1
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Chen X, Wang W, Huang J, Wu J, Chen L, Cai C, Cai S, Chen Z. Ultrafast water–fat separation using deep learning–based single‐shot MRI. Magn Reson Med 2022; 87:2811-2825. [DOI: 10.1002/mrm.29172] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 12/13/2021] [Accepted: 01/07/2022] [Indexed: 12/16/2022]
Affiliation(s)
- Xinran Chen
- Department of Electronic Science Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance School of Electronic Science and Engineering National Model Microelectronics College Xiamen University Xiamen Fujian People’s Republic of China
| | - Wei Wang
- Department of Electronic Science Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance School of Electronic Science and Engineering National Model Microelectronics College Xiamen University Xiamen Fujian People’s Republic of China
| | - Jianpan Huang
- Department of Biomedical Engineering City University of Hong Kong Hong Kong People’s Republic of China
| | - Jian Wu
- Department of Electronic Science Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance School of Electronic Science and Engineering National Model Microelectronics College Xiamen University Xiamen Fujian People’s Republic of China
| | - Lin Chen
- Department of Electronic Science Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance School of Electronic Science and Engineering National Model Microelectronics College Xiamen University Xiamen Fujian People’s Republic of China
| | - Congbo Cai
- Department of Electronic Science Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance School of Electronic Science and Engineering National Model Microelectronics College Xiamen University Xiamen Fujian People’s Republic of China
| | - Shuhui Cai
- Department of Electronic Science Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance School of Electronic Science and Engineering National Model Microelectronics College Xiamen University Xiamen Fujian People’s Republic of China
| | - Zhong Chen
- Department of Electronic Science Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance School of Electronic Science and Engineering National Model Microelectronics College Xiamen University Xiamen Fujian People’s Republic of China
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2
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Lee PK, Yoon D, Sandberg JK, Vasanawala SS, Hargreaves BA. Volumetric and multispectral DWI near metallic implants using a non-linear phase Carr-Purcell-Meiboom-Gill diffusion preparation. Magn Reson Med 2022; 87:2650-2666. [PMID: 35014729 DOI: 10.1002/mrm.29153] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 12/20/2021] [Accepted: 12/22/2021] [Indexed: 12/15/2022]
Abstract
PURPOSE DWI near metal implants has not been widely explored due to substantial challenges associated with through-slice and in-plane distortions, the increased encoding requirement of different spectral bins, and limited SNR. There is no widely adopted clinical protocol for DWI near metal since the commonly used EPI trajectory fails completely due to distortion from extreme off-resonance ranging from 2 to 20 kHz. We present a sequence that achieves DWI near metal with moderate b-values (400-500 s/mm2 ) and volumetric coverage in clinically feasible scan times. THEORY AND METHODS Multispectral excitation with Cartesian sampling, view angle tilting, and kz phase encoding reduce in-plane and through-plane off-resonance artifacts, and Carr-Purcell-Meiboom-Gill (CPMG) spin-echo refocusing trains counteract T2* effects. The effect of random phase on the refocusing train is eliminated using a stimulated echo diffusion preparation. Root-flipped Shinnar-Le Roux refocusing pulses permits preparation of a high spectral bandwidth, which improves imaging times by reducing the number of excitations required to cover the desired spectral range. B1 sensitivity is reduced by using an excitation that satisfies the CPMG condition in the preparation. A method for ADC quantification insensitive to background gradients is presented. RESULTS Non-linear phase refocusing pulses reduces the peak B1 by 46% which allows RF bandwidth to be doubled. Simulations and phantom experiments show that a non-linear phase CPMG pulse pair reduces B1 sensitivity. Application in vivo demonstrates complementary contrast to conventional multispectral acquisitions and improved visualization compared to DW-EPI. CONCLUSION Volumetric and multispectral DW imaging near metal can be achieved with a 3D encoded sequence.
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Affiliation(s)
- Philip K Lee
- Radiology, Stanford University, Stanford, California, USA.,Electrical Engineering, Stanford University, Stanford, California, USA
| | - Daehyun Yoon
- Radiology, Stanford University, Stanford, California, USA
| | | | | | - Brian A Hargreaves
- Radiology, Stanford University, Stanford, California, USA.,Electrical Engineering, Stanford University, Stanford, California, USA.,Bioengineering, Stanford University, Stanford, California, USA
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3
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Martinho RP, Bao Q, Markovic S, Preise D, Sasson K, Agemy L, Scherz A, Frydman L. Identification of variable stages in murine pancreatic tumors by a multiparametric approach employing hyperpolarized 13 C MRSI, 1 H diffusivity and 1 H T 1 MRI. NMR IN BIOMEDICINE 2021; 34:e4446. [PMID: 33219722 DOI: 10.1002/nbm.4446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Revised: 10/28/2020] [Accepted: 10/29/2020] [Indexed: 06/11/2023]
Abstract
This study explored the usefulness of multiple quantitative MRI approaches to detect pancreatic ductal adenocarcinomas in two murine models, PAN-02 and KPC. Methods assayed included 1 H T1 and T2 measurements, quantitative diffusivity mapping, magnetization transfer (MT) 1 H MRI throughout the abdomen and hyperpolarized 13 C spectroscopic imaging. The progress of the disease was followed as a function of its development; studies were also conducted for wildtype control mice and for mice with induced mild acute pancreatitis. Customized methods developed for scanning the motion- and artifact-prone mice abdomens allowed us to obtain quality 1 H images for these targeted regions. Contrasts between tumors and surrounding tissues, however, were significantly different. Anatomical images, T2 maps and MT did not yield significant contrast unless tumors were large. By contrast, tumors showed statistically lower diffusivities than their surroundings (≈8.3 ± 0.4 x 10-4 for PAN-02 and ≈10.2 ± 0.6 x 10-4 for KPC vs 13 ± 1 x 10-3 mm2 s-1 for surroundings), longer T1 relaxation times (≈1.44 ± 0.05 for PAN-02 and ≈1.45 ± 0.05 for KPC vs 0.95 ± 0.10 seconds for surroundings) and significantly higher lactate/pyruvate ratios by hyperpolarized 13 C MR (0.53 ± 0.2 for PAN-02 and 0.78 ± 0.2 for KPC vs 0.11 ± 0.04 for control and 0.31 ± 0.04 for pancreatitis-bearing mice). Although the latter could also distinguish early-stage tumors from healthy animal controls, their response was similar to that in our pancreatitis model. Still, this ambiguity could be lifted using the 1 H-based reporters. If confirmed for other kinds of pancreatic tumors this means that these approaches, combined, can provide a route to an early detection of pancreatic cancer.
