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Storey P, Novikov DS. Signatures of microstructure in gradient-echo and spin-echo signals. Magn Reson Med 2024; 92:269-288. [PMID: 38520259 DOI: 10.1002/mrm.30022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 01/06/2024] [Accepted: 01/08/2024] [Indexed: 03/25/2024]
Abstract
PURPOSE To determine whether the spatial scale and magnetic susceptibility of microstructure can be evaluated robustly from the decay of gradient-echo and spin-echo signals. THEORY AND METHODS Gradient-echo and spin-echo images were acquired from suspensions of spherical polystyrene microbeads of 10, 20, and 40 μm nominal diameter. The sizes of the beads and their magnetic susceptibility relative to the medium were estimated from the signal decay curves, using a lookup table generated from Monte Carlo simulations and an analytic model based on the Gaussian phase approximation. RESULTS Fitting Monte Carlo predictions to spin-echo data yielded acceptable estimates of microstructural parameters for the 20 and 40 μm microbeads. Using gradient-echo data, the Monte Carlo lookup table provided satisfactory parameter estimates for the 20 μm beads but unstable results for the diameter of the largest beads. Neither spin-echo nor gradient-echo data allowed accurate parameter estimation for the smallest beads. The analytic model performed poorly over all bead sizes. CONCLUSIONS Microstructural sources of magnetic susceptibility produce distinctive non-exponential signatures in the decay of gradient-echo and spin-echo signals. However, inverting the problem to extract microstructural parameters from the signals is nontrivial and, in certain regimes, ill-conditioned. For microstructure with small characteristic length scales, parameter estimation is hampered by the difficulty of acquiring accurate data at very short echo times. For microstructure with large characteristic lengths, the gradient-echo signal approaches the static-dephasing regime, where it becomes insensitive to size. Applicability of the analytic model was further limited by failure of the Gaussian phase approximation for all but the smallest beads.
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Affiliation(s)
- Pippa Storey
- Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA
| | - Dmitry S Novikov
- Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA
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Ishida M, Yerly J, Ito H, Takafuji M, Nakamori S, Takase S, Ichiba Y, Komori Y, Dohi K, Piccini D, Bastiaansen JA, Stuber M, Sakuma H. Optimal Protocol for Contrast-enhanced Free-running 5D Whole-heart Coronary MR Angiography at 3T. Magn Reson Med Sci 2024; 23:225-237. [PMID: 36682776 PMCID: PMC11024717 DOI: 10.2463/mrms.tn.2022-0086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 11/11/2022] [Indexed: 01/20/2023] Open
Abstract
Free-running 5D whole-heart coronary MR angiography (MRA) is gaining in popularity because it reduces scanning complexity by removing the need for specific slice orientations, respiratory gating, or cardiac triggering. At 3T, a gradient echo (GRE) sequence is preferred in combination with contrast injection. However, neither the injection scheme of the gadolinium (Gd) contrast medium, the choice of the RF excitation angle, nor the dedicated image reconstruction parameters have been established for 3T GRE free-running 5D whole-heart coronary MRA. In this study, a Gd injection scheme, RF excitation angles of lipid-insensitive binominal off-resonance RF excitation (LIBRE) pulse for valid fat suppression and continuous data acquisition, and compressed-sensing reconstruction regularization parameters were optimized for contrast-enhanced free-running 5D whole-heart coronary MRA using a GRE sequence at 3T. Using this optimized protocol, contrast-enhanced free-running 5D whole-heart coronary MRA using a GRE sequence is feasible with good image quality at 3T.
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Affiliation(s)
- Masaki Ishida
- Department of Radiology, Mie University Hospital, Tsu, Mie, Japan
| | - Jérôme Yerly
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
- Center for Biomedical Imaging (CIBM), Lausanne, Switzerland
| | - Haruno Ito
- Department of Radiology, Mie University Hospital, Tsu, Mie, Japan
| | | | - Shiro Nakamori
- Department of Cardiology, Mie University Hospital, Tsu, Mie, Japan
| | - Shinichi Takase
- Department of Radiology, Mie University Hospital, Tsu, Mie, Japan
| | | | | | - Kaoru Dohi
- Department of Cardiology, Mie University Hospital, Tsu, Mie, Japan
| | - Davide Piccini
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
- Center for Biomedical Imaging (CIBM), Lausanne, Switzerland
- Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland
| | - Jessica A.M. Bastiaansen
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
- Center for Biomedical Imaging (CIBM), Lausanne, Switzerland
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital Bern University Hospital, University of Bern, Bern, Switzerland
| | - Matthias Stuber
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
- Center for Biomedical Imaging (CIBM), Lausanne, Switzerland
| | - Hajime Sakuma
- Department of Radiology, Mie University Hospital, Tsu, Mie, Japan
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Buttiens A, Simko M, Van Goethem J. Vacuum Phenomenon in the Lumbar Spine: Pilot Study for Accuracy of Magnetic Resonance Imaging. J Belg Soc Radiol 2023; 107:83. [PMID: 37928056 PMCID: PMC10624138 DOI: 10.5334/jbsr.3118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 10/12/2023] [Indexed: 11/07/2023] Open
Abstract
Objectives Vacuum phenomenon (VP) is defined as air within a joint. Many pathologies are associated with VP, mainly degenerative disease and trauma. Although patients with intradiscal gas may be asymptomatic, it promotes disc degeneration and can eventually become painful. VP is suspected to be an indicator of segmental mobility, helping in determining the extent of spinal fusion in a preoperative setting. This could make the detection of VP useful on routine magnetic resonance imaging (MRI) of the lower spine. We determined the accuracy of MRI in detecting intradiscal gas through a retrospective observational study. Materials and methods The study population consists of 37 consecutive patients with low back pain who were scheduled for treatment with spinal infiltrations and received a computed tomography and MRI scan within a maximum time interval of 3 months. Spin echo (SE) T1 and T2 and gradient echo (GE) T1 sequences were analyzed. All scans were randomly coded and evaluated by two observers: an experienced neuroradiologist and a radiology resident for the presence of VP. Results GE-imaging revealed a high accuracy with a sensitivity of 89.3%-92% and a specificity of 89.7-95.3% between both observers. In comparison to a sensitivity of 31.5%-76.3% for T1- and 8.5%-86.4% for T2-imaging and a specificity of 95%-100% for T1- and 63.7%-100% for T2-imaging with respective accuracy of 68.1%-85.7% and 54.6%-68.9%. We notice a moderate interobserver variability for the T1 (κ = 0.462) weighted imaging, no agreement for T2 (κ = 0.057) weighted imaging, and almost perfect interobserver variability for the GE sequence (κ = 0.889). Conclusion The presence of VP in degenerative disc disease is a sign of segmental instability which is important for planning spinal fusion surgery. Our study showed that VP can be detected on MRI of the lumbar spine with high accuracy and almost perfect interobserver agreement by adding GE sequences to the scanning protocol.
