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Kim SE, Parker DL, Roberts JA, Treiman GS, Alexander M, Baradaran H, de Havenon A, McNally JS. Differentiation of symptomatic and asymptomatic carotid intraplaque hemorrhage using 3D high-resolution diffusion-weighted stack of stars imaging. NMR IN BIOMEDICINE 2021; 34:e4582. [PMID: 34296793 DOI: 10.1002/nbm.4582] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 06/14/2021] [Accepted: 06/15/2021] [Indexed: 06/13/2023]
Abstract
Ischemic events related to carotid disease are far more strongly associated with plaque instability than stenosis. 3D high-resolution diffusion-weighted (DW) imaging can provide quantitative diffusion measurements on carotid atherosclerosis and may improve detection of vulnerable intraplaque hemorrhage (IPH). The 3D DW-stack of stars (SOS) sequence was implemented with 3D SOS acquisition combined with DW preparation. After simulation of signals created from 3D DW-SOS, phantom studies were performed. Three healthy subjects and 20 patients with carotid disease were recruited. Apparent diffusion coefficient (ADC) values were statistically analyzed on three subgroups by using a two-group comparison Wilcoxon-Mann-Whitney U test with p values less than 0.05: symptomatic versus asymptomatic; IPH-positive versus IPH-negative; and IPH-positive symptomatic versus asymptomatic plaques to determine the relationship with plaque vulnerability. ADC values calculated by 3D DW-SOS provided values similar to those calculated from other techniques. Mean ADC of symptomatic plaque was significantly lower than asymptomatic plaque (0.68 ± 0.18 vs. 0.98 ± 0.16 x 10-3 mm2 /s, p < 0.001). ADC was also significantly lower in IPH-positive versus IPH-negative plaque (0.68 ± 0.13 vs. 1.04 ± 0.11 x 10-3 mm2 /s, p < 0.001). Additionally, ADC was significantly lower in symptomatic versus asymptomatic IPH-positive plaque (0.57 ± 0.09 vs. 0.75 ± 0.11 x 10-3 mm2 /s, p < 0.001). Our results provide strong evidence that ADC measurements from 3D DW-SOS correlate with the symptomatic status of extracranial internal carotid artery plaque. Further, ADC improved discrimination of symptomatic plaque in IPH. These data suggest that diffusion characteristics may improve detection of destabilized plaque leading to elevated stroke risk.
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Affiliation(s)
- Seong-Eun Kim
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Dennis L Parker
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - John A Roberts
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Gerald S Treiman
- Department of Veterans Affairs, VASLCHCS, Salt Lake City, Utah, USA
| | - Matthew Alexander
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Hediyeh Baradaran
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Adam de Havenon
- Department of Neurology, University of Utah, Salt Lake City, Utah, USA
| | - J Scott McNally
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
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Zhang J, Liu S, Dai E, Ye X, Shi D, Wu Y, Lu J, Guo H. Slab boundary artifact correction in multislab imaging using convolutional-neural-network-enabled inversion for slab profile encoding. Magn Reson Med 2021; 87:1546-1560. [PMID: 34655095 DOI: 10.1002/mrm.29047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 09/23/2021] [Accepted: 09/25/2021] [Indexed: 11/06/2022]
Abstract
PURPOSE This study aims to propose a novel algorithm for slab boundary artifact correction in both single-band multislab imaging and simultaneous multislab (SMSlab) imaging. THEORY AND METHODS In image domain, the formation of slab boundary artifacts can be regarded as modulating the artifact-free images using the slab profiles and introducing aliasing along the slice direction. Slab boundary artifact correction is the inverse problem of this process. An iterative algorithm based on convolutional neural networks (CNNs) is proposed to solve the problem, termed CNN-enabled inversion for slab profile encoding (CPEN). Diffusion-weighted SMSlab images and reference images without slab boundary artifacts were acquired in 7 healthy subjects for training. Images of 5 healthy subjects were acquired for testing, including single-band multislab and SMSlab images with 1.3-mm or 1-mm isotropic resolution. CNN-enabled inversion for slab profile encoding was compared with a previously reported method (i.e., nonlinear inversion for slab profile encoding [NPEN]). RESULTS CNN-enabled inversion for slab profile encoding reduces the slab boundary artifacts in both single-band multislab and SMSlab images. It also suppresses the slab boundary artifacts in the diffusion metric maps. Compared with NPEN, CPEN shows fewer residual artifacts in different acquisition protocols and more significant improvements in quantitative assessment, and it also accelerates the computation by more than 35 times. CONCLUSION CNN-enabled inversion for slab profile encoding can reduce the slab boundary artifacts in multislab acquisitions. It shows better slab boundary artifact correction capacity, higher robustness, and computation efficiency when compared with NPEN. It has the potential to improve the accuracy of multislab acquisitions in high-resolution DWI and functional MRI.
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Affiliation(s)
- Jieying Zhang
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, People's Republic of China
| | - Simin Liu
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, People's Republic of China
| | - Erpeng Dai
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, People's Republic of China.,Department of Radiology, Stanford University, Stanford, California, USA
| | - Xinyu Ye
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, People's Republic of China
| | - Diwei Shi
- Center for Nano and Micro Mechanics, Tsinghua University, Beijing, People's Republic of China
| | - Yuhsuan Wu
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, People's Republic of China
| | - Jie Lu
- Department of Radiology and Nuclear Medicine, Xuanwu Hospital, Capital Medical University, Beijing, People's Republic of China
| | - Hua Guo
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, People's Republic of China
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Lee SY, Meyer BP, Kurpad SN, Budde MD. Diffusion-prepared fast spin echo for artifact-free spinal cord imaging. Magn Reson Med 2021; 86:984-994. [PMID: 33720450 DOI: 10.1002/mrm.28751] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 01/07/2021] [Accepted: 02/05/2021] [Indexed: 12/13/2022]
Abstract
PURPOSE Diffusion MRI provides unique contrast important for the detection and examination of pathophysiology after acute neurologic insults, including spinal cord injury. Diffusion weighted imaging of the rodent spinal cord has typically been evaluated with axial EPI readout. However, Diffusion weighted imaging is prone to motion artifacts, whereas EPI is prone to susceptibility artifacts. In the context of acute spinal cord injury, diffusion filtering has previously been shown to improve detection of injury by minimizing the confounding effects of edema. We propose a diffusion-preparation module combined with a rapid acquisition with relaxation enhancement readout to minimize artifacts for sagittal imaging. METHODS Sprague-Dawley rats with cervical contusion spinal cord injury were scanned at 9.4 Tesla. The sequence optimization included the evaluation of motion-compensated encoding diffusion gradients, gating strategy, and different spinal cord-specific diffusion-weighting schemes. RESULTS A diffusion-prepared rapid acquisition with relaxation enhancement achieved high-quality images free from susceptibility artifacts with both second-order motion-compensated encoding and gating necessary for reduction of motion artifacts. Axial diffusivity obtained from the filtered diffusion-encoding scheme had greater lesion-to-healthy tissue contrast (52%) compared to the similar metric from DTI (25%). CONCLUSION This work demonstrated the feasibility of high-quality diffusion sagittal imaging in the rodent cervical cord with diffusion-prepared relaxation enhancement. The sequence and results are expected to improve injury detection and evaluation in acute spinal cord injury.
