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Schilling KG, Combes AJE, Ramadass K, Rheault F, Sweeney G, Prock L, Sriram S, Cohen-Adad J, Gore JC, Landman BA, Smith SA, O'Grady KP. Influence of preprocessing, distortion correction and cardiac triggering on the quality of diffusion MR images of spinal cord. Magn Reson Imaging 2024; 108:11-21. [PMID: 38309376 PMCID: PMC11218893 DOI: 10.1016/j.mri.2024.01.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 01/04/2024] [Accepted: 01/14/2024] [Indexed: 02/05/2024]
Abstract
Diffusion MRI of the spinal cord (SC) is susceptible to geometric distortion caused by field inhomogeneities, and prone to misalignment across time series and signal dropout caused by biological motion. Several modifications of image acquisition and image processing techniques have been introduced to overcome these artifacts, but their specific benefits are largely unproven and warrant further investigations. We aim to evaluate two specific aspects of image acquisition and processing that address image quality in diffusion studies of the spinal cord: susceptibility corrections to reduce geometric distortions, and cardiac triggering to minimize motion artifacts. First, we evaluate 4 distortion preprocessing strategies on 7 datasets of the cervical and lumbar SC and find that while distortion correction techniques increase geometric similarity to structural images, they are largely driven by the high-contrast cerebrospinal fluid, and do not consistently improve the geometry within the cord nor improve white-to-gray matter contrast. We recommend at a minimum to perform bulk-motion correction in preprocessing and posit that improvements/adaptations are needed for spinal cord distortion preprocessing algorithms, which are currently optimized and designed for brain imaging. Second, we design experiments to evaluate the impact of removing cardiac triggering. We show that when triggering is foregone, images are qualitatively similar to triggered sequences, do not have increased prevalence of artifacts, and result in similar diffusion tensor indices with similar reproducibility to triggered acquisitions. When triggering is removed, much shorter acquisitions are possible, which are also qualitatively and quantitatively similar to triggered sequences. We suggest that removing cardiac triggering for cervical SC diffusion can be a reasonable option to save time with minimal sacrifice to image quality.
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Affiliation(s)
- Kurt G Schilling
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA.
| | - Anna J E Combes
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Karthik Ramadass
- Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, USA; Department of Computer Science, Vanderbilt University, Nashville, TN, USA
| | - Francois Rheault
- Medical Imaging and Neuroinformatic (MINi) Lab, Department of Computer Science, University of Sherbrooke, Canada
| | - Grace Sweeney
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Logan Prock
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Subramaniam Sriram
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada; Functional Neuroimaging Unit, CRIUGM, University of Montreal, Montreal, QC, Canada; Mila - Quebec AI Institute, Montreal, QC, Canada; Centre de recherche du CHU Sainte-Justine, Université de Montréal, Montreal, QC, Canada
| | - John C Gore
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Bennett A Landman
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, USA; Department of Computer Science, Vanderbilt University, Nashville, TN, USA
| | - Seth A Smith
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Kristin P O'Grady
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
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Dependence of apparent diffusion coefficient on slice position in magnetic resonance diffusion imaging. Magn Reson Imaging 2023; 99:41-47. [PMID: 36682397 DOI: 10.1016/j.mri.2023.01.009] [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: 06/19/2022] [Revised: 01/11/2023] [Accepted: 01/11/2023] [Indexed: 01/21/2023]
Abstract
PURPOSE The position dependence of the apparent diffusion coefficient (ADC) in magnetic resonance imaging (MRI) by echo-planar imaging (EPI)- and turbo spin echo (TSE)-diffusion-weighted imaging (DWI) was assessed using phantoms. METHODS Six pure water-filled containers were placed parallel to the direction of the static magnetic field from the center of the magnetic field to the foot direction (five containers) and the head direction (one container). Six slice positions were set, and a cross-section image was scanned at the center of each container using a 1.5-T MRI scanner. Diffusion times for both EPI- and TSE-DWI were matched as much as possible. The slice thickness was adjusted to match the signal-to-noise ratio (SNR) at the center of the magnetic field for both sequences. A B1 map was analyzed. The ADC and SNR at each position of both sequences were tested using the Wilcoxon signed-rank test (P = 0.05) and compared using Friedman and Steel-Dwass multiple comparison tests (P = 0.05). Pearson correlation coefficients between ADC and SNR and between ADC and flip angle (FA) were calculated. RESULTS ADC decreased significantly with distance from the center of the magnetic field for both EPI-DWI and TSE-DWI (P < 0.05). TSE-ADC was significantly higher than EPI-ADC for all combinations (P < 0.01). Based on the Friedman test, the SNR of EPI- and TSE-DWI was significantly different and depended on the slice position (P < 0.01). The Pearson correlation coefficient between ADC and SNR was 0.78 in EPI-DWI and 0.60 in TSE-DWI, whereas that between ADC and FA was 0.97 in EPI-DWI and 0.94 in TSE-DWI. The FA decreased by 0.048 and 0.047° per mm from the center of the magnetic field to head and foot directions, respectively. CONCLUSION ADC depends on the slice position and decreases with an increase in distance from the magnetic field center. Caution should be taken when comparing and quantitatively evaluating the ADC at sites shifted in the long-axis direction.
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Dai E, Mani M, McNab JA. Multi-band multi-shot diffusion MRI reconstruction with joint usage of structured low-rank constraints and explicit phase mapping. Magn Reson Med 2023; 89:95-111. [PMID: 36063492 PMCID: PMC9887994 DOI: 10.1002/mrm.29422] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 08/01/2022] [Accepted: 08/02/2022] [Indexed: 02/02/2023]
Abstract
PURPOSE To develop a joint reconstruction method for multi-band multi-shot diffusion MRI. THEORY AND METHODS Multi-band multi-shot EPI acquisition is an effective approach for high-resolution diffusion MRI, but requires specific algorithms to correct the inter-shot phase variations. The phase correction can be done by first estimating the explicit phase map and then feeding it into the k-space signal formulation model. Alternatively, the phase information can be used indirectly as structured low-rank constraints in k-space. The 2 methods differ in reconstruction accuracy and efficiency. We aim to combine the 2 different approaches for improved image quality and reconstruction efficiency simultaneously, termed "joint usage of structured low-rank constraints and explicit phase mapping" (JULEP). The proposed JULEP reconstruction is tested on both single-band and multi-band, multi-shot diffusion data, with different resolutions and b values. The results of JULEP are compared with conventional methods with explicit phase mapping (i.e., multiplexed sensitivity-encoding [MUSE]) and structured low-rank constraints (i.e., MUSSELS), and another joint reconstruction method (i.e., network estimated artifacts for tempered reconstruction [NEATR]). RESULTS JULEP improves the quality of the navigator and subsequently facilitates the reconstruction of final diffusion images. Compared with all 3 other methods (MUSE, MUSSELS, and NEATR), JULEP mitigates residual structural bias and improves temporal SNRs in the final diffusion image, particularly at high multi-band factors. Compared with MUSSELS, JULEP also improves computational efficiency. CONCLUSION The proposed JULEP method significantly improves the image quality and reconstruction efficiency of multi-band multi-shot diffusion MRI, which can promote a broader application of high-resolution diffusion MRI.
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Affiliation(s)
- Erpeng Dai
- Department of Radiology, Stanford University, Stanford, CA, United States
| | - Merry Mani
- Department of Radiology, University of Iowa, Iowa City, IA, United States
- Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States
| | - Jennifer A McNab
- Department of Radiology, Stanford University, Stanford, CA, United States
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Lee SK, Bernstein MA. Systematic Dimensional Analysis of the Scaling Relationship for Gradient and Shim Coil Design Parameters. Magn Reson Med 2022; 88:1901-1911. [PMID: 35666832 PMCID: PMC9893842 DOI: 10.1002/mrm.29316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 04/22/2022] [Accepted: 05/07/2022] [Indexed: 02/04/2023]
Abstract
PURPOSE To demonstrate systematic, linear algebra-based, dimensional analysis to derive a scaling relationship among the design parameters of MRI gradient and harmonic shim coils. THEORY AND METHODS The dimensions of five physical quantities relevant for gradient coil design (inductance, gradient amplitude, inner diameter [ d $$ d $$ ], current, and the permeability of free space) were decomposed into fundamental units, and their exponents were arranged into a dimensional matrix. The resulting set of homogenous equations was solved using standard linear algebraic methods. Inclusion of the number of turns as an additional unit yielded a 5 × 5 dimensional matrix with a unique, nontrivial solution. The analysis was extended to harmonic shim coils. The gradient coil scaling relationship was compared with data from 24 published gradient coil sets. RESULTS Only when the unit of turns was included did the linear algebra-based analysis uniquely produce the known scaling relationship that gradient inductance is proportional to gradient efficiency squared times d 5 $$ {d}^5 $$ . By applying the same methodology to an lth order shim coil, a novel result is obtained: Shim inductance is proportional to its efficiency squared times d 2 l + 3 $$ {d}^{2l+3} $$ . The predicted power-law relationship between inductance-normalized gradient efficiency and the diameter accounted for > 92% of the efficiency variation of the surveyed gradient coils. A dimensionless parameter is proposed as an intrinsic figure-of-merit of gradient coil efficiency. CONCLUSION Systematic application of linear algebra-based dimensional analysis can provide new insight in gradient and shim coil design by revealing fundamental scaling relations and helping to guide the design and comparison of coils with different diameters.