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Clark R, Ferreira A, Behr S. Significance of intramedullary T2 * signal voids in the magnetic resonance imaging of paraplegic deep pain-negative dogs following intervertebral disc extrusion at short-term follow-up. Front Vet Sci 2023; 10:1248024. [PMID: 37781293 PMCID: PMC10533920 DOI: 10.3389/fvets.2023.1248024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 08/10/2023] [Indexed: 10/03/2023] Open
Abstract
Introduction Dogs presenting as paraplegic without nociception due to a thoracolumbar intervertebral disc extrusion provide a difficult decision to both the clinician and the owner. The prognosis when performing surgical decompression remains guarded. Aside from significant extradural compression, these dogs often have a significant secondary spinal cord injury, which has shown to be an important factor in determining both the likelihood of developing progressive myelomalacia and the return to ambulation. Materials and methods This is a retrospective, observational, single centre study including 82 dogs presenting as paraplegic with absent nociception diagnosed with an intervertebral disc extrusion. Patients underwent MRI of the thoracolumbar spine, including a gradient echo sequence which was evaluated for the presence of intramedullary signal void artefacts. Decompressive surgery was performed, and patients were evaluated for the presence of nociception at short term follow up (at least four weeks post-surgery). Results Overall, 59.8% of patients regained nociception within the study period. This number was significantly reduced to 33.3% when multiple gradient echo signal voids were present (compared to 67.3% of dogs without signal voids). There was no significant difference in the rate of developing progressive myelomalacia between groups. Conclusions This paper adds to the existing literature and suggests that the gradient echo sequence may be of use when assessing acute spinal cord injury in the context of intervertebral disc extrusion and how it relates to prognosis.
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Affiliation(s)
- Robert Clark
- Neurology and Neurosurgery, Willows Veterinary Centre and Referral Service, Part of Linnaeus Veterinary Limited, Solihull, United Kingdom
| | - Amy Ferreira
- Diagnostic Imaging, Willows Veterinary Centre and Referral Service, Solihull, United Kingdom
| | - Sebastien Behr
- Neurology and Neurosurgery, Willows Veterinary Centre and Referral Service, Part of Linnaeus Veterinary Limited, Solihull, United Kingdom
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Muacevic A, Adler JR, Bandari R, Kumar M, Kumar P. Long-Segment Epidural Hemorrhage of the Cervical and Dorsal Spine: A Case Report of a Rare Complication of Dengue Virus Disease. Cureus 2023; 15:e33435. [PMID: 36751224 PMCID: PMC9897698 DOI: 10.7759/cureus.33435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2023] [Indexed: 01/09/2023] Open
Abstract
Dengue hemorrhagic fever is a severe form of dengue virus disease, characterized by minor to major bleeding, thrombocytopenia, and plasma leakage. Common hemorrhagic manifestations include epistaxis, gum bleeding, gastrointestinal bleeding, hypermenorrhea, and hematuria. Intracranial hemorrhage is one of the most fatal manifestations of central nervous system involvement by dengue disease which is a part of the expanded dengue syndrome. Here we present a case of A 37-year-old male patient who presented with complaints of intermittent high-grade fever and generalized weakness four days prior to consultation. Laboratory investigations revealed mild thrombocytopenia and positive dengue serology. Magnetic resonance imaging of the brain and spine revealed mild diffuse subarachnoid hemorrhage in bilateral parieto-occipital lobes with long segment cervical and dorsal spinal epidural hemorrhage.
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Soldati E, Vicente J, Guenoun D, Bendahan D, Pithioux M. Validation and Optimization of Proximal Femurs Microstructure Analysis Using High Field and Ultra-High Field MRI. Diagnostics (Basel) 2021; 11:1603. [PMID: 34573945 PMCID: PMC8466948 DOI: 10.3390/diagnostics11091603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 08/25/2021] [Accepted: 08/31/2021] [Indexed: 11/18/2022] Open
Abstract
Trabecular bone could be assessed non-invasively using MRI. However, MRI does not yet provide resolutions lower than trabecular thickness and a comparative analysis between different MRI sequences at different field strengths and X-ray microtomography (μCT) is still missing. In this study, we compared bone microstructure parameters and bone mineral density (BMD) computed using various MRI approaches, i.e., turbo spin echo (TSE) and gradient recalled echo (GRE) images used at different magnetic fields, i.e., 7T and 3T. The corresponding parameters computed from μCT images and BMD derived from dual-energy X-ray absorptiometry (DXA) were used as the ground truth. The correlation between morphological parameters, BMD and fracture load assessed by mechanical compression tests was evaluated. Histomorphometric parameters showed a good agreement between 7T TSE and μCT, with 8% error for trabecular thickness with no significative statistical difference and a good intraclass correlation coefficient (ICC > 0.5) for all the extrapolated parameters. No correlation was found between DXA-BMD and all morphological parameters, except for trabecular interconnectivity (R2 > 0.69). Good correlation (p-value < 0.05) was found between failure load and trabecular interconnectivity (R2 > 0.79). These results suggest that MRI could be of interest for bone microstructure assessment. Moreover, the combination of morphological parameters and BMD could provide a more comprehensive view of bone quality.
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Affiliation(s)
- Enrico Soldati
- Aix Marseille Univ, CNRS, IUSTI, 13453 Marseille, France;
- Aix Marseille Univ, CNRS, CRMBM, 13385 Marseille, France;
- Aix Marseille Univ, CNRS, ISM, 13288 Marseille, France; (D.G.); (M.P.)
| | - Jerome Vicente
- Aix Marseille Univ, CNRS, IUSTI, 13453 Marseille, France;
| | - Daphne Guenoun
- Aix Marseille Univ, CNRS, ISM, 13288 Marseille, France; (D.G.); (M.P.)
- Department of Radiology, Institute for Locomotion, Sainte-Marguerite Hospital, Aix Marseille Univ, APHM, CNRS, ISM, 13274 Marseille, France
| | - David Bendahan
- Aix Marseille Univ, CNRS, CRMBM, 13385 Marseille, France;
| | - Martine Pithioux
- Aix Marseille Univ, CNRS, ISM, 13288 Marseille, France; (D.G.); (M.P.)
- Department of Orthopaedics and Traumatology, Institute for Locomotion, Sainte-Marguerite Hospital, Aix Marseille Univ, APHM, CNRS, ISM, 13274 Marseille, France
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Liu Y, Ye Q, Zeng F, Jiang X, Cai B, Lv W, Wen J. Library-driven approach for fast implementation of the voxel spread function to correct magnetic field inhomogeneity artifacts for gradient-echo sequences. Med Phys 2021; 48:3714-3720. [PMID: 33914914 DOI: 10.1002/mp.14904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 03/15/2021] [Accepted: 04/12/2021] [Indexed: 11/10/2022] Open
Abstract
PURPOSE Previously developed Voxel Spread Function (VSF) method (Yablonskiy, et al, MRM, 2013;70:1283) provides solution to correct artifacts induced by macroscopic magnetic field inhomogeneity in the images obtained by multi-Gradient-Recalled-Echo (mGRE) techniques. The goal of this study was to develop a library-driven approach for fast VSF implementation. METHODS The VSF approach describes the contribution of the magnetic field inhomogeneity effects on the mGRE signal decay in terms of the F-function calculated from mGRE phase and magnitude images. A pre-calculated library accounting for a variety of background field gradients caused by magnetic field inhomogeneity was used herein to speed up the calculation of F-function. Quantitative R2* maps from the mGRE data collected from two healthy volunteers were generated using the library as validation. RESULTS As compared with direct calculation of the F-function based on a voxel-wise approach, the new library-driven method substantially reduces computational time from several hours to few minutes, while, at the same time, providing similar accuracy of R2* mapping. CONCLUSION The new procedure proposed in this study provides a fast post-processing algorithm that can be incorporated in the quantitative analysis of mGRE data to account for background field inhomogeneity artifacts, thus can facilitate the applications of mGRE-based quantitative techniques in clinical practices.