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Affiliation(s)
- Seung-Yi Lee
- Neuroscience Doctoral Program, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.,Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Briana P Meyer
- Neuroscience Doctoral Program, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.,Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Shekar N Kurpad
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Matthew D Budde
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.,Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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4
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Wu D, Liu D, Hsu YC, Li H, Sun Y, Qin Q, Zhang Y. Diffusion-prepared 3D gradient spin-echo sequence for improved oscillating gradient diffusion MRI. Magn Reson Med 2020; 85:78-88. [PMID: 32643240 DOI: 10.1002/mrm.28401] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 06/03/2020] [Accepted: 06/07/2020] [Indexed: 12/22/2022]
Abstract
PURPOSE Oscillating gradient (OG) enables the access of short diffusion times for time-dependent diffusion MRI (dMRI); however, it poses several technical challenges for clinical use. This study proposes a 3D oscillating gradient-prepared gradient spin-echo (OGprep-GRASE) sequence to improve SNR and shorten acquisition time for OG dMRI on clinical scanners. METHODS The 3D OGprep-GRASE sequence consisted of global saturation, diffusion encoding, fat saturation, and GRASE readout modules. Multiplexed sensitivity-encoding reconstruction was used to correct the phase errors between multiple shots. We compared the scan time and SNR of the proposed sequence and the conventional 2D-EPI sequence for OG dMRI at 30-90-mm slice coverage. We also examined the time-dependent diffusivity changes with OG dMRI acquired at frequencies of 50 Hz and 25 Hz and pulsed-gradient dMRI at diffusion times of 30 ms and 60 ms. RESULTS The OGprep-GRASE sequence reduced the scan time by a factor of 1.38, and increased the SNR by 1.74-2.27 times compared with 2D EPI for relatively thick slice coverage (60-90 mm). The SNR gain led to improved diffusion-tensor reconstruction in the multishot protocols. Image distortion in 2D-EPI images was also reduced in GRASE images. Diffusivity measurements from the pulsed-gradient dMRI and OG dMRI showed clear diffusion-time dependency in the white matter and gray matter of the human brain, using both the GRASE and EPI sequences. CONCLUSION The 3D OGprep-GRASE sequence improved scan time and SNR and reduced image distortion compared with the 2D multislice acquisition for OG dMRI on a 3T clinical system, which may facilitate the clinical translation of time-dependent dMRI.
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Affiliation(s)
- Dan Wu
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Dapeng Liu
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Csenter for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| | - Yi-Cheng Hsu
- MR Collaboration, Siemens Healthcare China, Shanghai, China
| | - Haotian Li
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yi Sun
- MR Collaboration, Siemens Healthcare China, Shanghai, China
| | - Qin Qin
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,F.M. Kirby Research Csenter for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| | - Yi Zhang
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China.,Department of Neurology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
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5
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Jeong KE, Hsu EW, Jeong EK. Diffusion MRI using two-dimensional single-shot radial imaging (2D ss-rDWI) with variable flip angle and random view ordering. Magn Reson Imaging 2019; 61:273-284. [PMID: 31009689 DOI: 10.1016/j.mri.2019.04.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 03/21/2019] [Accepted: 04/17/2019] [Indexed: 12/25/2022]
Abstract
PURPOSE The main objective of this study is to develop a 2D single-shot radial-DWI (2D ss-rDWI) technique to reduce motion artifacts and geometric distortion in DW images. METHOD A diffusion-preparation module is developed and applied prior to the data acquisition. Because the diffusion-prepared longitudinal magnetization is measured over multiple RF excitations in each shot, 2D ss-rDWI is subject to low signal-to-noise ratio (SNR). We used variable-flip angle (VFA), random view ordering (RVO), and sliding spokes, and compared the performances to constant flip angle (CFA), smooth view ordering (SVO), and identical spoke averaging, respectively. For each technique, we performed numerical simulation and MRI experiments on a fluid phantom as well as in-vivo human brain studies with a 3 T MRI system. RESULTS Using VFA, optimal SNR was acquired for 2D ss-rDWI. Using SVO, the high signal is clustered at specific quadrant in 2D k-space: the first quadrant using high initial flip angle or the last quadrant using the low flip angle. This clustered signal in k-space led to geometric distortion in image space. 2D ss-rDWI using RVO spreads the high signaled spokes over all angular directions and removes the view-order-related distortion. The in-vivo images using 2D ss-rDWI with VFA and RVO show no geometric distortion at the skull base brain, but greatly reduced SNR compared with those using 2D ss-DWEPI. CONCLUSION 2D ss-rDWI is optimized by using VFA with RVO. The resultant DWI using 2D ss-rDWI is insensitive to motion-induced artifacts and geometric distortion. Even with low SNR, it may be useful for DWI of organs limited by severe susceptibility-induced geometric distortion.
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Affiliation(s)
- Kyle E Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, United States of America; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States of America
| | - Edward W Hsu
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States of America
| | - Eun-Kee Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, United States of America; Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, United States of America.
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Holdsworth SJ, O'Halloran R, Setsompop K. The quest for high spatial resolution diffusion-weighted imaging of the human brain in vivo. NMR IN BIOMEDICINE 2019; 32:e4056. [PMID: 30730591 DOI: 10.1002/nbm.4056] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 09/11/2018] [Accepted: 11/08/2018] [Indexed: 06/09/2023]
Abstract
Diffusion-weighted imaging, a contrast unique to MRI, is used for assessment of tissue microstructure in vivo. However, this exquisite sensitivity to finer scales far above imaging resolution comes at the cost of vulnerability to errors caused by sources of motion other than diffusion motion. Addressing the issue of motion has traditionally limited diffusion-weighted imaging to a few acquisition techniques and, as a consequence, to poorer spatial resolution than other MRI applications. Advances in MRI imaging methodology have allowed diffusion-weighted MRI to push to ever higher spatial resolution. In this review we focus on the pulse sequences and associated techniques under development that have pushed the limits of image quality and spatial resolution in diffusion-weighted MRI.
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Affiliation(s)
- Samantha J Holdsworth
- Department of Anatomy Medical Imaging & Centre for Brain Research, University of Auckland, Auckland, New Zealand
| | | | - Kawin Setsompop
- Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA
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7
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Thapa B, Sapkota N, Lee Y, Jeong K, Rose J, Shah LM, Bisson E, Jeong EK. Ultra-high-b radial diffusion-weighted imaging (UHb-rDWI) of human cervical spinal cord. J Magn Reson Imaging 2018; 49:204-211. [PMID: 29707845 DOI: 10.1002/jmri.26169] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Accepted: 04/05/2018] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Injury in the cervical spinal cord (CSC) can lead to varying degrees of neurologic deficit and persistent disability. Diffusion tensor imaging (DTI) is a promising method to evaluate white matter integrity and pathology. However, the conventional DTI results are limited with respect to the specific details of neuropathology and microstructural architecture. In this study we used ultrahigh-b radial-DWI (UHb-rDWI) with b-values ranging from 0 to ∼7500 s/mm2 and calculated decay constant (DH ) at the high b-values, which gives much deeper insight about the microscopic environment of CSC white matter. PURPOSE To evaluate a novel diffusion MRI, UHb-rDWI technique for imaging of the CSC. STUDY TYPE Longitudinal. SUBJECTS Four healthy controls, each scanned twice. FIELD STRENGTH/SEQUENCE 3T/2D single shot diffusion-weighted stimulated echo planar imaging with reduced field of view. ASSESSMENT The signal from each pixel of b0 (b = 0) and b-value (b ≠ 0) images were fitted to a biexponential function and normalized. The signal-b curve is obtained by dividing the latter curve by the former. DH was obtained from the curve at b >4000 s/mm2 . A Monte-Carlo Simulation (MCS) was performed to investigate how DH changes upon the increased water-exchange at the CSC. RESULTS The signal-b curves plotted at multiple levels of healthy CSC are almost identical on two successive scans and show a biexponential decay behavior: fast exponential decay at lower b-values and much slower decay at UHb-values. The mean values of DH were measured as (0.0607 ± 0.02531) ×10-3 and (0.0357 ± 0.02072) ×10-3 s/mm2 at the lateral funiculus and posterior column, respectively. MCS of diffusion MRI shows that the DH is elevated by increased water exchange between the intra- and extraaxonal spaces. DATA CONCLUSION UHb-rDWI signal-b plots of the normal CSC were highly reproducible on successive scans and their biexponential decay behavior can be used to characterize normal spinal white matter. LEVEL OF EVIDENCE 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:204-211.