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Reduced field-of-view and multi-shot DWI acquisition techniques: Prospective evaluation of image quality and distortion reduction in prostate cancer imaging. Magn Reson Imaging 2022; 93:108-114. [DOI: 10.1016/j.mri.2022.08.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 08/03/2022] [Accepted: 08/03/2022] [Indexed: 11/20/2022]
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Dai E, Lee PK, Dong Z, Fu F, Setsompop K, McNab JA. Distortion-Free Diffusion Imaging Using Self-Navigated Cartesian Echo-Planar Time Resolved Acquisition and Joint Magnitude and Phase Constrained Reconstruction. IEEE TRANSACTIONS ON MEDICAL IMAGING 2022; 41:63-74. [PMID: 34383645 PMCID: PMC8799377 DOI: 10.1109/tmi.2021.3104291] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Echo-planar time resolved imaging (EPTI) is an effective approach for acquiring high-quality distortion-free images with a multi-shot EPI (ms-EPI) readout. As with traditional ms-EPI acquisitions, inter-shot phase variations present a main challenge when incorporating EPTI into a diffusion-prepared pulse sequence. The aim of this study is to develop a self-navigated Cartesian EPTI-based (scEPTI) acquisition together with a magnitude and phase constrained reconstruction for distortion-free diffusion imaging. A self-navigated Cartesian EPTI-based diffusion-prepared pulse sequence is designed. The different phase components in EPTI diffusion signal are analyzed and an approach to synthesize a fully phase-matched navigator for the inter-shot phase correction is demonstrated. Lastly, EPTI contains richer magnitude and phase information than conventional ms-EPI, such as the magnitude and phase correlations along the temporal dimension. The potential of these magnitude and phase correlations to enhance the reconstruction is explored. The reconstruction results with and without phase matching and with and without phase or magnitude constraints are compared. Compared with reconstruction without phase matching, the proposed phase matching method can improve the accuracy of inter-shot phase correction and reduce signal corruption in the final diffusion images. Magnitude constraints further improve image quality by suppressing the background noise and thereby increasing SNR, while phase constraints can mitigate possible image blurring from adding magnitude constraints. The high-quality distortion-free diffusion images and simultaneous diffusion-relaxometry imaging capacity provided by the proposed EPTI design represent a highly valuable tool for both clinical and neuroscientific assessments of tissue microstructure.
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Takatsu Y, Yamamura K, Yamatani Y, Takahashi D, Yoshida R, Asahara M, Honda M, Miyati T. Echo-planar imaging is superior to fast spin-echo diffusion-weighted imaging for cranioplasty using titanium mesh in brain magnetic resonance imaging: a phantom study. Radiol Phys Technol 2021; 15:89-99. [PMID: 34855114 DOI: 10.1007/s12194-021-00646-y] [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: 12/19/2020] [Revised: 11/21/2021] [Accepted: 11/22/2021] [Indexed: 12/01/2022]
Abstract
This study aimed to compare the radiofrequency (RF) shielding effects of titanium mesh of echo-planar imaging (EPI) versus fast spin-echo (FSE) diffusion-weighted imaging (DWI) to establish a suitable sequence for patients who undergo cranioplasty and for whom titanium mesh was used in brain magnetic resonance imaging (MRI). A 1.5-T MRI scanner with clinical setting sequences was used. A phantom for the examination constructed using a sucrose solution in a plastic container was used to compare the signal attenuation (SA) ratio, area of RF shielding effect (Area), normalized absolute average deviation (NAAD), and apparent diffusion coefficient (ADC) between EPI and FSE-DWI. EPI provided significantly better SA ratio, Area, and NAAD (P < 0.01). When the number of slices increased, the RF shielding became more negative. There was no significant difference in the ADC. Regardless of the k-trajectory, EPI-DWI had a lower RF shielding effect than FSE-DWI in patients undergoing cranioplasty.
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Affiliation(s)
- Yasuo Takatsu
- Department of System Control Engineering, Graduate School of Engineering, Tokushima Bunri University, 1314-1 Shido, Sanuki-City, Kagawa, 769-2193, Japan. .,Department of Radiological Technology, Faculty of Health and Welfare, Tokushima Bunri University, 1314-1 Shido, Sanuki-City, Kagawa, 769-2193, Japan. .,Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan.
| | - Kenichiro Yamamura
- Department of Radiological Technology, Faculty of Health and Welfare, Tokushima Bunri University, 1314-1 Shido, Sanuki-City, Kagawa, 769-2193, Japan
| | - Yuya Yamatani
- Division of Central Radiology, Nara Medical University Hospital, 840, Shijo-cho, Kashihara, Nara, 634-8522, Japan
| | - Daisuke Takahashi
- Department of Radiological Technology, Iwate Prefectural Central Hospital, 4-1, 1 Cho-me, Ueda, Morioka City, Iwate, 020-0066, Japan
| | - Rei Yoshida
- Department of Radiology, Kurihara Central Hospital, 3-3-1 Miyano cyuou, Tsukidate, Kurihara-City, Miyagi, 987-2205, Japan
| | - Masaki Asahara
- Department of Radiological Technology, Faculty of Health and Welfare, Tokushima Bunri University, 1314-1 Shido, Sanuki-City, Kagawa, 769-2193, Japan
| | - Michitaka Honda
- Department of Radiological Technology, Faculty of Health and Welfare, Tokushima Bunri University, 1314-1 Shido, Sanuki-City, Kagawa, 769-2193, Japan
| | - Tosiaki Miyati
- Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan
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Wang DJJ, Le Bihan D, Krishnamurthy R, Smith M, Ho ML. Noncontrast Pediatric Brain Perfusion: Arterial Spin Labeling and Intravoxel Incoherent Motion. Magn Reson Imaging Clin N Am 2021; 29:493-513. [PMID: 34717841 DOI: 10.1016/j.mric.2021.06.002] [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] [Indexed: 12/23/2022]
Abstract
Noncontrast magnetic resonance imaging techniques for measuring brain perfusion include arterial spin labeling (ASL) and intravoxel incoherent motion (IVIM). These techniques provide noninvasive and repeatable assessment of cerebral blood flow or cerebral blood volume without the need for intravenous contrast. This article discusses the technical aspects of ASL and IVIM with a focus on normal physiologic variations, technical parameters, and artifacts. Multiple pediatric clinical applications are presented, including tumors, stroke, vasculopathy, vascular malformations, epilepsy, migraine, trauma, and inflammation.
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Affiliation(s)
- Danny J J Wang
- USC Institute for Neuroimaging and Informatics, SHN, 2025 Zonal Avenue, Health Sciences Campus, Los Angeles, CA 90033, USA
| | - Denis Le Bihan
- NeuroSpin, Centre d'études de Saclay, Bâtiment 145, Gif-sur-Yvette 91191, France
| | - Ram Krishnamurthy
- Department of Radiology, Nationwide Children's Hospital, 700 Children's Drive - ED4, Columbus, OH 43205, USA
| | - Mark Smith
- Department of Radiology, Nationwide Children's Hospital, 700 Children's Drive - ED4, Columbus, OH 43205, USA
| | - Mai-Lan Ho
- Department of Radiology, Nationwide Children's Hospital, 700 Children's Drive - ED4, Columbus, OH 43205, USA.
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Versteeg E, van der Velden TA, van Leeuwen CC, Borgo M, Huijing ER, Hendriks AD, Hendrikse J, Klomp DWJ, Siero JCW. A plug-and-play, lightweight, single-axis gradient insert design for increasing spatiotemporal resolution in echo planar imaging-based brain imaging. NMR IN BIOMEDICINE 2021; 34:e4499. [PMID: 33619838 PMCID: PMC8244051 DOI: 10.1002/nbm.4499] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 02/09/2021] [Accepted: 02/11/2021] [Indexed: 05/25/2023]
Abstract
The goal of this study was to introduce and evaluate the performance of a lightweight, high-performance, single-axis (z-axis) gradient insert design primarily intended for high-resolution functional magnetic resonance imaging, and aimed at providing both ease of use and a boost in spatiotemporal resolution. The optimal winding positions of the coil were obtained using a genetic algorithm with a cost function that balanced gradient performance (minimum 0.30 mT/m/A) and field linearity (≥16 cm linear region). These parameters were verified using field distribution measurements by B0 -mapping. The correction of geometrical distortions was performed using theoretical field distribution of the coil. Simulations and measurements were performed to investigate the echo planar imaging echo-spacing reduction due to the improved gradient performance. The resulting coil featured a 16-cm linear region, a weight of 45 kg, an installation time of 15 min, and a maximum gradient strength and slew rate of 200 mT/m and 1300 T/m/s, respectively, when paired with a commercially available gradient amplifier (940 V/630 A). The field distribution measurements matched the theoretically expected field. By utilizing the theoretical field distribution, geometrical distortions were corrected to within 6% of the whole-body gradient reference image in the target region. Compared with a whole-body gradient set, a maximum reduction in echo-spacing of a factor of 2.3 was found, translating to a 344 μs echo-spacing, for a field of view of 192 mm, a receiver bandwidth of 920 kHz and a gradient amplitude of 112 mT/m. We present a lightweight, single-axis gradient insert design that can provide high gradient performance and an increase in spatiotemporal resolution with correctable geometrical distortions while also offering a short installation time of less than 15 min and minimal system modifications.
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Affiliation(s)
- Edwin Versteeg
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | | | | | | | - Erik R. Huijing
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | - Arjan D. Hendriks
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | - Jeroen Hendrikse
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | - Dennis W. J. Klomp
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | - Jeroen C. W. Siero
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
- Spinoza Center for NeuroimagingAmsterdamthe Netherlands
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Dai E, Liu S, Guo H. High-resolution whole-brain diffusion MRI at 3T using simultaneous multi-slab (SMSlab) acquisition. Neuroimage 2021; 237:118099. [PMID: 33940144 DOI: 10.1016/j.neuroimage.2021.118099] [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: 12/12/2020] [Revised: 03/20/2021] [Accepted: 04/24/2021] [Indexed: 01/23/2023] Open
Abstract
High-resolution diffusion MRI (dMRI) is a crucial tool in neuroscience studies to detect fine fiber structure, depict complex fiber architecture and analyze cortical anisotropy. However, high-resolution dMRI is limited by its intrinsically low SNR due to diffusion attenuation. A series of techniques have been proposed to improve the SNR performance, but most of them are at the cost of long scan time, which in turn sacrifice the SNR efficiency, especially for large FOV imaging, such as whole-brain imaging. Recently, a combination of 3D multi-slab acquisition and simultaneous multi-slice (SMS) excitation, namely simultaneous multi-slab (SMSlab), has been demonstrated to have potential for high-resolution diffusion imaging with high SNR and SNR efficiency. In our previous work, we have proposed a 3D Fourier encoding and reconstruction framework for SMSlab acquisition. In this study, we extend this 3D k-space framework to diffusion imaging, by developing a novel navigator acquisition strategy and exploring a k-space-based phase correction method. In vivo brain data are acquired using the proposed SMSlab method and compared with a series of different acquisitions, including the traditional 3D multi-slab, 2D SMS and 2D single-shot EPI (ss-EPI) acquisitions. The results demonstrate that SMSlab has a better SNR performance compared with 3D multi-slab and 2D SMS. The detection capacity of fine fiber structures is improved using SMSlab, compared with the low-resolution diffusion imaging using conventional 2D ss-EPI.