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Affiliation(s)
- Ying Liu
- Department of Radiology, The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Qiong Ye
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, China
| | - Feiyan Zeng
- Department of Radiology, The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Xiaohua Jiang
- The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Bin Cai
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, MO, USA
| | - Weifu Lv
- Department of Radiology, The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Jie Wen
- Department of Radiology, The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
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Walter WR, Alizai H, Bruno M, Portugal S, Burke CJ. Real-time dynamic 3-T MRI assessment of spine kinematics: a feasibility study utilizing three different fast pulse sequences. Acta Radiol 2021; 62:58-66. [PMID: 32233646 DOI: 10.1177/0284185120913000] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Half-Fourier acquisition single-shot turbo spin-echo (HASTE), continuous radial gradient-echo (GRE), and True FISP allow real-time dynamic assessment of the spine. PURPOSE To evaluate the feasibility of adding dynamic sequences to routine spine magnetic resonance imaging (MRI) for assessment of spondylolisthesis. MATERIAL AND METHODS Retrospective review was performed of patients referred for dynamic MRI of the cervical or lumbar spine between January 2017 and 2018 who had flexion-extension radiographs within two months of MRI. Exclusion criteria were: incomplete imaging; spinal hardware; and inability to tolerate dynamic examination. Blinded, independent review by two board-certified musculoskeletal radiologists was performed to assess for spondylolisthesis (>3 mm translation); consensus review of dynamic radiographs served as the gold standard. Cervical spinal cord effacement was assessed. Inter-reader agreement and radiographic concordance was calculated for each sequence. RESULTS Twenty-one patients were included (8 men, 13 women; mean age 47.9 ± 16.5 years). Five had MRI of the cervical spine and 16 had MRI of the lumbar spine. Mean acquisition time was 18.4 ± 1.7 min with dynamic sequences in the range of 58-77 s. HASTE and True FISP had the highest inter-reader reproducibility (κ = 0.88). Reproducibility was better for the lumbar spine (κ = 0.94) than the cervical spine (κ = 0.28). Sensitivity of sequences for spondylolisthesis was in the range of 68.8%-78.6%. All three sequences had high accuracy levels: ≥90.5% averaged across the cervical and lumbar spine. Cervical cord effacement was observed during dynamic MRI in two cases (100% agreement). CONCLUSION Real-time dynamic MRI sequences added to spine MRI protocols provide reliable and accurate assessment of cervical and lumbar spine spondylolisthesis during flexion and extension.
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Affiliation(s)
| | - Hamza Alizai
- Texas Scottish Rite Hospital for Children, Dallas, TX, USA
| | - Mary Bruno
- Department of Radiology, NYU Langone Health, New York, NY, USA
| | - Salvador Portugal
- Department of Rehabilitation Medicine, NYU Langone Health, New York, NY, USA
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Zhang Y, Guan Y, Liang Q, Yang G, Chen J. Application of three-dimensional fast gradient echo sequence in observation of craniocervical junctional ligament. Zhong Nan Da Xue Xue Bao Yi Xue Ban 2020; 45:1199-1203. [PMID: 33268581 DOI: 10.11817/j.issn.1672-7347.2020.190271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVES To explore the value of three-dimensional fast gradient echo sequence (3D-GRE) in observation of the craniocervical junctional ligament. METHODS A total of 21 healthy volunteers underwent 3D-GRE imaging. The imaging data was imported into the post-processing workstation. The structures of the ligaments in the craniocervical junctional area were observed and evaluated by multiplanar reconstruction technique. RESULTS The features of ligaments in the craniocervical junction were shown clearly for all the 21 cases of volunteers. The scan time was 267-294 s. After the treatment with the three-dimensional reconstruction technique, the signal characteristics and the running structure of the transverse ligament, the alar ligament, the serrated ligament and the lamina could be effectively displayed. CONCLUSIONS The 3D-GRE can evaluate the three-dimensional data of craniocervical junctional ligament in a short period of time. Post-processing reconstruction technique can clearly evaluate the structure characteristics of each ligament, which can lay a foundation for further application in craniocerebral trauma patients.
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Affiliation(s)
- Ying Zhang
- Department of Radiology, Haikou Hospital Affiliated to Xiangya School of Medicine, Central South University, Haikou 570208.
| | - Ying Guan
- Department of Ultrasound, First Affiliated Hospital of Hainan Medical College, Haikou 570201, China
| | - Qizhou Liang
- Department of Radiology, Haikou Hospital Affiliated to Xiangya School of Medicine, Central South University, Haikou 570208
| | - Guang Yang
- Department of Radiology, Haikou Hospital Affiliated to Xiangya School of Medicine, Central South University, Haikou 570208
| | - Jianqiang Chen
- Department of Radiology, Haikou Hospital Affiliated to Xiangya School of Medicine, Central South University, Haikou 570208.
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Florkow MC, Zijlstra F, Willemsen K, Maspero M, van den Berg CAT, Kerkmeijer LGW, Castelein RM, Weinans H, Viergever MA, van Stralen M, Seevinck PR. Deep learning-based MR-to-CT synthesis: The influence of varying gradient echo-based MR images as input channels. Magn Reson Med 2020; 83:1429-1441. [PMID: 31593328 PMCID: PMC6972695 DOI: 10.1002/mrm.28008] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 08/30/2019] [Accepted: 08/31/2019] [Indexed: 01/15/2023]
Abstract
PURPOSE To study the influence of gradient echo-based contrasts as input channels to a 3D patch-based neural network trained for synthetic CT (sCT) generation in canine and human populations. METHODS Magnetic resonance images and CT scans of human and canine pelvic regions were acquired and paired using nonrigid registration. Magnitude MR images and Dixon reconstructed water, fat, in-phase and opposed-phase images were obtained from a single T1 -weighted multi-echo gradient-echo acquisition. From this set, 6 input configurations were defined, each containing 1 to 4 MR images regarded as input channels. For each configuration, a UNet-derived deep learning model was trained for synthetic CT generation. Reconstructed Hounsfield unit maps were evaluated with peak SNR, mean absolute error, and mean error. Dice similarity coefficient and surface distance maps assessed the geometric fidelity of bones. Repeatability was estimated by replicating the training up to 10 times. RESULTS Seventeen canines and 23 human subjects were included in the study. Performance and repeatability of single-channel models were dependent on the TE-related water-fat interference with variations of up to 17% in mean absolute error, and variations of up to 28% specifically in bones. Repeatability, Dice similarity coefficient, and mean absolute error were statistically significantly better in multichannel models with mean absolute error ranging from 33 to 40 Hounsfield units in humans and from 35 to 47 Hounsfield units in canines. CONCLUSION Significant differences in performance and robustness of deep learning models for synthetic CT generation were observed depending on the input. In-phase images outperformed opposed-phase images, and Dixon reconstructed multichannel inputs outperformed single-channel inputs.
