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Abbasi-Rad S, Norris DG. Adiabatic null passage for on-resonance magnetization transfer preparation. Magn Reson Med 2024; 91:133-148. [PMID: 37598419 DOI: 10.1002/mrm.29835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Revised: 07/08/2023] [Accepted: 08/01/2023] [Indexed: 08/22/2023]
Abstract
PURPOSE We propose a novel RF pulse providing an adiabatic null passage (ANP) for magnetization transfer preparation with improved insensitivity toB 1 + $$ {\mathrm{B}}_1^{+} $$ and B0 inhomogeneities and mitigated direct saturation and T2 effects. METHOD The phase modulation function of a 6-ms time-resampled frequency offset-corrected pulse was modified to achieve zero flip angle at the end of the pulse. The spectral response was simulated, and its insensitivity to B0 andB 1 + $$ {\mathrm{B}}_1^{+} $$ was investigated and compared with a phase-inverted (12 ¯ $$ \overline{2} $$ 1-1 ¯ $$ \overline{1} $$ 21 ¯ $$ \overline{1} $$ ) binomial pulse. The proposed pulse was implemented in a 2D-EPI pulse sequence to generate magnetization transfer (MT) contrast and MT ratio (MTR) maps. In vivo experiments were performed on 3 healthy participants with power-matched settings for ANP and the binomial pulse with the following parameters: 6-ms binomial pulse with a flip angle of 107° (shortest element) and pulse repetition period (PRP) of TRslice = 59 ms, three experiments with 6-ms ANP and constant MT used overdrive factor (OF)/PRP values of 1/TRslice ,2 $$ \sqrt{2} $$ /2TRslice , and3 $$ \sqrt{3} $$ /3TRslice . RESULTS At gray matter (white matter) in vivo, the MTR decreased from 61% (64%) at OF = 1 to 38% (42%) applying ANP with an OF =3 $$ \sqrt{\mathsf{3}} $$ and PRP = 3 TRslice , demonstrating the mitigation of T2 /direct effect by 22% (22%). Bloch-McConnell simulations gave similar values. In vivo experiments showed significant improvement in the MTR values for areas with high B0 inhomogeneity. CONCLUSION ANP pulse was shown to be advantageous over its binomial counterpart in providing MT contrast by mitigating the T2 effect and direct saturation of the liquid pool as well as reduced sensitivity toB 1 + $$ {\mathrm{B}}_1^{+} $$ and B0 inhomogeneity.
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Affiliation(s)
- Shahrokh Abbasi-Rad
- Donders Institute for Brain, Cognition and Behaviour, Donders Centre for Cognitive Neuroimaging, Radboud University Nijmegen, Nijmegen, Netherlands
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - David G Norris
- Donders Institute for Brain, Cognition and Behaviour, Donders Centre for Cognitive Neuroimaging, Radboud University Nijmegen, Nijmegen, Netherlands
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany
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Priovoulos N, de Oliveira IAF, Poser BA, Norris DG, van der Zwaag W. Combining arterial blood contrast with BOLD increases fMRI intracortical contrast. Hum Brain Mapp 2023; 44:2509-2522. [PMID: 36763562 PMCID: PMC10028680 DOI: 10.1002/hbm.26227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 01/20/2023] [Accepted: 01/26/2023] [Indexed: 02/11/2023] Open
Abstract
BOLD fMRI is widely applied in human neuroscience but is limited in its spatial specificity due to a cortical-depth-dependent venous bias. This reduces its localization specificity with respect to neuronal responses, a disadvantage for neuroscientific research. Here, we modified a submillimeter BOLD protocol to selectively reduce venous and tissue signal and increase cerebral blood volume weighting through a pulsed saturation scheme (dubbed Arterial Blood Contrast) at 7 T. Adding Arterial Blood Contrast on top of the existing BOLD contrast modulated the intracortical contrast. Isolating the Arterial Blood Contrast showed a response free of pial-surface bias. The results suggest that Arterial Blood Contrast can modulate the typical fMRI spatial specificity, with important applications in in-vivo neuroscience.
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Affiliation(s)
- Nikos Priovoulos
- Spinoza Center for Neuroimaging, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
- Computational Cognitive Neuroscience and Neuroimaging, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
| | - Icaro Agenor Ferreira de Oliveira
- Spinoza Center for Neuroimaging, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
- Computational Cognitive Neuroscience and Neuroimaging, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
- Experimental and Applied Psychology, VU University, Amsterdam, The Netherlands
| | - Benedikt A Poser
- MR-Methods Group, Maastricht Brain Imaging Center, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands
| | - David G Norris
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands
- Erwin L. Hahn Institute for MRI, University of Duisburg-Essen, Essen, Germany
| | - Wietske van der Zwaag
- Spinoza Center for Neuroimaging, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
- Computational Cognitive Neuroscience and Neuroimaging, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
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3
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Chai Y, Li L, Wang Y, Huber L, Poser BA, Duyn J, Bandettini PA. Magnetization transfer weighted EPI facilitates cortical depth determination in native fMRI space. Neuroimage 2021; 242:118455. [PMID: 34364993 PMCID: PMC8520138 DOI: 10.1016/j.neuroimage.2021.118455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 07/23/2021] [Accepted: 08/03/2021] [Indexed: 11/25/2022] Open
Abstract
The increased availability of ultra-high field scanners provides an opportunity to perform fMRI at sub-millimeter spatial scales and enables in vivo probing of laminar function in the human brain. In most previous studies, the definition of cortical layers, or depths, is based on an anatomical reference image that is collected by a different acquisition sequence and exhibits different geometric distortion compared to the functional images. Here, we propose to generate the anatomical image with the fMRI acquisition technique by incorporating magnetization transfer (MT) weighted imaging. Small flip angle binomial pulse trains are used as MT preparation, with a flexible duration (several to tens of milliseconds), which can be applied before each EPI segment without constraining the acquisition length (segment or slice number). The method's feasibility was demonstrated at 7T for coverage of either a small slab or the near-whole brain at 0.8 mm isotropic resolution. Tissue contrast was found to be similar to that obtained with a state-of-art anatomical reference based on MP2RAGE. This MT-weighted EPI image allows an automatic reconstruction of the cortical surface to support laminar analysis in native fMRI space, obviating the need for distortion correction and registration.
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Affiliation(s)
- Yuhui Chai
- Section on Functional Imaging Methods, Laboratory of Brain and Cognition, NIMH, NIH, Bethesda 20892, MD, United States.
| | - Linqing Li
- Functional MRI Core, NIMH, NIH, Bethesda, MD, United States
| | - Yicun Wang
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, NINDS, NIH, Bethesda, MD, United States
| | - Laurentius Huber
- Maastricht Brain Imaging Center, Faculty of Psychology and Neuroscience, University of Maastricht, the Netherlands
| | - Benedikt A Poser
- Maastricht Brain Imaging Center, Faculty of Psychology and Neuroscience, University of Maastricht, the Netherlands
| | - Jeff Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, NINDS, NIH, Bethesda, MD, United States
| | - Peter A Bandettini
- Section on Functional Imaging Methods, Laboratory of Brain and Cognition, NIMH, NIH, Bethesda 20892, MD, United States; Functional MRI Core, NIMH, NIH, Bethesda, MD, United States
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4
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Optimizing neuromelanin contrast in the substantia nigra and locus coeruleus using a magnetization transfer contrast prepared 3D gradient recalled echo sequence. Neuroimage 2020; 218:116935. [DOI: 10.1016/j.neuroimage.2020.116935] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 05/06/2020] [Accepted: 05/07/2020] [Indexed: 12/12/2022] Open
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5
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Huang X, Schurr RN, Wang S, Miao Q, Li T, Jia G. Development of Radiofrequency Saturation Amplitude-independent Quantitative Markers for Magnetization Transfer MRI of Prostate Cancer. Curr Med Imaging 2020; 16:695-702. [PMID: 32723241 DOI: 10.2174/1573405615666190318153328] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 02/06/2019] [Accepted: 03/19/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND In the United States, prostate cancer has a relatively large impact on men's health. Magnetic resonance imaging (MRI) is useful for the diagnosis and treatment of prostate cancer. INTRODUCTION The purpose of this study was to develop a quantitative marker for use in prostate cancer magnetization transfer (MT) magnetic resonance imaging (MRI) studies that is independent of radiofrequency (RF) saturation amplitude. METHODS Eighteen patients with biopsy-proven prostate cancer were enrolled in this study. MTMRI images were acquired using four RF saturation amplitudes at 33 frequency offsets. ROIs were delineated for the peripheral zone (PZ), central gland (CG), and tumor. Z-spectral data were collected in each region and fit to a three-parameter equation. The three parameters are: the magnitude of the bulk water pool (Aw), the full width at half maximum of the water pool (Gw), and the magnitude of the bound pool (Ab), while, the slopes from the linear regressions of Gw and Ab on RF saturation amplitude (called kAb and kGw) were used as quantitative markers. RESULTS A pairwise statistically significant difference was found between the PZ and tumor regions for the two saturation amplitude-independent quantitative markers. No pairwise statistically significant differences were found between the CG and tumor regions for any quantitative markers. CONCLUSION The significant differences between the values of the two RF saturation amplitudeindependent quantitative markers in the PZ and tumor regions reveal that these markers may be capable of distinguishing healthy PZ tissue from prostate cancer.