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Affiliation(s)
- Ricardo P Martinho
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Qingjia Bao
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Stefan Markovic
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Dina Preise
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Keren Sasson
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Lilach Agemy
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Avigdor Scherz
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
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4
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Otikovs M, Nissan N, Furman-Haran E, Anaby D, Allweis TM, Agassi R, Sklair-Levy M, Frydman L. Diffusivity in breast malignancies analyzed for b > 1000 s/mm 2 at 1 mm in-plane resolutions: Insight from Gaussian and non-Gaussian behaviors. J Magn Reson Imaging 2020; 53:1913-1925. [PMID: 33368734 DOI: 10.1002/jmri.27489] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 12/10/2020] [Accepted: 12/10/2020] [Indexed: 12/20/2022] Open
Abstract
Diffusion-weighted imaging (DWI) can improve breast cancer characterizations, but often suffers from low image quality -particularly at informative b > 1000 s/mm2 values. The aim of this study was to evaluate multishot approaches characterizing Gaussian and non-Gaussian diffusivities in breast cancer. This was a prospective study, in which 15 subjects, including 13 patients with biopsy-confirmed breast cancers, were enrolled. DWI was acquired at 3 T using echo planar imaging (EPI) with and without zoomed excitations, readout-segmented EPI (RESOLVE), and spatiotemporal encoding (SPEN); dynamic contrast-enhanced (DCE) data were collected using three-dimensional gradient-echo T1 weighting; anatomies were evaluated with T2 -weighted two-dimensional turbo spin-echo. Congruence between malignancies delineated by DCE was assessed against high-resolution DWI scans with b-values in the 0-1800 s/mm2 range, as well as against apparent diffusion coefficient (ADC) and kurtosis maps. Data were evaluated by independent magnetic resonance scientists with 3-20 years of experience, and radiologists with 6 and 20 years of experience in breast MRI. Malignancies were assessed from ADC and kurtosis maps, using paired t tests after confirming that these values had a Gaussian distribution. Agreements between DWI and DCE datasets were also evaluated using Sorensen-Dice similarity coefficients. Cancerous and normal tissues were clearly separable by ADCs: by SPEN their average values were (1.03 ± 0.17) × 10-3 and (1.69 ± 0.19) × 10-3 mm2 /s (p < 0.0001); by RESOLVE these values were (1.16 ± 0.16) × 10-3 and (1.52 ± 0.14) × 10-3 (p = 0.00026). Kurtosis also distinguished lesions (K = 0.64 ± 0.15) from normal tissues (K = 0.45 ± 0.05), but only when measured by SPEN (p = 0.0008). The best statistical agreement with DCE-highlighted regions arose for SPEN-based DWIs recorded with b = 1800 s/mm2 (Sorensen-Dice coefficient = 0.67); DWI data recorded with b = 850 and 1200 s/mm2 , led to lower coefficients. Both ADC and kurtosis maps highlighted the breast malignancies, with ADCs providing a more significant separation. The most promising alternative for contrast-free delineations of the cancerous lesions arose from b = 1800 s/mm2 DWI. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 3.
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Affiliation(s)
- Martins Otikovs
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Noam Nissan
- Department of Radiology, Sheba-Medical-Center, Ramat-Gan, Israel
| | - Edna Furman-Haran
- Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel.,Azrieli National Center for Brain Imaging, Weizmann Institute of Science, Rehovot, Israel
| | - Debbie Anaby
- Department of Radiology, Sheba-Medical-Center, Ramat-Gan, Israel
| | - Tanir M Allweis
- Department of Surgery, Kaplan Medical Center, Rehovot, Israel
| | - Ravit Agassi
- Department of Surgery, Ben Gurion University Hospital, Beer Sheba, Israel
| | - Miri Sklair-Levy
- Department of Radiology, Sheba-Medical-Center, Ramat-Gan, Israel.,Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.,Azrieli National Center for Brain Imaging, Weizmann Institute of Science, Rehovot, Israel
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5
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Yon M, Bao Q, Chitrit OJ, Henriques RN, Shemesh N, Frydman L. High-Resolution 3D in vivo Brain Diffusion Tensor Imaging at Ultrahigh Fields: Following Maturation on Juvenile and Adult Mice. Front Neurosci 2020; 14:590900. [PMID: 33328861 PMCID: PMC7714913 DOI: 10.3389/fnins.2020.590900] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 09/22/2020] [Indexed: 12/20/2022] Open
Abstract
Diffusion tensor imaging (DTI) is a well-established technique for mapping brain microstructure and white matter tracts in vivo. High resolution DTI, however, is usually associated with low intrinsic sensitivity and therefore long acquisition times. By increasing sensitivity, high magnetic fields can alleviate these demands, yet high fields are also typically associated with significant susceptibility-induced image distortions. This study explores the potential arising from employing new pulse sequences and emerging hardware at ultrahigh fields, to overcome these limitations. To this end, a 15.2 T MRI instrument equipped with a cryocooled surface transceiver coil was employed, and DTI experiments were compared between SPatiotemporal ENcoding (SPEN), a technique that tolerates well susceptibility-induced image distortions, and double-sampled Spin-Echo Echo-Planar Imaging (SE-EPI) methods. Following optimization, SE-EPI afforded whole brain DTI maps at 135 μm isotropic resolution that possessed higher signal-to-noise ratios (SNRs) than SPEN counterparts. SPEN, however, was a better alternative to SE-EPI when focusing on challenging regions of the mouse brain -including the olfactory bulb and the cerebellum. In these instances, the higher robustness of fully refocused SPEN acquisitions coupled to its built-in zooming abilities, provided in vivo DTI maps with 75 μm nominal isotropic spatial resolution. These DTI maps, and in particular the mean diffusion direction (MDD) details, exhibited variations that matched very well the anatomical features known from histological brain Atlases. Using these capabilities, the development of the olfactory bulb (OB) in live mice was followed from week 1 post-partum, until adulthood. The diffusivity of this organ showed a systematic decrease in its overall isotropic value and increase in its fractional anisotropy with age; this maturation was observed for all regions used in the OB's segmentation but was most evident for the lobules' centers, in particular for the granular cell layer. The complexity of the OB neuronal connections also increased during maturation, as evidenced by the growth in directionalities arising in the mean diffusivity direction maps.
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Affiliation(s)
- Maxime Yon
- Department of Chemical and Biological Physics, Weizmann Institute, Rehovot, Israel
| | - Qingjia Bao
- Department of Chemical and Biological Physics, Weizmann Institute, Rehovot, Israel
| | | | | | - Noam Shemesh
- Champalimaud Research, Champalimaud Centre for the Unknown, Lisbon, Portugal
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute, Rehovot, Israel
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6
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Yon M, de Almeida Martins JP, Bao Q, Budde MD, Frydman L, Topgaard D. Diffusion tensor distribution imaging of an in vivo mouse brain at ultrahigh magnetic field by spatiotemporal encoding. NMR IN BIOMEDICINE 2020; 33:e4355. [PMID: 32812669 PMCID: PMC7583469 DOI: 10.1002/nbm.4355] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/27/2020] [Accepted: 05/29/2020] [Indexed: 05/08/2023]
Abstract
Diffusion tensor distribution (DTD) imaging builds on principles from diffusion, solid-state and low-field NMR spectroscopies, to quantify the contents of heterogeneous voxels as nonparametric distributions, with tensor "size", "shape" and orientation having direct relations to corresponding microstructural properties of biological tissues. The approach requires the acquisition of multiple images as a function of the magnitude, shape and direction of the diffusion-encoding gradients, leading to long acquisition times unless fast image read-out techniques like EPI are employed. While in previous in vivo human brain studies performed at 3 T this proved a viable option, porting these measurements to very high magnetic fields and/or to heterogeneous organs induces B0 - and B1 -inhomogeneity artifacts that challenge the limits of EPI. To overcome such challenges, we demonstrate here that high spatial resolution DTD of mouse brain can be carried out at 15.2 T with a surface-cryoprobe, by relying on SPatiotemporal ENcoding (SPEN) imaging sequences. These new acquisition and data-processing protocols are demonstrated with measurements on in vivo mouse brain, and validated with synthetic phantoms designed to mimic the diffusion properties of white matter, gray matter and cerebrospinal fluid. While still in need of full extensions to 3D mappings and of scanning additional animals to extract more general physiological conclusions, this work represents another step towards the model-free, noninvasive in vivo characterization of tissue microstructure and heterogeneity in animal models, at ≈0.1 mm resolutions.