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Affiliation(s)
- Erpeng Dai
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China; Department of Radiology, Stanford University, Stanford, CA, United States
| | - Simin Liu
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China
| | - Hua Guo
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China.
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de Almeida Martins J, Tax C, Szczepankiewicz F, Jones D, Westin CF, Topgaard D. Transferring principles of solid-state and Laplace NMR to the field of in vivo brain MRI. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2020; 1:27-43. [PMID: 37904884 PMCID: PMC10500744 DOI: 10.5194/mr-1-27-2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 02/18/2020] [Indexed: 11/01/2023]
Abstract
Magnetic resonance imaging (MRI) is the primary method for noninvasive investigations of the human brain in health, disease, and development but yields data that are difficult to interpret whenever the millimeter-scale voxels contain multiple microscopic tissue environments with different chemical and structural properties. We propose a novel MRI framework to quantify the microscopic heterogeneity of the living human brain as spatially resolved five-dimensional relaxation-diffusion distributions by augmenting a conventional diffusion-weighted imaging sequence with signal encoding principles from multidimensional solid-state nuclear magnetic resonance (NMR) spectroscopy, relaxation-diffusion correlation methods from Laplace NMR of porous media, and Monte Carlo data inversion. The high dimensionality of the distribution space allows resolution of multiple microscopic environments within each heterogeneous voxel as well as their individual characterization with novel statistical measures that combine the chemical sensitivity of the relaxation rates with the link between microstructure and the anisotropic diffusivity of tissue water. The proposed framework is demonstrated on a healthy volunteer using both exhaustive and clinically viable acquisition protocols.
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Affiliation(s)
- João P. de Almeida Martins
- Division of Physical Chemistry, Department of Chemistry, Lund
University, Lund, Sweden
- Random Walk Imaging AB, Lund, Sweden
| | - Chantal M. W. Tax
- Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff
University, Cardiff, UK
| | - Filip Szczepankiewicz
- Harvard Medical School, Boston, MA, USA
- Radiology, Brigham and Women's Hospital, Boston, MA, USA
| | - Derek K. Jones
- Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff
University, Cardiff, UK
- Mary MacKillop Institute for Health Research, Australian Catholic
University, Melbourne, Australia
| | - Carl-Fredrik Westin
- Harvard Medical School, Boston, MA, USA
- Radiology, Brigham and Women's Hospital, Boston, MA, USA
| | - Daniel Topgaard
- Division of Physical Chemistry, Department of Chemistry, Lund
University, Lund, Sweden
- Random Walk Imaging AB, Lund, Sweden
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12
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Liebig PA, Heidemann RM, Hensel B, Porter DA. A new approach to accelerate readout segmented EPI with compressed sensing. Magn Reson Med 2019; 84:321-326. [PMID: 31880343 DOI: 10.1002/mrm.28116] [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: 08/05/2019] [Revised: 10/28/2019] [Accepted: 11/18/2019] [Indexed: 11/07/2022]
Abstract
PURPOSE High resolution diffusion-weighted imaging is limited by susceptibility-induced distortions and relaxation-induced blurring. Segmented acquisition techniques can address these limitations at the expense of a prolonged scan time. If segmentation is performed along the readout direction, e.g., in RESOLVE (readout segmentation of long and variable echo-trains), scan time can be reduced by readout (RO) partial Fourier methods, or simultaneous multi-slice (SMS) methods. In this paper, we present a new approach to additionally accelerate the image acquisition called variable segment (VASE) RESOLVE. METHODS To avoid discontinuities at the boundaries of the segments, the phase evolution and therefore the effective echo-spacing needs to be adjusted. To achieve this, we use higher undersampling factors in the outer parts of k-space. Simultaneously we increase the width of the outer segments resulting in an increase of the echo-spacing. Because of this variation, we introduce a kind of randomization to the sampling scheme. This enables the use of compressed sensing reconstruction techniques, which results in improved image quality compared to standard parallel imaging methods. RESULTS The RMS errors for the VASE RESOLVE acquisitions were lower compared to the standard reconstructions. The VASE RESOLVE in vivo images show a higher apparent signal to noise ratio. CONCLUSION VASE RESOLVE is a new approach to further decrease the acquisition time of RO segmented acquisitions. Compared to RESOLVE with SMS, VASE RESOLVE additionally reduces the acquisition time by a factor of 2.
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Affiliation(s)
- Patrick Alexander Liebig
- Center of Medical Physics and Biomedical Engineering, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.,Siemens Healthcare GmbH, Erlangen, Germany.,Imaging Centre of Excellence, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | | | - Bernhard Hensel
- Center of Medical Physics and Biomedical Engineering, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - David Andrew Porter
- Imaging Centre of Excellence, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom
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Wáng YXJ, Wang X, Wu P, Wang Y, Chen W, Chen H, Li J. Topics on quantitative liver magnetic resonance imaging. Quant Imaging Med Surg 2019; 9:1840-1890. [PMID: 31867237 DOI: 10.21037/qims.2019.09.18] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Liver magnetic resonance imaging (MRI) is subject to continuous technical innovations through advances in hardware, sequence and novel contrast agent development. In order to utilize the abilities of liver MR to its full extent and perform high-quality efficient exams, it is mandatory to use the best imaging protocol, to minimize artifacts and to select the most adequate type of contrast agent. In this article, we review the routine clinical MR techniques applied currently and some latest developments of liver imaging techniques to help radiologists and technologists to better understand how to choose and optimize liver MRI protocols that can be used in clinical practice. This article covers topics on (I) fat signal suppression; (II) diffusion weighted imaging (DWI) and intravoxel incoherent motion (IVIM) analysis; (III) dynamic contrast-enhanced (DCE) MR imaging; (IV) liver fat quantification; (V) liver iron quantification; and (VI) scan speed acceleration.
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Affiliation(s)
- Yì Xiáng J Wáng
- Department of Imaging and Interventional Radiology, Faculty of Medicine, The Chinese University of Hong Kong, New Territories, Hong Kong SAR, China
| | | | - Peng Wu
- Philips Healthcare (Suzhou) Co., Ltd., Suzhou 215024, China
| | - Yajie Wang
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China
| | - Weibo Chen
- Philips Healthcare, Shanghai 200072, China.,Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai 200062, China
| | - Huijun Chen
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China
| | - Jianqi Li
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai 200062, China
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Yang Z, Zhao B, Pei Y, Yang B, Lu H. A "flared-end" gradient coil with outer-wall direct cooling for human brain imaging: A feasibility study. Magn Reson Imaging 2019; 62:191-198. [PMID: 31306733 DOI: 10.1016/j.mri.2019.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Revised: 07/11/2019] [Accepted: 07/11/2019] [Indexed: 11/16/2022]
Abstract
Optimal gradient performance is arguably a pre-requisite to realize the full potential of ultrahigh field magnetic resonance imaging (MRI). The values of using tailored gradient coils for brain imaging have been well acknowledged. Unfortunately, conventional head-only gradient coils have two major technical limitations, i.e. limited shoulder clearance and limited cooling capacity. A design, coined "flared-end" gradient coil, combined with a cooling method, named "outer-wall direct cooling", is proposed to address these problems. The "flared-end" design permits brain access to the center of gradient coil. The "flared end" structure is 3D-printed. It has electrical winding patterns (grooves) on one side and evenly spaced cooling channels on the opposite side. Electrical conductor (copper wire) is fixed into the grooves; coolant is in direct contact with the outer surface of the electrical conductor above each cooling channel, eliminating interfacial thermal resistance between coolant and copper wires. Heat transfer area is thus determined by the size and the number of cooling channels. This approach allows high electric current density for high gradient field strength while maintaining high cooling efficiency. Additionally, the symmetric coil geometry guarantees intrinsic torque balance. As a proof of concept, we have made a gradient coil prototype without active shielding. This coil has an inner diameter of 0.3 m, and is capable of generating 0.337, 0.225 and 0.485 mT/m/A along X, Y and Z, respectively. Active shielding was designed theoretically, but not pursued in the construction of this coil prototype. The new coil geometry and cooling method offer a novel avenue for new gradient coils tailored for human brain imaging at ultrahigh field.
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Affiliation(s)
- Zhi Yang
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA
| | - Beihan Zhao
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA
| | - Yong Pei
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA
| | - Bao Yang
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA.
| | - Hanbing Lu
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA.
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N Ray, Vyas S, Khandelwal N, Bansal R, Lal V. Papilloedema: diffusion-weighted imaging of optic nerve head. Clin Radiol 2019; 74:652.e11-652.e19. [PMID: 31202568 DOI: 10.1016/j.crad.2019.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 05/02/2019] [Indexed: 10/26/2022]
Abstract
AIM To establish the correlation between clinical grading of papilloedema and diffusion abnormalities of optic nerve head (ONH) on diffusion-weighted imaging (DWI). MATERIALS AND METHODS Brain magnetic resonance imaging (MRI), including readout segmented echo planar imaging-based DWI, was performed in 32 patients with papilloedema and the same number of age- and sex-matched controls. Clinical grading of papilloedema was done according to the modified Frisén scale. Two neuroradiologists independently evaluated the MRI for ONH hyperintensity and apparent diffusion coefficient (ADC) value of ONH. The comparison between papilloedema clinical grade and qualitative grade of ONH hyperintensity and its presence between cases and control groups were done using the Chi-square test and Fisher's exact test, respectively. The comparison between mean ADC value of ONH among different grades and between cases and controls were done using analysis of variance (ANOVA)-F-test and Student's t-test, respectively. Receiver operating characteristic (ROC) analysis was done to calculate a cut-off ADC value between the case and control groups. RESULTS Significant correlation between ONH hyperintensity and mean ADC value of ONH with clinical grades of papilloedema and between cases and control groups were found. ONH hyperintensity was found to be a highly sensitive (87.5% for both) and specific (specificity 97.1% and 98.6% for two observers) sign of papilloedema. A mean cut-off ONH ADC value was found to have high sensitivity (96.83%) and specificity (95.31%) to distinguish between the cases and controls. CONCLUSIONS Diffusion parameters of ONH have significant correlation with clinical grading of papilloedema and can serve as a surrogate marker for intracranial pressure.
