k(b,eff) (298.15 K) = (3.009 ± 0.16) × 10⁹ Hz l/mol and the effective activation energy E(A,b,eff) = (32.27 ± 7.43) kJ/mol at a buffer concentration of c(buffer) = (1/15) M. As expected, a strong dependence of k(sw) on temperature was observed. The extrapolation of the exchange-rate constant to in vivo conditions (pH = 7.1, T = 37 °C) led to the value of the exchange-rate constant k(sw) = 1499 Hz. With the explicit function k(sw) (pH, T) available, absolute-pH CEST imaging could be realized and experimentally verified in vitro. By means of our calibration method it is possible to adjust the guanidinium proton exchange-rate constant k(sw) to any desired value by preparing creatine model solutions with a specific pH and temperature.
Collapse
Affiliation(s)
- Steffen Goerke
- Deutsches Krebsforschungszentrum [German Cancer Research Center] (DKFZ), Department of Medical Physics in Radiology, Heidelberg, Germany
| | | | | |
Collapse
|
85
|
Xu J, Zaiss M, Zu Z, Li H, Xie J, Gochberg DF, Bachert P, Gore JC. On the origins of chemical exchange saturation transfer (CEST) contrast in tumors at 9.4 T. NMR IN BIOMEDICINE 2014; 27:406-16. [PMID: 24474497 PMCID: PMC3972041 DOI: 10.1002/nbm.3075] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 11/07/2013] [Accepted: 12/20/2013] [Indexed: 05/08/2023]
Abstract
Chemical exchange saturation transfer (CEST) provides an indirect means to detect exchangeable protons within tissues through their effects on the water signal. Previous studies have suggested that amide proton transfer (APT) imaging, a specific form of CEST, detects endogenous amide protons with a resonance frequency offset 3.5 ppm downfield from water, and thus may be sensitive to variations in mobile proteins/peptides in tumors. However, as CEST measurements are influenced by various confounding effects, such as spillover saturation, magnetization transfer (MT) and MT asymmetry, the mechanism or degree of increased APT signal in tumors is not certain. In addition to APT, nuclear Overhauser enhancement (NOE) effects upfield from water may also provide distinct information on tissue composition. In the current study, APT, NOE and several other MR parameters were measured and compared comprehensively in order to elucidate the origins of APT and NOE contrasts in tumors at 9.4 T. In addition to conventional CEST methods, a new intrinsic inverse metric was applied to correct for relaxation and other effects. After corrections for spillover, MT and T1 effects, corrected APT in tumors was found not to be significantly different from that in normal tissues, but corrected NOE effects in tumors showed significant decreases compared with those in normal tissues. Biochemical measurements verified that there was no significant enhancement of protein contents in the tumors studied, consistent with the corrected APT measurements and previous literature, whereas quantitative MT data showed decreases in the fractions of immobile macromolecules in tumors. Our results may assist in the better understanding of the contrast depicted by CEST imaging in tumors, and in the development of improved APT and NOE measurements for cancer imaging.