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Affiliation(s)
- Mateusz C. Florkow
- Image Sciences InstituteUniversity Medical Center UtrechtUtrechtNetherlands
| | - Frank Zijlstra
- Image Sciences InstituteUniversity Medical Center UtrechtUtrechtNetherlands
| | - Koen Willemsen
- Department of OrthopedicsUniversity Medical Center UtrechtUtrechtNetherlands
| | - Matteo Maspero
- Department of RadiotherapyDivision of Imaging & OncologyUniversity Medical Center UtrechtUtrechtNetherlands
- Computational Imaging Group for MR diagnostics & TherapyCenter for Image SciencesUniversity Medical Center UtrechtUtrechtNetherlands
| | - Cornelis A. T. van den Berg
- Department of RadiotherapyDivision of Imaging & OncologyUniversity Medical Center UtrechtUtrechtNetherlands
- Computational Imaging Group for MR diagnostics & TherapyCenter for Image SciencesUniversity Medical Center UtrechtUtrechtNetherlands
| | - Linda G. W. Kerkmeijer
- Department of RadiotherapyDivision of Imaging & OncologyUniversity Medical Center UtrechtUtrechtNetherlands
| | - René M. Castelein
- Department of OrthopedicsUniversity Medical Center UtrechtUtrechtNetherlands
| | - Harrie Weinans
- Department of OrthopedicsUniversity Medical Center UtrechtUtrechtNetherlands
| | - Max A. Viergever
- Image Sciences InstituteUniversity Medical Center UtrechtUtrechtNetherlands
| | - Marijn van Stralen
- Image Sciences InstituteUniversity Medical Center UtrechtUtrechtNetherlands
- MRIguidance B.VUtrechtNetherlands
| | - Peter R. Seevinck
- Image Sciences InstituteUniversity Medical Center UtrechtUtrechtNetherlands
- MRIguidance B.VUtrechtNetherlands
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Kagerer SM, van Bergen JMG, Li X, Quevenco FC, Gietl AF, Studer S, Treyer V, Meyer R, Kaufmann PA, Nitsch RM, van Zijl PCM, Hock C, Unschuld PG. APOE4 moderates effects of cortical iron on synchronized default mode network activity in cognitively healthy old-aged adults. Alzheimers Dement (Amst) 2020; 12:e12002. [PMID: 32211498 PMCID: PMC7085281 DOI: 10.1002/dad2.12002] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Revised: 10/21/2019] [Accepted: 11/01/2019] [Indexed: 12/18/2022]
Abstract
INTRODUCTION Apolipoprotein E ε4 (APOE4)-related genetic risk for sporadic Alzheimer's disease is associated with an early impairment of cognitive brain networks. The current study determines relationships between APOE4 carrier status, cortical iron, and cortical network-functionality. METHODS Sixty-nine cognitively healthy old-aged individuals (mean age [SD] 66.1 [± 7.2] years; Mini-Mental State Exam [MMSE] 29.3 ± 1.1) were genotyped for APOE4 carrier-status and received 3 Tesla magnetic resonance imaging (MRI) for blood oxygen level-dependent functional magnetic resonance imaging (MRI) at rest, three-dimensional (3D)-gradient echo (six echoes) for cortical gray-matter, non-heme iron by quantitative susceptibility mapping, and 18F-flutemetamol positron emission tomography for amyloid-β. RESULTS A spatial pattern consistent with the default mode network (DMN) could be identified by independent component analysis. DMN activity was enhanced in APOE4 carriers and related to cortical iron burden. APOE4 and cortical iron synergistically interacted with DMN activity. Secondary analysis revealed a positive, APOE4 associated, relationship between cortical iron and DMN connectivity. DISCUSSION Our findings suggest that APOE4 moderates effects of iron on brain functionality prior to manifestation of cognitive impairment.
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Affiliation(s)
- Sonja M. Kagerer
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- Department of Psychogeriatric MedicinePsychiatric University Hospital Zurich (PUK)ZurichSwitzerland
| | | | - Xu Li
- The Russell H. Morgan Department of Radiology and Radiological ScienceDivision of MR ResearchThe Johns Hopkins University School of MedicineBaltimoreMarylandUSA
- F.M. Kirby Research Center for Functional Brain ImagingKennedy Krieger InstituteBaltimoreMarylandUSA
| | | | - Anton F. Gietl
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- Department of Psychogeriatric MedicinePsychiatric University Hospital Zurich (PUK)ZurichSwitzerland
| | - Sandro Studer
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
| | - Valerie Treyer
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- Department of Nuclear MedicineUniversity Hospital Zurich and University of ZurichZurichSwitzerland
| | - Rafael Meyer
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- Department of Psychogeriatric MedicinePsychiatric University Hospital Zurich (PUK)ZurichSwitzerland
| | - Philipp A. Kaufmann
- Department of Nuclear MedicineUniversity Hospital Zurich and University of ZurichZurichSwitzerland
| | - Roger M. Nitsch
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- Neuroscience Center ZurichUniversity of Zurich and ETH ZurichZurichSwitzerland
- NeurimmuneSchlierenSwitzerland
| | - Peter C. M. van Zijl
- The Russell H. Morgan Department of Radiology and Radiological ScienceDivision of MR ResearchThe Johns Hopkins University School of MedicineBaltimoreMarylandUSA
- F.M. Kirby Research Center for Functional Brain ImagingKennedy Krieger InstituteBaltimoreMarylandUSA
| | - Christoph Hock
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- Neuroscience Center ZurichUniversity of Zurich and ETH ZurichZurichSwitzerland
- NeurimmuneSchlierenSwitzerland
| | - Paul G. Unschuld
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- Department of Psychogeriatric MedicinePsychiatric University Hospital Zurich (PUK)ZurichSwitzerland
- Neuroscience Center ZurichUniversity of Zurich and ETH ZurichZurichSwitzerland
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12
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Wang X, Hernando D, Reeder SB. Phase-based T 2 mapping with gradient echo imaging. Magn Reson Med 2019; 84:609-619. [PMID: 31872470 DOI: 10.1002/mrm.28138] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 10/31/2019] [Accepted: 11/27/2019] [Indexed: 12/12/2022]
Abstract
PURPOSE Transverse relaxation time (T2 ) mapping with MRI has a plethora of clinical and research applications. Current T2 mapping techniques are based primarily on spin-echo (SE) relaxometry strategies that rely on the signal magnitude, and often suffer from lengthy acquisition times. In this work, we propose a phase-based T2 mapping technique where T2 information is encoded into the signal phase of rapid gradient echo (GRE) acquisitions. THEORY Bloch equation simulations demonstrate that the phase of GRE acquisitions obtained with a very small inter-repetition RF phase increment has a strong monotonic dependence on T2 , resulting from coherent transverse magnetization. This T2 -dependent phase behavior forms the basis of the proposed T2 mapping technique. To isolate T2 -dependent phase from background phase, at least 2 data sets with different RF phase increments are acquired. The proposed method can also be combined with chemical shift encoded MRI to separate water and fat signals. METHODS The feasibility of the proposed technique was validated in a phantom experiment. In vivo feasibility was demonstrated in the brain, knee, abdomen, and pelvis. Comparisons were made with SE-based T2 mapping, spectroscopy, and T2 values from the literature. RESULTS The proposed method produced accurate T2 maps compared with SE-based T2 mapping in the phantom. Good qualitative agreement was observed in vivo between the proposed method and the reference. T2 measured in various anatomies agreed well with values reported in the literature. CONCLUSION A phase-based T2 mapping technique was developed and its feasibility demonstrated in phantoms and in vivo.