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Affiliation(s)
- Bijaya Thapa
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah, USA
| | - Nabraj Sapkota
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah, USA
| | - YouJung Lee
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
| | - Kyle Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Bioengineering, University of Utah, Salt Lake City, Utah, USA
| | | | - Lubdha M Shah
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Erica Bisson
- Department of Neurosurgery, University of Utah, Salt Lake City, Utah, USA
| | - Eun-Kee Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
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Zhang Q, Coolen BF, Versluis MJ, Strijkers GJ, Nederveen AJ. Diffusion-prepared stimulated-echo turbo spin echo (DPsti-TSE): An eddy current-insensitive sequence for three-dimensional high-resolution and undistorted diffusion-weighted imaging. NMR IN BIOMEDICINE 2017; 30:e3719. [PMID: 28295736 DOI: 10.1002/nbm.3719] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 01/10/2017] [Accepted: 02/04/2017] [Indexed: 06/06/2023]
Abstract
In this study, we present a new three-dimensional (3D), diffusion-prepared turbo spin echo sequence based on a stimulated-echo read-out (DPsti-TSE) enabling high-resolution and undistorted diffusion-weighted imaging (DWI). A dephasing gradient in the diffusion preparation module and rephasing gradients in the turbo spin echo module create stimulated echoes, which prevent signal loss caused by eddy currents. Near to perfect agreement of apparent diffusion coefficient (ADC) values between DPsti-TSE and diffusion-weighted echo planar imaging (DW-EPI) was demonstrated in both phantom transient signal experiments and phantom imaging experiments. High-resolution and undistorted DPsti-TSE was demonstrated in vivo in prostate and carotid vessel wall. 3D whole-prostate DWI was achieved with four b values in only 6 min. Undistorted ADC maps of the prostate peripheral zone were obtained at low and high imaging resolutions with no change in mean ADC values [(1.60 ± 0.10) × 10-3 versus (1.60 ± 0.02) × 10-3 mm2 /s]. High-resolution 3D DWI of the carotid vessel wall was achieved in 12 min, with consistent ADC values [(1.40 ± 0.23) × 10-3 mm2 /s] across different subjects, as well as slice locations through the imaging volume. This study shows that DPsti-TSE can serve as a robust 3D diffusion-weighted sequence and is an attractive alternative to the traditional two-dimensional DW-EPI approaches.
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Affiliation(s)
- Qinwei Zhang
- Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands
| | - Bram F Coolen
- Department of Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, the Netherlands
| | | | - Gustav J Strijkers
- Department of Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, the Netherlands
| | - Aart J Nederveen
- Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands
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Van AT, Cervantes B, Kooijman H, Karampinos DC. Analysis of phase error effects in multishot diffusion-prepared turbo spin echo imaging. Quant Imaging Med Surg 2017; 7:238-250. [PMID: 28516049 DOI: 10.21037/qims.2017.04.01] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND To characterize the effect of phase errors on the magnitude and the phase of the diffusion-weighted (DW) signal acquired with diffusion-prepared turbo spin echo (dprep-TSE) sequences. METHODS Motion and eddy currents were identified as the main sources of phase errors. An analytical expression for the effect of phase errors on the acquired signal was derived and verified using Bloch simulations, phantom, and in vivo experiments. RESULTS Simulations and experiments showed that phase errors during the diffusion preparation cause both magnitude and phase modulation on the acquired data. When motion-induced phase error (MiPe) is accounted for (e.g., with motion-compensated diffusion encoding), the signal magnitude modulation due to the leftover eddy-current-induced phase error cannot be eliminated by the conventional phase cycling and sum-of-squares (SOS) method. By employing magnitude stabilizers, the phase-error-induced magnitude modulation, regardless of its cause, was removed but the phase modulation remained. The in vivo comparison between pulsed gradient and flow-compensated diffusion preparations showed that MiPe needed to be addressed in multi-shot dprep-TSE acquisitions employing magnitude stabilizers. CONCLUSIONS A comprehensive analysis of phase errors in dprep-TSE sequences showed that magnitude stabilizers are mandatory in removing the phase error induced magnitude modulation. Additionally, when multi-shot dprep-TSE is employed the inconsistent signal phase modulation across shots has to be resolved before shot-combination is performed.
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Affiliation(s)
- Anh T Van
- Zentralinstitut für Medizintechnik, Technical University of Munich, Garching, Germany
| | - Barbara Cervantes
- Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany
| | | | - Dimitrios C Karampinos
- Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany
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10
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Wu W, Koopmans PJ, Frost R, Miller KL. Reducing slab boundary artifacts in three-dimensional multislab diffusion MRI using nonlinear inversion for slab profile encoding (NPEN). Magn Reson Med 2016; 76:1183-95. [PMID: 26510172 PMCID: PMC4854328 DOI: 10.1002/mrm.26027] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 10/05/2015] [Accepted: 10/05/2015] [Indexed: 01/30/2023]
Abstract
PURPOSE To propose a method to reduce the slab boundary artifacts in three-dimensional multislab diffusion MRI. METHODS Bloch simulation is used to investigate the effects of multiple factors on slab boundary artifacts, including characterization of residual errors on diffusion quantification. A nonlinear inversion method is proposed to simultaneously estimate the slab profile and the underlying (corrected) image. RESULTS Correction results of numerical phantom and in vivo data demonstrate that the method can effectively remove slab boundary artifacts for diffusion data. Notably, the nonlinear inversion is also successful at short TR, a regimen where previously proposed methods (slab profile encoding and weighted average) retain residual artifacts in both diffusion-weighted images and diffusion metrics (mean diffusion coefficient and fractional anisotropy). CONCLUSION The nonlinear inversion for removing slab boundary artifacts provides improvements over existing methods, particularly at the short TRs required to maximize SNR efficiency. Magn Reson Med 76:1183-1195, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Affiliation(s)
- Wenchuan Wu
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
| | - Peter J Koopmans
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Robert Frost
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Karla L Miller
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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11
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Taouli B, Beer AJ, Chenevert T, Collins D, Lehman C, Matos C, Padhani AR, Rosenkrantz AB, Shukla-Dave A, Sigmund E, Tanenbaum L, Thoeny H, Thomassin-Naggara I, Barbieri S, Corcuera-Solano I, Orton M, Partridge SC, Koh DM. Diffusion-weighted imaging outside the brain: Consensus statement from an ISMRM-sponsored workshop. J Magn Reson Imaging 2016; 44:521-40. [PMID: 26892827 PMCID: PMC4983499 DOI: 10.1002/jmri.25196] [Citation(s) in RCA: 127] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 01/28/2016] [Accepted: 01/30/2016] [Indexed: 12/11/2022] Open
Abstract
The significant advances in magnetic resonance imaging (MRI) hardware and software, sequence design, and postprocessing methods have made diffusion-weighted imaging (DWI) an important part of body MRI protocols and have fueled extensive research on quantitative diffusion outside the brain, particularly in the oncologic setting. In this review, we summarize the most up-to-date information on DWI acquisition and clinical applications outside the brain, as discussed in an ISMRM-sponsored symposium held in April 2015. We first introduce recent advances in acquisition, processing, and quality control; then review scientific evidence in major organ systems; and finally describe future directions. J. Magn. Reson. Imaging 2016;44:521-540.