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Affiliation(s)
- N Ray
- Department of Radiodiagnosis and Imaging, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
| | - S Vyas
- Department of Radiodiagnosis and Imaging, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India.
| | - N Khandelwal
- Department of Radiodiagnosis and Imaging, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
| | - R Bansal
- Department of Ophthalmology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
| | - V Lal
- Department of Neurology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
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Gaspar AS, Nunes RG, Ferrazzi G, Hughes EJ, Hutter J, Malik SJ, McCabe L, Baruteau KP, Rutherford MA, Hajnal JV, Price AN. Optimizing maternal fat suppression with constrained image-based shimming in fetal MR. Magn Reson Med 2019; 81:477-485. [PMID: 30058204 PMCID: PMC6282825 DOI: 10.1002/mrm.27375] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 05/02/2018] [Accepted: 05/03/2018] [Indexed: 12/21/2022]
Abstract
PURPOSE Echo planar imaging (EPI) is the primary sequence for functional and diffusion MRI. In fetal applications, the large field of view needed to encode the maternal abdomen leads to prolonged EPI readouts, which may be further extended due to safety considerations that limit gradient performance. The resulting images become very sensitive to water-fat shift and susceptibility artefacts. The purpose of this study was to reduce artefacts and increase stability of EPI in fetal brain imaging, balancing local field homogeneity across the fetal brain with longer range variations to ensure compatibility with fat suppression of the maternal abdomen. METHODS Spectral Pre-saturation with Inversion-Recovery (SPIR) fat suppression was optimized by investigating SPIR pulse frequency offsets. Subsequently, fetal brain EPI data were acquired using image-based (IB) shimming on 6 pregnant women by (1) minimizing B0 field variations within the fetal brain (localized IB shimming) and (2) with added constraint to limit B0 variation in maternal fat (fat constrained IB shimming). RESULTS The optimal offset for the SPIR pulse at 3 Tesla was 550 Hz. Both shimming approaches had similar performances in terms of B0 homogeneity within the brain, but constrained IB shimming enabled higher fat suppression efficiency. CONCLUSION Optimized SPIR in combination with constrained IB shimming can improve maternal fat suppression while minimizing EPI distortions in the fetal brain.
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Affiliation(s)
- Andreia S. Gaspar
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
- Institute for Systems and Robotics/Department of Bioengineering, Instituto Superior TécnicoUniversidade de LisboaLisbonPortugal
- Instituto de Biofísica e Engenharia BiomédicaFaculdade de Ciências da Universidade de LisboaCampo GrandeLisbonPortugal
| | - Rita G. Nunes
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
- Institute for Systems and Robotics/Department of Bioengineering, Instituto Superior TécnicoUniversidade de LisboaLisbonPortugal
- Instituto de Biofísica e Engenharia BiomédicaFaculdade de Ciências da Universidade de LisboaCampo GrandeLisbonPortugal
| | - Giulio Ferrazzi
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Emer J. Hughes
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Jana Hutter
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Shaihan J. Malik
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Laura McCabe
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Kelly P. Baruteau
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
- Lysholm Department of Neuroradiology, National Hospital for Neurology and NeurosurgeryUniversity College London Hospitals NHS Foundation TrustLondonUnited Kingdom
| | - Mary A. Rutherford
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Joseph V. Hajnal
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Anthony N. Price
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
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17
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Accelerated silent echo-planar imaging. Magn Reson Imaging 2018; 55:81-85. [PMID: 30236603 DOI: 10.1016/j.mri.2018.09.016] [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: 05/04/2018] [Revised: 09/13/2018] [Accepted: 09/16/2018] [Indexed: 11/21/2022]
Abstract
PURPOSE The standard approach to Echo-Planar Imaging (EPI) is to use trapezoidal readout (RO) gradients with blipped phase-encoding (PE) gradients. Sinusoidal RO gradients with constant PE gradients can reduce acoustic noise. However, this sequence, originally introduced by Mansfield et al., constitutes major challenges for Cartesian parallel imaging techniques. In this study two alternatives to reconstruct a non-blipped EPI are proposed and evaluated. THEORY AND METHODS The first method separates the acquired k-space data into odd and even echoes and applies Cartesian GRAPPA separately to each partial data set. Afterwards, the resulting reconstructed data sets for each echo are summed in image space. In the second method, an iterative parallel-imaging algorithm is used to reconstruct images from the highly non-Cartesian data samples. RESULTS Compared to blipped-EPI, the first method reduces image SNR depending on the acceleration factor between 11% and 60%. For an acceleration factor of 3 folding artefacts appear. The second method produces slight fold-over artefacts although image SNR is on the same level as the blipped approach. CONCLUSION In this study, we have introduced two new approaches to EPI that allow the use of Cartesian parallel imaging in conjunction with continuous data sampling. In addition to providing a reduction in acoustic noise compared to the standard blipped PE EPI sequence, the proposed techniques improve sampling efficiency, resulting in a reduction of the echo-spacing. Of the two methods, the second approach, based on an iterative image reconstruction, provides higher SNR, but requires a longer reconstruction time.
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18
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Hutter J, Christiaens DJ, Schneider T, Cordero-Grande L, Slator PJ, Deprez M, Price AN, Tournier JD, Rutherford M, Hajnal JV. Slice-level diffusion encoding for motion and distortion correction. Med Image Anal 2018; 48:214-229. [PMID: 29966941 PMCID: PMC6191883 DOI: 10.1016/j.media.2018.06.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 06/08/2018] [Accepted: 06/18/2018] [Indexed: 11/23/2022]
Abstract
Breaks the conventional one-volume one-encoding paradigm in diffusion MRI. Higher temporal sampling of anatomically reliable b0 slices. Allows more robust distortion and motion correction. Additional benefits include quicker scans by reduced thermal heating.
Advances in microstructural modelling are leading to growing requirements on diffusion MRI acquisitions, namely sensitivity to smaller structures and better resolution of the geometric orientations. The resulting acquisitions contain highly attenuated images that present particular challenges when there is motion and geometric distortion. This study proposes to address these challenges by breaking with the conventional one-volume-one-encoding paradigm employed in conventional diffusion imaging using single-shot Echo Planar Imaging. By enabling free choice of the diffusion encoding on the slice level, a higher temporal sampling of slices with low b-value can be achieved. These allow more robust motion correction, and in combination with a second reversed phase-encoded echo, also dynamic distortion correction. These proposed advances are validated on phantom and adult experiments and employed in a study of eight foetal subjects. Equivalence in obtained diffusion quantities with the conventional method is demonstrated as well as benefits in distortion and motion correction. The resulting capability can be combined with any acquisition parameters including multiband imaging and allows application to diffusion MRI studies in general.
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Affiliation(s)
- Jana Hutter
- Centre for the developing Brain, King's College London, London, UK.
| | | | | | | | - Paddy J Slator
- Centre for Medical Image Computing and Department of Computer Science, University College London, London, UK
| | - Maria Deprez
- Centre for the developing Brain, King's College London, London, UK
| | - Anthony N Price
- Centre for the developing Brain, King's College London, London, UK
| | | | - Mary Rutherford
- Centre for the developing Brain, King's College London, London, UK
| | - Joseph V Hajnal
- Centre for the developing Brain, King's College London, London, UK
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Yousaf T, Dervenoulas G, Politis M. Advances in MRI Methodology. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2018; 141:31-76. [DOI: 10.1016/bs.irn.2018.08.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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20
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Lanzman RS, Wittsack HJ. Diffusion tensor imaging in abdominal organs. NMR IN BIOMEDICINE 2017; 30:e3434. [PMID: 26556181 DOI: 10.1002/nbm.3434] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 09/18/2015] [Accepted: 09/20/2015] [Indexed: 06/05/2023]
Abstract
Initially, diffusion tensor imaging (DTI) was mainly applied in studies of the human brain to analyse white matter tracts. As DTI is outstanding for the analysis of tissue´s microstructure, the interest in DTI for the assessment of abdominal tissues has increased continuously in recent years. Tissue characteristics of abdominal organs differ substantially from those of the human brain. Further peculiarities such as respiratory motion and heterogenic tissue composition lead to difficult conditions that have to be overcome in DTI measurements. Thus MR measurement parameters have to be adapted for DTI in abdominal organs. This review article provides information on the technical background of DTI with a focus on abdominal imaging, as well as an overview of clinical studies and application of DTI in different abdominal regions. Copyright © 2015 John Wiley & Sons, Ltd.
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Affiliation(s)
- Rotem Shlomo Lanzman
- Medical Faculty, Department of Diagnostic and Interventional Radiology, University of Dusseldorf, Dusseldorf, Germany
| | - Hans-Jörg Wittsack
- Medical Faculty, Department of Diagnostic and Interventional Radiology, University of Dusseldorf, Dusseldorf, Germany
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21
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Pirimoglu B, Sade R, Ogul H, Kantarci M, Eren S, Levent A. How Can New Imaging Modalities Help in the Practice of Radiology? Eurasian J Med 2017; 48:213-221. [PMID: 28149149 DOI: 10.5152/eajm.2016.0260] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The purpose of this article was to provide an up-to-date review on the spectrum of new imaging applications in the practice of radiology. New imaging techniques have been developed with the objective of obtaining structural and functional analyses of different body systems. Recently, new imaging modalities have aroused the interest of many researchers who are studying the applicability of these modalities in the evaluation of different organs and diseases. In this review article, we present the efficiency and utilization of current imaging modalities in daily radiological practice.