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Affiliation(s)
- Xunan Huang
- Xi'an Key Laboratory of Big Data and Intelligent Vision, School of Computer Science and Technology, Xidian University, Xi'an, Shaanxi 710071, China
| | - Ryan N Schurr
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, 70803, United States
| | - Shuzhen Wang
- Xi'an Key Laboratory of Big Data and Intelligent Vision, School of Computer Science and Technology, Xidian University, Xi'an, Shaanxi 710071, China
| | - Qiguang Miao
- Xi'an Key Laboratory of Big Data and Intelligent Vision, School of Computer Science and Technology, Xidian University, Xi'an, Shaanxi 710071, China
| | - Tanping Li
- School of Physics and Optoelectronic Engineering, Xidian University, Xi'an, Shaanxi 710071, China
| | - Guang Jia
- Xi'an Key Laboratory of Big Data and Intelligent Vision, School of Computer Science and Technology, Xidian University, Xi'an, Shaanxi 710071, China
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6
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van Gelderen P, Duyn JH. Background suppressed magnetization transfer MRI. Magn Reson Med 2019; 83:883-891. [PMID: 31502706 DOI: 10.1002/mrm.27978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 07/26/2019] [Accepted: 08/08/2019] [Indexed: 11/07/2022]
Abstract
PURPOSE Up to 30% of the hydrogen atoms in brain tissue are part of molecules ("semisolids") other than water. In MRI, their magnetization is typically not observed directly, but can influence the water magnetization through magnetization transfer (MT). Comparison of MRI scans differentially sensitized to MT allows estimation of the semisolid fraction and potential changes with disease. Here, we present an approach designed to improve this estimate by measuring the size of the MT effect in a single scan. METHODS A stimulated echo sequence was used to generate a spatial pattern in the longitudinal water magnetization, which was then given time to exchange with semisolids. After saturating the remaining water magnetization, reverse exchange was allowed to partly re-establish the original water magnetization pattern. The third excitation pulse then formed a stimulated echo out of this pattern. RESULTS MT data were obtained on 10 human subjects at 7 T with varying exchange times. The images showed the expected time dependence of signal associated with the forward and reverse exchange processes. Excellent suppression of non-exchanging background signal was achieved. As expected, this suppression came at the price of a substantial reduction in exchange-related signal (by ~75% compared to the signal in saturation recovery MT), in part because of the reliance on a 2-step exchange process. CONCLUSION The results demonstrate an MT signal can be observed in a single acquisition without subtraction. This may be advantageous for MT measurements when signal instabilities related to motion and physiological variations exceed thermal noise sources.
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Affiliation(s)
- Peter van Gelderen
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Jeff H Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
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7
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Varma G, Girard OM, Mchinda S, Prevost VH, Grant AK, Duhamel G, Alsop DC. Low duty-cycle pulsed irradiation reduces magnetization transfer and increases the inhomogeneous magnetization transfer effect. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 296:60-71. [PMID: 30212729 DOI: 10.1016/j.jmr.2018.08.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 07/27/2018] [Accepted: 08/18/2018] [Indexed: 06/08/2023]
Abstract
Intense off-resonant RF irradiation can lead to saturation of the macromolecular pool magnetization and enhance bound pool dipolar order responsible for the inhomogeneous magnetization transfer (ihMT) effect, but the intensity of RF power in human imaging studies is limited by safety constraints on RF heating. High RF intensities can still be achieved if applied in short pulses with low duty-cycle. Here we investigate the benefits of low duty-cycle irradiation for MT and ihMT studies with both theoretical and experimental methods. Solutions for pulsed irradiation of a two-pool model including dipolar order effects were implemented. Experiments were conducted at 3 T in the brain and through the calf of healthy human subjects. 2D echo planar images were acquired following a preparation of RF irradiation with a 2 s train of 5 ms pulses repeated from between 10 to 100 ms for duty-cycles (DCs) of 50% to 5%, and at varying offset frequencies, and time averaged RF powers. MT and ihMT data were measured in regions of interest within gray matter, white matter and muscle, and fit to the model. RF irradiation effects on signal intensity were reduced at 5% relative to 50% DCs. This reduced RF effect was much larger for single than dual frequency irradiation. 5% DC irradiation reduced single and dual frequency MT ratios but increased ihMT ratios up to 3 fold in brain tissues. Muscle ihMT increased by an even larger factor, depending on the frequency and applied power. The model predicted these changes with duty-cycle. The model fit the data well and constrained model parameters. Low duty-cycle pulsed irradiation reduces MT effects and markedly increases dipolar order effects. This approach is an attractive method to enhance ihMT signal-to-noise ratio and demonstrates a measurable ihMT effect in muscle tissue at 3 T under acceptable specific absorption rates. The effects of duty-cycle changes demonstrated in a separate MT/ihMT preparation provide a route for new applications in magnetization-prepared MRI sequences.
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Affiliation(s)
- G Varma
- Department of Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA.
| | - O M Girard
- Aix Marseille Univ, CNRS, CRMBM, Marseille, France
| | - S Mchinda
- Aix Marseille Univ, CNRS, CRMBM, Marseille, France
| | - V H Prevost
- Aix Marseille Univ, CNRS, CRMBM, Marseille, France
| | - A K Grant
- Department of Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
| | - G Duhamel
- Aix Marseille Univ, CNRS, CRMBM, Marseille, France
| | - D C Alsop
- Department of Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
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8
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Zhao X, Song HK, Wehrli FW. In vivo bone 31 P relaxation times and their implications on mineral quantification. Magn Reson Med 2018; 80:2514-2524. [PMID: 29744923 PMCID: PMC6226373 DOI: 10.1002/mrm.27230] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2018] [Revised: 03/13/2018] [Accepted: 03/31/2018] [Indexed: 12/23/2022]
Abstract
PURPOSE The intersubject variations in bone phosphorus-31 (31 P) T1 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> , as well as the implications on in vivo 31 P MRI-based bone mineral quantification, were investigated at 3T field strength. METHODS A technique that isolates the bone signal from the composite in vivo 31 P spectrum was first evaluated via simulation and experiments ex vivo and subsequently applied to measure the T1 of bone 31 P collectively with a spectroscopic saturation recovery sequence in a group of healthy subjects aged 26 to 76 years. <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> was derived from the bone signal linewidth. The density of bone 31 P was derived for all subjects from 31 P zero TE images acquired in the same scan session using the measured relaxation times. Test-retest experiments were also performed to evaluate repeatability of this in vivo MRI-based bone mineral quantification protocol. RESULTS The T1 obtained in vivo using the proposed spectral separation method combined with saturation recovery sequence is 38.4 ± 1.5 s for the subjects studied. Average 31 P density found was 6.40 ± 0.58 mol/L (corresponding to 1072 ± 98 mg/cm3 mineral density), in good agreement with an earlier study in specimens from donors of similar age range. Neither the relaxation times (P = 0.18 for T1 , P = 0.99 for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> ) nor 31 P density (P = 0.55) were found to correlate with subject age. Average coefficients of variation for the repeat study were 1.5%, 2.6%, and 4.4% for bone 31 P T1 , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> , and density, respectively. CONCLUSION Neither 31 P T1 nor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> varies significantly in healthy adults across a 50-year age range, therefore obviating the need for subject-specific measurements.