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Affiliation(s)
- Bachir Taouli
- Department of Radiology and Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Ambros J. Beer
- Department of Nuclear Medicine, University Hospital Ulm, Ulm, Germany
| | - Thomas Chenevert
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
| | - David Collins
- CR UK Cancer Imaging Centre, Institute of Cancer Research and Department of Radiology, Royal Marsden Hospital, London, UK
| | - Constance Lehman
- Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Celso Matos
- Department of Radiology, Champalimaud Clinical Centre, Lisbon, Portugal
| | | | | | - Amita Shukla-Dave
- Departments of Medical Physics and Radiology, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
| | - Eric Sigmund
- Irene and Bernard Schwartz Center for Biomedical Imaging (CBI) and Center for Advanced Imaging and Innovation (CAIR), Department of Radiology, NYU Langone Medical Center, New York, New York, USA
| | - Lawrence Tanenbaum
- Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Harriet Thoeny
- Department of Diagnostic Radiology, Inselspital Bern, Bern, Switzerland
| | | | | | - Idoia Corcuera-Solano
- Department of Radiology and Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Matthew Orton
- CR UK Cancer Imaging Centre, Institute of Cancer Research and Department of Radiology, Royal Marsden Hospital, London, UK
| | | | - Dow-Mu Koh
- Institute of Cancer Research and Department of Radiology, Royal Marsden Hospital, London, UK
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12
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Diffusion tensor imaging focusing on lower cervical spinal cord using 2D reduced FOV interleaved multislice single-shot diffusion-weighted echo-planar imaging: comparison with conventional single-shot diffusion-weighted echo-planar imaging. Magn Reson Imaging 2015; 33:401-6. [DOI: 10.1016/j.mri.2015.01.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Revised: 09/16/2014] [Accepted: 01/10/2015] [Indexed: 11/19/2022]
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13
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3D Multi-slab diffusion-weighted readout-segmented EPI with real-time cardiac-reordered k-space acquisition. Magn Reson Med 2013; 72:1565-79. [DOI: 10.1002/mrm.25062] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 10/19/2013] [Accepted: 11/08/2013] [Indexed: 11/07/2022]
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14
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Seo HS, Kim SE, Rose J, Hadley JR, Parker DL, Jeong EK. Diffusion tensor imaging of extraocular muscle using two-dimensional single-shot interleaved multiple inner volume imaging diffusion-weighted EPI at 3 tesla. J Magn Reson Imaging 2013; 38:1162-8. [DOI: 10.1002/jmri.24095] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 02/05/2013] [Indexed: 11/06/2022] Open
Affiliation(s)
- Hyung Suk Seo
- Utah Center for Advanced Imaging Research; University of Utah; Salt Lake City Utah USA
- Department of Radiology; Korea University; Ansan Korea
| | - Seong-Eun Kim
- Utah Center for Advanced Imaging Research; University of Utah; Salt Lake City Utah USA
- Department of Radiology; University of Utah; Salt Lake City Utah USA
| | - John Rose
- Department of Neurology; University of Utah; Salt Lake City Utah USA
| | - J. Rock Hadley
- Utah Center for Advanced Imaging Research; University of Utah; Salt Lake City Utah USA
- Department of Radiology; University of Utah; Salt Lake City Utah USA
| | - Dennis L. Parker
- Utah Center for Advanced Imaging Research; University of Utah; Salt Lake City Utah USA
- Department of Radiology; University of Utah; Salt Lake City Utah USA
| | - Eun-Kee Jeong
- Utah Center for Advanced Imaging Research; University of Utah; Salt Lake City Utah USA
- Department of Radiology; University of Utah; Salt Lake City Utah USA
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15
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Engström M, Skare S. Diffusion-weighted 3D multislab echo planar imaging for high signal-to-noise ratio efficiency and isotropic image resolution. Magn Reson Med 2013; 70:1507-14. [DOI: 10.1002/mrm.24594] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Revised: 11/16/2012] [Accepted: 11/20/2012] [Indexed: 11/05/2022]
Affiliation(s)
- Mathias Engström
- Department of Clinical Neuroscience; Karolinska Institutet; Stockholm Sweden
- Department of Neuroradiology; Karolinska University Hospital; Stockholm Sweden
| | - Stefan Skare
- Department of Clinical Neuroscience; Karolinska Institutet; Stockholm Sweden
- Department of Neuroradiology; Karolinska University Hospital; Stockholm Sweden
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16
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Abstract
We describe a cardiac gated high in-plane resolution axial human cervical spinal cord diffusion tensor imaging (DTI) protocol. Multiple steps were taken to optimize both image acquisition and image processing. The former includes slice-by-slice cardiac triggering and individually tiltable slices. The latter includes (i) iterative 2D retrospective motion correction, (ii) image intensity outlier detection to minimize the influence of physiological noise, (iii) a non-linear DTI estimation procedure incorporating non-negative eigenvalue priors, and (iv) tract-specific region-of-interest (ROI) identification based on an objective geometry reference. Using these strategies in combination, radial diffusivity (λ(⊥)) was reproducibly measured in white matter (WM) tracts (adjusted mean [95% confidence interval]=0.25 [0.22, 0.29] μm(2)/ms), lower than previously reported λ(⊥) values in the in vivo human spinal cord DTI literature. Radial diffusivity and fractional anisotropy (FA) measured in WM varied from rostral to caudal as did mean translational motion, likely reflecting respiratory motion effect. Given the considerable sensitivity of DTI measurements to motion artifact, we believe outlier detection is indispensable in spinal cord diffusion imaging. We also recommend using a mixed-effects model to account for systematic measurement bias depending on cord segment.
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17
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Lundell H, Barthelemy D, Biering-Sørensen F, Cohen-Adad J, Nielsen JB, Dyrby TB. Fast diffusion tensor imaging and tractography of the whole cervical spinal cord using point spread function corrected echo planar imaging. Magn Reson Med 2012; 69:144-9. [PMID: 22396180 DOI: 10.1002/mrm.24235] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 01/09/2012] [Accepted: 02/03/2012] [Indexed: 11/10/2022]
Abstract
Diffusion tensor imaging has been used in a number of spinal cord studies, but severe distortions caused by susceptibility induced field inhomogeneities limit its applicability to investigate small volumes within acceptable acquisition times. A way to evaluate image distortions is to map the point spread function of the voxel intensity in a reference scan. In this study, the point spread function was mapped for an echo-planar imaging sequence in the human cervical spinal cord with isotropic resolution and large field of view. Correction with the point spread function map improved anatomical consistency, and full cervical tractography was thereby possible from a C1 seed region in healthy controls and one individual with spinal cord injury. It is suggested that point spread function mapping of the spinal cord can be used in combination with sequence-based methods for reduction of susceptibility artifacts or in high-field imaging settings where off-resonance effects are pronounced.
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Affiliation(s)
- Henrik Lundell
- Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark.