Collapse
Affiliation(s)
- Junzhong Xu
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Moritz Zaiss
- Department of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ, German Cancer Research Center), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
| | - Zhongliang Zu
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Hua Li
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37232, USA
| | - Jingping Xie
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Daniel F. Gochberg
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37232, USA
| | - Peter Bachert
- Department of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ, German Cancer Research Center), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
| | - John C. Gore
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37232, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232, USA
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| |
Collapse
|
86
|
Zaiss M, Xu J, Goerke S, Khan IS, Singer RJ, Gore JC, Gochberg DF, Bachert P. Inverse Z-spectrum analysis for spillover-, MT-, and T1 -corrected steady-state pulsed CEST-MRI--application to pH-weighted MRI of acute stroke. NMR IN BIOMEDICINE 2014; 27:240-52. [PMID: 24395553 PMCID: PMC4520220 DOI: 10.1002/nbm.3054] [Citation(s) in RCA: 219] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/08/2013] [Accepted: 10/30/2013] [Indexed: 05/03/2023]
Abstract
Endogenous chemical exchange saturation transfer (CEST) effects are always diluted by competing effects, such as direct water proton saturation (spillover) and semi-solid macromolecular magnetization transfer (MT). This leads to unwanted T2 and MT signal contributions that lessen the CEST signal specificity to the underlying biochemical exchange processes. A spillover correction is of special interest for clinical static field strengths and protons resonating near the water peak. This is the case for all endogenous CEST agents, such as amide proton transfer, -OH-CEST of glycosaminoglycans, glucose or myo-inositol, and amine exchange of creatine or glutamate. All CEST effects also appear to be scaled by the T1 relaxation time of water, as they are mediated by the water pool. This forms the motivation for simple metrics that correct the CEST signal. Based on eigenspace theory, we propose a novel magnetization transfer ratio (MTRRex ), employing the inverse Z-spectrum, which eliminates spillover and semi-solid MT effects. This metric can be simply related to Rex , the exchange-dependent relaxation rate in the rotating frame, and ka , the inherent exchange rate. Furthermore, it can be scaled by the duty cycle, allowing for simple translation to clinical protocols. For verification, the amine proton exchange of creatine in solutions with different agar concentrations was studied experimentally at a clinical field strength of 3 T, where spillover effects are large. We demonstrate that spillover can be properly corrected and that quantitative evaluation of pH and creatine concentration is possible. This proves that MTRRex is a quantitative and biophysically specific CEST-MRI metric. Applied to acute stroke induced in rat brain, the corrected CEST signal shows significantly higher contrast between the stroke area and normal tissue, as well as less B1 dependence, than conventional approaches.
Collapse
Affiliation(s)
- Moritz Zaiss
- Department of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ, German Cancer Research Center), Heidelberg, Germany
- Correspondence to: M. Zaiss, German Cancer Research Center (DKFZ), Department of Medical Physics in Radiology, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
| | - Junzhong Xu
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Steffen Goerke
- Department of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ, German Cancer Research Center), Heidelberg, Germany
| | - Imad S. Khan
- Section of Neurosurgery, Geisel School of Medicine at Dartmouth, Lebanon, NH
| | - Robert J. Singer
- Section of Neurosurgery, Geisel School of Medicine at Dartmouth, Lebanon, NH
| | - John C. Gore
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Daniel F. Gochberg
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
| | - Peter Bachert
- Department of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ, German Cancer Research Center), Heidelberg, Germany
| |
Collapse
|
87
|
Chan KWY, Yu T, Qiao Y, Liu Q, Yang M, Patel H, Liu G, Kinzler KW, Vogelstein B, Bulte JWM, van Zijl PCM, Hanes J, Zhou S, McMahon MT. A diaCEST MRI approach for monitoring liposomal accumulation in tumors. J Control Release 2014; 180:51-9. [PMID: 24548481 DOI: 10.1016/j.jconrel.2014.02.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 01/30/2014] [Accepted: 02/07/2014] [Indexed: 11/28/2022]
Abstract
Nanocarrier-based chemotherapy allows preferential delivery of therapeutics to tumors and has been found to improve the efficacy of cancer treatment. However, difficulties in tracking nanocarriers and evaluating their pharmacological fates in patients have limited judicious selection of patients to those who might most benefit from nanotherapeutics. To enable the monitoring of nanocarriers in vivo, we developed MRI-traceable diamagnetic Chemical Exchange Saturation Transfer (diaCEST) liposomes. The diaCEST liposomes were based on the clinical formulation of liposomal doxorubicin (i.e. DOXIL®) and were loaded with barbituric acid (BA), a small, organic, biocompatible diaCEST contrast agent. The optimized diaCEST liposomal formulation with a BA-to-lipid ratio of 25% exhibited 30% contrast enhancement at B1=4.7μT in vitro. The contrast was stable, with ~80% of the initial CEST signal sustained over 8h in vitro. We used the diaCEST liposomes to monitor the response to tumor necrosis factor-alpha (TNF-α), an agent in clinical trials that increases vascular permeability and uptake of nanocarriers into tumors. After systemic administration of diaCEST liposomes to mice bearing CT26 tumors, we found an average diaCEST contrast at the BA frequency (5ppm) of 0.4% at B1=4.7μT while if TNF-α was co-administered the contrast increased to 1.5%. This novel approach provides a non-radioactive, non-metallic, biocompatible, semi-quantitative, and clinically translatable approach to evaluate the tumor targeting of stealth liposomes in vivo, which may enable personalized nanomedicine.