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Affiliation(s)
- Xia Zhao
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Hee Kwon Song
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Felix W Wehrli
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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9
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Yuan J, Patterson AJ, Ruetten PPR, Reid SA, Gillard JH, Graves MJ. A Comparison of Black-blood T 2 Mapping Sequences for Carotid Vessel Wall Imaging at 3T: An Assessment of Accuracy and Repeatability. Magn Reson Med Sci 2018. [PMID: 29515084 PMCID: PMC6326764 DOI: 10.2463/mrms.mp.2017-0141] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Purpose: This study is to compare the accuracy of four different black-blood T2 mapping sequences in carotid vessel wall. Methods: Four different black-blood T2 mapping sequences were developed and tested through phantom experiments and 17 healthy volunteers. The four sequences were: 1) double inversion-recovery (DIR) prepared 2D multi-echo spin-echo (MESE); 2) DIR-prepared 2D multi-echo fast spin-echo (MEFSE); 3) improved motion-sensitized driven-equilibrium (iMSDE) prepared 3D FSE and 4) iMSDE prepared 3D fast spoiled gradient echo (FSPGR). The concordance correlation coefficient and Bland–Altman statistics were used to compare the sequences with a gold-standard 2D MESE, without blood suppression in phantom studies. The volunteers were scanned twice to test the repeatability. Mean and standard deviation of vessel wall T2, signal-to-noise (SNR), the coefficient of variance and interclass coefficient (ICC) of the two scans were compared. Results: The phantom study demonstrated that T2 measurements had high concordance with respect to the gold-standard (all r values >0.9). In the volunteer study, the DIR 2D MEFSE had significantly higher T2 values than the other three sequences (P < 0.01). There was no difference in T2 measurements obtained using the other three sequences (P > 0.05). iMSDE 3D FSE had the highest SNR (P < 0.05) compared with the other three sequences. The 2D DIR MESE has the highest repeatability (ICC: 0.96, [95% CI: 0.88–0.99]). Conclusion: Although accurate T2 measurements can be achieved in phantom by the four sequences, in vivo vessel wall T2 quantification shows significant differences. The in vivo images can be influenced by multiple factors including black-blood preparation and acquisition method. Therefore, a careful choice of acquisition methods and analysis of the confounding factors are required for accurate in vivo carotid vessel wall T2 measurements. From the settings in this study, the iMSDE prepared 3D FSE is preferred for the future volunteer/patient scans.
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Affiliation(s)
- Jianmin Yuan
- Department of Radiology, University of Cambridge, Level 5, Box 218, Addenbrooke's Hospital
| | - Andrew J Patterson
- Department of Radiology, Cambridge University Hospitals NHS Foundation Trust
| | - Pascal P R Ruetten
- Department of Radiology, University of Cambridge, Level 5, Box 218, Addenbrooke's Hospital
| | | | - Jonathan H Gillard
- Department of Radiology, University of Cambridge, Level 5, Box 218, Addenbrooke's Hospital
| | - Martin J Graves
- Department of Radiology, University of Cambridge, Level 5, Box 218, Addenbrooke's Hospital.,Department of Radiology, Cambridge University Hospitals NHS Foundation Trust
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10
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Soustelle L, Lamy J, Rousseau F, Armspach JP, Loureiro de Sousa P. A diffusion-based method for long-T2suppression in steady state sequences: Validation and application for 3D-UTE imaging. Magn Reson Med 2017; 80:548-559. [DOI: 10.1002/mrm.27057] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 12/01/2017] [Accepted: 12/01/2017] [Indexed: 12/21/2022]
Affiliation(s)
- Lucas Soustelle
- Université de Strasbourg, CNRS, ICube, FMTS; Strasbourg France
| | - Julien Lamy
- Université de Strasbourg, CNRS, ICube, FMTS; Strasbourg France
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11
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van Gelderen P, Jiang X, Duyn JH. Rapid measurement of brain macromolecular proton fraction with transient saturation transfer MRI. Magn Reson Med 2016; 77:2174-2185. [PMID: 27342121 DOI: 10.1002/mrm.26304] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 04/18/2016] [Accepted: 05/19/2016] [Indexed: 01/08/2023]
Abstract
PURPOSE To develop an efficient MRI approach to estimate the nonwater proton fraction (f) in human brain. METHODS We implement a brief, efficient magnetization transfer (MT) pulse that selectively saturates the magnetization of the (semi-) solid protons, and monitor the transfer of this saturation to the water protons as a function of delay after saturation. RESULTS Analysis of the transient MT effect with two-pool model allowed robust extraction of f at both 3 and 7 T. This required estimating the longitudinal relaxation rate constant (R1,MP and R1,WP ) for both proton pools, which was achieved with the assumption of uniform R1,MP and R1,WP across brain tissues. Resulting values of f were approximately 50% higher than reported previously, which is partly attributed to MT-pulse efficiency and R1,MP being higher than assumed previously. CONCLUSION Experiments performed on human brain in vivo at 3 and 7 T demonstrate the ability of the method to robustly determine f in a scan time of approximately 5 min. Magn Reson Med 77:2174-2185, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Peter van Gelderen
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Xu Jiang
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Jeff H Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
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12
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Xu J, Chan KWY, Xu X, Yadav N, Liu G, van Zijl PCM. On-resonance variable delay multipulse scheme for imaging of fast-exchanging protons and semisolid macromolecules. Magn Reson Med 2016; 77:730-739. [PMID: 26900759 DOI: 10.1002/mrm.26165] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 01/21/2016] [Accepted: 01/24/2016] [Indexed: 12/27/2022]
Abstract
PURPOSE To develop an on-resonance variable delay multipulse (VDMP) scheme to image magnetization transfer contrast (MTC) and the chemical exchange saturation transfer (CEST) contrast of total fast-exchanging protons (TFP) with exchange rate above approximately 1 kHz. METHODS A train of high power binomial pulses was applied at the water resonance. The interpulse delay, called mixing time, was varied to observe its effect on the water signal reduction, allowing separation and quantification of MTC and CEST contributions as a result of their different proton transfer rates. The fast-exchanging protons in CEST and MTC are labeled together with the short T2 components in MTC and separated out using a variable mixing time. RESULTS Phantom studies of selected metabolite solutions (glucose, glutamate, creatine, myo-inositol), bovine serum albumin (BSA), and hair conditioner show the capability of on-resonance VDMP to separate out exchangeable protons with exchange rates above 1 kHz. Quantitative MTC and TFP maps were acquired on healthy mouse brains using this method, showing strong gray/white matter contrast for the slowly transferring MTC protons, whereas the TFP map was more uniform across the brain but somewhat higher in gray matter. CONCLUSIONS The new method provides a simple way of imaging fast-exchanging protons and MTC components with a slow transfer rate. Magn Reson Med 77:730-739, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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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
| | - Kannie W Y Chan
- 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
| | - Xiang Xu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Nirbhay 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
| | - Guanshu Liu
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
| | - 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
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13
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Andronesi OC, Bhat H, Reuter M, Mukherjee S, Caravan P, Rosen BR. Whole brain mapping of water pools and molecular dynamics with rotating frame MR relaxation using gradient modulated low-power adiabatic pulses. Neuroimage 2013; 89:92-109. [PMID: 24345390 DOI: 10.1016/j.neuroimage.2013.12.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 11/27/2013] [Accepted: 12/07/2013] [Indexed: 10/25/2022] Open
Abstract
Nuclear magnetic resonance (NMR) relaxation in the rotating frame is sensitive to molecular dynamics on the time scale of water molecules interacting with macromolecules or supramolecular complexes, such as proteins, myelin and cell membranes. Hence, longitudinal (T1ρ) and transverse (T2ρ) relaxation in the rotating frame may have a great potential to probe the macromolecular fraction of tissues. This stimulated a large interest in using this MR contrast to image brain under healthy and disease conditions. However, experimental challenges related to the use of intense radiofrequency irradiation have limited the widespread use of T1ρ and T2ρ imaging. Here, we present methodological development to acquire 3D high-resolution or 2D (multi-)slice selective T1ρ and T2ρ maps of the entire human brain within short acquisition times. These improvements are based on a class of gradient modulated adiabatic pulses that reduce the power deposition, provide slice selection, and mitigate artifacts resulting from inhomogeneities of B1 and B0 magnetic fields. Based on an analytical model of the T1ρ and T2ρ relaxation we compute the maps of macromolecular bound water fraction, correlation and exchange time constants as quantitative biomarkers informative of tissue macromolecular content. Results obtained from simulations, phantoms and five healthy subjects are included.