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18
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Park JK, Kim SE, Trieman GS, Parker D, Jeong EK. High-resolution diffusion-weighted imaging of neck lymph nodes using 2D-single-shot interleaved multiple inner volume imaging diffusion-weighted echo-planar imaging at 3T. AJNR Am J Neuroradiol 2011; 32:1173-7. [PMID: 21659484 DOI: 10.3174/ajnr.a2539] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE 2D-ss-IMIV-DWEPI is an ss-DWEPI with greatly reduced geometric distortion. The purposes of this paper are to 1) evaluate of the utility of 2D-ss-IMIV-DWEPI for high-resolution neck LN imaging; 2) determine whether 2D-ss-IMIV-DWEPI can depict normal LN hilum; and 3) evaluate whether the inclusion of LN hilum within ROIs affects the measured LN ADC. MATERIALS AND METHODS HR-DWI was acquired with 1-mm² in-plane resolution and 2-mm section thickness by using 2D-ss-IMIV-DWEPI. In total, 58 LNs from 18 subjects were evaluated. The ADC map was calculated by using DWI with b = 10 and 300 s/mm². In those LNs where the LN hilum could be recognized, the LN ADC was measured with and without inclusion of the hilum, and the mean difference of the resulting ADC values was determined. RESULTS The hilar structure was identified by DWI in 15 LNs. The ADC of the hilum was 1.981 ± 0.331 × 10⁻³ mm²/s. In these 15 LNs, the ADC value excluding hilar structure was significantly lower than the ADC value including hilar structure (0.983 ± 0.169 versus 1.206 ± 0.244 × 10⁻³ mm²/s; P < .0001). The mean ADC in a total of 58 LNs excluding the hilar structure was significantly lower than the value obtained including the hilar structure (1.034 ± 0.183 versus 1.095 ± 0.213 × 10⁻³ mm²/s; P = .0002). CONCLUSIONS HR-DWI of neck LNs obtained by using 2D-ss-IMIV-DWEPI could identify the hilar structure. The ADC of normal neck LNs seemed significantly different when the hilum was included. The results suggest that HR-DWI may be helpful to aid selection of proper ROIs within LNs for accurate and reliable ADC measurements.
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Affiliation(s)
- J K Park
- Utah Center for Advanced Imaging Research,University of Utah, Salt Lake City, Utah, USA
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19
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Cheng YW, Chung HW, Chen CY, Chou MC. Diffusion tensor imaging with cerebrospinal fluid suppression and signal-to-noise preservation using acquisition combining fluid-attenuated inversion recovery and conventional imaging: Comparison of fiber tracking. Eur J Radiol 2011; 79:113-7. [DOI: 10.1016/j.ejrad.2009.12.032] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 12/30/2009] [Indexed: 11/30/2022]
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20
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Targeted radiofrequency field mapping using 3D reduced field-of-view-catalyzed double-angle method. Magn Reson Imaging 2011; 29:1131-7. [PMID: 21705167 DOI: 10.1016/j.mri.2011.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Revised: 05/02/2011] [Accepted: 05/04/2011] [Indexed: 11/20/2022]
Abstract
PURPOSE The aim of this study was to develop a targeted volumetric radiofrequency field (B(1)(+)) mapping technique to provide region-of-interest B(1)(+) information. MATERIALS AND METHODS Targeted B(1)(+) maps were acquired using three-dimensional (3D) reduced field-of-view (FOV) inner-volume turbo spin echo-catalyzed double-angle method (DAM). Targeted B(1)(+) maps were compared with full-FOV B(1)(+) maps acquired using 3D catalyzed DAM in a phantom and in the brain of a healthy volunteer. In addition, targeted volumetric abdomeninal B(1)(+) mapping was demonstrated in the abdomen of another healthy volunteer. RESULTS The targeted reduced-FOV images demonstrated no aliasing artifacts in all experiments. Close match between targeted B(1)(+) map and reference full-FOV B(1)(+) map in the same region was observed, with percentage root-mean-squared error <0.4% in the phantom and <0.8% in the healthy volunteer brain. The abdominal B(1)(+) maps showed small B(1)(+) variation in the kidneys and liver from the healthy volunteer. CONCLUSION The proposed 3D reduced-FOV catalyzed DAM provides a rapid, simple and accurate method for targeted volumetric B(1)(+) mapping and can be easily implemented for applications related to radiofrequency field mapping in small targeted regions.
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21
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Holdsworth SJ, Yeom K, Skare S, Gentles AJ, Barnes PD, Bammer R. Clinical application of readout-segmented- echo-planar imaging for diffusion-weighted imaging in pediatric brain. AJNR Am J Neuroradiol 2011; 32:1274-9. [PMID: 21596809 DOI: 10.3174/ajnr.a2481] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE RS-EPI has been suggested as an alternative approach to EPI for high-resolution DWI with reduced distortions. To determine whether RS-EPI is a useful approach for routine clinical use, we implemented GRAPPA-accelerated RS-EPI DWI at our pediatric hospital and graded the images alongside standard accelerated (ASSET) EPI DWI used routinely for clinical studies. MATERIALS AND METHODS GRAPPA-accelerated RS-EPI DWIs and ASSET EPI DWIs were acquired on 35 pediatric patients using a 3T system in 35 pediatric patients. The images were graded alongside each other by using a 7-point Likert scale as follows: 1, nondiagnostic; 2, poor; 3, acceptable; 4, standard; 5, above average; 6, good; and 7, outstanding. RESULTS The following were the average scores for EPI and RS-EPI, respectively: resolution, 3.5/5.2; distortion level, 2.9/6.0; SNR, 3.4/4.1; lesion conspicuity, 3.3/5.9; and diagnostic confidence, 3.2/6.0. Overall, the RS-EPI had significantly improved diagnostic confidence and more reliably defined the extent and structure of several lesions. Although ASSET EPI scans had better SNR per scanning time, the higher spatial resolution as well as reduced blurring and distortions on RS-EPI scans helped to better reveal important anatomic details at the cortical-subcortical levels, brain stem, temporal and inferior frontal lobes, skull base, sinonasal cavity, cranial nerves, and orbits. CONCLUSIONS This work shows the importance of both resolution and decreased distortions in the clinics, which can be accomplished by a combination of parallel imaging and alternative k-space trajectories such as RS-EPI.
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Affiliation(s)
- S J Holdsworth
- Department of Radiology, Stanford University, Stanford, California, USA
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22
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Advanced imaging of anterior visual pathway ischemia: state of the art and future directions. J Neuroophthalmol 2010; 30:213-5. [PMID: 20818205 DOI: 10.1097/wno.0b013e3181f3a4a7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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23
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Shi X, Kim SE, Jeong EK. Single-shot T1 mapping using simultaneous acquisitions of spin- and stimulated-echo-planar imaging (2D ss-SESTEPI). Magn Reson Med 2010; 64:734-42. [PMID: 20564579 PMCID: PMC3091485 DOI: 10.1002/mrm.22367] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Accepted: 12/24/2009] [Indexed: 02/01/2023]
Abstract
The conventional stimulated-echo NMR sequence only measures the longitudinal component while discarding the transverse component, after tipping up the prepared magnetization. This transverse magnetization can be used to measure a spin echo, in addition to the stimulated echo. Two-dimensional single-shot spin- and stimulated-echo-planar imaging (ss-SESTEPI) is an echo-planar-imaging-based single-shot imaging technique that simultaneously acquires a spin-echo-planar image and a stimulated-echo-planar image after a single radiofrequency excitation. The magnitudes of the spin-echo-planar image and stimulated-echo-planar image differ by T(1) decay and diffusion weighting for perfect 90 degrees radiofrequency and thus can be used to rapidly measure T(1). However, the spatial variation of amplitude of radiofrequency field induces uneven splitting of the transverse magnetization for the spin-echo-planar image and stimulated-echo-planar image within the imaging field of view. Correction for amplitude of radiofrequency field inhomogeneity is therefore critical for two-dimensional ss-SESTEPI to be used for T(1) measurement. We developed a method for amplitude of radiofrequency field inhomogeneity correction by acquiring an additional stimulated-echo-planar image with minimal mixing time, calculating the difference between the spin echo and the stimulated echo and multiplying the stimulated-echo-planar image by the inverse functional map. Diffusion-induced decay is corrected by measuring the average diffusivity during the prescanning. Rapid single-shot T(1) mapping may be useful for various applications, such as dynamic T(1) mapping for real-time estimation of the concentration of contrast agent in dynamic contrast enhancement MRI.