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Affiliation(s)
- Maxime Yon
- Department of Chemical and Biological PhysicsWeizmann InstituteRehovotIsrael
| | - João P. de Almeida Martins
- Division of Physical Chemistry, Department of ChemistryLund UniversityLundSweden
- Random Walk Imaging ABLundSweden
| | - Qingjia Bao
- Department of Chemical and Biological PhysicsWeizmann InstituteRehovotIsrael
| | | | - Lucio Frydman
- Department of Chemical and Biological PhysicsWeizmann InstituteRehovotIsrael
| | - Daniel Topgaard
- Division of Physical Chemistry, Department of ChemistryLund UniversityLundSweden
- Random Walk Imaging ABLundSweden
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7
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Bao Q, Hadas R, Markovic S, Neeman M, Frydman L. Diffusion and perfusion MRI of normal, preeclamptic and growth-restricted mice models reveal clear fetoplacental differences. Sci Rep 2020; 10:16380. [PMID: 33009455 PMCID: PMC7532452 DOI: 10.1038/s41598-020-72885-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 08/28/2020] [Indexed: 12/13/2022] Open
Abstract
Diffusion-weighted MRI on rodents could be valuable to evaluate pregnancy-related dysfunctions, particularly in knockout models whose biological nature is well understood. Echo Planar Imaging’s sensitivity to motions and to air/water/fat heterogeneities, complicates these studies in the challenging environs of mice abdomens. Recently developed MRI methodologies based on SPatiotemporal ENcoding (SPEN) can overcome these obstacles, and deliver diffusivity maps at ≈150 µm in-plane resolutions. The present study exploits these capabilities to compare the development in wildtype vs vascularly-altered mice. Attention focused on the various placental layers—deciduae, labyrinth, trophoblast, fetal vessels—that the diffusivity maps could resolve. Notable differences were then observed between the placental developments of wildtype vs diseased mice; these differences remained throughout the pregnancies, and were echoed by perfusion studies relying on gadolinium-based dynamic contrast-enhanced MRI. Longitudinal monitoring of diffusivity in the animals throughout the pregnancies also showed differences between the development of the fetal brains in the wildtype and vascularly-altered mice, even if these disparities became progressively smaller as the pregnancies progressed. These results are analyzed on the basis of the known physiology of normal and preeclamptic pregnancies, as well as in terms of the potential that they might open for the early detection of disorders in human pregnancies.
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Affiliation(s)
- Qingjia Bao
- Department of Chemical and Biological Physics, Weizmann Institute, 7610001, Rehovot, Israel
| | - Ron Hadas
- Department of Biological Regulation, Weizmann Institute, 7610001, Rehovot, Israel
| | - Stefan Markovic
- Department of Chemical and Biological Physics, Weizmann Institute, 7610001, Rehovot, Israel
| | - Michal Neeman
- Department of Biological Regulation, Weizmann Institute, 7610001, Rehovot, Israel
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute, 7610001, Rehovot, Israel.
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8
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Huang J, Chen L, Chan KWY, Cai C, Cai S, Chen Z. Super-resolved water/fat image reconstruction based on single-shot spatiotemporally encoded MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 314:106736. [PMID: 32361511 DOI: 10.1016/j.jmr.2020.106736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 04/11/2020] [Accepted: 04/18/2020] [Indexed: 06/11/2023]
Abstract
Single-shot spatiotemporally encoded (SPEN) MRI has been validated to possess considerable performance in both spatial and temporal resolution. Water/fat separation is essential for MRI applications in which only water signal is needed. In this article, a super-resolved water/fat image reconstruction method (dubbed SWAF) combined prior knowledge was developed based on single-shot SPEN MRI. The point spread function of spatiotemporal encoding under multiple chemical shifts situation was derived and used for constructing an equation for SWAF image reconstruction. By processing the prior chemical shift information with filtering operation, an initial spin density profile of water/fat and a weighting matrix for water/fat residual artifacts suppression were obtained to guide the reconstruction process. A l1 norm minimization problem with regularization was exploited to reconstruct separated water/fat images with high spatial resolution and less residual/aliasing artifacts. Numeric simulation and experiments on water-oil phantom and rat abdomen/neck imaging demonstrated the effectiveness and robustness of this new method. The SWAF method proposed herein would promote the application of SPEN MRI in the cases where water/fat separation is required.
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Affiliation(s)
- Jianpan Huang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China; Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Lin Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Kannie W Y Chan
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Congbo Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China.
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China.
| | - Zhong Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
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9
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Bao Q, Liberman G, Solomon E, Frydman L. High-resolution diffusion MRI studies of development in pregnant mice visualized by novel spatiotemporal encoding schemes. NMR IN BIOMEDICINE 2020; 33:e4208. [PMID: 31809554 DOI: 10.1002/nbm.4208] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 10/08/2019] [Accepted: 10/11/2019] [Indexed: 06/10/2023]
Abstract
This study introduces an MRI approach to map diffusion of water in vivo with high resolution under challenging conditions; the approach's potential is then used in diffusivity characterizations of embryos and fetoplacental units in pregnant mice, as well as of newborn mice in their initial postnatal period. The method relies on performing self-referenced spatiotemporal encoded MRI acquisitions, which can achieve the motional and susceptibility immunities needed to target challenging regions such as a mouse's abdominal cavity in a single shot. When suitably combined with zooming-in and novel interleaving procedures, these scans can overcome the inhomogeneity and sensitivity challenges arising upon targeting ≈100 μm in-plane resolutions, and thereby enable longitudinal development studies of abdominal organs that have hitherto eluded in vivo diffusion-weighted imaging. This is employed here to follow processes related to embryonic implantation and placentation, including the final stages of mouse gastrulation, the development of white matter in fetal brains, the maturation of fetal spines, and the evolution of the different layers making up mouse hemochorial placentas. The protocol's ability to extract diffusivity information in challenging regions as a function of embryonic mouse development is thus demonstrated, and its usefulness as a tool for visualizing pregnancy-related developmental changes in rodents is discussed.
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Affiliation(s)
- Qingjia Bao
- Department of Chemical and Biological Physics, Weizmann Institute, Rehovot, Israel
| | - Gilad Liberman
- Department of Chemical and Biological Physics, Weizmann Institute, Rehovot, Israel
| | - Eddy Solomon
- Department of Chemical and Biological Physics, Weizmann Institute, Rehovot, Israel
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute, Rehovot, Israel
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10
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Huang Y, Zhang X, Guo H, Chen H, Guo D, Huang F, Xu Q, Qu X. Phase-constrained reconstruction of high-resolution multi-shot diffusion weighted image. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 312:106690. [PMID: 32066067 DOI: 10.1016/j.jmr.2020.106690] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 01/18/2020] [Accepted: 01/27/2020] [Indexed: 06/10/2023]
Abstract
Diffusion weighted imaging (DWI) is a unique examining method in tumor diagnosis, acute stroke evaluation. Single-shot echo planar imaging is currently conventional method for DWI. However, single-shot DWI suffers from image distortion, blurring and low spatial resolution. Although multi-shot DWI improves image resolution, it brings phase variations among different shots at the same time. In this paper, we introduce a smooth phase constraint of each shot image into multi-shot navigator-free DWI reconstruction by imposing the low-rankness of Hankel matrix constructed from the k-space data. Furthermore, we exploit the partial sum minimization of singular values to constrain the low-rankness of Hankel matrix. Results on brain imaging data show that the proposed method outperforms the state-of-the-art methods in terms of artifacts removal and our method potentially has the ability to reconstruct high number of shot of DWI.