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Affiliation(s)
- Ovidiu C Andronesi
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
| | - Himanshu Bhat
- Siemens Medical Solutions USA Inc, Charlestown, MA 02129, USA
| | - Martin Reuter
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Shreya Mukherjee
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Peter Caravan
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Bruce R Rosen
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
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Stoeck CT, Hu P, Peters DC, Kissinger KV, Goddu B, Goepfert L, Ngo L, Manning WJ, Kozerke S, Nezafat R. Optimization of on-resonant magnetization transfer contrast in coronary vein MRI. Magn Reson Med 2011; 64:1849-54. [PMID: 20938974 DOI: 10.1002/mrm.22581] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Magnetization transfer contrast has been used commonly for endogenous tissue contrast improvements in angiography, brain, body, and cardiac imaging. Both off-resonant and on-resonant RF pulses can be used to generate magnetization transfer based contrast. In this study, on-resonant magnetization transfer preparation using binomial pulses were optimized and compared with off-resonant magnetization transfer for imaging of coronary veins. Three parameters were studied with simulations and in vivo measurements: flip angle, pulse repetitions, and binomial pulse order. Subsequently, first or second order binomial on-resonant magnetization transfer pulses with eight repetitions of 720° and 240° flip angle were used for coronary vein MRI. Flip angles of 720° yielded contrast enhancement of 115% (P < 0.0006) for first order on-resonant and 95% (P < 0.0006) for off-resonant magnetization transfer. There was no statistically significance difference between off-resonant and on-resonant first order binomial Magnetization transfer at 720°. However, for off-resonance pulses, much more preparation time is needed when compared with the binomials but with considerably reduced specific absorption rate.
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Affiliation(s)
- Christian T Stoeck
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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15
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van Zijl PCM, Yadav NN. Chemical exchange saturation transfer (CEST): what is in a name and what isn't? Magn Reson Med 2011; 65:927-48. [PMID: 21337419 PMCID: PMC3148076 DOI: 10.1002/mrm.22761] [Citation(s) in RCA: 792] [Impact Index Per Article: 60.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Revised: 11/01/2010] [Accepted: 11/24/2010] [Indexed: 12/24/2022]
Abstract
Chemical exchange saturation transfer (CEST) imaging is a relatively new magnetic resonance imaging contrast approach in which exogenous or endogenous compounds containing either exchangeable protons or exchangeable molecules are selectively saturated and after transfer of this saturation, detected indirectly through the water signal with enhanced sensitivity. The focus of this review is on basic magnetic resonance principles underlying CEST and similarities to and differences with conventional magnetization transfer contrast. In CEST magnetic resonance imaging, transfer of magnetization is studied in mobile compounds instead of semisolids. Similar to magnetization transfer contrast, CEST has contributions of both chemical exchange and dipolar cross-relaxation, but the latter can often be neglected if exchange is fast. Contrary to magnetization transfer contrast, CEST imaging requires sufficiently slow exchange on the magnetic resonance time scale to allow selective irradiation of the protons of interest. As a consequence, magnetic labeling is not limited to radio-frequency saturation but can be expanded with slower frequency-selective approaches such as inversion, gradient dephasing and frequency labeling. The basic theory, design criteria, and experimental issues for exchange transfer imaging are discussed. A new classification for CEST agents based on exchange type is proposed. The potential of this young field is discussed, especially with respect to in vivo application and translation to humans.
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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, Maryland 21205, USA.
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Carl M, Bydder M, Du J, Takahashi A, Han E. Optimization of RF excitation to maximize signal and T2 contrast of tissues with rapid transverse relaxation. Magn Reson Med 2011; 64:481-90. [PMID: 20665792 DOI: 10.1002/mrm.22433] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ultrashort echo time MRI requires specialized pulse sequences to overcome the short T(2) of the MR signal encountered in tissues such as ligaments, tendon, or cortical bone. Theoretical work is presented, supported by simulations and experimental data on optimizing the radiofrequency excitation to maximize signal-to-noise ratio and contrast-to-noise ratio. The theoretical calculations and simulations are based on the classic Bloch equations and lead to a closed form expression for the optimal radiofrequency pulse parameters to maximize the MR signal in the presence of rapid T(2) decay. In the steady state, the spoiled gradient recalled echo signal amplitude in response to the radiofrequency excitation pulses is not maximized by the classic Ernst angle but by a more general criterion we call "generalized Ernst angle." Finally, it is shown that T(2) contrast is maximized by flipping the magnetization at the Ernst angle with a radiofrequency pulse duration proportional to the targeted T(2). Experimental studies on short T(2) phantoms confirm these optimization criteria for both signal-to-noise ratio and contrast-to-noise ratio.
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17
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MTR variations in normal adult brain structures using balanced steady-state free precession. Neuroradiology 2010; 53:159-67. [DOI: 10.1007/s00234-010-0714-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Accepted: 04/30/2010] [Indexed: 11/25/2022]
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18
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Viswanathan S, Kovacs Z, Green KN, Ratnakar SJ, Sherry AD. Alternatives to gadolinium-based metal chelates for magnetic resonance imaging. Chem Rev 2010; 110:2960-3018. [PMID: 20397688 PMCID: PMC2874212 DOI: 10.1021/cr900284a] [Citation(s) in RCA: 310] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Subha Viswanathan
- Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390 and Department of Chemistry, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080
| | - Zoltan Kovacs
- Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390 and Department of Chemistry, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080
| | - Kayla N. Green
- Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390 and Department of Chemistry, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080
| | - S. James Ratnakar
- Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390 and Department of Chemistry, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080
| | - A. Dean Sherry
- Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390 and Department of Chemistry, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080
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19
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Sharma R. Microimaging of hairless rat skin by magnetic resonance at 900 MHz. Magn Reson Imaging 2009; 27:240-55. [DOI: 10.1016/j.mri.2008.06.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Revised: 06/11/2008] [Accepted: 06/30/2008] [Indexed: 11/15/2022]
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Techawiboonwong A, Song HK, Leonard MB, Wehrli FW. Cortical bone water: in vivo quantification with ultrashort echo-time MR imaging. Radiology 2008; 248:824-33. [PMID: 18632530 DOI: 10.1148/radiol.2482071995] [Citation(s) in RCA: 164] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
PURPOSE To develop and evaluate a method based on ultrashort echo-time radial magnetic resonance (MR) imaging to quantify bone water (BW) concentration as a new metric of bone quality in human cortical bone in vivo. MATERIALS AND METHODS Human subject studies were institutional review board approved and HIPAA compliant; informed consent was obtained. Cortical BW concentration was determined with custom-designed MR imaging sequences at 3.0 T and was validated in sheep and human cortical bone by using exchange of native water with deuterium oxide (D(2)O). The submillisecond T2* of BW requires correction for relaxation losses during the radiofrequency pulse. BW was measured at the tibial midshaft in healthy pre- and postmenopausal women (mean age, 34.6 and 69.4 years, respectively; n = 5 in each group) and in patients receiving maintenance hemodialysis (mean age, 51.8 years; n = 6) and was compared with bone mineral density (BMD) at the same site at peripheral quantitative computed tomography, as well as with BMD of the lumbar spine and hip at dual x-ray absorptiometry. Data were analyzed by using the Pearson correlation coefficient and two-sided t tests as appropriate. RESULTS Excellent agreement was obtained ex vivo between the water displaced by using D(2)O exchange and water measured with respect to a reference sample (r(2) = 0.99, P < .001). In vivo, BW in the postmenopausal group was greater by 65% (28.7% +/- 1.3 [standard deviation] vs 17.4% +/- 2.2, P < .001) than in the premenopausal group, and patients with renal osteodystrophy had higher BW (41.4% +/- 9.6) than the premenopausal group by 135% (P < .001) and the postmenopausal group by 43% (P = .02). BMD showed an opposite behavior, with much smaller group differences. Because the majority of BW is in the pore system of cortical bone, this parameter provides a surrogate measure for cortical porosity. CONCLUSION A new MR imaging-based method for quantifying BW noninvasively has been demonstrated.