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Affiliation(s)
- Xiaoke Wang
- Department of Radiology, University of Wisconsin, Madison, Wisconsin.,Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin
| | - Diego Hernando
- Department of Radiology, University of Wisconsin, Madison, Wisconsin.,Department of Medical Physics, University of Wisconsin, Madison, Wisconsin
| | - Scott B Reeder
- Department of Radiology, University of Wisconsin, Madison, Wisconsin.,Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin.,Department of Medical Physics, University of Wisconsin, Madison, Wisconsin.,Department of Medicine, University of Wisconsin, Madison, Wisconsin.,Department of Emergency Medicine, University of Wisconsin, Madison, Wisconsin
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13
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Abstract
STUDY DESIGN An in vitro magnetic resonance imaging (MRI) study. OBJECTIVE Investigate the potential of high-field MRI for producing higher quality images of the intervertebral disc (IVD) to better distinguish structural details. SUMMARY OF BACKGROUND DATA Higher spatial and contrast resolution are important advantages when imaging the complex tissue structures in the spine such as the IVDs. However, at present it is challenging to capture the substructural details in the IVD such as the lamellae. METHODS Three MRI sequences; two-dimensional proton-density-weighted Turbo-Spin-Echo (PD-TSE), 2D T2-weighted Turbo-Spin-Echo (T2W-TSE) with fat-saturation (FS), and 3D Spoiled-Gradient-Echo (3D-GE), were modified based on the image quality and scan duration. IVDs of three intact cadaveric lumbar-spines (T12-S1, Age 83-94 yr) were imaged using these optimized sequences. Thereafter each IVD was transversely sectioned and the exposed surfaces were photographed. Landmark observations from corresponding MRI slices and photographs were compared to confirm the MRI captured morphology. The image quality was evaluated using signal-to-noise ratio (SNR), and relative-contrast values. Finally, the underlying tissue structures, including specific pathological features, were qualitatively compared between the MR images and photographs. RESULTS Observations from photographs and corresponding MRI slices matched well. The PD-TSE sequence had better overall SNR, but the relative contrast between the tissue types was relatively poor. The 3D-GE sequence had higher relative contrast between the IVD and bone, but not between annulus and nucleus regions. The T2W images provided the best relative contrast between the annulus and nucleus, however the standard deviations here were high. Structural details including fissures, vascular and granular tissue proliferation, and pathologies in the endplate region, were identifiable from the MR images obtained using the optimized sequences. CONCLUSION The results demonstrate the potential of high-field MRI to capture the IVD structural details. Since the acquisition durations were within clinically acceptable levels, these methodological improvements have the potential to enhance clinical diagnostics. LEVEL OF EVIDENCE 4.
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14
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Büyükşerbetçi G, Saka E, Oğuz KK, Göçmen R, Arsava EM, Topçuoğlu MA. Cognitive Dysfunction in Relation to Topography and Burden of Cerebral Microbleeds. Noro Psikiyatr Ars 2018; 55:84-90. [PMID: 30042647 DOI: 10.29399/npa.23018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 12/03/2017] [Indexed: 12/31/2022]
Abstract
Introduction Contribution of cerebral microbleeds (CMBs) on cognitive dysfunctions in elderly patients with otherwise asymptomatic white matter lesions (WMLs) is not well-documented. Methods MRI parameters of cerebral atrophy, CMBs and WMLs were herein analyzed in relation to global and main domains (attention, executive, memory, visuospatial, language) of cognitive function. Eighty-five patients older than 50, without neurodegenerative/cerebrovascular disease, but had CMBs were recruited from 2562 with T2*-gradient-echo MR imaging during one-year period. Results Global cognition, evaluated by mini-mental status examination (MMSE), was impaired (score ≤24) in 42%. In contrast to CMBs load, WML burden and temporal atrophy were significantly higher in cases with MMSE≤24. Cholinergic Pathways HyperIntensities Scale (CHIPS) was positively correlated with global cognitive dysfunction but its CMB counterpart, Cholinergic Pathways Bleeding Scale described herein, was not. However, burden of CMBs in thalamic/cortical regions predicted language dysfunction. Conclusion Cognitive dysfunction associated with CMBs may be dependent on their distribution rather than their absolute number.
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Affiliation(s)
- Gülseren Büyükşerbetçi
- Department of Neurology, Balıkesir University Hospital, Balıkesir, Turkey.,Department of Neurology, Hacettepe University Medical School Hospital, Ankara, Turkey
| | - Esen Saka
- Department of Neurology, Hacettepe University Medical School Hospital, Ankara, Turkey
| | - Kader Karli Oğuz
- Department of Radiology, Hacettepe University Medical School Hospital, Ankara, Turkey
| | - Rahşan Göçmen
- Department of Radiology, Hacettepe University Medical School Hospital, Ankara, Turkey
| | - Ethem Murat Arsava
- Department of Neurology, Hacettepe University Medical School Hospital, Ankara, Turkey
| | - Mehmet Akif Topçuoğlu
- Department of Neurology, Hacettepe University Medical School Hospital, Ankara, Turkey
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15
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Nakamura M, Shibata S, Yamasaki T, Ueno M, Nakanishi I, Matsumoto KI, Kamada T, Yamada KI, Aoki I. Feasibility of magnetic resonance redox imaging at low magnetic field: comparison at 1 T and 7 T. Am J Transl Res 2017; 9:4481-4491. [PMID: 29118910 PMCID: PMC5666057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 07/12/2017] [Indexed: 06/07/2023]
Abstract
The effect of different static magnetic field strengths, 1 T or 7 T, on the quality of nitroxyl radical-based magnetic resonance redox imaging (MRRI) was examined. A stable nitroxyl radical, 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl (MC-PROXYL), was used as a T1 contrast agent. Phantoms and animals were scanned at 1 T and 7 T using a similar gradient echo sequence. The quality of T1-weighted images and susceptibility of T1-weighted signals were compared. The nitroxyl radical-based T1-weighted signal enhancement ratio was higher at 1 T compared with at 7 T when the identical phantom was scanned using a similar gradient echo sequence. The gradient echo scanning at 7 T was sensitive to movement and/or flux of the sample solution, which could result in the distortion of baseline T1-weighted signals. No such wobbling of the signal was observed when the experiment was done at 1 T. The detection at the lower field is less affected by voltex flow in the sample, much stable T1-weighted signal detection is available at the lower field. The visual characteristics of in vivo nitroxyl decay profiles were similar between the 1 T and 7 T experiments, except noises were large at 1 T. The correlation trends of in vivo decay constants among brain regions also similar between 1 T and 7 T experiments. Nitroxyl radical-based MRRI could be an adequate theranostic tool when performed on clinically popular low magnetic field MRI instruments.