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Affiliation(s)
- Yiman Huang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, School of Electronic Science and Engineering, Xiamen University, Xiamen 361005, China
| | - Xinlin Zhang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, School of Electronic Science and Engineering, Xiamen University, Xiamen 361005, China
| | - Hua Guo
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing 100084, China
| | - Huijun Chen
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing 100084, China
| | - Di Guo
- School of Computer and Information Engineering, Fujian Provincial University Key Laboratory of Internet of Things Application Technology, Xiamen University of Technology, Xiamen 361024, China
| | - Feng Huang
- Neusoft Medical System, Shanghai 200241, China
| | - Qin Xu
- Neusoft Medical System, Shanghai 200241, China
| | - Xiaobo Qu
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, School of Electronic Science and Engineering, Xiamen University, Xiamen 361005, China.
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11
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Solomon E, Liberman G, Nissan N, Furman‐Haran E, Sklair‐Levy M, Frydman L. Diffusion‐weighted breast MRI of malignancies with submillimeter resolution and immunity to artifacts by spatiotemporal encoding at 3T. Magn Reson Med 2020; 84:1391-1403. [DOI: 10.1002/mrm.28213] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Revised: 01/20/2020] [Accepted: 01/22/2020] [Indexed: 11/08/2022]
Affiliation(s)
- Eddy Solomon
- Department of Chemical and Biological Physics Weizmann Institute of Science Rehovot Israel
| | - Gilad Liberman
- Department of Chemical and Biological Physics Weizmann Institute of Science Rehovot Israel
| | - Noam Nissan
- Department of Radiology Sheba‐Medical‐Center Ramat‐Gan Israel
| | - Edna Furman‐Haran
- Life Sciences Core Facilities Weizmann Institute of Science Rehovot Israel
| | - Miri Sklair‐Levy
- Department of Radiology Sheba‐Medical‐Center Ramat‐Gan Israel
- Sackler School of Medicine Tel‐Aviv University Tel‐Aviv Israel
| | - Lucio Frydman
- Department of Chemical and Biological Physics Weizmann Institute of Science Rehovot Israel
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12
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Leftin A, Rosenberg JT, Yuan X, Ma T, Grant SC, Frydman L. Multiparametric classification of sub-acute ischemic stroke recovery with ultrafast diffusion, 23 Na, and MPIO-labeled stem cell MRI at 21.1 T. NMR IN BIOMEDICINE 2020; 33:e4186. [PMID: 31797472 PMCID: PMC8170591 DOI: 10.1002/nbm.4186] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 07/11/2019] [Accepted: 07/22/2019] [Indexed: 05/05/2023]
Abstract
MRI leverages multiple modes of contrast to characterize stroke. High-magnetic-field systems enhance the performance of these MRI measurements. Previously, we have demonstrated that individually sodium and stem cell tracking metrics are enhanced at ultrahigh field in a rat model of stroke, and we have developed robust single-scan diffusion-weighted imaging approaches that utilize spatiotemporal encoding (SPEN) of the apparent diffusion coefficient (ADC) for these challenging field strengths. Here, we performed a multiparametric study of middle cerebral artery occlusion (MCAO) biomarker evolution focusing on comparison of these MRI biomarkers for stroke assessment during sub-acute recovery in rat MCAO models at 21.1 T. T2 -weighted MRI was used as the benchmark for identification of the ischemic lesion over the course of the study. The number of MPIO-induced voids measured by gradient-recalled echo, the SPEN measurement of ADC, and 23 Na MRI values were determined in the ischemic area and contralateral hemisphere, and relative performances for stroke classification were compared by receiver operator characteristic analysis. These measurements were associated with unique time-dependent trajectories during stroke recovery that changed the sensitivity and specificity for stroke monitoring during its evolution. Advantages and limitations of these contrasts, and the use of ultrahigh field for multiparametric stroke assessment, are discussed.
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Affiliation(s)
- Avigdor Leftin
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
- Department of Radiology, Stony Brook Medicine, Stony Brook University, Stony Brook, NY, USA
| | - Jens T Rosenberg
- The National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA
| | - Xuegang Yuan
- FAMU-FSU Chemical and Biochemical Engineering, Florida State University, Tallahassee, FL, USA
| | - Teng Ma
- FAMU-FSU Chemical and Biochemical Engineering, Florida State University, Tallahassee, FL, USA
| | - Samuel C Grant
- The National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA
- FAMU-FSU Chemical and Biochemical Engineering, Florida State University, Tallahassee, FL, USA
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
- FAMU-FSU Chemical and Biochemical Engineering, Florida State University, Tallahassee, FL, USA
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13
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Ryu J, Han S, Oh S, Lee J, Kim S, Park J. A new ultrafast 3D gradient echo‐based imaging method using quadratic‐phase encoding. Magn Reson Med 2019; 82:237-250. [DOI: 10.1002/mrm.27711] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 02/05/2019] [Accepted: 02/05/2019] [Indexed: 12/25/2022]
Affiliation(s)
- Jae‐Kyun Ryu
- Center for Neuroscience Imaging Research Institute for Basic Science Suwon Republic of Korea
- Department of Biomedical Engineering Sungkyunkwan University Suwon Republic of Korea
| | - SoHyun Han
- Athinoula A. Martinos Center for Biomedical Imaging Massachusetts General Hospital Charlestown Massachusetts
| | - Se‐Hong Oh
- Division of Biomedical Engineering Hankuk University of Foreign Studies Yongin Republic of Korea
| | - Joonsung Lee
- Center for Neuroscience Imaging Research Institute for Basic Science Suwon Republic of Korea
| | - Seong‐Gi Kim
- Center for Neuroscience Imaging Research Institute for Basic Science Suwon Republic of Korea
- Department of Biomedical Engineering Sungkyunkwan University Suwon Republic of Korea
| | - Jang‐Yeon Park
- Center for Neuroscience Imaging Research Institute for Basic Science Suwon Republic of Korea
- Department of Biomedical Engineering Sungkyunkwan University Suwon Republic of Korea
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14
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Wi S, Schurko RW, Frydman L. Broadband adiabatic inversion cross-polarization phenomena in the NMR of rotating solids. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2018; 94:31-53. [PMID: 30125798 DOI: 10.1016/j.ssnmr.2018.08.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 08/08/2018] [Indexed: 06/08/2023]
Abstract
We explore the use of cross-polarization magic-angle spinning (CPMAS) methods incorporating an adiabatic frequency sweep in a standard Hartman-Hahn CPMAS pulse scheme, to achieve signal enhancements in solid-state NMR spectra of rare spins under fast MAS spinning rates, including spin-1/2, integer spin, and half-integer spin nuclides. These experiments, dubbed Broadband Adiabatic INversion Cross-Polarization Magic-Angle Spinning (BRAIN-CPMAS) experiments, involve an adiabatic inversion pulse on the S-channel of a rare spin nuclide while simultaneously applying a conventional spin-locking pulse on the I-channel (1H). The signal enhancement imparted by this CP scheme on the S-spin is broadbanded, while employing low RF field strengths on both I- and S-channels. A feature demanded by these BRAIN-CPMAS methods is to impose a selective adiabatic frequency sweep over a single MAS spinning centerband or sideband, to avoid interference between the MAS modulation and sweeps over multiple sidebands. Upon implementing this swept-CP method, a number of MAS-driven processes happen, including broadband zero- and double-quantum CP transfers, and MAS-driven rotary-resonance phenomena. When this CP method is applied to integer and half-integer quadrupolar nuclei at very fast MAS spinning rates, a favorable double-quantum CP condition is found that can be easily achieved, and avoids the level-crossings among various ms energy levels that complicate quadrupolar CPMAS NMR experiments along lines first shown by Alex Vega. An additional CP mechanism was found in the 1H-2H case, involving static-like zero-quantum CP modes driven by a quadrupole-modulated RF-dipolar zero-order recoupling under MAS. All these phenomena were examined using average Hamiltonian theory, numerical simulations, and experiments on model compounds. Sensitivity-enhanced, distortion-free CP over wide bandwidths were predicted and observed for S = 1/2 and for S = 1 (2H) under fast MAS rates. BRAIN-CPMAS also delivered undistorted central transition NMR spectra of half-integer quadrupolar nuclei, while utilizing low RF field strengths that avoid complex level-crossing effects under high MAS rates.