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Affiliation(s)
- Aranee Techawiboonwong
- Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, 3400 Spruce St, 1 Founders, MRI Education Center, Philadelphia, PA 19104, USA
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21
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Techawiboonwong A, Song HK, Wehrli FW. In vivo MRI of submillisecond T(2) species with two-dimensional and three-dimensional radial sequences and applications to the measurement of cortical bone water. NMR IN BIOMEDICINE 2008; 21:59-70. [PMID: 17506113 DOI: 10.1002/nbm.1179] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Water in dense collagenous tissues such as tendons and ligaments, as well as water in cortical bone that occupies the spaces of the lacuno-canicular system or is tightly bound to collagen, is not ordinarily detectable by MRI. Water proton T(2) in these structures is generally less than 1 ms. Recent advances in instrumentation in conjunction with non-Cartesian imaging strategies now allow center of k-space to be scanned 100 micros or less after excitation. We examined the performance of two radial pulse sequences, a 2D sequence with half-pulse excitation and a new 3D hybrid sequence with variable-echo Cartesian encoding in the third dimension, on a whole-body 3 T scanner. Both pulse sequences used long-T(2) soft-tissue suppression pulses. The half-pulse slice profiles observed experimentally agreed well with those computed on the basis of a numerical solution of Bloch equations. The techniques yielded a signal-to-noise ratio of the order of 25 in 9 min scan time at a nominal voxel size of 0.58 x 0.58 x 8 mm(3) and 50-90 micros 'echo time' in the cortex of the tibial mid-shaft. With the use of an external reference, the water volume fraction of cortical bone in four subjects (mean +/- SD age 32.25 +/- 5.3 years) was found to be 22.5 +/- 2.7%, in good agreement with literature values.
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Affiliation(s)
- Aranee Techawiboonwong
- Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA
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22
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Vinogradov E, Zhang S, Lubag A, Balschi JA, Sherry AD, Lenkinski RE. On-resonance low B1 pulses for imaging of the effects of PARACEST agents. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2005; 176:54-63. [PMID: 15979362 DOI: 10.1016/j.jmr.2005.05.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Revised: 05/08/2005] [Accepted: 05/18/2005] [Indexed: 05/03/2023]
Abstract
Application of the exchange-sensitive, low-power RF pulses positioned on the bulk water resonance for imaging of the effects of PARACEST agents is proposed as an alternative to the standard CW off-resonance irradiation. Specifically, we applied a low-power WALTZ-16 RF train, with the 90 degrees pulse unit replaced by a pulse of the fixed length (WALTZ-16*). Using this sequence, the bulk water signal was found to be sensitive to exchange lifetimes with PARACEST complex bound protons, the transverse relaxation time of bulk water, and longitudinal relaxation time of bound protons. In this report, the concept of using WALTZ-16* to "activate" a PARACEST effect is introduced and some of the salient features of this technique with respect to experimental conditions and performance levels are discussed. Computational predictions are verified and explored by comparison with experimental spectroscopic and imaging data. It is shown that WALTZ-16* can be used to detect PARACEST agents with an RF intensity as low as 200 Hz for concentrations as low as a few tens of microM for lanthanide chelates having appropriate water-exchange rates (Tm,Dy).
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Affiliation(s)
- Elena Vinogradov
- Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA.
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23
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Tyler DJ, Gowland PA. Rapid quantitation of magnetization transfer using pulsed off-resonance irradiation and echo planar imaging. Magn Reson Med 2005; 53:103-9. [PMID: 15690508 DOI: 10.1002/mrm.20323] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A technique for producing a quantitative measure of magnetization transfer parameters in a clinically feasible time scale is proposed. The combination of pulsed off-resonance irradiation and echo planar imaging has produced an imaging sequence that negates the need for continuous wave irradiation and allows the approach to steady-state conditions to be studied. Data analysis involves the step-by-step numerical solution of the modified Bloch equations to generate a quantitative model of the measured signal intensity based on the relative size of the bound proton pool and the bound proton pool transverse relaxation time. The sequence and model are applied to the study of a series of agar gels of varying concentrations and the results are compared to those from the literature.
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Affiliation(s)
- Damian J Tyler
- Magnetic Resonance Centre, School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
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24
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Levesque I, Sled JG, Narayanan S, Santos AC, Brass SD, Francis SJ, Arnold DL, Pike GB. The role of edema and demyelination in chronic T1 black holes: A quantitative magnetization transfer study. J Magn Reson Imaging 2005; 21:103-10. [PMID: 15666408 DOI: 10.1002/jmri.20231] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To use quantitative magnetization transfer imaging (qMTI) in an investigation of T1-weighted hypointensity observed in clinical magnetic resonance imaging (MRI) scans of multiple sclerosis (MS) patients, which has previously been proposed as a more specific indicator of tissue damage than the more commonly detected T2 hyperintensity. MATERIALS AND METHODS A cross-sectional study of 10 MS patients was performed using qMTI. A total of 60 MTI measurements were collected in each patient at a resolution of 2 x 2 x 7 mm, over a range of saturation pulses. The observed T1 and T2 were also measured. qMT model parameters were estimated using a voxel-by-voxel fit. RESULTS A total of 65 T2-hyperintense lesions were identified; 53 were also T1 hypointense. In these black holes, the qMTI-derived semisolid pool fraction F correlated negatively with T(1,obs) (r2 = 0.76; P < 0.0001). The water pool absolute size (PDf) showed a weaker correlation with T(1,obs) (positive, r2 = 0.53; P < 0.0001). The magnetization transfer ratio (MTR) showed a similarly strong correlation with F and a weaker correlation with PDf (r2 = 0.18; P < 0.04). CONCLUSION T1 increases in chronic black holes strongly correlated with the decline in semisolid pool size, and somewhat less to the confounding effect of edema. MTR was less sensitive than T(1,obs) to liquid pool changes associated with edema.
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Affiliation(s)
- Ives Levesque
- McConnell Brain Imaging Centre, Montréal Neurological Institute, McGill University, Montréal, H3A 2B4 Québec, Canada.
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25
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Helms G, Hagberg GE. Pulsed saturation of the standard two-pool model for magnetization transfer. Part I: The steady state. ACTA ACUST UNITED AC 2004. [DOI: 10.1002/cmr.a.20004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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26
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Gochberg DF, Gore JC. Quantitative imaging of magnetization transfer using an inversion recovery sequence. Magn Reson Med 2003; 49:501-5. [PMID: 12594753 DOI: 10.1002/mrm.10386] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A new imaging method has been developed for quantitatively measuring magnetization transfer (MT). It uses a simple inversion recovery sequence, although one with very short (milliseconds) inversion times, and thus can be implemented on clinical imaging systems with little modification to existing pulse sequences. The sequence requires an inversion pulse with a length much longer than T(2m) (typically 10 micros) and much shorter than T(2f) (typically tens of ms) and 1/k(mf) (typically tens of ms), where T(2m) and T(2f) are the transverse relaxation times of the immobile macromolecular and free water protons, respectively, and k(mf) is the rate of MT between these populations. The resultant NMR signal is sensitive to MT when this inversion pulse affects the mobile and immobile proton pools to different degrees and by appropriate analysis of the signals obtained for different inversion times, quantitative information can be derived on the macromolecular content and exchange rates within the sample. The method has been used in conjunction with echo planar imaging to produce maps of the spatial distribution of the macromolecular content and MT rate in cross-linked bovine serum albumin. Comparisons between this method and other quantitative MT techniques are discussed.
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Affiliation(s)
- Daniel F Gochberg
- Diagnostic Radiology, Yale University School of Medicine, Yale University, New Haven, Connecticut, USA.
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27
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Tsukushi S, Takahashi M, Miyagi N, Matsushima S, Andoh M, Kinosada Y. Magnetization transfer ratios of musculoskeletal tumors. J Orthop Sci 2003; 7:524-7. [PMID: 12355124 DOI: 10.1007/s007760200093] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The magnetization transfer method is a relatively new technique that creates contrast by the exchange of magnetization protons associated with macromolecules and bulk water protons through cross-relaxation or chemical exchange. We measured the magnetization transfer ratio (MTR) and compared it with the DNA index to determine whether MTR can serve as an indicator of malignancy in musculoskeletal tumors. The DNA index correlated with MTR in such musculoskeletal tumors ( P < 0.05). This suggests that MTR can be used as a parameter to quantitatively indicate malignancy.
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Affiliation(s)
- Satoshi Tsukushi
- Department of Orthopaedic Surgery, Nagoya Memorial Hospital, 4-305 Hirabari, Tenpaku-ku, Nagoya 468-0011, Japan
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Abstract
Magnetic resonance coronary angiography (MRCA) has witnessed tremendous technical advances over the past decade. Although high-quality images of the coronary arteries have been demonstrated, this imaging modality is not performed routinely today. The fundamental properties of the coronary arteries deterring noninvasive imaging are well known. This article provides an overview of the developmental efforts to overcome these challenges, and highlights key technical and clinical advances. The future prospect of MRCA depends on clinical implementation of the technique. In order to meet this challenge, the following issues must be addressed: contrast- and signal-to-noise ratio, temporal and spatial resolution, and scan protocol.