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Affiliation(s)
- Berhan Pirimoglu
- Department of Radiology, Ataturk University School of Medicine, Erzurum, Turkey
| | - Recep Sade
- Department of Radiology, Ataturk University School of Medicine, Erzurum, Turkey
| | - Hayri Ogul
- Department of Radiology, Ataturk University School of Medicine, Erzurum, Turkey
| | - Mecit Kantarci
- Department of Radiology, Ataturk University School of Medicine, Erzurum, Turkey
| | - Suat Eren
- Department of Radiology, Ataturk University School of Medicine, Erzurum, Turkey
| | - Akın Levent
- Department of Radiology, Ataturk University School of Medicine, Erzurum, Turkey
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22
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ANDICA CHRISTINA, SAITO ASAMI, MURATA SYO, HATTORI AKI, IKENOUCHI YUTAKA, HORI MASAAKI, AOKI SHIGEKI. Diffusion Magnetic Resonance Imaging: From Isotropic Diffusion-Weighted Imaging to Diffusion Tensor Imaging and Beyond. JUNTENDO MEDICAL JOURNAL 2017. [DOI: 10.14789/jmj.63.285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- CHRISTINA ANDICA
- Department of Radiology, Juntendo University Graduate School of Medicine
| | - ASAMI SAITO
- Department of Radiology, Juntendo University Graduate School of Medicine
| | - SYO MURATA
- Department of Radiology, Juntendo University Graduate School of Medicine
| | - AKI HATTORI
- Department of Radiology, Juntendo University Graduate School of Medicine
| | - YUTAKA IKENOUCHI
- Department of Radiology, Juntendo University Graduate School of Medicine
| | - MASAAKI HORI
- Department of Radiology, Juntendo University Graduate School of Medicine
| | - SHIGEKI AOKI
- Department of Radiology, Juntendo University Graduate School of Medicine
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23
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Weavers PT, Shu Y, Tao S, Huston J, Lee SK, Graziani D, Mathieu JB, Trzasko JD, Foo TKF, Bernstein MA. Technical Note: Compact three-tesla magnetic resonance imager with high-performance gradients passes ACR image quality and acoustic noise tests. Med Phys 2016; 43:1259-64. [PMID: 26936710 DOI: 10.1118/1.4941362] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE A compact, three-tesla magnetic resonance imaging (MRI) system has been developed. It features a 37 cm patient aperture, allowing the use of commercial receiver coils. Its design allows simultaneously for gradient amplitudes of 85 millitesla per meter (mT/m) sustained and 700 tesla per meter per second (T/m/s) slew rates. The size of the gradient system allows for these simultaneous performance targets to be achieved with little or no peripheral nerve stimulation, but also raises a concern about the geometric distortion as much of the imaging will be done near the system's maximum 26 cm field-of-view. Additionally, the fast switching capability raises acoustic noise concerns. This work evaluates the system for both the American College of Radiology's (ACR) MRI image quality protocol and the Food and Drug Administration's (FDA) nonsignificant risk (NSR) acoustic noise limits for MR. Passing these two tests is critical for clinical acceptance. METHODS In this work, the gradient system was operated at the maximum amplitude and slew rate of 80 mT/m and 500 T/m/s, respectively. The geometric distortion correction was accomplished by iteratively determining up to the tenth order spherical harmonic coefficients using a fiducial phantom and position-tracking software, with seventh order correction utilized in the ACR test. Acoustic noise was measured with several standard clinical pulse sequences. RESULTS The system passes all the ACR image quality tests. The acoustic noise as measured when the gradient coil was inserted into a whole-body MRI system conforms to the FDA NSR limits. CONCLUSIONS The compact system simultaneously allows for high gradient amplitude and high slew rate. Geometric distortion concerns have been mitigated by extending the spherical harmonic correction to higher orders. Acoustic noise is within the FDA limits.
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Affiliation(s)
| | | | | | | | - Seung-Kyun Lee
- GE Global Research, Niskayuna, NY 12309, USA and CNIR, Department of Biomedical Engineering, Sungkyunkwan University, Suwon 440-746, South Korea
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Shatil AS, Matsuda KM, Figley CR. A Method for Whole Brain Ex Vivo Magnetic Resonance Imaging with Minimal Susceptibility Artifacts. Front Neurol 2016; 7:208. [PMID: 27965620 PMCID: PMC5126074 DOI: 10.3389/fneur.2016.00208] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 11/08/2016] [Indexed: 11/29/2022] Open
Abstract
Magnetic resonance imaging (MRI) is a non-destructive technique that is capable of localizing pathologies and assessing other anatomical features (e.g., tissue volume, microstructure, and white matter connectivity) in postmortem, ex vivo human brains. However, when brains are removed from the skull and cerebrospinal fluid (i.e., their normal in vivo magnetic environment), air bubbles and air–tissue interfaces typically cause magnetic susceptibility artifacts that severely degrade the quality of ex vivo MRI data. In this report, we describe a relatively simple and cost-effective experimental setup for acquiring artifact-free ex vivo brain images using a clinical MRI system with standard hardware. In particular, we outline the necessary steps, from collecting an ex vivo human brain to the MRI scanner setup, and have also described changing the formalin (as might be necessary in longitudinal postmortem studies). Finally, we share some representative ex vivo MRI images that have been acquired using the proposed setup in order to demonstrate the efficacy of this approach. We hope that this protocol will provide both clinicians and researchers with a straight-forward and cost-effective solution for acquiring ex vivo MRI data from whole postmortem human brains.
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Affiliation(s)
- Anwar S Shatil
- Biomedical Engineering Graduate Program, University of Manitoba, Winnipeg, MB, Canada; Neuroscience Research Program, Winnipeg Health Sciences Centre, Kleysen Institute for Advanced Medicine, Winnipeg, MB, Canada
| | - Kant M Matsuda
- Biomedical Engineering Graduate Program, University of Manitoba, Winnipeg, MB, Canada; Department of Pathology, University of Manitoba, Winnipeg, MB, Canada
| | - Chase R Figley
- Biomedical Engineering Graduate Program, University of Manitoba, Winnipeg, MB, Canada; Neuroscience Research Program, Winnipeg Health Sciences Centre, Kleysen Institute for Advanced Medicine, Winnipeg, MB, Canada; Department of Radiology, University of Manitoba, Winnipeg, MB, Canada; Division of Diagnostic Imaging, Winnipeg Health Sciences Centre, Winnipeg, MB, Canada; Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA
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25
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Lawrence EM, Warren AY, Priest AN, Barrett T, Goldman DA, Gill AB, Gnanapragasam VJ, Sala E, Gallagher FA. Evaluating Prostate Cancer Using Fractional Tissue Composition of Radical Prostatectomy Specimens and Pre-Operative Diffusional Kurtosis Magnetic Resonance Imaging. PLoS One 2016; 11:e0159652. [PMID: 27467064 PMCID: PMC4965080 DOI: 10.1371/journal.pone.0159652] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 07/05/2016] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Evaluating tissue heterogeneity using non-invasive imaging could potentially improve prostate cancer assessment and treatment. METHODS 20 patients with intermediate/high-risk prostate cancer underwent diffusion kurtosis imaging, including calculation of apparent diffusion (Dapp) and kurtosis (Kapp), prior to radical prostatectomy. Whole-mount tissue composition was quantified into: cellularity, luminal space, and fibromuscular stroma. Peripheral zone tumors were subdivided according to Gleason score. RESULTS Peripheral zone tumors had increased cellularity (p<0.0001), decreased fibromuscular stroma (p<0.05) and decreased luminal space (p<0.0001). Gleason score ≥4+3 tumors had significantly increased cellularity and decreased fibromuscular stroma compared to Gleason score ≤3+4 (p<0.05). In tumors, there was a significant positive correlation between median Kapp and cellularity (ρ = 0.50; p<0.05), and a negative correlation with fibromuscular stroma (ρ = -0.45; p<0.05). In normal tissue, median Dapp had a significant positive correlation with luminal space (ρ = 0.65; p<0.05) and a negative correlation with cellularity (ρ = -0.49; p<0.05). Median Kapp and Dapp varied significantly between tumor and normal tissue (p<0.0001), but only median Kapp was significantly different between Gleason score ≥4+3 and ≤3+4 (p<0.05). CONCLUSIONS Peripheral zone tumors have increased cellular heterogeneity which is reflected in mean Kapp, while normal prostate has a more homogeneous luminal space and cellularity better represented by Dapp.
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Affiliation(s)
- Edward M. Lawrence
- Department of Radiology, University of Cambridge, Addenbrooke’s hospital, Cambridge, United Kingdom
- Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Ave, New York, NY, United States of America
| | - Anne Y. Warren
- Department of Histopathology, University of Cambridge, Addenbrooke’s hospital, Cambridge, United Kingdom
| | - Andrew N. Priest
- Department of Radiology, University of Cambridge, Addenbrooke’s hospital, Cambridge, United Kingdom
| | - Tristan Barrett
- Department of Radiology, University of Cambridge, Addenbrooke’s hospital, Cambridge, United Kingdom
| | - Debra A. Goldman
- Department of Epidemiology & Biostatistics, Memorial Sloan Kettering Cancer Center, 1275 York Ave, New York, NY, United States of America
| | - Andrew B. Gill
- Department of Radiology, University of Cambridge, Addenbrooke’s hospital, Cambridge, United Kingdom
| | - Vincent J. Gnanapragasam
- Department of Urology, University of Cambridge, Addenbrooke’s hospital, Cambridge, United Kingdom
| | - Evis Sala
- Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Ave, New York, NY, United States of America
| | - Ferdia A. Gallagher
- Department of Radiology, University of Cambridge, Addenbrooke’s hospital, Cambridge, United Kingdom
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Dai E, Ma X, Zhang Z, Yuan C, Guo H. Simultaneous multislice accelerated interleaved EPI DWI using generalized blipped-CAIPI acquisition and 3D K-space reconstruction. Magn Reson Med 2016; 77:1593-1605. [DOI: 10.1002/mrm.26249] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 03/08/2016] [Accepted: 03/29/2016] [Indexed: 12/22/2022]
Affiliation(s)
- Erpeng Dai
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University; Beijing China
| | - Xiaodong Ma
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University; Beijing China
| | - Zhe Zhang
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University; Beijing China
| | - Chun Yuan
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University; Beijing China
- Department of Radiology; University of Washington; Seattle WA USA
| | - Hua Guo
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University; Beijing China
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Characterization and Correction of Geometric Distortions in 814 Diffusion Weighted Images. PLoS One 2016; 11:e0152472. [PMID: 27027775 PMCID: PMC4814112 DOI: 10.1371/journal.pone.0152472] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2015] [Accepted: 03/15/2016] [Indexed: 12/21/2022] Open
Abstract
Introduction Diffusion Weighted Imaging (DWI), which is based on Echo Planar Imaging (EPI) protocols, is becoming increasingly important for neurosurgical applications. However, its use in this context is limited in part by significant spatial distortion inherent to EPI. Method We evaluated an efficient algorithm for EPI distortion correction (EPIC) across 814 DWI scans from 250 brain tumor patients and quantified the magnitude of geometric distortion for whole brain and multiple brain regions. Results Evaluation of the algorithm’s performance revealed significantly higher mutual information between T1-weighted pre-contrast images and corrected b = 0 images than the uncorrected b = 0 images (p < 0.001). The distortion magnitude across all voxels revealed a median EPI distortion effect of 2.1 mm, ranging from 1.2 mm to 5.9 mm, the 5th and 95th percentile, respectively. Regions adjacent to bone-air interfaces, such as the orbitofrontal cortex, temporal poles, and brain stem, were the regions most severely affected by DWI distortion. Conclusion Using EPIC to estimate the degree of distortion in 814 DWI brain tumor images enabled the creation of a topographic atlas of DWI distortion across the brain. The degree of displacement of tumors boundaries in uncorrected images is severe but can be corrected for using EPIC. Our results support the use of distortion correction to ensure accurate and careful application of DWI to neurosurgical practice.