Collapse
Affiliation(s)
- Kannie W Y Chan
- Russell H. Morgan Department of Radiology and Radiological Sciences, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore 21287, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore 21205, USA; Center for Nanomedicine, The Johns Hopkins University School of Medicine, Baltimore 21287, USA; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore 21205, USA
| | - Tao Yu
- Center for Nanomedicine, The Johns Hopkins University School of Medicine, Baltimore 21287, USA; Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore 21205, USA
| | - Yuan Qiao
- The Ludwig Center and Howard Hughes Medical Institute at the Hopkins-Kimmel Comprehensive Cancer Center, Baltimore 21287, USA
| | - Qiang Liu
- The Ludwig Center and Howard Hughes Medical Institute at the Hopkins-Kimmel Comprehensive Cancer Center, Baltimore 21287, USA
| | - Ming Yang
- Center for Nanomedicine, The Johns Hopkins University School of Medicine, Baltimore 21287, USA; Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore 21205, USA
| | - Himatkumar Patel
- Center for Nanomedicine, The Johns Hopkins University School of Medicine, Baltimore 21287, USA
| | - Guanshu Liu
- Russell H. Morgan Department of Radiology and Radiological Sciences, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore 21287, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore 21205, USA
| | - Kenneth W Kinzler
- The Ludwig Center and Howard Hughes Medical Institute at the Hopkins-Kimmel Comprehensive Cancer Center, Baltimore 21287, USA
| | - Bert Vogelstein
- The Ludwig Center and Howard Hughes Medical Institute at the Hopkins-Kimmel Comprehensive Cancer Center, Baltimore 21287, USA
| | - Jeff W M Bulte
- Russell H. Morgan Department of Radiology and Radiological Sciences, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore 21287, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore 21205, USA; Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore 21205, USA; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore 21205, USA
| | - Peter C M van Zijl
- Russell H. Morgan Department of Radiology and Radiological Sciences, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore 21287, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore 21205, USA
| | - Justin Hanes
- Center for Nanomedicine, The Johns Hopkins University School of Medicine, Baltimore 21287, USA; Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore 21205, USA; Department of Ophthalmology, The Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore 21287, USA
| | - Shibin Zhou
- The Ludwig Center and Howard Hughes Medical Institute at the Hopkins-Kimmel Comprehensive Cancer Center, Baltimore 21287, USA
| | - Michael T McMahon
- Russell H. Morgan Department of Radiology and Radiological Sciences, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore 21287, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore 21205, USA; Center for Nanomedicine, The Johns Hopkins University School of Medicine, Baltimore 21287, USA.
| |
Collapse
|
88
|
Zu Z, Xu J, Li H, Chekmenev EY, Quarles CC, Does MD, Gore JC, Gochberg DF. Imaging amide proton transfer and nuclear overhauser enhancement using chemical exchange rotation transfer (CERT). Magn Reson Med 2013; 72:471-6. [PMID: 24302497 DOI: 10.1002/mrm.24953] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 08/14/2013] [Accepted: 08/21/2013] [Indexed: 12/27/2022]
Abstract
PURPOSE This study investigates amide proton transfer (APT) and nuclear overhauser enhancement (NOE) in phantoms and 9L tumors in rat brains at 9.4 Tesla, using a recently developed method that can isolate different contributions to exchange. METHODS Chemical exchange rotation transfer (CERT) was used to quantify APT and NOEs through subtraction of signals acquired at two irradiation flip angles, but with the same average irradiation power. RESULTS CERT separates and quantifies specific APT and NOE signals without contamination from other proton pools, and thus overcomes a key shortcoming of conventional CEST asymmetry approaches. CERT thus has increased specificity, though at the cost of decreased signal strength. In vivo experiments show that the APT effect acquired with CERT in 9L rat tumors (3.1%) is relatively greater than that in normal tissue (2.5%), which is consistent with previous CEST asymmetry analysis. The NOE effect centered at -1.6 ppm shows substantial image contrast within the tumor and between the tumor and the surrounding tissue, while the NOE effect centered at -3.5 ppm shows little contrast. CONCLUSION CERT provides an image contrast that is more specific to chemical exchange than conventional APT by means of asymmetric CEST Z-spectra analysis.