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Affiliation(s)
- Phillip C Yang
- Department of Medicine, Stanford University Medical Center, 300 Pasteur Drive, H2157, Stanford, CA 94305-5233, USA.
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29
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Abstract
A new flow suppression method has been proposed for the acquisition of blood-suppressed (black-blood) images in combination with administration of a positive contrast agent. The technique employs the quadruple inversion-recovery (QIR) preparative pulse sequence, which consists of two double-inversion modules followed by two delays. Within each double inversion, a nonselective RF pulse is immediately followed by a slice-selective one. The time intervals of the sequence can be calculated using an algorithm based on minimization of the variation of a signal equation over an entire range of T(1) occurring in blood before and after contrast administration. QIR is highly insensitive to variations of T(1), providing efficient suppression of a flow signal with T(1) in a range of 200-1200 ms. The technique utilizes identical scan parameters for pre- and postcontrast acquisition, and thus allows reliable quantitative interpretation of contrast enhancement (CE). The clinical application of QIR was demonstrated in high-resolution, contrast-enhanced, black-blood imaging of atherosclerotic plzzaque.
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Affiliation(s)
- Vasily L Yarnykh
- Department of Radiology, University of Washington, Seattle, Washington 98195, USA.
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30
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Yao L, Thomasson D. Magnetization transfer contrast in rapid three-dimensional MR imaging using segmented radiofrequency prepulses. AJR Am J Roentgenol 2002; 179:863-5. [PMID: 12239025 DOI: 10.2214/ajr.179.4.1790863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Lawrence Yao
- Department of Radiology, National Institutes of Health, Bldg. 10, Rm. 1C-640, 10 Center Dr., MSC 1182, Bethesda, MD 20892-1182, USA
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31
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Sled JG, Pike GB. Quantitative imaging of magnetization transfer exchange and relaxation properties in vivo using MRI. Magn Reson Med 2001; 46:923-31. [PMID: 11675644 DOI: 10.1002/mrm.1278] [Citation(s) in RCA: 299] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We describe a novel imaging technique that yields all of the observable properties of the binary spin-bath model for magnetization transfer (MT) and demonstrate this method for in vivo studies of the human head. Based on a new model of the steady-state behavior of the magnetization during a pulsed MT-weighted imaging sequence, this approach yields parametric images of the fractional size of the restricted pool, the magnetization exchange rate, the T(2) of the restricted pool, as well as the relaxation times in the free pool. Validated experimentally on agar gels and samples of uncooked beef, we demonstrate the method's application on two normal subjects and a patient with multiple sclerosis.
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Affiliation(s)
- J G Sled
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
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32
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Abstract
This review deals with magnetization transfer (MT) effects observed in in vivo NMR spectroscopy. The basic experimental methods of MT experiments, the underlying kinetic mechanisms as well as the evaluation of measured data by fits to two- or three-pool models are described. Experimental results of both (31)P and (1)H in vivo MRS are reviewed showing the potential of MT experiments to characterize kinetic equilibrium reactions. This includes reactions where all involved components are MR visible, as well as situations where one indirectly measures pools of bound spins which cannot directly be observed in vivo. In particular, MT effects are described which have been observed in in vivo (1)H NMR spectra measured on the animal or human brain or on skeletal muscle. Possible mechanisms for the strong MT effects observed for the signals of creatine/phosphocreatine, lactate, alcohol and other metabolites are discussed. It is also emphasized that MT effects caused by water suppression techniques may lead to systematic errors in the quantification of in vivo (1)H NMR spectra.
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Affiliation(s)
- D Leibfritz
- Universität Bremen, Fachbereich 2, NW 2, D-28334 Bremen, Germany
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33
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Henkelman RM, Stanisz GJ, Graham SJ. Magnetization transfer in MRI: a review. NMR IN BIOMEDICINE 2001; 14:57-64. [PMID: 11320533 DOI: 10.1002/nbm.683] [Citation(s) in RCA: 605] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
This review describes magnetization transfer (MT) contrast in magnetic resonance imaging. A qualitative description of how MT works is provided along with experimental evidence that leads to a quantitative model for MT in tissues. The implementation of MT saturation in imaging sequences and the interpretation of the MT-induced signal change in terms of exchange processes and direct effects are presented. Finally, highlights of clinical uses of MT are outlined and future directions for investigation proposed.
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Affiliation(s)
- R M Henkelman
- Department of Medical Biophysics University of Toronto, Toronto, Canada.
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Abstract
Magnetization transfer imaging is a modality capable of examining the non-water components of brain tissue by examining the effects they have on water protons. It may be used qualitatively to increase the visibility of lesions seen during magnetic resonance angiography and following the administration of an intravenous paramagnetic contrast medium. Quantitatively, it can be used to examine the effect of pathology on magnetization transfer contrast, to provide a measurement of myelination, as well as to quantify disease progression in trauma, neoplasia, neurodegeneration and other disorders of the brain. This paper reviews the theory of magnetization transfer imaging, its applications, and provides an example of its use in examining the canine brain.
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Affiliation(s)
- C H Vite
- Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, USA
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Vavasour IM, Whittall KP, Li DK, MacKay AL. Different magnetization transfer effects exhibited by the short and long T(2) components in human brain. Magn Reson Med 2000; 44:860-6. [PMID: 11108622 DOI: 10.1002/1522-2594(200012)44:6<860::aid-mrm6>3.0.co;2-c] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Magnetization transfer ratios (MTRs) were measured separately for the two T(2) components in white matter. For both binomial and off-resonance sinc MT pulses, the MTR was larger for the short T(2) component than for the long T(2) component. This differential MT effect disappeared for delays between the MT pulse and the multi-echo pulse sequence longer than 200 msec, indicating exchange between the two components. When using the sinc MT pulse, the MTR for the short T(2) component was similar for different white matter structures, whereas it varied for different white matter structures when using the binomial pulse-a phenomenon attributed to direct saturation. When the sinc pulse frequency was brought closer to resonance, MTRs in white matter and doped water phantoms increased for both components but more so for the shorter T(2) component. This behavior was consistent with a Bloch equation model of direct saturation.
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Affiliation(s)
- I M Vavasour
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
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36
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Pike GB, De Stefano N, Narayanan S, Worsley KJ, Pelletier D, Francis GS, Antel JP, Arnold DL. Multiple sclerosis: magnetization transfer MR imaging of white matter before lesion appearance on T2-weighted images. Radiology 2000; 215:824-30. [PMID: 10831705 DOI: 10.1148/radiology.215.3.r00jn02824] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To determine the evolution of magnetization transfer (MT) in white matter regions before and after plaque development in patients with multiple sclerosis (MS). MATERIALS AND METHODS In a 5-year longitudinal evaluation, 30 patients with MS underwent conventional magnetic resonance (MR) imaging, MT MR imaging, and clinical assessment. Cross-sectional data in 12 healthy subjects were also collected. Semiautomated lesion classification with use of T2-weighted MR images was used to measure the time course of the MT ratio (calculated with MR data acquired without and with MT saturation) in every voxel and to help analyze the relationship with the status of lesions depicted on T2-weighted images. RESULTS There was a significant (P <.001) temporal decline in lesion MT ratio after lesion appearance on T2-weighted images. A significant (P <. 001) progressive decline in MT ratio was also present in voxels that later became lesions, prior to initial detection on T2-weighted images. Even 1(1/2) years prior to lesion appearance, the MT ratio (33.3%) in regions destined to become such lesions was significantly (P <.001) lower than that in both white matter in healthy subjects (41.3%) and other normal-appearing white matter in patients with MS (38.1%). CONCLUSION The MT ratio reveals progressive focal abnormalities in MS that antedate by up to 2 years the appearance of lesions on T2-weighted MR images.
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Affiliation(s)
- G B Pike
- McConnell Brain Imaging Center, Montreal Neurological Institute, 3801 University St, Montreal, Québec, Canada.