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Affiliation(s)
- Sungsool Wi
- National High Magnetic Field Laboratory, Tallahassee, FL, 32304, USA.
| | - Robert W Schurko
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario, NPB 3P4, Canada
| | - Lucio Frydman
- National High Magnetic Field Laboratory, Tallahassee, FL, 32304, USA; Department of Chemical and Biological Physics, Weizmann Institute of Sciences, Rehovot, 76100, Israel.
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15
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Solomon E, Liberman G, Zhang Z, Frydman L. Diffusion MRI measurements in challenging head and brain regions via cross-term spatiotemporally encoding. Sci Rep 2017; 7:18010. [PMID: 29269941 PMCID: PMC5740132 DOI: 10.1038/s41598-017-17947-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 11/29/2017] [Indexed: 11/24/2022] Open
Abstract
Cross-term spatiotemporal encoding (xSPEN) is a recently introduced imaging approach delivering single-scan 2D NMR images with unprecedented resilience to field inhomogeneities. The method relies on performing a pre-acquisition encoding and a subsequent image read out while using the disturbing frequency inhomogeneities as part of the image formation processes, rather than as artifacts to be overwhelmed by the application of external gradients. This study introduces the use of this new single-shot MRI technique as a diffusion-monitoring tool, for accessing regions that have hitherto been unapproachable by diffusion-weighted imaging (DWI) methods. In order to achieve this, xSPEN MRI’s intrinsic diffusion weighting effects are formulated using a customized, spatially-localized b-matrix analysis; with this, we devise a novel diffusion-weighting scheme that both exploits and overcomes xSPEN’s strong intrinsic weighting effects. The ability to provide reliable and robust diffusion maps in challenging head and brain regions, including the eyes and the optic nerves, is thus demonstrated in humans at 3T. New avenues for imaging other body regions are also briefly discussed.
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Affiliation(s)
- Eddy Solomon
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Gilad Liberman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Zhiyong Zhang
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel.
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16
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Multiple-coil k
-space interpolation enhances resolution in single-shot spatiotemporal MRI. Magn Reson Med 2017; 79:796-805. [DOI: 10.1002/mrm.26731] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 04/02/2017] [Accepted: 04/03/2017] [Indexed: 12/17/2022]
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17
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Liberman G, Frydman L. Reducing SAR requirements in multislice volumetric single-shot spatiotemporal MRI by two-dimensional RF pulses. Magn Reson Med 2017; 77:1959-1965. [PMID: 27203401 PMCID: PMC5184845 DOI: 10.1002/mrm.26270] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 04/17/2016] [Accepted: 04/17/2016] [Indexed: 12/15/2022]
Abstract
PURPOSE Spatiotemporal encoding (SPEN) can deliver single-scan MR images without folding complications and with increased robustness to chemical shift and susceptibility artifacts. Yet, it does so at the expense of relatively high specific absorption rates (SAR) owing to its reliance on frequency-swept pulses. This study describes SPEN implementations aimed at full three-dimensional (3D) multislice imaging, possessing reduced SAR thanks to an implementation based on new 2D radiofrequency (RF) pulses. METHODS Fully refocused spin- and stimulated-echo SPEN sequences incorporating 2D spatial/spatial swept RF pulses were implemented at 3 Tesla and compared to echo planar imaging. The use of effective 90-degree slice-selective excitation pulses enabled the scanning of 3D volumes with a low SAR. RESULTS Experiments validating the theoretical expectations were carried out on phantoms and on human volunteers, including zooming and diffusion measurements. The chosen sequences showed much smaller SARs than EPI, while delivering similar sensitivities when targeting human brain and fewer distortions when targeting human breast. CONCLUSION Two-dimensional RF pulses can exploit SPEN's advantages while fulfilling the SAR and multislice coverage demands required for clinical imaging. Magn Reson Med 77:1959-1965, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Gilad Liberman
- 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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18
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Lin G, Zheng S, Liao X. Signal attenuation of PFG restricted anomalous diffusions in plate, sphere, and cylinder. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 272:25-36. [PMID: 27616657 DOI: 10.1016/j.jmr.2016.08.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 08/29/2016] [Accepted: 08/30/2016] [Indexed: 06/06/2023]
Abstract
Pulsed field gradient (PFG) NMR is a noninvasive tool to study anomalous diffusion, which exists widely in many systems such as in polymer or biological systems, in porous material, in single file structures and in fractal geometries. In a real system, the diffusion could be a restricted or a tortuous anomalous diffusion, rather than a free diffusion as the domains for fast and slow transport could coexist. Though there are signal attenuation expressions for free anomalous diffusion in literature, the signal attenuation formalisms for restricted anomalous diffusion is very limited, except for a restricted time-fractional diffusion within a plate reported recently. To better understand the PFG restricted fractional diffusion, in this paper, the PFG signal attenuation expressions were derived for three typical structures (plate, sphere, and cylinder) based on two models: fractal derivative model and fractional derivative model. These signal attenuation expressions include two parts, the time part Tn(t) and the space part Xn(r). Unlike normal diffusion, the time part Tn(t) in time-fractional diffusion can be either a Mittag-Leffler function from the fractional derivative model or a stretched exponential function from the fractal derivative model. However, provided the restricted normal diffusion and the restricted time-fractional diffusion are in an identical structure, they will have the same space part Xn(r) as both diffusions have the same space derivative parameter β equaling 2, therefore, they should have similar diffractive patterns. The restricted general fractional diffusion within a plate is also investigated, which indicates that at a long time limit, the diffusion type is insignificant to the diffractive pattern that depends only on the structure and the gradient pulses. The expressions describing the time-dependent behaviors of apparent diffusion coefficient Df,app for restricted anomalous diffusion are also proposed in this paper. Both the short and long time-dependent behaviors of Df,app are distinct from that of normal diffusion. The general expressions for PFG restricted curvilinear diffusion of tube model were derived in a conventional way and its result agree with that obtained from the fractional derivative model with α equaling 1/2. Additionally, continuous-time random walk simulation was performed to give good support to the theoretical results. These theoretical results reported here will be valuable for researchers in analyzing PFG anomalous diffusion.