Collapse
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
| | | | | | | | | | | | | | | |
Collapse
|
89
|
Zaiss M, Bachert P. Chemical exchange saturation transfer (CEST) and MRZ-spectroscopyin vivo: a review of theoretical approaches and methods. Phys Med Biol 2013; 58:R221-69. [DOI: 10.1088/0031-9155/58/22/r221] [Citation(s) in RCA: 216] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
|
90
|
Sun PZ, Wang Y, Xiao G, Wu R. Simultaneous experimental determination of labile proton fraction ratio and exchange rate with irradiation radio frequency power-dependent quantitative CEST MRI analysis. CONTRAST MEDIA & MOLECULAR IMAGING 2013; 8:246-51. [PMID: 23606428 DOI: 10.1002/cmmi.1524] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 11/22/2012] [Accepted: 11/26/2012] [Indexed: 12/20/2022]
Abstract
Chemical exchange saturation transfer (CEST) imaging is sensitive to dilute proteins/peptides and microenvironmental properties, and has been increasingly evaluated for molecular imaging and in vivo applications. However, the experimentally measured CEST effect depends on the CEST agent concentration, exchange rate and relaxation time. In addition, there may be non-negligible direct radio-frequency (RF) saturation effects, particularly severe for diamagnetic CEST (DIACEST) agents owing to their relatively small chemical shift difference from that of the bulk water resonance. As such, the commonly used asymmetry analysis only provides CEST-weighted information. Recently, it has been shown with numerical simulation that both labile proton concentration and exchange rate can be determined by evaluating the RF power dependence of DIACEST effect. To validate the simulation results, we prepared and imaged two CEST phantoms: a pH phantom of serially titrated pH at a fixed creatine concentration and a concentration phantom of serially varied creatine concentration titrated to the same pH, and solved the labile proton fraction ratio and exchange rate per-pixel. For the concentration phantom, we showed that the labile proton fraction ratio is proportional to the CEST agent concentration with negligible change in the exchange rate. Additionally, we found the exchange rate of the pH phantom is dominantly base-catalyzed with little difference in the labile proton fraction ratio. In summary, our study demonstrated quantitative DIACEST MRI, which remains promising to augment the conventional CEST-weighted MRI analysis.
Collapse
Affiliation(s)
- Phillip Zhe Sun
- Athinoula A Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | | | | | | |
Collapse
|
91
|
Chan KWY, Bulte JWM, McMahon MT. Diamagnetic chemical exchange saturation transfer (diaCEST) liposomes: physicochemical properties and imaging applications. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2013; 6:111-24. [PMID: 24339357 DOI: 10.1002/wnan.1246] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Chemical exchange saturation transfer (CEST) is a new type of magnetic resonance imaging (MRI) contrast based on labile spins which rapidly exchange with solvent, resulting in an amplification of signal which allows detection of solute protons at millimolar to micromolar concentrations. An additional feature of these agents is that natural organic and biodegradable compounds can provide strong CEST contrast, allowing the development of diamagnetic CEST (diaCEST) MRI contrast agents. The sensitivity of the CEST approach per unit of agent increases further when diaCEST contrast agents are loaded into liposomes to become diaCEST liposomes. In this review, we will discuss the unique and favorable features of diaCEST liposomes which are well suited for in vivo imaging. diaCEST liposomes are nanocarriers which feature high concentrations of encapsulated contrast material, controlled release of payload, and an adjustable coating for passive or active tumor targeting. These liposomes have water permeable bilayers and both the interior and exterior can be fine-tuned for many biomedical applications. Furthermore, a number of liposome formulations are used in the clinic including Doxil™, which is an approved product for treating patients with cancer for decades, rapid translation of these materials can be envisaged. diaCEST liposomes have shown promise in imaging of cancer, and monitoring of chemotherapy and cell transplants. The unique features of diaCEST liposomes are discussed to provide an overview of the applications currently envisioned for this new technology and to provide an overall insight of their potential.