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37
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Abstract
Investigation of the cause of image artifacts generated by a magnetization transfer (MT) sequence using binomial-pulse trains led to findings of imperfections in the pulses. These imperfections caused anomalous direct saturation of the free water, which was localized due to the static magnetic field inhomogeneity. In the case of single binomial pulses a loss of overall MT response across the field of view results. Two methods of correcting the imperfections and removing the artifact have been established using interactive adjustment of sub-pulse lobes and phase swapping of pulse trains. These imperfections may be present in many systems and may have led to erroneous judgements of the value of binomial pulses for MT imaging. A technique for interrogating the frequency spectrum of the binomial-pulse train has been utilized, allowing its optimization. The use of accurate and optimized binomial pulses may yet prove to be preferable to pulsed off-resonance methods for quantitative, clinical MT imaging.
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Affiliation(s)
- N P Davies
- Medical Physics Group, School of Physics, University of Exeter, Exeter EX4 4QL, United Kingdom.
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39
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Helms G, Frahm J. Magnetization transfer attenuation of creatine resonances in localized proton MRS of human brain in vivo. NMR IN BIOMEDICINE 1999; 12:490-494. [PMID: 10668041 DOI: 10.1002/(sici)1099-1492(199912)12:8<490::aid-nbm593>3.0.co;2-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
To assess putative magnetization transfer effects on the proton resonances of cerebral metabolites in human brain, we performed quantitative proton magnetic resonance spectroscopy (2.0 T, STEAM, TR/TE/TM = 6000/40/10 ms, LCModel data evaluation) of white matter (7.68 mL, 10 healthy young subjects) in the absence and presence of fast repetitive off-resonance irradiation (2.1 kHz from the water resonance) using a train of 100 Gaussian-shaped RF pulses (12.8 ms duration, 120 Hz nominal bandwidth, 40 ms repetition period, 1080 degrees nominal flip angle). A comparison of pertinent metabolite concentrations revealed a magnetization transfer attenuation factor of the methyl and methylene resonances of creatine and phosphocreatine of 0.87 +/- 0.05 (p < 0.01). No attenuation was observed for the resonances of N-acetylaspartate and N-acetylaspartylglutamate, glutamate and glutamine, choline-containing compounds, and myo-inositol. The finding for total creatine is in excellent agreement with data reported for rat brain. The results are consistent with the hypothesis of a chemical exchange of mobile creatine or phosphocreatine molecules with a small immobilized or 'bound' pool.
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Affiliation(s)
- G Helms
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, D-37070 Göttingen, Germany.
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40
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Abstract
A magnetization-transfer (MT) CPMG hybrid experiment was performed to analyze T(2) relaxation and MT characteristics in bovine optic nerve. Two exchanging liquid pools with their own, independent MT characteristics were necessary to model both the T(2) relaxation and the MT data. The model agrees well with the experimental data and yields physically realistic parameters. The MT effect for myelin water is approximately nine time larger than that for intra/intercellular water, indicating that the MT characteristics observed for white matter are mainly related to myelin. The model can be used to probe parameters that would be difficult to achieve experimentally. The exchange process between the two tissue compartments does not drastically affect the amplitudes and relaxation rates of the T(2) components, but is fast enough to significantly influence their MT characteristics. Although, both the MT and T(2) experiments described in this paper are too time consuming to be applied in routine clinical work, presented results can be useful in interpreting clinical pulse sequences that are sensitive to myelin. Magn Reson Med 42:1128-1136, 1999.
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Affiliation(s)
- G J Stanisz
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.
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41
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Roell SA, Dreher W, Leibfritz D. Combining CW and pulsed saturation allows in vivo quantitation of magnetization transfer observed for total creatine by (1)H-NMR-spectroscopy of rat brain. Magn Reson Med 1999; 42:222-7. [PMID: 10440945 DOI: 10.1002/(sici)1522-2594(199908)42:2<222::aid-mrm2>3.0.co;2-d] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Selective saturation of bound nuclei attenuates the MR visible CH(2) and the CH(3) signal of total creatine (tCr) in rat brain in vivo. The low contrast to noise ratio achieved during the limited experiment time makes it difficult to quantify the effect. It is shown that by combining data from continuous-wave and pulsed saturation experiments, quantitation is possible using the standard magnetization transfer model. The model parameters obtained are the transverse relaxation time of the bound spin fraction B, T2R = 31 +/- 8 micros, the exchange rate r(x) = 0.36 +/- 0.04 s(-1), and the concentration ratio of bound nuclei taking part in the exchange to free tCr magnetization, f = M0B/M0A = 0.04 +/- 0.01. The phenomenon can be explained by either an intermolecular exchange of free and bound creatine molecules or by through-space interaction with bound nuclei showing not necessarily the same chemical shift. Magn Reson Med 42:222-227, 1999.
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Affiliation(s)
- S A Roell
- Universität Bremen, Fachbereich 2 (Chemie), Bremen, Germany
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42
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Vinitski S, Gonzalez CF, Knobler R, Andrews D, Iwanaga T, Curtis M. Fast tissue segmentation based on a 4D feature map in characterization of intracranial lesions. J Magn Reson Imaging 1999; 9:768-76. [PMID: 10373024 DOI: 10.1002/(sici)1522-2586(199906)9:6<768::aid-jmri3>3.0.co;2-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The aim of this work was to develop a fast and accurate method for tissue segmentation in magnetic resonance imaging (MRI) based on a four-dimensional (4D) feature map and compare it with that derived from a 3D feature map. High-resolution MRI was performed in 5 normal individuals, in 12 patients with brain multiple sclerosis (MS), and 9 patients with malignant brain tumors. Three inputs (proton-density, T2-weighted fast spin-echo, and T1-weighted spin-echo MR images) were routinely utilized. As a fourth input, either magnetization transfer MRT was used or T1-weighted post-contrast MRI (in patients only). A modified k-nearest neighbor segmentation algorithm was optimized for maximum computation speed and high-quality segmentation. In that regard, we a) discarded the redundant seed points; b) discarded the points within 0.5 standard deviation from the cluster center that were non-overlapping with other tissue; and c) removed outlying seed points outside 5 times the standard deviation from the cluster center of each tissue class. After segmentation, a stack of color-coded segmented images was created. Our new technique utilizing all four MRI inputs provided better segmentation than that based on three inputs (P < 0.001 for MS and P < 0.001 for tumors). The tissues were smoother due to the reduction of statistical noise, and the delineation of the tissues became sharper. Details that were previously blurred or invisible now became apparent. In normal persons a detailed depiction of deep gray matter nuclei was obtained. In malignant tumors, up to five abnormal tissue types were identified: 1) solid tumor core, 2) cyst, 3) edema in white matter 4) edema in gray matter, and 5) necrosis. Delineation of MS plaque in different stages of demyelination became much sharper. In conclusion, the proposed methodology warrants further development and clinical evaluation.
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Affiliation(s)
- S Vinitski
- Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania 19107, USA
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43
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Abstract
New spectroscopic and imaging methods have been developed for quantitatively measuring magnetization transfer (MT). These methods use trains of radiofrequency (rf) pulses with pulse separations much longer than 1/k(mf) and pulse durations much shorter than 1/k(mf), where k(mf) is the rate of MT from the immobile (macromolecular) protons to the mobile (free water) protons. Signal sensitivity to MT occurs when these pulses affect the mobile and immobile proton pools to different degrees. The signal from water may be quantitatively related to the macromolecular content of the sample using theory. The method has been used to make quantitative measurements of macromolecular content in cross-linked bovine serum albumin and employed in conjunction with echoplanar imaging to produce maps of the spatial distribution of the macromolecular content.
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Affiliation(s)
- D F Gochberg
- Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut, USA
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Berry I, Barker GJ, Barkhof F, Campi A, Dousset V, Franconi JM, Gass A, Schreiber W, Miller DH, Tofts PS. A multicenter measurement of magnetization transfer ratio in normal white matter. J Magn Reson Imaging 1999; 9:441-6. [PMID: 10194715 DOI: 10.1002/(sici)1522-2586(199903)9:3<441::aid-jmri12>3.0.co;2-r] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
To assess the importance of intercenter variations when measuring magnetization transfer ratio (MTR) in the brain, six European centers measured MTR in normal white matter. MTR ranged from 9 to 51 percent units (25 sequences). The effective flip angle of the saturating pulse divided by the pulse repetition time (ENRsat degrees/msec) was a good predictor of MTR (MTR = 3.25 ENRsat).