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Affiliation(s)
- Guoxing Lin
- Carlson School of Chemistry and Biochemistry, Clark University, Worcester, MA 01610, United States.
| | - Shaokuan Zheng
- Department of Radiology, UMASS Medical School, Worcester, MA 01655, United States
| | - Xinli Liao
- Chemistry Department, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
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19
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Lin G. Instantaneous signal attenuation method for analysis of PFG fractional diffusions. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 269:36-49. [PMID: 27209371 DOI: 10.1016/j.jmr.2016.05.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 04/15/2016] [Accepted: 05/12/2016] [Indexed: 06/05/2023]
Abstract
An instantaneous signal attenuation (ISA) method for analyzing pulsed field gradient (PFG) fractional diffusion (FD) has been developed, which is modified from the propagator approach developed in 2001 by Lin et al. for analyzing PFG normal diffusion. Both, the current ISA method and the propagator method have the same fundamental basis that the total signal attenuation (SA) is the accumulation of all the ISA, and the ISA is the average SA of the whole diffusion system at each moment. However, the manner of calculating ISA is different. Unlike the use of the instantaneous propagator in the propagator method, the current method directly calculates ISA as A(K(t'),t'+dt')/A(K(t'),t'), where A(K(t'),t'+dt') and A(K(t'),t') are the SA. This modification makes the current method applicable to PFG FD as the instantaneous propagator may not be obtainable in FD. The ISA method was applied to study PFG SA including the effect of finite gradient pulse widths (FGPW) for free FD, restricted FD and the FD affected by a non-homogeneous gradient field. The SA expressions were successfully obtained for all three types of free FDs while other current methods still have difficulty in obtaining all of them. The results from this method agree with reported results such as that obtained by the effective phase shift diffusion equation (EPSDE) method. The M-Wright phase distribution approximation was also used to derive an SA expression for time FD as a comparison, which agrees with ISA method. Additionally, the continuous-time random walk (CTRW) simulation was performed to simulate the SA of PFG FD, and the simulation results agree with the analytical results. Particularly, the CTRW simulation results give good support to the analytical results including FGPW effect for free FD and restricted time FD based on a fractional derivative model where there have been no corresponding theoretical reports to date. The theoretical SA expressions including FGPW obtained here such as [Formula: see text] may be applied to analyze PFG FD in polymer or biological systems with improved accuracy where SGP approximation cannot be satisfied. The method can perhaps provide new insight to FD MRI and hence benefit the development of diffusion biomarkers based on fractional derivative.
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Affiliation(s)
- Guoxing Lin
- Carlson School of Chemistry and Biochemistry, Clark University, Worcester, MA 01610, United States.
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20
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Huang J, Zhang M, Lu J, Cai C, Chen L, Cai S. A fast chemical exchange saturation transfer imaging scheme based on single-shot spatiotemporal encoding. Magn Reson Med 2016; 77:1786-1796. [PMID: 27120691 DOI: 10.1002/mrm.26258] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 03/30/2016] [Accepted: 04/01/2016] [Indexed: 01/31/2023]
Abstract
PURPOSE To design a new approach that can not only keep the spatial and temporal resolution but also have better built-in immunity to magnetic field inhomogeneity and chemical shift effects than the single-shot echo planar imaging (EPI) for chemical exchange saturation transfer (CEST) MRI. METHOD The single-shot spatiotemporally encoded (SPEN) MRI sequence was combined with a continuous wave saturation pulse for fast CEST MRI (CEST-SPEN MRI). The resulting images were super-resolved reconstructed by a hybrid method that solves the l1 norm minimization together with total variation (TV) regularization. Partial Lorentzian fitting was used to analyze the subsequent Z-spectra. RESULTS Experimental results of a creatine phantom and in vivo tumor rat brains show that CEST-SPEN MRI has good capability in providing CEST-based and NOE-based contrast images. CONCLUSIONS Compared with CEST-EPI, CEST-SPEN MRI has better immunity to magnetic field inhomogeneity and provides better contrast images within identical acquisition time, especially under an identical inhomogeneous field. Magn Reson Med 77:1786-1796, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Jianpan Huang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Miao Zhang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Jianhua Lu
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China.,Meizhouwan Vocational Technology College, Putian, China
| | - Congbo Cai
- Department of Communication Engineering, Xiamen University, Xiamen, China
| | - Lin Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
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21
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Solomon E, Liberman G, Nissan N, Frydman L. Robust diffusion tensor imaging by spatiotemporal encoding: Principles and in vivo demonstrations. Magn Reson Med 2016; 77:1124-1133. [PMID: 26968710 DOI: 10.1002/mrm.26197] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 02/11/2016] [Accepted: 02/11/2016] [Indexed: 12/19/2022]
Abstract
PURPOSE Evaluate the usefulness of single-shot and of interleaved spatiotemporally encoded (SPEN) methods to perform diffusion tensor imaging (DTI) under various preclinical and clinical settings. METHODS A formalism for analyzing SPEN DTI data is presented, tailored to account for the spatially dependent b-matrix weightings introduced by the sequence's use of swept pulses acting while in the presence of field gradients. Using these b-matrix calculations, SPEN's ability to deliver DTI measurements was tested on phantoms as well as ex vivo and in vivo. In the latter case, DTI involved scans on mice brains and on human lactating breasts. RESULTS For both ex vivo and in vivo investigations, SPEN data proved less sensitive to distortions arising from Bo field inhomogeneities and from eddy currents, than conventional single-shot alternatives. Further resolution enhancement could be achieved using referenceless methods for interleaved SPEN data acquisitions. CONCLUSION The robustness of SPEN-based sequences vis-à-vis field instabilities and heterogeneities, enables the implementation of DTI experiments with good sensitivity and resolution even in challenging environments in both preclinical and clinical settings. Magn Reson Med 77:1124-1133, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Eddy Solomon
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Gilad Liberman
- 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
| | - Lucio Frydman
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
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22
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Hansen B, Lund TE, Sangill R, Stubbe E, Finsterbusch J, Jespersen SN. Experimental considerations for fast kurtosis imaging. Magn Reson Med 2015; 76:1455-1468. [PMID: 26608731 DOI: 10.1002/mrm.26055] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 10/22/2015] [Accepted: 10/24/2015] [Indexed: 12/18/2022]
Abstract
PURPOSE The clinical use of kurtosis imaging is impeded by long acquisitions and postprocessing. Recently, estimation of mean kurtosis tensor W¯ and mean diffusivity ( D¯) was made possible from 13 distinct diffusion weighted MRI acquisitions (the 1-3-9 protocol) with simple postprocessing. Here, we analyze the effects of noise and nonideal diffusion encoding, and propose a new correction strategy. We also present a 1-9-9 protocol with increased robustness to experimental imperfections and minimal additional scan time. This refinement does not affect computation time and also provides a fast estimate of fractional anisotropy (FA). THEORY AND METHODS 1-3-9/1-9-9 data are acquired in rat and human brains, and estimates of D¯, FA, W¯ from human brains are compared with traditional estimates from an extensive diffusion kurtosis imaging data set. Simulations are used to evaluate the influence of noise and diffusion encodings deviating from the scheme, and the performance of the correction strategy. Optimal b-values are determined from simulations and data. RESULTS Accuracy and precision in D¯ and W¯ are comparable to nonlinear least squares estimation, and is improved with the 1-9-9 protocol. The compensation strategy vastly improves parameter estimation in nonideal data. CONCLUSION The framework offers a robust and compact method for estimating several diffusion metrics. The protocol is easily implemented. Magn Reson Med 76:1455-1468, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Affiliation(s)
- Brian Hansen
- Center of Functionally Integrative Neuroscience (CFIN) and MINDLab, Clinical Institute, Aarhus University, Aarhus, Denmark
| | - Torben E Lund
- Center of Functionally Integrative Neuroscience (CFIN) and MINDLab, Clinical Institute, Aarhus University, Aarhus, Denmark
| | - Ryan Sangill
- Center of Functionally Integrative Neuroscience (CFIN) and MINDLab, Clinical Institute, Aarhus University, Aarhus, Denmark
| | - Ebbe Stubbe
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | - Jürgen Finsterbusch
- Institut für Systemische Neurowissenschaften, Universitätsklinikum Hamburg-Eppendorf, Germany
| | - Sune Nørhøj Jespersen
- Center of Functionally Integrative Neuroscience (CFIN) and MINDLab, Clinical Institute, Aarhus University, Aarhus, Denmark. .,Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark.