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Rösch J, Ott M, Heismann B, Doerfler A, Engelhorn T, Sembritzki K, Grodzki DM. Quiet diffusion-weighted head scanning: Initial clinical evaluation in ischemic stroke patients at 1.5T. J Magn Reson Imaging 2016; 44:1238-1243. [DOI: 10.1002/jmri.25228] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 02/24/2016] [Indexed: 11/05/2022] Open
Affiliation(s)
- Julie Rösch
- Department of Neuroradiology; University Hospital Erlangen; Erlangen Germany
| | - Martin Ott
- Magnetic Resonance; Siemens Healthcare; Erlangen Germany
- Research Center for Magnetic-Resonance-Bavaria; Wuerzburg Germany
| | - Bjoern Heismann
- Magnetic Resonance; Siemens Healthcare; Erlangen Germany
- Friedrich-Alexander-University Erlangen-Nuremberg; Erlangen Germany
| | - Arnd Doerfler
- Department of Neuroradiology; University Hospital Erlangen; Erlangen Germany
| | - Tobias Engelhorn
- Department of Neuroradiology; University Hospital Erlangen; Erlangen Germany
| | - Klaus Sembritzki
- Friedrich-Alexander-University Erlangen-Nuremberg; Erlangen Germany
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Diffusion-weighted MRI for the assessment of liver fibrosis: principles and applications. BIOMED RESEARCH INTERNATIONAL 2015; 2015:874201. [PMID: 25866819 PMCID: PMC4383436 DOI: 10.1155/2015/874201] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 12/14/2014] [Accepted: 01/01/2015] [Indexed: 12/19/2022]
Abstract
The importance of an early identification of hepatic fibrosis has been emphasized, in order to start therapy and obtain fibrosis regression. Biopsy is the gold-standard method for the assessment of liver fibrosis in chronic liver diseases, but it is limited by complications, interobserver variability, and sampling errors. Several noninvasive methods have been recently introduced into clinical routine, in order to detect liver fibrosis early. One of the most diffuse approaches is represented by diffusion-weighted liver MRI. In this review, the main technical principles are briefly reported in order to explain the rationale for clinical applications. In addition, roles of apparent diffusion coefficient, intravoxel incoherent motion, and relative apparent diffusion coefficient are also reported, showing their advantages and limits.
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Lövblad KO, Altrichter S, Mendes Pereira V, Vargas M, Marcos Gonzalez A, Haller S, Sztajzel R. Imaging of acute stroke: CT and/or MRI. J Neuroradiol 2015; 42:55-64. [DOI: 10.1016/j.neurad.2014.10.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 10/16/2014] [Accepted: 10/17/2014] [Indexed: 11/28/2022]
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Frost R, Jezzard P, Douaud G, Clare S, Porter DA, Miller KL. Scan time reduction for readout-segmented EPI using simultaneous multislice acceleration: Diffusion-weighted imaging at 3 and 7 Tesla. Magn Reson Med 2014; 74:136-149. [PMID: 25078777 PMCID: PMC4854329 DOI: 10.1002/mrm.25391] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 07/08/2014] [Accepted: 07/09/2014] [Indexed: 11/05/2022]
Abstract
PURPOSE Readout-segmented echo-planar imaging (rs-EPI) can provide high quality diffusion data because it is less prone to distortion and blurring artifacts than single-shot echo-planar imaging (ss-EPI), particularly at higher resolution and higher field. Readout segmentation allows shorter echo-spacing and echo train duration, resulting in reduced image distortion and blurring, respectively, in the phase-encoding direction. However, these benefits come at the expense of longer scan times because the segments are acquired in multiple repetitions times (TRs). This study shortened rs-EPI scan times by reducing the TR duration with simultaneous multislice acceleration. METHODS The blipped-CAIPI method for slice acceleration with reduced g-factor SNR loss was incorporated into the diffusion-weighted rs-EPI sequence. The rs- and ss-EPI sequences were compared at a range of resolutions at both 3 and 7 Tesla in terms of image fidelity and diffusion postprocessing results. RESULTS Slice-accelerated clinically useful trace-weighted images and tractography results are presented. Tractography analysis showed that the reduced artifacts in rs-EPI allowed better discrimination of tracts than ss-EPI. CONCLUSION Slice acceleration reduces rs-EPI scan times providing a practical alternative to diffusion-weighted ss-EPI with reduced distortion and high resolution. Magn Reson Med 74:136-149, 2015. © 2014 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Robert Frost
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Peter Jezzard
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Gwenaëlle Douaud
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Stuart Clare
- 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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Solomon E, Nissan N, Furman-Haran E, Seginer A, Shapiro-Feinberg M, Degani H, Frydman L. Overcoming limitations in diffusion-weighted MRI of breast by spatio-temporal encoding. Magn Reson Med 2014; 73:2163-73. [PMID: 25045867 DOI: 10.1002/mrm.25344] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 05/25/2014] [Accepted: 06/11/2014] [Indexed: 01/20/2023]
Abstract
PURPOSE Evaluating the usefulness of diffusion-weighted spatio-temporal encoding (SPEN) methods to provide quantitative apparent diffusion coefficient (ADC)-based characterizations of healthy and malignant human breast tissues, in comparison with results obtained using techniques based on spin-echo echo planar imaging (SE-EPI). METHODS Twelve healthy volunteers and six breast cancer patients were scanned at 3T using scanner-supplied diffusion-weighted imaging EPI sequences, as well as two fully refocused SPEN variants programmed in-house. Suitable codes were written to process the data, including calculations of the actual b-values and retrieval of the ADC maps. RESULTS Systematically better images were afforded by the SPEN scans, with negligible geometrical distortions and markedly weaker ghosting artifacts arising from either fat tissues or from strongly emitting areas such as cysts. SPEN-derived images provided improved characterizations of the fibroglandular tissues and of the lesions' contours. When translated into the calculation of the ADC maps, there were no significant differences between the mean ADCs derived from SPEN and SE-EPI: if reliable images were available, both techniques showed that ADCs decreased by nearly two-fold in the malignant lesion areas. CONCLUSION SPEN-based sequences yielded diffusion-weighted breast images with minimal artifacts and distortions, enabling the calculation of improved ADC maps and the identification of decreased ADCs in malignant regions.
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Affiliation(s)
- Eddy Solomon
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Noam Nissan
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.,Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Edna Furman-Haran
- Unit of Biological Services, Weizmann Institute of Science, Rehovot, Israel
| | - Amir Seginer
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | | | - Hadassa Degani
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Lucio Frydman
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
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Leftin A, Rosenberg JT, Solomon E, Calixto Bejarano F, Grant SC, Frydman L. Ultrafast in vivo diffusion imaging of stroke at 21.1 T by spatiotemporal encoding. Magn Reson Med 2014; 73:1483-9. [PMID: 24845125 DOI: 10.1002/mrm.25271] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2014] [Revised: 04/03/2014] [Accepted: 04/08/2014] [Indexed: 11/06/2022]
Abstract
PURPOSE This study quantifies in vivo ischemic stroke brain injuries in rats using ultrahigh-field single-scan MRI methods to assess variations in apparent diffusion coefficients (ADCs). METHODS Magnitude and diffusion-weighted spatiotemporally encoded imaging sequences were implemented on a 21.1 T imaging system, and compared with spin-echo and echo-planar imaging diffusion-weighted imaging strategies. ADC maps were calculated and used to evaluate the sequences according to the statistical comparisons of the ipsilateral and contralateral ADC measurements at 24, 48, and 72 h poststroke. RESULTS Susceptibility artifacts resulting from normative anatomy and pathological stroke conditions were particularly intense at 21.1 T. These artifacts strongly distorted single-shot diffusion-weighted echo-planar imaging experiments, but were reduced in four-segment interleaved echo-planar imaging acquisitions. By contrast, nonsegmented diffusion-weighted spatiotemporally encoded images were largely immune to field-dependent artifacts. Effects of stroke were apparent in both magnitude images and ADC maps of all sequences. When stroke recovery was followed by ADC variations, spatiotemporally encoded, echo-planar imaging, and spin-echo acquisitions revealed statistically significant increase in ADCs. CONCLUSIONS Consideration of experiment duration, image quality, and mapped ADC values provided by spatiotemporally encoded demonstrates that this single-shot acquisition is a method of choice for high-throughput, ultrahigh-field in vivo stroke quantification.