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Affiliation(s)
- Mizuki Nakamura
- Quantitative RedOx Sensing Team, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
- Graduate School of Medical and Pharmaceutical Sciences, Chiba University1-8-1 Inohana, Chuo-ku, Chiba 260-88670, Japan
- Present address: Department of Radiology, Kitasato University Hospital1-15-1 Kitasato, Minami-ku, Sagamihara-shi, Kanagawa 252-0375, Japan
| | - Sayaka Shibata
- Functional and Molecular Imaging Team, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Toshihide Yamasaki
- Department of Bio-functional Science, Faculty of Pharmaceutical Sciences, Kyushu University3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
- Present address: Biophysical Chemistry, Kobe Pharmaceutical University4-19-1 Motoyamakita, Higashinada, Kobe, Hyogo 658-8558, Japan
| | - Megumi Ueno
- Quantitative RedOx Sensing Team, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Ikuo Nakanishi
- Quantitative RedOx Sensing Team, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Ken-ichiro Matsumoto
- Quantitative RedOx Sensing Team, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Tadashi Kamada
- Clinical Research Cluster, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
- Graduate School of Medical and Pharmaceutical Sciences, Chiba University1-8-1 Inohana, Chuo-ku, Chiba 260-88670, Japan
| | - Ken-ichi Yamada
- Department of Bio-functional Science, Faculty of Pharmaceutical Sciences, Kyushu University3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
- JST, PRESTO4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Ichio Aoki
- Functional and Molecular Imaging Team, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
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16
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Cao P, Hyder F, Zhou IY, Zhang JW, Xie VB, Tsang A, Wu EX. Simultaneous spin-echo and gradient-echo BOLD measurements by dynamic MRS. NMR Biomed 2017; 30:e3745. [PMID: 28574615 DOI: 10.1002/nbm.3745] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/22/2017] [Accepted: 04/10/2017] [Indexed: 06/07/2023]
Abstract
This study aimed to dissociate the intravascular and extravascular contributions to spin-echo (SE) and gradient-echo (GE) blood oxygenation level-dependent (BOLD) signals at 7 T, using dynamic diffusion-weighted MRS. We simultaneously acquired SE and GE data using a point-resolved spectroscopy sequence with diffusion weightings of 0, 600, and 1200 s/mm2 . The BOLD signals were quantified by fitting the free induction decays starting from the SE center to a mono-exponential decay function. Without diffusion weighting, BOLD signals measured with SE and GE increased by 1.6 ± 0.5% (TESE = 40 ms) and 5.2 ± 1.4% (nominal TEGE = 40 ms) during stimulation, respectively. With diffusion weighting, the BOLD increase during stimulation measured with SE decreased from 1.6 ± 0.5% to 1.3 ± 0.4% (P < 0.001), whereas that measured by GE was unaffected (P > 0.05); the post-stimulation undershoots in the BOLD signal time courses were largely preserved in both SE and GE measurements. These results demonstrated the feasiblity of simultaneous SE and GE measurements of BOLD signals with and without interleaved diffusion weighting. The results also indicated a predominant extravascular contribution to the BOLD signal time courses, including post-stimulation undershoots in both SE and GE measurements at 7 T.
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Affiliation(s)
- Peng Cao
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, CA, USA
| | - Fahmeed Hyder
- Departments of Diagnostic Radiology and Biomedical Engineering, Yale University, New Haven, CT, USA
| | - Iris Y Zhou
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
| | - Jevin W Zhang
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
| | - Victor B Xie
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
| | - Adrian Tsang
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
| | - Ed X Wu
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
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17
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Kim JW, Kim SG, Park SH. Phase imaging with multiple phase-cycled balanced steady-state free precession at 9.4 T. NMR Biomed 2017; 30:e3699. [PMID: 28187250 DOI: 10.1002/nbm.3699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 12/23/2016] [Accepted: 12/29/2016] [Indexed: 06/06/2023]
Abstract
While phase imaging with a gradient echo (GRE) sequence is popular, phase imaging with balanced steady-state free precession (bSSFP) has been underexplored. The purpose of this study was to investigate anatomical and functional phase imaging with multiple phase-cycled bSSFP, in expectation of increasing spatial coverage of steep phase-change regions of bSSFP. Eight different dynamic 2D pass-band bSSFP studies at four phase-cycling (PC) angles and two TE /TR values were performed on rat brains at 9.4 T with electrical forepaw stimulation, in comparison with dynamic 2D GRE. Anatomical and functional phase images were obtained by averaging the dynamic phase images and mapping correlation between the dynamic images and the stimulation paradigm, and were compared with their corresponding magnitude images. Phase imaging with 3D pass-band and 3D transition-band bSSFP was also performed for comparison with 3D GRE phase imaging. Two strategies of combining the multiple phase-cycled bSSFP phase images were also proposed. Contrast between white matter and gray matter in bSSFP phase images significantly varied with PC angle and became twice as high as that of GRE phase images at a specific PC angle. With the same total scan time, the combined bSSFP phase images provided stronger phase contrast and visualized neuronal fiber-like structures more clearly than the GRE phase images. The combined phase images of both 3D pass-band and 3D transition-band bSSFP showed phase contrasts stronger than those of the GRE phase images in overall brain regions, even at a longer TE of 20 ms. In contrast, phase functional MRI (fMRI) signals were weak overall and mostly located in draining veins for both bSSFP and GRE. Multiple phase-cycled bSSFP phase imaging is a promising anatomical imaging technique, while its usage as fMRI does not seem desirable with the current approach.
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Affiliation(s)
- Jae-Woong Kim
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Seong-Gi Kim
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea
| | - Sung-Hong Park
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
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18
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Fatnassi C, Boucenna R, Zaidi H. Mixed model phase evolution for correction of magnetic field inhomogeneity effects in 3D quantitative gradient echo-based MRI. Med Phys 2017; 44:3739-3751. [PMID: 28477400 DOI: 10.1002/mp.12318] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 04/25/2017] [Accepted: 04/27/2017] [Indexed: 12/31/2022] Open
Abstract
PURPOSE In 3D gradient echo magnetic resonance imaging (MRI), strong field gradients B0macro are visually observed at air/tissue interfaces. At low spatial resolution in particular, the respective field gradients lead to an apparent increase in intravoxel dephasing, and subsequently, to signal loss or inaccurate R2* estimates. If the strong field gradients are measured, their influence can be removed by postprocessing. METHODS Conventional corrections usually assume a linear phase evolution with time. For high macroscopic gradient inhomogeneities near the edge of the brain and at the paranasal sinuses, however, this assumption is often broken. Herein, we explored a novel model that considers both linear and stochastic dependences of the phase evolution with echo time in the presence of weak and strong macroscopic field inhomogeneities. We tested the performance of the model at large field gradients using simulation, phantom, and human in vivo studies. RESULTS The performance of the proposed approach was markedly better than the standard correction method, providing a correction equivalent to that of the conventional approach in regions with high signal to noise ratio (SNR > 10), but appearing more robust in regions with low SNR (SNR < 4). CONCLUSION The proposed technique shows promise to improve R2* measurements in regions of large susceptibilities. The clinical and research applications still require further investigation.