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23
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Schmidt R, Mishkovsky M, Hyacinthe JN, Kunz N, Gruetter R, Comment A, Frydman L. Correcting surface coil excitation inhomogeneities in single-shot SPEN MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 259:199-206. [PMID: 26363583 PMCID: PMC5035682 DOI: 10.1016/j.jmr.2015.08.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 08/25/2015] [Accepted: 08/26/2015] [Indexed: 05/08/2023]
Abstract
Given their high sensitivity and ability to limit the field of view (FOV), surface coils are often used in magnetic resonance spectroscopy (MRS) and imaging (MRI). A major downside of surface coils is their inherent radiofrequency (RF) B1 heterogeneity across the FOV, decreasing with increasing distance from the coil and giving rise to image distortions due to non-uniform spatial responses. A robust way to compensate for B1 inhomogeneities is to employ adiabatic inversion pulses, yet these are not well adapted to all imaging sequences - including to single-shot approaches like echo planar imaging (EPI). Hybrid spatiotemporal encoding (SPEN) sequences relying on frequency-swept pulses provide another ultrafast MRI alternative, that could help solve this problem thanks to their built-in heterogeneous spatial manipulations. This study explores how this intrinsic SPEN-based spatial discrimination, could be used to compensate for the B1 inhomogeneities inherent to surface coils. Experiments carried out in both phantoms and in vivo rat brains demonstrate that, by suitably modulating the amplitude of a SPEN chirp pulse that progressively excites the spins in a direction normal to the coil, it is possible to compensate for the RF transmit inhomogeneities and thus improve sensitivity and image fidelity.
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Affiliation(s)
- Rita Schmidt
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Mor Mishkovsky
- Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Jean-Noel Hyacinthe
- School of health, University of Applied Sciences and Arts Western Switzerland, Geneva, Switzerland
| | - Nicolas Kunz
- Center of Biomedical Imaging (CIBM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Rolf Gruetter
- Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Center of Biomedical Imaging (CIBM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Arnaud Comment
- Institute of the Physics of Biological Systems, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Lucio Frydman
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
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24
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Lin G. An effective phase shift diffusion equation method for analysis of PFG normal and fractional diffusions. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 259:232-240. [PMID: 26384777 DOI: 10.1016/j.jmr.2015.08.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 08/23/2015] [Accepted: 08/26/2015] [Indexed: 06/05/2023]
Abstract
Pulsed field gradient (PFG) diffusion measurement has a lot of applications in NMR and MRI. Its analysis relies on the ability to obtain the signal attenuation expressions, which can be obtained by averaging over the accumulating phase shift distribution (APSD). However, current theoretical models are not robust or require approximations to get the APSD. Here, a new formalism, an effective phase shift diffusion (EPSD) equation method is presented to calculate the APSD directly. This is based on the idea that the gradient pulse effect on the change of the APSD can be viewed as a diffusion process in the virtual phase space (VPS). The EPSD has a diffusion coefficient, K(β)(t)D rad(β)/s(α), where α is time derivative order and β is a space derivative order, respectively. The EPSD equations of VPS are built based on the diffusion equations of real space by replacing the diffusion coefficients and the coordinate system (from real space coordinate to virtual phase coordinate). Two different models, the fractal derivative model and the fractional derivative model from the literature were used to build the EPSD fractional diffusion equations. The APSD obtained from solving these EPSD equations were used to calculate the PFG signal attenuation. From the fractal derivative model the attenuation is exp(-γ(β)g(β)δ(β)Df1t(α)), a stretched exponential function (SEF) attenuation, while from the fractional derivative model the attenuation is Eα,1(-γ(β)g(β)δ(β)Df2t(α)), a Mittag-Leffler function (MLF) attenuation. The MLF attenuation can be reduced to SEF attenuation when α=1, and can be approximated as a SEF attenuation when the attenuation is small. Additionally, the effect of finite gradient pulse widths (FGPW) is calculated. From the fractal derivative model, the signal attenuation including FGPW effect is exp[ -Df1∫0(τ) K(β)(t)dt(α)]. The results obtained in this study are in good agreement with the results in literature. Several expressions that describe signal attenuation have not been reported and that can be of great importance for the PFG experiments. This EPSD equation method provides a new, simple path to calculate signal attenuation of PFG NMR experiments.
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Affiliation(s)
- Guoxing Lin
- Carlson School of Chemistry and Biochemistry, Clark University, Worcester, MA 01610, United States.
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Schmidt R, Seginer A, Frydman L. Interleaved multishot imaging by spatiotemporal encoding: A fast, self-referenced method for high-definition diffusion and functional MRI. Magn Reson Med 2015; 75:1935-48. [DOI: 10.1002/mrm.25742] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 03/31/2015] [Accepted: 03/31/2015] [Indexed: 12/29/2022]
Affiliation(s)
- Rita Schmidt
- Chemical Physics Department; Weizmann Institute of Science; Rehovot Israel
| | - Amir Seginer
- Chemical Physics Department; Weizmann Institute of Science; Rehovot Israel
| | - Lucio Frydman
- Chemical Physics Department; Weizmann Institute of Science; Rehovot Israel
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26
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Solomon E, Nissan N, Schmidt R, Furman-Haran E, Ben-Aharon U, Frydman L. Removing silicone artifacts in diffusion-weighted breast MRI by means of shift-resolved spatiotemporally encoding. Magn Reson Med 2015; 75:2064-2071. [PMID: 26096754 DOI: 10.1002/mrm.25757] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 03/29/2015] [Accepted: 04/09/2015] [Indexed: 11/10/2022]
Abstract
PURPOSE Evaluate the usefulness of diffusion-weighted spatiotemporally encoded (SPEN) methods to obtain apparent diffusion coefficient (ADC) maps of fibroglandular human breast tissue, in the presence of silicone implants. METHODS Seven healthy volunteers with breast augmentation were scanned at 3 Tesla (T) using customized SPEN sequences yielding separate silicone and water (1) H images in one scan, together with their corresponding diffusion-weightings. RESULTS SPEN's ability to deliver multiple spectrally resolved images in a single scan, coupled to the method's substantial robustness to magnetic field heterogeneities, served to acquire ADC maps that could be freed from contributions that did not belong to fibroglandular tissue. CONCLUSION SPEN-based sequences incorporating spectral discrimination and diffusion-weighting enable the acquisition of reliable ADC maps despite the presence of dominant signals from silicone implants, thereby opening new screening possibilities for the identification of malignancies in breast augmented patients.
