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Stephan E. Maier - One of the best experts on this subject based on the ideXlab platform.
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Fast Diffusion Imaging with high angular resolution.
Magnetic resonance in medicine, 2016Co-Authors: Tzu Cheng Chao, Stephan E. Maier, Yuan George Chiou, Bruno MadoreAbstract:PURPOSE High angular resolution Diffusion Imaging (HARDI) is a well-established method to help reveal the architecture of nerve bundles, but long scan times and geometric distortions inherent to echo planar Imaging (EPI) have limited its integration into clinical protocols. METHODS A fast Imaging method is proposed here that combines accelerated multishot Diffusion Imaging (AMDI), multiplexed sensitivity encoding (MUSE), and crossing fiber angular resolution of intravoxel structure (CFARI) to reduce spatial distortions and reduce total scan time. A multishot EPI sequence was used to improve geometrical fidelity as compared to a single-shot EPI acquisition, and acceleration in both k-space and Diffusion sampling enabled reductions in scan time. The method is regularized and self-navigated for motion correction. Seven volunteers were scanned in this study, including four with volumetric whole brain acquisitions. RESULTS The average similarity of microstructural orientations between undersampled datasets and their fully sampled counterparts was above 85%, with scan times below 5 min for whole-brain acquisitions. Up to 2.7-fold scan time acceleration along with four-fold distortion reduction was achieved. CONCLUSION The proposed Imaging strategy can generate HARDI results with relatively good geometrical fidelity and low scan duration, which may help facilitate the transition of HARDI from a successful research tool to a practical clinical one. Magn Reson Med 77:696-706, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Chapter 28 – Diffusion Imaging of Brain Tumors
Handbook of Neuro-Oncology Neuroimaging, 2016Co-Authors: Stephan E. MaierAbstract:Magnetic resonance (MR) Diffusion Imaging is one of the more recent Imaging techniques that have been added to the palette of routinely applied techniques for diagnostic MR Imaging of the brain. This chapter discusses the added value of Diffusion Imaging in diagnostic Imaging of brain tumors. First, the most basic and most commonly utilized approach to Diffusion Imaging is discussed. This approach provides images of tissue-specific, single Diffusion coefficients that reflect the aggregate random motion of intra- and extracellular water. Such measurement of the water Diffusion coefficient within the tumor permits an approximate categorization of tumor type and, for some tumor types, even definitive diagnosis. These tumor-specific Diffusion coefficients are compared with Diffusion coefficients of normal brain tissues, secondary changes, stroke, abscess, and fluid-filled cysts. Furthermore, it is discussed how serially obtained Diffusion data are useful to document and even predict response to drug or radiation therapy within different areas of a tumor. Then, it is described how the monoparametric description of the MR Diffusion signal with a single Diffusion coefficient is incomplete and how additional Diffusion parameters derived from the analysis of highly Diffusion-weighted image data can contribute to the characterization of tumor tissue. Finally, it is reviewed how Diffusion tensor Imaging, which can measure the orientational dependence of restricted Diffusion in white matter, can be gainfully applied to determine white matter integrity in brain tumor patients. Nerve fiber tract visualization based on Diffusion tensor data promises to become indispensable for therapy planning and for intraoperative monitoring of surgical procedures. While Diffusion Imaging provides truly new and different information, it is plagued by low signal-to-noise ratio, coarse spatial resolution, and sometimes geometric deformation. More advanced applications are limited by extraordinarily long scan times.
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Accelerated multi-shot Diffusion Imaging.
Magnetic resonance in medicine, 2013Co-Authors: Bruno Madore, Yuan George Chiou, Renxin Chu, Tzu Cheng Chao, Stephan E. MaierAbstract:Purpose To reduce image distortion in MR Diffusion Imaging using an accelerated multi-shot method. Methods The proposed method exploits the fact that Diffusion-encoded data tend to be sparse when represented in the kb-kd space, where kb and kd are the Fourier transform duals of b and d, the b-factor and the Diffusion direction, respectively. Aliasing artifacts are displaced toward under-used regions of the kb-kd plane, allowing nonaliased signals to be recovered. A main characteristic of the proposed approach is how thoroughly the navigator information gets used during reconstruction: The phase of navigator images is used for motion correction, while the magnitude of the navigator signal in kb-kd space is used for regularization purposes. As opposed to most acceleration methods based on compressed sensing, the proposed method reduces the number of ky lines needed for each Diffusion-encoded image, but not the total number of images required. Consequently, it tends to be most effective at reducing image distortion rather than reducing total scan time. Results Results are presented for three volunteers with acceleration factors ranging from 4 to 8, with and without the inclusion of parallel Imaging. Conclusion An accelerated motion-corrected Diffusion Imaging method was introduced that achieves good image quality at relatively high acceleration factors. Magn Reson Med 72:324–336, 2014. © 2013 Wiley Periodicals, Inc.