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Affiliation(s)
- Xianfeng Shi
- University of Utah, Department of Physics Utah Center for Advanced Imaging Research 729 Arapeen Dr., Salt Lake City, Utah 84108
| | - Seong-Eun Kim
- University of Utah, Department of Radiology Utah Center for Advanced Imaging Research 729 Arapeen Dr., Salt Lake City, Utah 84108
| | - Eun-Kee Jeong
- University of Utah, Department of Radiology Utah Center for Advanced Imaging Research 729 Arapeen Dr., Salt Lake City, Utah 84108
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24
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Meurin A, Cernicanu A, Molinier S, Menegon P, Barreau X, Berge J, Dousset V. [Diffusion-weighted MR imaging of the spine and cord]. ACTA ACUST UNITED AC 2010; 91:352-66; quiz 367-8. [PMID: 20508570 DOI: 10.1016/s0221-0363(10)70051-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Due to its excellent sensitivity, MR imaging is invaluable for the evaluation of lesions of the cord and spine. Several studies dedicated to diffusion-weighted MR evaluation of the cord and spine have been published. While diffusion-weighted MR imaging of the brain is routinely performed, it is seldom performed when imaging the spine due to serious limitations. While anatomical limitations may not be changed, the voxel size, phase-encoding direction, mode of k-space filling, and acceleration factor are all parameters that can be optimized in order to routinely obtain diffusion-weighted imaging of the spine on 1.5T and 3T scanners.
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Affiliation(s)
- A Meurin
- Service de neuroradiologie diagnostique et interventionnelle, CHU de Bordeaux, Hôpital Pellegrin-Tripode, place Amélie Raba-Léon, 33076 Bordeaux cedex.
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25
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Kim TH, Zollinger L, Shi XF, Kim SE, Rose J, Patel AA, Jeong EK. Quantification of diffusivities of the human cervical spinal cord using a 2D single-shot interleaved multisection inner volume diffusion-weighted echo-planar imaging technique. AJNR Am J Neuroradiol 2010; 31:682-7. [PMID: 20019109 DOI: 10.3174/ajnr.a1881] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND AND PURPOSE DTI is a highly sensitive technique, which can detect pathology not otherwise noted with conventional imaging methods. This paper provides the atlas of reliable normative in vivo DTI parameters in the cervical spinal cord and its potential applications toward quantifying pathology. MATERIALS AND METHODS In our study, we created a reference of normal diffusivities of the cervical spinal cord by using a 2D ss-IMIV-DWEPI technique from 14 healthy volunteers and compared parameters with those in 8 patients with CSM. The 2D ss-IMIV-DWEPI technique was applied in each subject to acquire diffusion-weighted images. FA, lambda( parallel), and lambda( perpendicular) were calculated. A reference of normal DTI indices from 12 regions of interest was created and compared with DTI indices of 8 patients. RESULTS A map of reference diffusivity values was obtained from healthy controls. We found statistically significant differences in diffusivities between healthy volunteers and patients with CSM with different severities of disease, by using FA, lambda( parallel), and lambda( perpendicular) values. CONCLUSIONS DTI using 2D ss-IMIV-DWPEI is sensitive to spinal cord pathology. This technique can be used to detect and quantify the degree of pathology within the cervical spinal cord from multiple disease states.
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Affiliation(s)
- T H Kim
- Department of Radiology, Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, 84108-1218, USA
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26
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Kim SE, Jeong EK, Shi XF, Morrell G, Treiman GS, Parker DL. Diffusion-weighted imaging of human carotid artery using 2D single-shot interleaved multislice inner volume diffusion-weighted echo planar imaging (2D ss-IMIV-DWEPI) at 3T: diffusion measurement in atherosclerotic plaque. J Magn Reson Imaging 2010; 30:1068-77. [PMID: 19856440 DOI: 10.1002/jmri.21944] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To determine if 2D single-shot interleaved multislice inner volume diffusion-weighted echo planar imaging (ss-IMIV-DWEPI) can be used to obtain quantitative diffusion measurements that can assist in the identification of plaque components in the cervical carotid artery. MATERIALS AND METHODS The 2D ss-DWEPI sequence was combined with interleaved multislice inner volume region localization to obtain diffusion weighted images with 1 mm in-plane resolution and 2 mm slice thickness. Eleven subjects, six of whom have carotid plaque, were studied with this technique. The apparent diffusion coefficient (ADC) images were calculated using DW images with b = 10 s/mm(2) and b = 300 s/mm(2). RESULTS The mean ADC measurement in normal vessel wall of the 11 subjects was 1.28 +/- 0.09 x 10(-3) mm(2)/s. Six of the 11 subjects had carotid plaque and ADC measurements in plaque ranged from 0.29 to 0.87 x 10(-3) mm(2)/s. Of the 11 common carotid artery walls studied (33 images), at least partial visualization of the wall was obtained in all ADC images, more than 50% visualization in 82% (27/33 images), and full visualization in 18% (6/33 images). CONCLUSION 2D ss-IMIV-DWEPI can perform diffusion-weighted carotid magnetic resonance imaging (MRI) in vivo with reasonably high spatial resolution (1 x 1 x 2 mm(3)). ADC values of the carotid wall and plaque are consistent with similar values obtained from ex vivo endarterectomy specimens. The spread in ADC values obtained from plaque indicate that this technique could form a basis for plaque component identification in conjunction with other MRI/MRA techniques.
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Affiliation(s)
- Seong-Eun Kim
- Department of Radiology, Utah Center for Advanced Imaging Research, Salt Lake City, Utah 84108, USA.
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27
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Frank LR, Jung Y, Inati S, Tyszka JM, Wong EC. High efficiency, low distortion 3D diffusion tensor imaging with variable density spiral fast spin echoes (3D DW VDS RARE). Neuroimage 2009; 49:1510-23. [PMID: 19778618 DOI: 10.1016/j.neuroimage.2009.09.010] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Revised: 09/01/2009] [Accepted: 09/11/2009] [Indexed: 11/30/2022] Open
Abstract
We present an acquisition and reconstruction method designed to acquire high resolution 3D fast spin echo diffusion tensor images while mitigating the major sources of artifacts in DTI-field distortions, eddy currents and motion. The resulting images, being 3D, are of high SNR, and being fast spin echoes, exhibit greatly reduced field distortions. This sequence utilizes variable density spiral acquisition gradients, which allow for the implementation of a self-navigation scheme by which both eddy current and motion artifacts are removed. The result is that high resolution 3D DTI images are produced without the need for eddy current compensating gradients or B(0) field correction. In addition, a novel method for fast and accurate reconstruction of the non-Cartesian data is employed. Results are demonstrated in the brains of normal human volunteers.
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Affiliation(s)
- Lawrence R Frank
- Center for Scientific Computation in Imaging, San Diego, CA 92103, USA.