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Affiliation(s)
- Avigdor Leftin
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
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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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Kang JS, Klein JC, Baudrexel S, Deichmann R, Nolte D, Hilker R. White matter damage is related to ataxia severity in SCA3. J Neurol 2013; 261:291-9. [PMID: 24272589 DOI: 10.1007/s00415-013-7186-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 11/05/2013] [Accepted: 11/05/2013] [Indexed: 12/31/2022]
Abstract
Spinocerebellar ataxia type 3 (SCA3) is the most frequent inherited cerebellar ataxia in Europe, the US and Japan, leading to disability and death through motor complications. Although the affected protein ataxin-3 is found ubiquitously in the brain, grey matter atrophy is predominant in the cerebellum and the brainstem. White matter pathology is generally less severe and thought to occur in the brainstem, spinal cord, and cerebellar white matter. Here, we investigated both grey and white matter pathology in a group of 12 SCA3 patients and matched controls. We used voxel-based morphometry for analysis of tissue loss, and tract-based spatial statistics (TBSS) on diffusion magnetic resonance imaging to investigate microstructural pathology. We analysed correlations between microstructural properties of the brain and ataxia severity, as measured by the Scale for the Assessment and Rating of Ataxia (SARA) score. SCA3 patients exhibited significant loss of both grey and white matter in the cerebellar hemispheres, brainstem including pons and in lateral thalamus. On between-group analysis, TBSS detected widespread microstructural white matter pathology in the cerebellum, brainstem, and bilaterally in thalamus and the cerebral hemispheres. Furthermore, fractional anisotropy in a white matter network comprising frontal, thalamic, brainstem and left cerebellar white matter strongly and negatively correlated with SARA ataxia scores. Tractography identified the thalamic white matter thus implicated as belonging to ventrolateral thalamus. Disruption of white matter integrity in patients suffering from SCA3 is more widespread than previously thought. Moreover, our data provide evidence that microstructural white matter changes in SCA3 are strongly related to the clinical severity of ataxia symptoms.
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Affiliation(s)
- J-S Kang
- Department of Neurology, Goethe-University of Frankfurt, Schleusenweg 2-16, 60528, Frankfurt am Main, Germany
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Hegde JV, Mulkern RV, Panych LP, Fennessy FM, Fedorov A, Maier SE, Tempany CMC. Multiparametric MRI of prostate cancer: an update on state-of-the-art techniques and their performance in detecting and localizing prostate cancer. J Magn Reson Imaging 2013; 37:1035-54. [PMID: 23606141 DOI: 10.1002/jmri.23860] [Citation(s) in RCA: 170] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 09/04/2012] [Indexed: 12/15/2022] Open
Abstract
Magnetic resonance (MR) examinations of men with prostate cancer are most commonly performed for detecting, characterizing, and staging the extent of disease to best determine diagnostic or treatment strategies, which range from biopsy guidance to active surveillance to radical prostatectomy. Given both the exam's importance to individual treatment plans and the time constraints present for its operation at most institutions, it is essential to perform the study effectively and efficiently. This article reviews the most commonly employed modern techniques for prostate cancer MR examinations, exploring the relevant signal characteristics from the different methods discussed and relating them to intrinsic prostate tissue properties. Also, a review of recent articles using these methods to enhance clinical interpretation and assess clinical performance is provided. J. Magn. Reson. Imaging 2013;37:1035-1054. © 2013 Wiley Periodicals, Inc.
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Affiliation(s)
- John V Hegde
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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Solomon E, Shemesh N, Frydman L. Diffusion weighted MRI by spatiotemporal encoding: analytical description and in vivo validations. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 232:76-86. [PMID: 23562003 PMCID: PMC5040484 DOI: 10.1016/j.jmr.2013.02.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 02/19/2013] [Accepted: 02/27/2013] [Indexed: 05/02/2023]
Abstract
Diffusion-weighted (DW) MRI is a powerful modality for studying microstructure in normal and pathological tissues. The accuracy derived from DW MRI depends on the acquisition of quality images, and on a precise assessment of the b-values involved. Conventional DW MRI tends to be of limited use in regions suffering from large magnetic field or chemical shift heterogeneities, which severely distort the MR images. In this study we propose novel sequences based on SPatio-temporal ENcoding (SPEN), which overcome such shortcomings owing to SPEN's inherent robustness to offsets. SPEN, however, relies on the simultaneous application of gradients and radiofrequency-swept pulses, which may impart different diffusion weightings along the spatial axes. These will be further complicated in DW measurements by the diffusion-sensitizing gradients, and will in general lead to complex, spatially-dependent b-values. This study presents a formalism for analyzing these diffusion-weighted SPEN (dSPEN) data, which takes into account the concomitant effects of adiabatic pulses, of the imaging as well as diffusion gradients, and of the cross-terms between them. These analytical b-values derivations are subject to experimental validations in phantom systems and ex vivo spinal cords. Excellent agreement is found between the theoretical predictions and these dSPEN experiments. The ensuing methodology is then demonstrated by in vivo mapping of diffusion in human breast - organs where conventional k-space DW acquisition methods are challenged by both field and chemical shift heterogeneities. These studies demonstrate the increased robustness of dSPEN vis-à-vis comparable DW echo planar imaging, and demonstrate the value of this new methodology for medium- or high-field diffusion measurements in heterogeneous systems.
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Affiliation(s)
| | | | - Lucio Frydman
- Corresponding author. Fax: +972 8 9344123. (L. Frydman)
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Martin M. Measuring restriction sizes using diffusion weighted magnetic resonance imaging: a review. MAGNETIC RESONANCE INSIGHTS 2013; 6:59-64. [PMID: 25114548 PMCID: PMC4089833 DOI: 10.4137/mri.s11149] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This article reviews a new concept in magnetic resonance as applied to cellular and biological systems. Diffusion weighted magnetic resonance imaging can be used to infer information about restriction sizes of samples being measured. The measurements rely on the apparent diffusion coefficient changing with diffusion times as measurements move from restricted to free diffusion regimes. Pulsed gradient spin echo (PGSE) measurements are limited in the ability to shorten diffusion times and thus are limited in restriction sizes which can be probed. Oscillating gradient spin echo (OGSE) measurements could provide shorter diffusion times so smaller restriction sizes could be probed.
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Affiliation(s)
- Melanie Martin
- Department of Physics, University of Winnipeg and Department of Radiology, University of Manitoba
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39
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A historical overview of magnetic resonance imaging, focusing on technological innovations. Invest Radiol 2013; 47:725-41. [PMID: 23070095 DOI: 10.1097/rli.0b013e318272d29f] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Magnetic resonance imaging (MRI) has now been used clinically for more than 30 years. Today, MRI serves as the primary diagnostic modality for many clinical problems. In this article, historical developments in the field of MRI will be discussed with a focus on technological innovations. Topics include the initial discoveries in nuclear magnetic resonance that allowed for the advent of MRI as well as the development of whole-body, high field strength, and open MRI systems. Dedicated imaging coils, basic pulse sequences, contrast-enhanced, and functional imaging techniques will also be discussed in a historical context. This article describes important technological innovations in the field of MRI, together with their clinical applicability today, providing critical insights into future developments.
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40
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Dumez JN, Schmidt R, Frydman L. Simultaneous spatial and spectral selectivity by spatiotemporal encoding. Magn Reson Med 2013; 71:746-55. [DOI: 10.1002/mrm.24718] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Jean-Nicolas Dumez
- Department of Chemical Physics; Weizmann Institute of Science; Rehovot 76100 Israel
| | - Rita Schmidt
- Department of Chemical Physics; Weizmann Institute of Science; Rehovot 76100 Israel
| | - Lucio Frydman
- Department of Chemical Physics; Weizmann Institute of Science; Rehovot 76100 Israel
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41
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Soares JM, Marques P, Alves V, Sousa N. A hitchhiker's guide to diffusion tensor imaging. Front Neurosci 2013; 7:31. [PMID: 23486659 PMCID: PMC3594764 DOI: 10.3389/fnins.2013.00031] [Citation(s) in RCA: 494] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 02/23/2013] [Indexed: 12/16/2022] Open
Abstract
Diffusion Tensor Imaging (DTI) studies are increasingly popular among clinicians and researchers as they provide unique insights into brain network connectivity. However, in order to optimize the use of DTI, several technical and methodological aspects must be factored in. These include decisions on: acquisition protocol, artifact handling, data quality control, reconstruction algorithm, and visualization approaches, and quantitative analysis methodology. Furthermore, the researcher and/or clinician also needs to take into account and decide on the most suited software tool(s) for each stage of the DTI analysis pipeline. Herein, we provide a straightforward hitchhiker's guide, covering all of the workflow's major stages. Ultimately, this guide will help newcomers navigate the most critical roadblocks in the analysis and further encourage the use of DTI.
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Affiliation(s)
- José M. Soares
- Life and Health Science Research Institute (ICVS), School of Health Sciences, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga/Guimarães, Portugal
| | - Paulo Marques
- Life and Health Science Research Institute (ICVS), School of Health Sciences, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga/Guimarães, Portugal
- Department of Informatics, University of MinhoBraga, Portugal
| | - Victor Alves
- Department of Informatics, University of MinhoBraga, Portugal
| | - Nuno Sousa
- Life and Health Science Research Institute (ICVS), School of Health Sciences, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga/Guimarães, Portugal
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Chen NK, Guidon A, Chang HC, Song AW. A robust multi-shot scan strategy for high-resolution diffusion weighted MRI enabled by multiplexed sensitivity-encoding (MUSE). Neuroimage 2013; 72:41-7. [PMID: 23370063 DOI: 10.1016/j.neuroimage.2013.01.038] [Citation(s) in RCA: 235] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 01/03/2013] [Accepted: 01/13/2013] [Indexed: 12/21/2022] Open
Abstract
Diffusion weighted magnetic resonance imaging (DWI) data have been mostly acquired with single-shot echo-planar imaging (EPI) to minimize motion induced artifacts. The spatial resolution, however, is inherently limited in single-shot EPI, even when the parallel imaging (usually at an acceleration factor of 2) is incorporated. Multi-shot acquisition strategies could potentially achieve higher spatial resolution and fidelity, but they are generally susceptible to motion-induced phase errors among excitations that are exacerbated by diffusion sensitizing gradients, rendering the reconstructed images unusable. It has been shown that shot-to-shot phase variations may be corrected using navigator echoes, but at the cost of imaging throughput. To address these challenges, a novel and robust multi-shot DWI technique, termed multiplexed sensitivity-encoding (MUSE), is developed here to reliably and inherently correct nonlinear shot-to-shot phase variations without the use of navigator echoes. The performance of the MUSE technique is confirmed experimentally in healthy adult volunteers on 3Tesla MRI systems. This newly developed technique should prove highly valuable for mapping brain structures and connectivities at high spatial resolution for neuroscience studies.
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Affiliation(s)
- Nan-Kuei Chen
- Brain Imaging and Analysis Center, Duke University Medical Center, Box 2737, Hock Plaza, Durham, NC 27710, USA.