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restricted Diffusion in spinal cord infarction demonstrated by magnetic resonance line scan Diffusion Imaging
Stroke, 2012Co-Authors: Raul G Nogueira, Rafael M Ferreira, Ellen P Grant, Stephan E. Maier, Walter J Koroshetz, R. G. Gonzalez, Kevin N ShethAbstract:Background and Purpose—We report on the use of line scan Diffusion magnetic resonance Imaging in the evaluation of spinal cord infarctions. Methods—Data on 19 patients with clinical findings consistent with spinal cord infarctions and abnormal findings on line scan Diffusion Imaging were reviewed. The Apparent Diffusion Coefficient (ADC) measurements for the normal spinal cord and for the areas of abnormality were calculated from trace ADC maps. Results—Restricted Diffusion was found in all 19 patients. Absolute ADC values in the ischemic area ranged between 395.4 and 575.8×10−6 mm2/s, with ADC ratios ranging between 39.4% and 57.4%. Conclusions—Line scan Diffusion Imaging is technically feasible and appears to be a reliable method to diagnose spinal cord infarction in the acute setting.
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Diffusion Imaging of brain tumors.
NMR in biomedicine, 2010Co-Authors: Stephan E. Maier, Yanping Sun, Robert V. MulkernAbstract:MR Imaging offers a tremendous armamentarium of different methods that can be employed in brain tumor characterization. MR Diffusion Imaging has become a widely accepted method for probing the presence of fluid pools and molecular tissue water mobility. For most clinical applications of Diffusion Imaging, it is assumed that the Diffusion signal vs Diffusion weighting factor b decays monoexponentially. Within this framework, measurement of a single Diffusion coefficient in brain tumors permits an approximate categorization of tumor type and for some tumors definitive diagnosis. In most brain tumors, when compared to normal brain tissue, the Diffusion coefficient is elevated. The presence of peritumoral edema, which also exhibits an elevated Diffusion coefficient, often precludes delineation of the tumor based on Diffusion information alone. Serially obtained Diffusion data is useful to document and even predict cellular response to drug or radiation therapy. Diffusion measurements in tissues over an extended range of b-factors have clearly shown that the mono-parametric description of the MR Diffusion signal decay is incomplete. Very high Diffusion weighting on clinical systems requires substantial compromise in spatial resolution. But after suitable analysis, superior separation of malignant brain tumors, peritumoral edema, and normal brain tissue can be achieved. These findings are also discussed in light of tissue-specific differences in membrane structure and the restrictions membranes exert on Diffusion. Finally, measurement of the directional dependence of Diffusion permits assessment of white matter integrity and dislocation. Such information, particularly in conjunction with advanced post-processing, is considered immensely useful for therapy planning. Diffusion Imaging, which permits monoexponential analysis and provides directional Diffusion information, is performed routinely in brain tumor patients. More advanced methods require improvement in acquisition speed and spatial resolution to gain clinical acceptance.
Owen J Arthurs - One of the best experts on this subject based on the ideXlab platform.