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28
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Deng J, Larson AC. Multishot targeted PROPELLER magnetic resonance imaging: description of the technique and initial applications. Invest Radiol 2009; 44:454-62. [PMID: 19465860 PMCID: PMC2888134 DOI: 10.1097/rli.0b013e3181a8b015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To test the feasibility of combining inner-volume imaging (IVI) techniques with conventional multishot periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) techniques for targeted-PROPELLER magnetic resonance imaging. MATERIALS AND METHODS Perpendicular section-selective gradients for spatially selective excitation and refocusing RF pulses were applied to limit the refocused field-of-view (FOV) along the phase-encoding direction for each rectangular blade image. We performed comparison studies in phantoms and normal volunteers by using targeted-PROPELLER methods for a wide range of imaging applications that commonly use turbo-spin-echo (TSE) approaches (brain, abdominal, vessel wall, cardiac). RESULTS In these initial studies, we demonstrated the feasibility of using targeted-PROPELLER approaches to limit the imaging FOV thereby reducing the number of blades or permitting increased spatial resolution without commensurate increases in scan time. Both phantom and in vivo motion studies demonstrated the potential for more robust regional self-navigated motion correction compared with conventional full FOV PROPELLER methods. CONCLUSION We demonstrated that the reduced FOV targeted-PROPELLER technique offers the potential for reducing imaging time, increasing spatial resolution, and targeting specific areas for robust regional motion correction.
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Affiliation(s)
- Jie Deng
- Department of Radiology, Northwestern University, Chicago, IL, USA
- Department of Biomedical Engineering, Northwestern University, Chicago, IL, USA
| | - Andrew C. Larson
- Department of Radiology, Northwestern University, Chicago, IL, USA
- Department of Biomedical Engineering, Northwestern University, Chicago, IL, USA
- Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL, USA
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29
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Laun F, Stieltjes B, Schlüter M, Rupp R, Schad LR. Reproducible evaluation of spinal cord DTI using an optimized inner volume sequence in combination with probabilistic ROI analysis. Z Med Phys 2009; 19:11-20. [PMID: 19459581 DOI: 10.1016/j.zemedi.2008.07.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The purpose of this work was to reliably acquire and evaluate diffusion tensor data of the cervical spine. Thereto, we describe an optimized, time-efficient inner-volume echo planar imaging sequence. Multislice capability is achieved by restoring the magnetization in neighbouring slices early during the twice refocused diffusion preparation. The acquired diffusion images showed compelling image quality. To reduce the arbitrariness of conventional region of interest (ROI) analysis, a tissue classification algorithm was applied. The classification was independent of the ROI shape and hence, a reliable and stable evaluation of the diffusion tensor could be achieved. The mean fractional anisotropy (FA) of five healthy subjects decreased from C1 (FA = 0.81 +/- 0.03) to C7 (FA = 0.60 +/- 0.03), while the mean apparent diffusion coefficient (ADC) increased from C1 (ADC= 0.78 +/- 0.08 microm2/ms) to C7 (ADC = 1.08 +/- 0.08 microm2/ms). In subsequent measurements of the individual healthy subjects, the standard deviation of the FA was 0.024 +/- 0.011 and the standard deviation of the ADC was 0.045 +/- 0.017 microm2/ms. The FA values of a patient with acute ischemic spinal trauma were significantly lower and changed more drastically than ADC values. Here, absolute FA ranged from 0.23 to 0.42, showing that DTI of the spine may serve as surrogate marker for tissue integrity and therapy monitoring.
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Affiliation(s)
- Frederik Laun
- German Cancer Research Center, Department of Medical Physics in Radiology, Im Neuenheimer Feld 280, 69210 Heidelberg.
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30
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Jung Y, Samsonov AA, Block WF, Lazar M, Lu A, Liu J, Alexander AL. 3D diffusion tensor MRI with isotropic resolution using a steady-state radial acquisition. J Magn Reson Imaging 2009; 29:1175-84. [PMID: 19388107 DOI: 10.1002/jmri.21663] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To obtain diffusion tensor images (DTI) over a large image volume rapidly with 3D isotropic spatial resolution, minimal spatial distortions, and reduced motion artifacts, a diffusion-weighted steady-state 3D projection (SS 3DPR) pulse sequence was developed. MATERIALS AND METHODS A diffusion gradient was inserted in a SS 3DPR pulse sequence. The acquisition was synchronized to the cardiac cycle, linear phase errors were corrected along the readout direction, and each projection was weighted by measures of consistency with other data. A new iterative parallel imaging reconstruction method was also implemented for removing off-resonance and undersampling artifacts simultaneously. RESULTS The contrast and appearance of both the fractional anisotropy and eigenvector color maps were substantially improved after all correction techniques were applied. True 3D DTI datasets were obtained in vivo over the whole brain (240 mm field of view in all directions) with 1.87 mm isotropic spatial resolution, six diffusion encoding directions in under 19 minutes. CONCLUSION A true 3D DTI pulse sequence with high isotropic spatial resolution was developed for whole brain imaging in under 20 minutes. To minimize the effects of brain motion, a cardiac synchronized, multiecho, DW-SSFP pulse sequence was implemented. Motion artifacts were further reduced by a combination of linear phase correction, corrupt projection detection and rejection, sampling density reweighting, and parallel imaging reconstruction. The combination of these methods greatly improved the quality of 3D DTI in the brain.
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Affiliation(s)
- Youngkyoo Jung
- Department of Radiology, University of California, San Diego, California, USA
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Axial diffusivity is the primary correlate of axonal injury in the experimental autoimmune encephalomyelitis spinal cord: a quantitative pixelwise analysis. J Neurosci 2009; 29:2805-13. [PMID: 19261876 DOI: 10.1523/jneurosci.4605-08.2009] [Citation(s) in RCA: 380] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The dissociation between magnetic resonance imaging (MRI) and permanent disability in multiple sclerosis (MS), termed the clinicoradiological paradox, can primarily be attributed to the lack of specificity of conventional, relaxivity-based MRI measurements in detecting axonal damage, the primary pathological correlate of long-term impairment in MS. Diffusion tensor imaging (DTI) has shown promise in specifically detecting axonal damage and demyelination in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). To quantify the specificity of DTI in detecting axonal injury, in vivo DTI maps from the spinal cords of mice with EAE and quantitative histological maps were both registered to a common space. A pixelwise correlation analysis between DTI parameters, histological metrics, and EAE scores revealed a significant correlation between the water diffusion parallel to the white matter fibers, or axial diffusivity, and EAE score. Furthermore, axial diffusivity was the primary correlate of quantitative staining for neurofilaments (SMI31), markers of axonal integrity. Both axial diffusivity and neurofilament staining were decreased throughout the entire white matter, not solely within the demyelinated lesions seen in EAE. In contrast, although anisotropy was significantly correlated with EAE score, it was not correlated with axonal damage. The results demonstrate a strong, quantitative relationship between axial diffusivity and axonal damage and show that anisotropy is not specific for axonal damage after inflammatory demyelination.
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Dowell NG, Jenkins TM, Ciccarelli O, Miller DH, Wheeler-Kingshott CAM. Contiguous-slice zonally oblique multislice (CO-ZOOM) diffusion tensor imaging: examples of in vivo spinal cord and optic nerve applications. J Magn Reson Imaging 2009; 29:454-60. [PMID: 19161202 DOI: 10.1002/jmri.21656] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To describe and demonstrate a new technique that allows diffusion tensor imaging of small structures such as the spinal cord (SC) and optic nerve (ON) with contiguous slices and reduced image distortions using a narrow field of view (FOV). MATERIALS AND METHODS Images were acquired with a modified single-shot echo-planar imaging (EPI) sequence that contains a refocusing radio frequency (RF) pulse in the presence of the phase-encoding (rather than slice-select) gradient. As a result, only a narrow volume may be both excited and refocused, removing the problem of signal aliasing for narrow FOVs. Two variants of this technique were developed: cardiac gating is included in the study of the SC to reduce pulsation artifacts, whereas inversion-recovery (IR) cerebrospinal fluid (CSF) suppression is utilized in the study of the ON to eliminate partial volume effects. The technique was evaluated with phantoms, and mean diffusivity (MD) and fractional anisotropy (FA) measurements were made in the SC and ON of two healthy volunteers. RESULTS The technique provides contiguous-slice, reduced-FOV images that do not suffer from aliasing and have reduced magnetic susceptibility artifacts. MD and FA values determined here lie within the ranges quoted in the literature. CONCLUSION Contiguous-slice zonally orthogonal multislice (CO-ZOOM-EPI is a new technique for diffusion-weighted imaging of small structures such as the ON and SC with high resolution and reduced distortions due to susceptibility variations. This technique is able to acquire contiguous slices that may allow further nerve-tracking analyses.