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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
| | - Rita Schmidt
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Edna Furman-Haran
- Unit of Biological Services, Weizmann Institute of Science, Rehovot, Israel
| | | | - Lucio Frydman
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
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Chen Y, Chen S, Zhong J, Chen Z. Reference-free unwarping of single-shot spatiotemporally encoded MRI using asymmetric self-refocused echoes acquisition. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 254:1-9. [PMID: 25768263 DOI: 10.1016/j.jmr.2015.02.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2014] [Revised: 02/05/2015] [Accepted: 02/09/2015] [Indexed: 06/04/2023]
Abstract
This paper presents a phase evolution rewinding algorithm for correcting the geometric and intensity distortions in single-shot spatiotemporally encoded (SPEN) MRI with acquisition of asymmetric self-refocused echo trains. Using the field map calculated from the phase distribution of the source image, the off-resonance induced phase errors are successfully rewound through deconvolution. The alias-free partial Fourier transform reconstruction helps improve the signal-to-noise ratio of the field maps and the output images. The effectiveness of the proposed algorithm was validated through 7 T MRI experiments on a lemon, a water phantom, and in vivo rat head. SPEN imaging was evaluated using rapid acquisition by sequential excitation and refocusing (RASER) which produces uniform T2 weighting. The results indicate that the new technique can more robustly deal with the cases in which the images obtained with conventional single-shot spin-echo EPI are difficult to be restored due to serious field variations.
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Affiliation(s)
- Ying Chen
- Department of Electronic Science, Fijian Provincial Key Laboratory of Plasma and Magnetic Resonance, State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen, China; Center for Brain Imaging Science and Technology, Zhejiang University, Hangzhou, China
| | - Song Chen
- Center for Brain Imaging Science and Technology, Zhejiang University, Hangzhou, China
| | - Jianhui Zhong
- Center for Brain Imaging Science and Technology, Zhejiang University, Hangzhou, China.
| | - Zhong Chen
- Department of Electronic Science, Fijian Provincial Key Laboratory of Plasma and Magnetic Resonance, State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen, China.
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Viallon M, Cuvinciuc V, Delattre B, Merlini L, Barnaure-Nachbar I, Toso-Patel S, Becker M, Lovblad KO, Haller S. State-of-the-art MRI techniques in neuroradiology: principles, pitfalls, and clinical applications. Neuroradiology 2015; 57:441-67. [PMID: 25859832 DOI: 10.1007/s00234-015-1500-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 02/04/2015] [Indexed: 12/20/2022]
Abstract
This article reviews the most relevant state-of-the-art magnetic resonance (MR) techniques, which are clinically available to investigate brain diseases. MR acquisition techniques addressed include notably diffusion imaging (diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), and diffusion kurtosis imaging (DKI)) as well as perfusion imaging (dynamic susceptibility contrast (DSC), arterial spin labeling (ASL), and dynamic contrast enhanced (DCE)). The underlying models used to process these images are described, as well as the theoretic underpinnings of quantitative diffusion and perfusion MR imaging-based methods. The technical requirements and how they may help to understand, classify, or follow-up neurological pathologies are briefly summarized. Techniques, principles, advantages but also intrinsic limitations, typical artifacts, and alternative solutions developed to overcome them are discussed. In this article, we also review routinely available three-dimensional (3D) techniques in neuro MRI, including state-of-the-art and emerging angiography sequences, and briefly introduce more recently proposed 3D quantitative neuro-anatomy sequences, and new technology, such as multi-slice and multi-transmit imaging.
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Affiliation(s)
- Magalie Viallon
- CREATIS, UMR CNRS 5220 - INSERM U1044, INSA de Lyon, Université de Lyon, Lyon, France,
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Li J, Zhang M, Chen L, Cai C, Sun H, Cai S. Reduced field-of-view imaging for single-shot MRI with an amplitude-modulated chirp pulse excitation and Fourier transform reconstruction. Magn Reson Imaging 2015; 33:503-15. [PMID: 25721996 DOI: 10.1016/j.mri.2015.02.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 01/21/2015] [Accepted: 02/16/2015] [Indexed: 11/18/2022]
Abstract
PURPOSE We employ an amplitude-modulated chirp pulse to selectively excite spins in one or more regions of interest (ROIs) to realize reduced field-of-view (rFOV) imaging based on single-shot spatiotemporally encoded (SPEN) sequence and Fourier transform reconstruction. MATERIALS AND METHODS The proposed rFOV imaging method was theoretically analyzed and illustrated with numerical simulation and tested with phantom experiments and in vivo rat experiments. In addition, point spread function was applied to demonstrate the feasibility of the proposed method. To evaluate the proposed method, the rFOV results were compared with those obtained using the EPI method with orthogonal RF excitation. RESULTS The simulation and experimental results show that the proposed method can image one or two separated ROIs along the SPEN dimension in a single shot with higher spatial resolution, less sensitive to field inhomogeneity, and practically no aliasing artifacts. In addition, the proposed method may produce rFOV images with comparable signal-to-noise ratio to the rFOV EPI images. CONCLUSION The proposed method is promising for the applications under severe susceptibility heterogeneities and for imaging separate ROIs simultaneously.
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Affiliation(s)
- Jing Li
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Miao Zhang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Lin Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Congbo Cai
- Department of Communication Engineering, Xiamen University, Xiamen, China.
| | - Huijun Sun
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China.
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Li J, Chen L, Cai S, Cai C, Zhong J, Chen Z. Imaging with referenceless distortion correction and flexible regions of interest using single-shot biaxial spatiotemporally encoded MRI. Neuroimage 2015; 105:93-111. [DOI: 10.1016/j.neuroimage.2014.10.041] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 09/28/2014] [Accepted: 10/14/2014] [Indexed: 11/24/2022] Open
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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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Major mouse placental compartments revealed by diffusion-weighted MRI, contrast-enhanced MRI, and fluorescence imaging. Proc Natl Acad Sci U S A 2014; 111:10353-8. [PMID: 24969421 DOI: 10.1073/pnas.1401695111] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mammalian models, and mouse studies in particular, play a central role in our understanding of placental development. Magnetic resonance imaging (MRI) could be a valuable tool to further these studies, providing both structural and functional information. As fluid dynamics throughout the placenta are driven by a variety of flow and diffusion processes, diffusion-weighted MRI could enhance our understanding of the exchange properties of maternal and fetal blood pools--and thereby of placental function. These studies, however, have so far been hindered by the small sizes, the unavoidable motions, and the challenging air/water/fat heterogeneities, associated with mouse placental environments. The present study demonstrates that emerging methods based on the spatiotemporal encoding (SPEN) of the MRI information can robustly overcome these obstacles. Using SPEN MRI in combination with albumin-based contrast agents, we analyzed the diffusion behavior of developing placentas in a cohort of mice. These studies successfully discriminated the maternal from the fetal blood flows; the two orders of magnitude differences measured in these fluids' apparent diffusion coefficients suggest a nearly free diffusion behavior for the former and a strong flow-based component for the latter. An intermediate behavior was observed by these methods for a third compartment that, based on maternal albumin endocytosis, was associated with trophoblastic cells in the interphase labyrinth. Structural features associated with these dynamic measurements were consistent with independent intravital and ex vivo fluorescence microscopy studies and are discussed within the context of the anatomy of developing mouse placentas.
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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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