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high resolution isotropic Diffusion Imaging in post mortem neonates a feasibility study
British Journal of Radiology, 2018Co-Authors: Amy R Mcdowell, Susan C Shelmerdine, David W Carmichael, Owen J ArthursAbstract:OBJECTIVE: To investigate the potential of advanced Diffusion Imaging in Post-Mortem MRI (PMMR) at 3T. Methods: We acquired PMMR brain and body Imaging in 12 neonates, mean gestational age 33.4 weeks (range 29-37 weeks) at 3T and 1.5T. Head and body Diffusion Imaging at 1.5T using bipolar Diffusion encoding and single-shot echo-planar Imaging (EPI) for acquisition (TE 96ms; TR 2700ms; voxel size 1.8x1.8mm in-plane with slice thickness 5mm; b values of 500 and 1000 s/mm2 applied in three orthogonal directions; total acquisition time 2:12). A whole-body 3T Diffusion Imaging protocol using monopolar Diffusion encoding and simultaneous multi-slice EPI acquisition with gradients applied in 12 uniformly distributed directions were obtained (TE 53.4ms; TR 5600ms; 1.8mm isotropic; multi-band factor 2; b-values of 250, 750, 1250 and 1750 s/mm2; acquisition time 2:09 for a single b-value,). Results: There was significant improvement in image quality in multiband, multi-slice Diffusion PMMR protocol. On visual assessment of image quality, 1.5T DWI scored poorly (mean 2.4 SD ± 0.47), and all 3T b values individually scored significantly higher (p < 0.001) apart from b = 250 which was not significantly different. CONCLUSION: Recent advances in Diffusion sequences and hardware utilising higher field strengths and gradient performance allows whole-body Diffusion PMMR Imaging at high resolution with improved image quality compared to the current clinical approach. Advances in knowledge: We have demonstrated feasibility of a multi-slice, multi-band quantitative Diffusion Imaging sequence in the perinatal post-mortem setting. This will allow more detailed and quantitative clinical PMMR investigations using Diffusion MRI in the future.
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High resolution isotropic Diffusion Imaging in post-mortem neonates: a feasibility study.
British Journal of Radiology, 2018Co-Authors: Amy R Mcdowell, Susan C Shelmerdine, David W Carmichael, Owen J ArthursAbstract:OBJECTIVE: To investigate the potential of advanced Diffusion Imaging in Post-Mortem MRI (PMMR) at 3T. Methods: We acquired PMMR brain and body Imaging in 12 neonates, mean gestational age 33.4 weeks (range 29-37 weeks) at 3T and 1.5T. Head and body Diffusion Imaging at 1.5T using bipolar Diffusion encoding and single-shot echo-planar Imaging (EPI) for acquisition (TE 96ms; TR 2700ms; voxel size 1.8x1.8mm in-plane with slice thickness 5mm; b values of 500 and 1000 s/mm2 applied in three orthogonal directions; total acquisition time 2:12). A whole-body 3T Diffusion Imaging protocol using monopolar Diffusion encoding and simultaneous multi-slice EPI acquisition with gradients applied in 12 uniformly distributed directions were obtained (TE 53.4ms; TR 5600ms; 1.8mm isotropic; multi-band factor 2; b-values of 250, 750, 1250 and 1750 s/mm2; acquisition time 2:09 for a single b-value,). Results: There was significant improvement in image quality in multiband, multi-slice Diffusion PMMR protocol. On visual assessment of image quality, 1.5T DWI scored poorly (mean 2.4 SD ± 0.47), and all 3T b values individually scored significantly higher (p
Lawrence L Wald - One of the best experts on this subject based on the ideXlab platform.
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high fidelity high isotropic resolution Diffusion Imaging through gslider acquisition with b 1 and t 1 corrections and integrated δb 0 rx shim array
Magnetic Resonance in Medicine, 2020Co-Authors: Congyu Liao, Jason P Stockmann, Qiyuan Tian, Berkin Bilgic, Nicolas Arango, Mary Kate Manhard, Susie Y Huang, William A Grissom, Lawrence L WaldAbstract:PURPOSE: B1+ and T1 corrections and dynamic multicoil shimming approaches were proposed to improve the fidelity of high-isotropic-resolution generalized slice-dithered enhanced resolution (gSlider) Diffusion Imaging. METHODS: An extended reconstruction incorporating B1+ inhomogeneity and T1 recovery information was developed to mitigate slab-boundary artifacts in short-repetition time (TR) gSlider acquisitions. Slab-by-slab dynamic B0 shimming using a multicoil integrated ΔB0 /Rx shim array and high in-plane acceleration (Rinplane = 4) achieved with virtual-coil GRAPPA were also incorporated into a 1-mm isotropic resolution gSlider acquisition/reconstruction framework to achieve a significant reduction in geometric distortion compared to single-shot echo planar Imaging (EPI). RESULTS: The slab-boundary artifacts were alleviated by the proposed B1+ and T1 corrections compared to the standard gSlider reconstruction pipeline for short-TR acquisitions. Dynamic shimming provided >50% reduction in geometric distortion compared to conventional global second-order shimming. One-millimeter isotropic resolution Diffusion data show that the typically problematic temporal and frontal lobes of the brain can be imaged with high geometric fidelity using dynamic shimming. CONCLUSIONS: The proposed B1+ and T1 corrections and local-field control substantially improved the fidelity of high-isotropic-resolution Diffusion Imaging, with reduced slab-boundary artifacts and geometric distortion compared to conventional gSlider acquisition and reconstruction. This enabled high-fidelity whole-brain 1-mm isotropic Diffusion Imaging with 64 Diffusion directions in 20 min using a 3T clinical scanner.