Collapse
Affiliation(s)
- Kannie W Y Chan
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | | | | |
Collapse
|
92
|
Klomp DWJ, Dula AN, Arlinghaus LR, Italiaander M, Dortch RD, Zu Z, Williams JM, Gochberg DF, Luijten PR, Gore JC, Yankeelov TE, Smith SA. Amide proton transfer imaging of the human breast at 7T: development and reproducibility. NMR IN BIOMEDICINE 2013; 26:1271-7. [PMID: 23559550 PMCID: PMC3726578 DOI: 10.1002/nbm.2947] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 02/07/2013] [Accepted: 02/19/2013] [Indexed: 05/03/2023]
Abstract
Chemical exchange saturation transfer (CEST) can offer information about protons associated with mobile proteins through the amide proton transfer (APT) effect, which has been shown to discriminate tumor from healthy tissue and, more recently, has been suggested as a prognosticator of response to therapy. Despite this promise, APT effects are small (only a few percent of the total signal), and APT imaging is often prone to artifacts resulting from system instability. Here we present a procedure that enables the detection of APT effects in the human breast at 7T while mitigating these issues. Adequate signal-to-noise ratio (SNR) was achieved via an optimized quadrature RF breast coil and 3D acquisitions. To reduce the influence of fat, effective fat suppression schemes were developed that did not degrade SNR. To reduce the levels of ghosting artifacts, dummy scans have been integrated into the scanning protocol. Compared with results obtained at 3T, the standard deviation of the measured APT effect was reduced by a factor of four at 7T, allowing for the detection of APT effects with a standard deviation of 1% in the human breast at 7T. Together, these results demonstrate that the APT effect can be reliably detected in the healthy human breast with a high level of precision at 7T.
Collapse
Affiliation(s)
- Dennis W. J. Klomp
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
- Institute of Imaging Science, Vanderbilt, Nashville, USA
| | - Adrienne N. Dula
- Institute of Imaging Science, Vanderbilt, Nashville, USA
- Department of Radiology and Radiological Sciences, Vanderbilt, Nashville, USA
| | | | - Michel Italiaander
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Richard D. Dortch
- Institute of Imaging Science, Vanderbilt, Nashville, USA
- Department of Radiology and Radiological Sciences, Vanderbilt, Nashville, USA
| | - Zhongliang Zu
- Institute of Imaging Science, Vanderbilt, Nashville, USA
| | - Jason M. Williams
- Institute of Imaging Science, Vanderbilt, Nashville, USA
- Department of Radiology and Radiological Sciences, Vanderbilt, Nashville, USA
| | | | - Peter R. Luijten
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - John C. Gore
- Institute of Imaging Science, Vanderbilt, Nashville, USA
- Department of Radiology and Radiological Sciences, Vanderbilt, Nashville, USA
- Department of Biomedical Engineering, Vanderbilt, Nashville, USA
- Department of Molecular Physiology and Biophysics, Vanderbilt, Nashville, USA
- Department of Physics, Vanderbilt, Nashville, USA
| | - Thomas E. Yankeelov
- Institute of Imaging Science, Vanderbilt, Nashville, USA
- Department of Radiology and Radiological Sciences, Vanderbilt, Nashville, USA
- Department of Biomedical Engineering, Vanderbilt, Nashville, USA
- Department of Physics, Vanderbilt, Nashville, USA
- Department of Cancer Biology, Vanderbilt, Nashville, USA
| | - Seth A. Smith
- Institute of Imaging Science, Vanderbilt, Nashville, USA
- Department of Radiology and Radiological Sciences, Vanderbilt, Nashville, USA
- Department of Biomedical Engineering, Vanderbilt, Nashville, USA
- Department of Physics, Vanderbilt, Nashville, USA
| |
Collapse
|
93
|
Murase K. A theoretical and numerical consideration of the longitudinal and transverse relaxations in the rotating frame. Magn Reson Imaging 2013; 31:1544-58. [PMID: 23993793 DOI: 10.1016/j.mri.2013.07.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 06/29/2013] [Accepted: 07/02/2013] [Indexed: 11/17/2022]