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Winston GP. The physical and biological basis of quantitative parameters derived from diffusion MRI. Quant Imaging Med Surg 2013; 2:254-65. [PMID: 23289085 DOI: 10.3978/j.issn.2223-4292.2012.12.05] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 12/19/2012] [Indexed: 11/14/2022]
Abstract
Diffusion magnetic resonance imaging is a quantitative imaging technique that measures the underlying molecular diffusion of protons. Diffusion-weighted imaging (DWI) quantifies the apparent diffusion coefficient (ADC) which was first used to detect early ischemic stroke. However this does not take account of the directional dependence of diffusion seen in biological systems (anisotropy).Diffusion tensor imaging (DTI) provides a mathematical model of diffusion anisotropy and is widely used. Parameters, including fractional anisotropy (FA), mean diffusivity (MD), parallel and perpendicular diffusivity can be derived to provide sensitive, but non-specific, measures of altered tissue structure. They are typically assessed in clinical studies by voxel-based or region-of-interest based analyses.The increasing recognition of the limitations of the diffusion tensor model has led to more complex multi-compartment models such as CHARMED, AxCaliber or NODDI being developed to estimate microstructural parameters including axonal diameter, axonal density and fiber orientations. However these are not yet in routine clinical use due to lengthy acquisition times.In this review, I discuss how molecular diffusion may be measured using diffusion MRI, the biological and physical bases for the parameters derived from DWI and DTI, how these are used in clinical studies and the prospect of more complex tissue models providing helpful micro-structural information.
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Affiliation(s)
- Gavin P Winston
- Epilepsy Society MRI Unit, Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK
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Abstract
INTRODUCTION The past decade has seen an explosion of functional magnetic resonance imaging (MRI) studies in neuroscience. As the technology progresses, it is now possible to carry out longitudinal studies using functional MRI. Such studies can be used to understand the progression of mental and neurological disorders and the effectiveness of different treatments by obtaining direct measures of brain activity as well as markers of tissue health and connectivity. AREAS COVERED We review six popular neuroimaging tools that can be used for longitudinal studies: blood oxygen level-dependent (BOLD)-weighted imaging, BOLD-based functional connectivity, arterial spin labeling, dynamic R2* imaging, voxel-based morphometry, and diffusion tensor imaging. EXPERT OPINION Each of these techniques is targeted to probe a specific feature of brain function or brain structure and can reveal important information about the progression of a pathological condition. We anticipate that in the near future, the MRI techniques discussed here may become standard tools in clinical use and will not be used for research purposes only.
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Affiliation(s)
- Luis Hernandez-Garcia
- University of Michigan, FMRI Laboratory , 2360 Bonisteel Blvd, room 1096, Ann Arbor, MI 48109-2108 , USA +1 734 763 9254 ;
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Ahn S, Lee SK. Diffusion tensor imaging: exploring the motor networks and clinical applications. Korean J Radiol 2011; 12:651-61. [PMID: 22043146 PMCID: PMC3194768 DOI: 10.3348/kjr.2011.12.6.651] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 06/03/2011] [Indexed: 01/23/2023] Open
Abstract
With the advances in diffusion magnetic resonance (MR) imaging techniques, diffusion tensor imaging (DTI) has been applied to a number of neurological conditions because DTI can demonstrate microstructures of the brain that are not assessable with conventional MR imaging. Tractography based on DTI offers gross visualization of the white matter fiber architecture in the human brain in vivo. Degradation of restrictive barriers and disruption of the cytoarchitecture result in changes in the diffusion of water molecules in various pathological conditions, and these conditions can also be assessed with DTI. Yet many factors may influence the ability to apply DTI clinically, so these techniques have to be used with a cautious hand.
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Affiliation(s)
- Sungsoo Ahn
- Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Korea
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46
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Chiaradia M, Baranes L, Pigneur F, Djabbari M, Zegai B, Brugières P, Zerbib P, Decaens T, Deux JF, Kobeiter H, Rahmouni A, Luciani A. Liver magnetic resonance diffusion weighted imaging: 2011 update. Clin Res Hepatol Gastroenterol 2011; 35:539-48. [PMID: 21700529 DOI: 10.1016/j.clinre.2011.05.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 05/03/2011] [Indexed: 02/04/2023]
Abstract
Diffusion-Weighted-Imaging (DWI) assesses proton motion on a cellular scale. Owing to recent instrumentation developments, diffusion sequences are now routinely used for liver imaging. This review will go through the physical principles that underlie this technique, and then highlight up-to-date liver applications including quantification of liver fibrosis, focal lesions detection and characterization, and therapy response monitoring.
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Affiliation(s)
- Mélanie Chiaradia
- Imagerie medicale, AP-HP, groupe Henri-Mondor Albert-Chenevier, 51, avenue du Maréchal-de-Lattre-de-Tassigny, 94010 Creteil, France
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47
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Feldman RE, Scholl TJ, Alford JK, Handler WB, Harris CT, Chronik BA. Results for diffusion-weighted imaging with a fourth-channel gradient insert. Magn Reson Med 2011; 66:1798-808. [PMID: 21604300 DOI: 10.1002/mrm.22971] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 02/16/2011] [Accepted: 03/25/2011] [Indexed: 02/02/2023]
Abstract
Diffusion-weighted imaging suffers from motion artifacts and relatively low signal quality due to the long echo times required to permit the diffusion encoding. We investigated the inclusion of a noncylindrical fourth gradient coil, dedicated entirely to diffusion encoding, into the imaging system. Standard three-axis whole body gradients were used during image acquisition, but we designed and constructed an insert coil to perform diffusion encodings. We imaged three phantoms on a 3-T system with a range of diffusion coefficients. Using the insert gradient, we were able to encode b values of greater than 1300 s/mm(2) with an echo time of just 83 ms. Images obtained using the insert gradient had higher signal to noise ratios than those obtained using the whole body gradient: at 500 s/mm(2) there was a 18% improvement in signal to noise ratio, at 1000 s/mm(2) there was a 39% improvement in signal to noise ratio, and at 1350 s/mm(2) there was a 56% improvement in signal to noise ratio. Using the insert gradient, we were capable of doing diffusion encoding at high b values by using relatively short echo times.
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Affiliation(s)
- Rebecca E Feldman
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada.
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48
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Abstract
Liver metastases are the most frequently encountered malignant liver lesions in the Western countries. Accurate diagnosis of liver metastases is essential for appropriate management of these patients. Multiple imaging modalities, including ultrasound, CT, positron emission tomography, and MRI, are available for the evaluation of patients with suspected or known liver metastases. Contrast-enhanced MRI has a high accuracy for detection and characterization of liver lesions. Additionally, diffusion-weighted MRI (DWI) has been gaining increasing attention. It is a noncontrast technique that is easy to perform, could be incorporated in routine clinical protocols, and has the potential to provide tissue characterization. This article discusses the basic principles of DWI and discusses its emerging role in the detection of liver metastases in patients with extrahepatic malignancies.
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Affiliation(s)
- Hersh Chandarana
- Department of Radiology, NYU Langone Medical Center, 550 First Avenue, New York, NY 10016, USA
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49
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Klein JC, Lorenz B, Kang JS, Baudrexel S, Seifried C, van de Loo S, Steinmetz H, Deichmann R, Hilker R. Diffusion tensor imaging of white matter involvement in essential tremor. Hum Brain Mapp 2010; 32:896-904. [PMID: 20572209 DOI: 10.1002/hbm.21077] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Revised: 03/18/2010] [Accepted: 03/19/2010] [Indexed: 11/09/2022] Open
Abstract
This study set out to determine whether there is white matter involvement in essential tremor (ET), the most common movement disorder. We collected diffusion MRI and analysed differences in fractional anisotropy (FA) and mean diffusivity (MD) between ET patients and control subjects as markers of white matter integrity. We used both classical ROI-based statistics and whole-brain analysis techniques, including voxel-wise analysis with SPM5 and tract-based spatial statistics (TBSS). Using region of interest (ROI) analysis, we found increased MD bilaterally in the inferior cerebellar peduncles (ICP) and reduced FA in the right-sided ICP of ET patients. Whole-brain analyses with TBSS detected increased MD distributed in both motor and nonmotor white matter fibers of ET patients predominantly in the left parietal white matter, while there were no significant FA differences in these areas between ET patients and controls. Voxel-wise analysis with SPM detected significant increase of MD congruent with the highest probability of difference as detected by TBSS. VBM analysis of T1 images did not detect significant differences in either gray or white matter density between our study groups. In summary, we found evidence for changes in white matter MRI properties in ET. The circumscript pathology of the ICP corroborates the pathogenetic concept of the cerebellum and its projections as key structures for tremor generation in ET. Moreover, increased diffusivity in white matter structures of both hemispheres suggests widespread alterations of fiber integrity in motor and nonmotor networks in ET patients. The underlying cause of the DTI changes observed remains to be elucidated.
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Affiliation(s)
- Johannes C Klein
- Department of Neurology, Goethe-University, Frankfurt am Main, Germany.
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50
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Trieu J, Wu L. Liver MRI Technique: Pulse Sequences and Contrast Agents. J Med Imaging Radiat Sci 2010; 41:47-56. [PMID: 31051817 DOI: 10.1016/j.jmir.2010.01.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Revised: 01/24/2010] [Accepted: 01/25/2010] [Indexed: 01/16/2023]
Abstract
Developments in magnetic resonance imaging (MRI) techniques have expanded the role of MRI in evaluating the liver. Although a single optimized protocol for standard hepatic MRI examination has not been established or agreed on, key elements to a successful exam are generally accepted. In determining the "best" protocol, one must first understand the numerous pulse sequences and contrast agents available to the technologist and how each contributes to the final interpretation by the radiologist. This article will attempt to review the most commonly used pulse sequences for imaging the liver, with comment on their uses, advantages, and limitations. The spectrum of contrast agents available for use in liver MRI will also be discussed.
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Affiliation(s)
- Joseph Trieu
- Department of Radiology, Concord Hospital, Sydney, NSW, Australia.
| | - Louis Wu
- Department of Diagnostic Imaging, Oshawa General Hospital, Lakeridge Health, Oshawa, Ontario
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