Nicolas Arango - One of the best experts on this subject based on the ideXlab platform.
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high fidelity high isotropic resolution Diffusion Imaging through gslider acquisition with b 1 and t 1 corrections and integrated δb 0 rx shim array
Magnetic Resonance in Medicine, 2020Co-Authors: Congyu Liao, Jason P Stockmann, Qiyuan Tian, Berkin Bilgic, Nicolas Arango, Mary Kate Manhard, Susie Y Huang, William A Grissom, Lawrence L WaldAbstract:PURPOSE: B1+ and T1 corrections and dynamic multicoil shimming approaches were proposed to improve the fidelity of high-isotropic-resolution generalized slice-dithered enhanced resolution (gSlider) Diffusion Imaging. METHODS: An extended reconstruction incorporating B1+ inhomogeneity and T1 recovery information was developed to mitigate slab-boundary artifacts in short-repetition time (TR) gSlider acquisitions. Slab-by-slab dynamic B0 shimming using a multicoil integrated ΔB0 /Rx shim array and high in-plane acceleration (Rinplane = 4) achieved with virtual-coil GRAPPA were also incorporated into a 1-mm isotropic resolution gSlider acquisition/reconstruction framework to achieve a significant reduction in geometric distortion compared to single-shot echo planar Imaging (EPI). RESULTS: The slab-boundary artifacts were alleviated by the proposed B1+ and T1 corrections compared to the standard gSlider reconstruction pipeline for short-TR acquisitions. Dynamic shimming provided >50% reduction in geometric distortion compared to conventional global second-order shimming. One-millimeter isotropic resolution Diffusion data show that the typically problematic temporal and frontal lobes of the brain can be imaged with high geometric fidelity using dynamic shimming. CONCLUSIONS: The proposed B1+ and T1 corrections and local-field control substantially improved the fidelity of high-isotropic-resolution Diffusion Imaging, with reduced slab-boundary artifacts and geometric distortion compared to conventional gSlider acquisition and reconstruction. This enabled high-fidelity whole-brain 1-mm isotropic Diffusion Imaging with 64 Diffusion directions in 20 min using a 3T clinical scanner.
Marco Catani - One of the best experts on this subject based on the ideXlab platform.
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Diffusion Imaging Methods in Language Sciences
The Oxford Handbook of Neurolinguistics, 2019Co-Authors: Stephanie J. Forkel, Marco CataniAbstract:The field of neuroanatomy of language is moving forward at a fast pace. This progression is partially due to the development of Diffusion tractography, which has been used to describe white matter connections in the living human brain. For the field of neurolinguistics, this advancement is timely and important for two reasons. First, it allows clinical researchers to liberate themselves from neuroanatomical models of language derived from animal studies. Second, for the first time, it offers the possibility of testing network correlates of neurolinguistic models directly in the human brain. This chapter introduces the reader to general principles of Diffusion Imaging and tractography. Examples of its applications to normal language and its disorders will be used to explicate its potentials and limitations.
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Imaging white-matter pathways of the auditory system with Diffusion Imaging tractography.
Handbook of clinical neurology, 2015Co-Authors: Chiara Maffei, Guadalupe Soria, Alberto Prats-galino, Marco CataniAbstract:The recent advent of Diffusion Imaging tractography has opened a new window into the in vivo white-matter anatomy of the human brain. This is of particular importance for the connections of the auditory system, which may have undergone substantial development in humans in relation to language. However, tractography of the human auditory pathways has proved to be challenging due to current methodologic limitations and the intrinsic anatomic features of the subcortical connections that carry acoustic information in the brainstem. More reliable findings are forthcoming from tractography studies of corticocortical connections associated with language processing. In this chapter we introduce the reader to basic principles of Diffusion Imaging and tractography. A selected review of the tractography studies of the auditory pathways will be presented, with particular attention given to the cerebral association pathways of the temporal lobe. Finally, new Diffusion methods based on advanced model for mapping fiber crossing will be discussed in the context of the auditory and language networks.