Abstract
We previously derived a simple equation for solving time-dependent Bloch equations by a matrix operation. The purpose of this study was to present a theoretical and numerical consideration of the longitudinal (R1ρ=1/T1ρ) and transverse relaxation rates in the rotating frame (R2ρ=1/T2ρ), based on this method. First, we derived an equation describing the time evolution of the magnetization vector (M(t)) by expanding the matrix exponential into the eigenvalues and the corresponding eigenvectors using diagonalization. Second, we obtained the longitudinal magnetization vector in the rotating frame (M1ρ(t)) by taking the inner product of M(t) and the eigenvector with the smallest eigenvalue in modulus, and then we obtained the transverse magnetization vector in the rotating frame (M2ρ(t)) by subtracting M1ρ(t) from M(t). For comparison, we also computed the spin-locked magnetization vector. We derived the exact solutions for R1ρ and R2ρ from the eigenvalues, and compared them with those obtained numerically from M1ρ(t) and M2ρ(t), respectively. There was excellent agreement between them. From the exact solutions for R1ρ and R2ρ, R2ρ was found to be given by R2ρ=(2R2+R1)/2-R1ρ/2, where R1 and R2 denote the conventional longitudinal and transverse relaxation rates, respectively. We also derived M1ρ(t) and M2ρ(t) for bulk water protons, in which the effect of chemical exchange was taken into account using a 2-pool chemical exchange model, and we compared the R1ρ and R2ρ values obtained from the eigenvalues and those obtained numerically from M1ρ(t) and M2ρ(t). There was also excellent agreement between them. In conclusion, this study will be useful for better understanding of the longitudinal and transverse relaxations in the rotating frame and for analyzing the contrast mechanisms in T1ρ- and T2ρ-weighted MRI.
Collapse
Affiliation(s)
- Kenya Murase
- Department of Medical Physics and Engineering, Division of Medical Technology and Science, Faculty of Health Science, Graduate School of Medicine, Osaka University, 1-7 Yamadaoka, Suita, Osaka 565-0871, Japan.
| |
Collapse
|
94
|
Yang X, Song X, Li Y, Liu G, Banerjee SR, Pomper MG, McMahon MT. Salicylic acid and analogues as diaCEST MRI contrast agents with highly shifted exchangeable proton frequencies. Angew Chem Int Ed Engl 2013; 52:8116-9. [PMID: 23794432 PMCID: PMC3819166 DOI: 10.1002/anie.201302764] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 05/27/2013] [Indexed: 12/27/2022]
Affiliation(s)
- Xing Yang
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 991 N. Broadway Baltimore, Maryland 21287 (USA)
| | - Xiaolei Song
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 991 N. Broadway Baltimore, Maryland 21287 (USA)
| | - Yuguo Li
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 991 N. Broadway Baltimore, Maryland 21287 (USA)
| | - Guanshu Liu
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 991 N. Broadway Baltimore, Maryland 21287 (USA); F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, 707 N. Broadway Ave., Baltimore, Maryland 21287 (USA)
| | - Sangeeta Ray Banerjee
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 991 N. Broadway Baltimore, Maryland 21287 (USA)
| | - Martin G. Pomper
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 991 N. Broadway Baltimore, Maryland 21287 (USA)
| | - Michael T. McMahon
- The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, 991 N. Broadway Baltimore, Maryland 21287 (USA); F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, 707 N. Broadway Ave., Baltimore, Maryland 21287 (USA)
| |
Collapse
|
95
|