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Affiliation(s)
- I Berry
- Service de Neuroradiologie, University Hospitals, Toulouse, France
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45
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Rand T, Imhof H, Czerny C, Breitenseher M, Machold K, Turetschek K, Trattnig S. Discrimination between fluid, synovium, and cartilage in patients with rheumatoid arthritis: contrast enhanced Spin Echo versus non-contrast-enhanced fat-suppressed Gradient Echo MR imaging. Clin Radiol 1999; 54:107-10. [PMID: 10050739 DOI: 10.1016/s0009-9260(99)91070-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
PURPOSE The aim of this study was to compare fat-suppressed T1-weighted 3D-Gradient Echo (GE)-images and conventional T1-weighted contrast-enhanced SE images in the assessment of patients with rheumatoid arthritis in an attempt to improve discrimination of inflamed synovium, joint fluid, and cartilage. PATIENTS AND METHODS 28 knee joints in 20 patients with rheumatoid arthritis were examined with a 3 D-GE-T1 weighted sequence with frequency-selective fat suppression (Flash 3D fat sat) and T1-weighted SE-sequences after intravenous gadolinium-containing contrast agent administration using a 1.5T system. Differentiation of cartilage, synovium, and joint effusion was assessed on both sequences qualitatively by two observers and quantitatively by signal intensity measurements. RESULTS Qualititative analysis revealed higher grading rates for cartilage/fluid differentiation with fat-suppressed T1-weighted GE images than contrast enhanced T1-SE images. Quantitative analysis by measurements of contrast-to-noise ratios revealed significantly higher rates for the Flash 3D fat sat with regard to cartilage/fluid discrimination, significantly higher rates for T1-SE post-contrast for cartilage/synovium discrimination, and significantly higher rates for T1-SE post-contrast for synovium/fluid discrimination. CONCLUSION 3D-GE-imaging with fat-suppressed T1 weighted sequences allows sufficient differentiation of cartilage and joint fluid in patients with rheumatoid arthritis without application of contrast agents and may assist in monitoring disease progression and response to therapy. The higher contrast to noise ratios of cartilage/synovium and synovium/fluid on T1-SE images following administration of gadolinium-containing contrast agents may improve detection of disease activity.
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Affiliation(s)
- T Rand
- Department of Radiology, University of Vienna, Austria
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Abstract
Our goal was to characterize pathological tissues of liver by magnetic resonance (MR)-related parameters such as T1 and magnetization transfer (MT) indices and to evaluate the clinical efficacy of MT contrast (C) in diagnosis of liver diseases via binomial pulsed saturation, with and without the administration of the paramagnetic agent gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Fifty-one cases of liver disorders were included in this study. Among the more important findings were the following: a) cirrhotic livers have significantly higher MT indices than normal liver, while hepatoma, metastatic tumor and fatty liver have sub-normal MT indices; b) in general, although with notable exceptions, images with MT give significantly better contrast indices than control images; and c) MT with Gd-DTPA rarely fares any better than the MT technique alone, although again with notable exceptions. MTC is a potentially powerful technique for diagnosing liver diseases, provided it can be optimally exploited for each individual disease type.
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Affiliation(s)
- J H Chen
- Department of Radiology, China Medical College Hospital, Taichung, Taiwan
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47
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Sussman MS, Pauly JM, Wright GA. Design of practical T2-selective RF excitation (TELEX) pulses. Magn Reson Med 1998; 40:890-9. [PMID: 9840834 DOI: 10.1002/mrm.1910400615] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Traditional T2-based imaging techniques are geared toward imaging long-T2 species. Traditional techniques are, therefore, not optimal in clinical situations where the information of interest lies in the short-T2 species. T2-selective RF excitation (TELEX) is a technique for obtaining a T2-based contrast that highlights short-T2 values while suppressing long-T2 values-opposite to traditional T2 contrast. Previously, TELEX has been demonstrated qualitatively to highlight only very short-T2 values (T2 approximately 0.001 s). When applied to longer T2 values (T2 > or = 0.01 s), TELEX becomes sensitive to deltaB0 non-uniformities. This restricts its application to problems in which the T2 of interest is very short. In this study, TELEX is characterized quantitatively. Furthermore, a bandwidth broadening scheme is developed that reduces the deltaB0 sensitivity of TELEX. This permits the technique to be applied to longer T2 values. The capabilities and limitations of a practical implementation of TELEX are discussed.
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Affiliation(s)
- M S Sussman
- Department of Medical Biophysics, Sunnybrook Health Science Centre, University of Toronto, North York, Ontario, Canada
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Grenier D, Deval S, Briguet A. A new approach for on-resonance magnetization transfer parameter optimization. MAGMA (NEW YORK, N.Y.) 1998; 7:131-40. [PMID: 10050939 DOI: 10.1007/bf02591330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
On-resonance radio frequency pulse sequences for magnetization transfer are optimized using a frequency domain approach. The method presented here was developed using binomial pulses and it is demonstrated that a simple analysis leads to accurate sequence parameters that can be used directly for magnetic resonance imaging. With thus optimized parameters it is possible to produce an efficient saturation of protons having short transverse relaxation time while protons with long transverse relaxation time are kept nearly unaffected by the radio frequency. The method is particularly well suited to the design of new magnetization transfer sequences and to the estimation of the limits of the accuracy of a T2 selection. Additionally in vitro tests have been performed on beef tendon oriented with a zero fiber to field angle.
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Affiliation(s)
- D Grenier
- CNRS UPRESA 5012, Laboratoire de Résonance Magnétique nucléaire, CPE-Université Claude Bernard Lyon 1, Villeurbanne, France
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Pachot-Clouard M, Vaufrey F, Darrasse L, Toussainti JF. Magnetization transfer characteristics in atherosclerotic plaque components assessed by adapted binomial preparation pulses. MAGMA (NEW YORK, N.Y.) 1998; 7:9-15. [PMID: 9877454 DOI: 10.1007/bf02592251] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Increasing the contrast between atheromatous plaque components is a major issue in cardiovascular MRI research. It would allow one to identify unstable plaque by differentiating the lipid core associated with vulnerability, from the fibrous cap, considered as a factor of stability. T2 and diffusion-weighted imaging have already provided satisfying results. Magnetization transfer (MT) between restricted protons Hr and free-water protons Hf could achieve a different contrast related to collagen and lipoprotein macromolecules present in the fibrous cap and lipid core, respectively. The purpose of this work was to evaluate in vitro the MT effect produced by adapted T2-selective 1-3-3-1 binomial pulses on isolated samples of atheromatous arteries at 3 T. A method based on simulation was used in order to improve the MT specificity: it is shown that 50% 1-3-3-1 pulses (the percentage indicating the level of Hr saturation) allow an estimation of T2r, the Hr T2. Using this technique, magnetization transfer was observed for the first time in atherosclerotic plaque components, an effect more pronounced for the fibrous cap and media than for the lipid core and adventitia. The T2r estimation gave values ranging from 20 to 25 micros for the four samples. This preliminary study provides a basis for establishing an MT imaging sequence of atheromatous arteries, by using 50% 1-3-3-1 pulses calibrated for saturating protons with a 20 micros T2. This MT protocol should be further compared to T2 and diffusion-weighted imaging.
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Roell SA, Dreher W, Busch E, Leibfritz D. Magnetization transfer attenuates metabolite signals in tumorous and contralateral animal brain: in vivo observations by proton NMR spectroscopy. Magn Reson Med 1998; 39:742-8. [PMID: 9581605 DOI: 10.1002/mrm.1910390511] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Tumorous and contralateral rat brain was examined by in vivo single voxel proton NMR spectroscopy. Magnetization transfer (MT) experiments cause attenuation of various metabolite signals. Selective saturation of immobile metabolites was achieved by pulsed RF preirradiation. The method is compared with continuous wave MT generation. In contralateral tissue, MT attenuation is detected for both the CH3 and the CH2 protons of (phospho-)creatine (Cr + PCr) and for a signal at 3.44 ppm ascribed to taurine. Significant attenuation is also observed for a signal at 3.78 ppm that is commonly ascribed to the alphaCH proton of glutamate and glutamine (Glx); however, no effect is observed for the gammaCH2 protons of Glx. Within implanted F98 glioma tumors, only the CH3 signal of Cr + PCr shows significant MT attenuation. Although the MT effect detected for lactate in the tumors fails to reach significance, a significant effect is observed for the lactate signal acquired during 3 to 9 min postmortem.
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Affiliation(s)
- S A Roell
- Universität Bremen, Fachbereich 2 (Chemie), Germany
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