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Affiliation(s)
- Chemseddine Fatnassi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211, Geneva, Switzerland.,Radio-Oncology Institute, Clinique Bois-Cerf Hirslanden, CH-1006, Lausanne, Switzerland
| | - Rachid Boucenna
- Radio-Oncology Institute, Clinique Bois-Cerf Hirslanden, CH-1006, Lausanne, Switzerland
| | - Habib Zaidi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211, Geneva, Switzerland.,Geneva Neuroscience Centre, Geneva University, CH-1205, Geneva, Switzerland.,Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, 9700RB, Groningen, Netherlands.,Department of Nuclear Medicine, University of Southern Denmark, DK-500, Odense, Denmark
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19
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Lee J, Nam Y, Choi JY, Kim EY, Oh SH, Kim DH. Mechanisms of T 2 * anisotropy and gradient echo myelin water imaging. NMR Biomed 2017; 30:e3513. [PMID: 27060968 DOI: 10.1002/nbm.3513] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 01/26/2016] [Accepted: 02/17/2016] [Indexed: 06/05/2023]
Abstract
In MRI, structurally aligned molecular or micro-organization (e.g. axonal fibers) can be a source of substantial signal variations that depend on the structural orientation and the applied magnetic field. This signal anisotropy gives us a unique opportunity to explore information that exists at a resolution several orders of magnitude smaller than that of typical MRI. In this review, one of the signal anisotropies, T2 * anisotropy in white matter, and a related imaging method, gradient echo myelin water imaging (GRE-MWI), are explored. The T2 * anisotropy has been attributed to isotropic and anisotropic magnetic susceptibility of myelin and compartmentalized microstructure of white matter fibers (i.e. axonal, myelin, and extracellular space). The susceptibility and microstructure create magnetic frequency shifts that change with the relative orientation of the fiber and the main magnetic field, generating the T2 * anisotropy. The resulting multi-component magnitude decay and nonlinear phase evolution have been utilized for GRE-MWI, assisting in resolving the signal fraction of the multiple compartments in white matter. The GRE-MWI method has been further improved by signal compensation techniques including physiological noise compensation schemes. The T2 * anisotropy and GRE-MWI provide microstructural information on a voxel (e.g. fiber orientation and tissue composition), and may serve as sensitive biomarkers for microstructural changes in the brain. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Jongho Lee
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, Korea
| | - Yoonho Nam
- Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Joon Yul Choi
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, Korea
| | - Eung Yeop Kim
- Department of Radiology, Gachon University Gil Medical Center, Incheon, Korea
| | - Se-Hong Oh
- Imaging Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Dong-Hyun Kim
- Department of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea
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20
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Yuen J, Hung J, Wiggermann V, Robinson SD, McCormack R, d'Entremont AG, Rauscher A. Multi-echo GRE imaging of knee cartilage. J Magn Reson Imaging 2016; 45:1502-1513. [PMID: 27564991 DOI: 10.1002/jmri.25438] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 08/08/2016] [Indexed: 12/24/2022] Open
Abstract
PURPOSE To visualize healthy and abnormal articular cartilage, we investigated the potential of using the 3D multi-echo gradient echo (GRE) signal's magnitude and frequency and maps of T2* relaxation. MATERIALS AND METHODS After optimizing imaging parameters in five healthy volunteers, 3D multi-echo GRE magnetic resonance (MR) images were acquired at 3T in four patients with chondral damage prior to their arthroscopic surgery. Average magnitude and frequency information was extracted from the GRE images, and T2* maps were generated. Cartilage abnormalities were confirmed after arthroscopy and were graded using the Outerbridge classification scheme. Regions of interest were identified on average magnitude GRE images and compared to arthroscopy. RESULTS All four patients presented with regions of Outerbridge Grade I and II cartilage damage on arthroscopy. One patient had Grade III changes. Grade I, II, and III changes were detectable on average magnitude and T2* maps, while Grade II and higher changes were also observable on MR frequency maps. For average magnitude images of healthy volunteers, the signal-to-noise ratio of the magnitude image averaged over three echoes was 4.26 ± 0.32, 12.26 ± 1.09, 14.31 ± 1.93, and 13.36 ± 1.13 in bone, femoral, tibial, and patellar cartilage, respectively. CONCLUSION This proof-of-principle study demonstrates the feasibility of using different imaging contrasts from the 3D multi-echo GRE scan to visualize abnormalities of the articular cartilage. © 2016 International Society for Magnetic Resonance in Medicine Level of Evidence: 1 J. MAGN. RESON. IMAGING 2017;45:1502-1513.
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Affiliation(s)
- Joanna Yuen
- UBC MRI Research Centre, University of British Columbia, Vancouver, Canada.,Department of Pediatrics, University of British Columbia, Vancouver, Canada.,Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
| | - Jachin Hung
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
| | - Vanessa Wiggermann
- UBC MRI Research Centre, University of British Columbia, Vancouver, Canada.,Department of Pediatrics, University of British Columbia, Vancouver, Canada.,Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
| | - Simon D Robinson
- High Field Magnetic Resonance Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria
| | - Robert McCormack
- Department of Orthopaedics, University of British Columbia, Vancouver, Canada
| | - Agnes G d'Entremont
- Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada.,Centre for Hip Health and Mobility, University of British Columbia, Vancouver, Canada.,Child and Family Research Institute, University of British Columbia, Vancouver, Canada
| | - Alexander Rauscher
- UBC MRI Research Centre, University of British Columbia, Vancouver, Canada.,Department of Pediatrics, University of British Columbia, Vancouver, Canada.,Child and Family Research Institute, University of British Columbia, Vancouver, Canada
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21
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Tang MY, Chen TW, Huang XH, Li XH, Wang SY, Liu N, Zhang XM. Acute pancreatitis with gradient echo T2*-weighted magnetic resonance imaging. Quant Imaging Med Surg 2016; 6:157-67. [PMID: 27190768 DOI: 10.21037/qims.2016.04.03] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND To study gradient recalled echo (GRE) T2*-weighted imaging (T2*WI) for normal pancreas and acute pancreatitis (AP). METHODS Fifty-one patients without any pancreatic disorders (control group) and 117 patients with AP were recruited. T2* values derived from T2*WI of the pancreas were measured for the two groups. The severity of AP was graded by the magnetic resonance severity index (MRSI) and the Acute Physiology and Chronic Healthy Evaluation II (APACHE II) scoring system. Logistic regression was used to analyze the relationship between the T2* values and AP severity. The usefulness of the T2* value for diagnosing AP and the relationship between the T2* values and the severity of AP were analyzed. RESULTS On GRE-T2*WI, the normal pancreas showed a well-marinated and consistently homogeneous isointensity. Edematous AP, as well as the non-necrotic area in necrotizing AP, showed ill-defined but homogeneous signal intensity. AP with pancreatic hemorrhage showed a decreased T2* value and a signal loss on the signal decay curve. The T2* value of pancreas in the AP group was higher than that of the control group (t=-8.20, P<0.05). The T2* value tended to increase along with the increase in MRSI scores but not with the APACHE II scores (P>0.05). AP was associated with a one standard deviation increment in the T2* value (OR =1.37; 95% CI: 1.216-1.532). CONCLUSIONS T2*WI demonstrates a few characteristics of the normal pancreas and AP, which could potentially be helpful for detecting hemorrhage, and contributes to diagnosing AP and its severity.
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Affiliation(s)
- Meng Yue Tang
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, Wenhua Road 63, Nanchong 637000, China
| | - Tian Wu Chen
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, Wenhua Road 63, Nanchong 637000, China
| | - Xiao Hua Huang
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, Wenhua Road 63, Nanchong 637000, China
| | - Xing Hui Li
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, Wenhua Road 63, Nanchong 637000, China
| | - Si Yue Wang
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, Wenhua Road 63, Nanchong 637000, China
| | - Nian Liu
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, Wenhua Road 63, Nanchong 637000, China
| | - Xiao Ming Zhang
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, Wenhua Road 63, Nanchong 637000, China
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Khatamian YB, Golestani AM, Ragot DM, Chen JJ. Spin-Echo Resting-State Functional Connectivity in High-Susceptibility Regions: Accuracy, Reliability, and the Impact of Physiological Noise. Brain Connect 2016; 6:283-97. [PMID: 26842962 DOI: 10.1089/brain.2015.0365] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Gradient-echo (GE) echo-planar imaging (EPI) is the method of choice in blood-oxygenation level-dependent (BOLD) functional MRI (fMRI) studies, as it demonstrates substantially higher BOLD sensitivity than its spin-echo (SE) counterpart. However, it is also well known that the GE-EPI signal is prone to signal dropouts and shifts due to susceptibility effects near air-tissue interfaces. SE-EPI, in contrast, is minimally affected by these artifacts. In this study, we quantify, for the first time, the sensitivity and specificity of SE and GE EPI for resting-state fMRI functional connectivity (fcMRI) mapping, using the 1000-brain fcMRI atlas (Yeo et al., 2011 ) as the pseudoground truth. Moreover, we assess the influence of physiological processes on resting-state BOLD measured using both regular and ultrafast GE and SE acquisitions. Our work demonstrates that SE-EPI and GE-EPI are associated with similar sensitivities, specificities, and intersubject reproducibility in fcMRI for most brain networks, generated using both seed-based analysis and independent component analysis. More importantly, SE-based fcMRI measurements demonstrated significantly higher sensitivity, specificity, and intersubject reproducibility in high-susceptibility regions, spanning the limbic and frontal networks in the 1000-brain atlas. In addition, SE-EPI is significantly less sensitive to prominent sources of physiological noise, including low-frequency respiratory volume and heart rate variations. Our work suggests that SE-EPI should be increasingly adopted in the study of networks spanning susceptibility-affected brain regions, including those that are important to memory, language, and emotion.