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Affiliation(s)
- Nicholas G Dowell
- NMR Research Unit, Institute of Neurology, University College London, London, UK.
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Sarlls JE, Pierpaoli C. Diffusion-weighted radial fast spin-echo for high-resolution diffusion tensor imaging at 3T. Magn Reson Med 2008; 60:270-6. [PMID: 18666119 DOI: 10.1002/mrm.21639] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
There is a need for an imaging sequence that can provide high-resolution diffusion tensor images at 3T near air-tissue interfaces. By employing a radial fast spin-echo (FSE) collection in conjunction with magnitude filtered back-projection reconstruction, high-resolution diffusion-weighted images can be produced without susceptibility artifacts. However, violation of the Carr-Purcell-Meiboom-Gill (CPMG) condition of diffusion prepared magnetization is a prominent problem for FSE trains that is magnified at higher fields. The unique aspect of violating the CPMG condition in trajectories that oversample the center of k-space and the implications for choosing the solution are examined. For collecting diffusion-weighted radial-FSE data at 3T we propose mixed-CPMG phase cycling of RF refocusing pulses combined with a 300% wider refocusing than excitation slice. It is shown that this approach produces accurate diffusion values in a phantom, and can be used to collect undistorted, high-resolution diffusion tensor images of the human brain.
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Affiliation(s)
- Joelle E Sarlls
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Xu J, Sun SW, Naismith RT, Snyder AZ, Cross AH, Song SK. Assessing optic nerve pathology with diffusion MRI: from mouse to human. NMR IN BIOMEDICINE 2008; 21:928-40. [PMID: 18756587 PMCID: PMC2603138 DOI: 10.1002/nbm.1307] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The optic nerve is often affected in patients with glaucoma and multiple sclerosis. Conventional MRI can detect nerve damage, but it does not accurately assess the underlying pathologies. Mean diffusivity and diffusion anisotropy indices derived from diffusion tensor imaging have been shown to be sensitive to a variety of central nervous system white matter pathologies. Despite being sensitive, the lack of specificity limits the ability of these measures to differentiate the underlying pathology. Directional (axial and radial) diffusivities, measuring water diffusion parallel and perpendicular to the axonal tracts, have been shown to be specific to axonal and myelin damage in mouse models of optic nerve injury, including retinal ischemia and experimental autoimmune encephalomyelitis. The progression of Wallerian degeneration has also been detected using directional diffusivities after retinal ischemia. However, translating these findings to human optic nerve is technically challenging. The current status of diffusion MRI of human optic nerve, including imaging sequences and protocols, is summarized herein. Despite the lack of a consensus among different groups on the optimal sequence or protocol, increased mean diffusivity and decreased diffusion anisotropy have been observed in injured optic nerve from patients with chronic optic neuritis. From different mouse models of optic nerve injuries to the emerging studies on patients with optic neuritis, directional diffusivities show great potential to be specific biomarkers for axonal and myelin injury.
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Affiliation(s)
- Junqian Xu
- Department of Neurology Washington University in St. Louis, St. Louis, Missouri, USA
| | - Shu-Wei Sun
- Department of Radiology Washington University in St. Louis, St. Louis, Missouri, USA
| | - Robert T. Naismith
- Department of Neurology Washington University in St. Louis, St. Louis, Missouri, USA
| | - Abraham Z. Snyder
- Department of Neurology Washington University in St. Louis, St. Louis, Missouri, USA
- Department of Radiology Washington University in St. Louis, St. Louis, Missouri, USA
| | - Anne H. Cross
- Department of Neurology Washington University in St. Louis, St. Louis, Missouri, USA
| | - Sheng-Kwei Song
- Department of Radiology Washington University in St. Louis, St. Louis, Missouri, USA
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Cohen-Adad J, Benali H, Barrière G, Leblond H, Hoge R, Rossignol S. Développement clinique de l’IRM du tenseur de diffusion de la moelle épinière dans un contexte de lésion médullaire. Ing Rech Biomed 2008. [DOI: 10.1016/j.rbmret.2007.12.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Cohen-Adad J, Benali H, Hoge RD, Rossignol S. In vivo DTI of the healthy and injured cat spinal cord at high spatial and angular resolution. Neuroimage 2007; 40:685-697. [PMID: 18201909 DOI: 10.1016/j.neuroimage.2007.11.031] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Revised: 11/02/2007] [Accepted: 11/13/2007] [Indexed: 11/26/2022] Open
Abstract
Spinal cord diffusion tensor imaging (DTI) is challenging in many ways: the small size of the cord, physiological motion and susceptibility artifacts pose daunting obstacles to the acquisition of high-quality data. Here, we present DTI results computed from in vivo studies of the healthy and injured spinal cord of five cats. Both high spatial (1.1 mm3) and angular (55 directions) resolutions were used to optimise modelling of the diffusion process. Also, particular effort was directed towards a strategy that limits susceptibility artifacts. For validation purposes, acquisitions were repeated in two cats before and after making a spinal lesion. As a result, various axonal trajectories were identified by tractography including dorsal and ventral columns as well as lateral tracts. Also, fibre bundles showed robust disruption at the site of spinal cord injuries (partial and complete) via tractography, accompanied with significantly lower fractional anisotropy values at the site of lesions. Important outcomes of this work are (i) tractography-based localisation of anatomical tracts in the thoraco-lumbar spinal cord and (ii) in vivo assessment of axonal integrity following experimental spinal cord injury.
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Affiliation(s)
- J Cohen-Adad
- Groupe de Recherche sur le Système Nerveux Central, Department of Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada; INSERM U678, Université Pierre et Marie Curie (Paris VI), CHU Pitié-Salpêtrière, Paris, France; Unité de Neuroimagerie Fonctionnelle, CRIUGM, Université de Montréal, Montreal, QC, Canada; Institute of Biomedical Engineering, Department of Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada.
| | - H Benali
- INSERM U678, Université Pierre et Marie Curie (Paris VI), CHU Pitié-Salpêtrière, Paris, France; Unité de Neuroimagerie Fonctionnelle, CRIUGM, Université de Montréal, Montreal, QC, Canada
| | - R D Hoge
- Unité de Neuroimagerie Fonctionnelle, CRIUGM, Université de Montréal, Montreal, QC, Canada; Institute of Biomedical Engineering, Department of Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
| | - S Rossignol
- Groupe de Recherche sur le Système Nerveux Central, Department of Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada; Unité de Neuroimagerie Fonctionnelle, CRIUGM, Université de Montréal, Montreal, QC, Canada; Institute of Biomedical Engineering, Department of Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
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Cohen-Adad J, Benali H, Rossignol S. Methodology for MR diffusion tensor imaging of the cat spinal cord. ACTA ACUST UNITED AC 2007; 2007:323-6. [DOI: 10.1109/iembs.2007.4352289] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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