Xu J, Yadav NN, Bar-Shir A, Jones CK, Chan KWY, Zhang J, Walczak P, McMahon MT, van Zijl PCM. Variable delay multi-pulse train for fast chemical exchange saturation transfer and relayed-nuclear overhauser enhancement MRI. Magn Reson Med 2013; 71:1798-812. [PMID: 23813483 DOI: 10.1002/mrm.24850] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 05/25/2013] [Accepted: 05/27/2013] [Indexed: 12/14/2022]
Abstract
PURPOSE Chemical exchange saturation transfer (CEST) imaging is a new MRI technology allowing the detection of low concentration endogenous cellular proteins and metabolites indirectly through their exchangeable protons. A new technique, variable delay multi-pulse CEST (VDMP-CEST), is proposed to eliminate the need for recording full Z-spectra and performing asymmetry analysis to obtain CEST contrast. METHODS The VDMP-CEST scheme involves acquiring images with two (or more) delays between radiofrequency saturation pulses in pulsed CEST, producing a series of CEST images sensitive to the speed of saturation transfer. Subtracting two images or fitting a time series produces CEST and relayed-nuclear Overhauser enhancement CEST maps without effects of direct water saturation and, when using low radiofrequency power, minimal magnetization transfer contrast interference. RESULTS When applied to several model systems (bovine serum albumin, crosslinked bovine serum albumin, l-glutamic acid) and in vivo on healthy rat brain, VDMP-CEST showed sensitivity to slow to intermediate range magnetization transfer processes (rate < 100-150 Hz), such as amide proton transfer and relayed nuclear Overhauser enhancement-CEST. Images for these contrasts could be acquired in short scan times by using a single radiofrequency frequency. CONCLUSIONS VDMP-CEST provides an approach to detect CEST effect by sensitizing saturation experiments to slower exchange processes without interference of direct water saturation and without need to acquire Z-spectra and perform asymmetry analysis.
Collapse
Affiliation(s)
- Jiadi Xu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
96
|
Yang X, Song X, Li Y, Liu G, Ray Banerjee S, Pomper MG, McMahon MT. Salicylic Acid and Analogues as diaCEST MRI Contrast Agents with Highly Shifted Exchangeable Proton Frequencies. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201302764] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
97
|
Kogan F, Hariharan H, Reddy R. Chemical Exchange Saturation Transfer (CEST) Imaging: Description of Technique and Potential Clinical Applications. CURRENT RADIOLOGY REPORTS 2013; 1:102-114. [PMID: 23730540 PMCID: PMC3665411 DOI: 10.1007/s40134-013-0010-3] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Chemical exchange saturation transfer (CEST) is a magnetic resonance imaging (MRI) contrast enhancement technique that enables indirect detection of metabolites with exchangeable protons. Endogenous metabolites with exchangeable protons including many endogenous proteins with amide protons, glycosaminoglycans (GAG), glycogen, myo-inositol (MI), glutamate (Glu), creatine (Cr) and several others have been identified as potential in vivo endogenous CEST agents. These endogenous CEST agents can be exploited as non-invasive and non-ionizing biomarkers of disease diagnosis and treatment monitoring. This review focuses on the recent technical developments in endogenous in vivo CEST MRI from various metabolites as well as their potential clinical applications. The basic underlying principles of CEST, its potential limitations and new techniques to mitigate them are discussed.
Collapse
Affiliation(s)
- Feliks Kogan
- Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, B1 Stellar-Chance Labs, 422 Curie Boulevard, Philadelphia, PA 19104
| | - Hari Hariharan
- Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, B1 Stellar-Chance Labs, 422 Curie Boulevard, Philadelphia, PA 19104
| | - Ravinder Reddy
- Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, B1 Stellar-Chance Labs, 422 Curie Boulevard, Philadelphia, PA 19104
| |
Collapse
|