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Affiliation(s)
| | | | - Don M Ragot
- 1 Rotman Research Institute , Baycrest, Toronto, Canada .,2 Department of Medical Biophysics, University of Toronto , Toronto, Canada
| | - J Jean Chen
- 1 Rotman Research Institute , Baycrest, Toronto, Canada .,2 Department of Medical Biophysics, University of Toronto , Toronto, Canada
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Sukstanskii AL, Wen J, Cross AH, Yablonskiy DA. Simultaneous multi-angular relaxometry of tissue with MRI (SMART MRI): Theoretical background and proof of concept. Magn Reson Med 2016; 77:1296-1306. [PMID: 26991525 DOI: 10.1002/mrm.26176] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 01/29/2016] [Accepted: 01/31/2016] [Indexed: 01/09/2023]
Abstract
PURPOSE Accurate measurement of tissue-specific relaxation parameters is an ultimate goal of quantitative MRI. The objective of this study is to introduce a new technique, simultaneous multiangular relaxometry of tissue with MRI (SMART MRI), which provides naturally coregistered quantitative spin density, longitudinal and transverse relaxation rate constant maps along with parameters characterizing magnetization transfer (MT) effects. THEORY AND METHODS SMART MRI is based on a gradient-recalled echo MRI sequence with multiple flip angles and multiple gradient echoes and a derived theoretical expression for the MR signal generated in this experimental conditions. The theory, based on Bloch-McConnell equations, takes into consideration cross-relaxation between two water pools: "free" and "bound" to macromolecules. It describes the role of cross-relaxation effects in formation of longitudinal and transverse relaxation of "free" water signal, thus providing background for measurements of these effects without using MT pulses. Bayesian analysis is used to optimize SMART MRI sequence parameters. RESULTS Data obtained on three participants demonstrate feasibility of the proposed approach. CONCLUSION SMART MRI provides quantitative measurements of longitudinal and transverse relaxation rate constants of "free" water signal affected by cross-relaxation effects. It also provides information on some essential MT parameters without requiring off-resonance MT pulses. Magn Reson Med 77:1296-1306, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
| | - Jie Wen
- Department of Radiology, Washington University, St. Louis, Missouri, USA
| | - Anne H Cross
- Department of Radiology, Washington University, St. Louis, Missouri, USA
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Pavuluri K, Ramanathan KV. Gradient echo single scan inversion recovery: application to proton and fluorine relaxation studies. Magn Reson Chem 2016; 54:151-157. [PMID: 26364676 DOI: 10.1002/mrc.4332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 07/08/2015] [Accepted: 08/12/2015] [Indexed: 06/05/2023]
Abstract
Single scan longitudinal relaxation measurement experiments enable rapid estimation of the spin-lattice relaxation time (T1 ) as the time series of spin relaxation is encoded spatially in the sample at different slices resulting in an order of magnitude saving in time. We consider here a single scan inversion recovery pulse sequence that incorporates a gradient echo sequence. The proposed pulse sequence provides spectra with significantly enhanced signal to noise ratio leading to an accurate estimation of T1 values. The method is applicable for measuring a range of T1 values, thus indicating the possibility of routine use of the method for several systems. A comparative study of different single scan methods currently available is presented, and the advantage of the proposed sequence is highlighted. The possibility of the use of the method for the study of cross-correlation effects for the case of fluorine in a single shot is also demonstrated.
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Affiliation(s)
- KowsalyaDevi Pavuluri
- Department of Physics, Indian Institute of Science, Bangalore, India
- NMR Research Centre, Indian Institute of Science, Bangalore, India
| | - K V Ramanathan
- NMR Research Centre, Indian Institute of Science, Bangalore, India
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Wijayathunga VN, Ridgway JP, Ingham E, Treanor D, Carey D, Bulpitt A, Magee D, Damion R, Wilcox RK. A Nondestructive Method to Distinguish the Internal Constituent Architecture of the Intervertebral Discs Using 9.4 Tesla Magnetic Resonance Imaging. Spine (Phila Pa 1976) 2015; 40:E1315-22. [PMID: 26244404 PMCID: PMC4684101 DOI: 10.1097/brs.0000000000001075] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN An in vitro study of the intervertebral disc (IVD) structure using 9.4T magnetic resonance imaging (MRI). OBJECTIVE Investigate the potential of ultrahigh-field strength MRI for higher quality 3-dimensional (3D) volumetric MRI datasets of the IVD to better distinguish structural details. SUMMARY OF BACKGROUND DATA MRI has the advantages of being nondestructive and 3D in comparison to most techniques used to obtain the structural details of biological tissues, however, its poor image quality at higher resolution is a limiting factor. Ultrahigh-field MRI could improve the imaging of biological tissues but the current understanding of its application for spinal tissue is limited. METHODS 2 ovine spinal segments (C7-T1, T2-T3) containing the IVD were separately imaged using 2 sequences; 3D spin echo (multislice-multiecho) pulse sequence for the C7-T1 sample and 3D gradient echo (fast-low-angle-shot) pulse sequence for the T2-T3 sample. The C7-T1 sample was subsequently decalcified and imaged again using the same scanning parameters. Histological sections obtained from the decalcified sample were stained followed by digital scanning. Observations from corresponding MRI slices and histological sections were compared as a method of confirmation of morphology captured under MRI. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and relative-contrast values were calculated for quantitative evaluation of image quality. RESULTS Measurements from histology sections and corresponding MRI slices matched well. Both sequences revealed finer details of the IVD structure. Under the spin echo sequence, the annulus lamellae architecture was distinguishable and the SNR and CNR values were higher. The relative contrast was considerably higher between high (nucleus) and low (bone) signal constituents, but between the nucleus and the annulus the relative contrast was low. Under the gradient echo sequence, although the relative contrasts between constituents were poor, the fiber orientation was clearly manifested. CONCLUSION The obtained positive results demonstrate the potential of ultrahigh-field strength MRI to nondestructively capture the IVD structure. LEVEL OF EVIDENCE N/A.
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Affiliation(s)
| | - John P. Ridgway
- Division of Medical Physics, University of Leeds, Leeds, United Kingdom
| | - Eileen Ingham
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, United Kingdom
| | - Darren Treanor
- The Leeds Institute of Cancer and Pathology, Leeds Teaching Hospitals NHS Trust, St James's University Hospital, Beckett Street, Leeds, United Kingdom
| | - Duane Carey
- School of Computing, University of Leeds, Leeds, United Kingdom
| | - Andy Bulpitt
- School of Computing, University of Leeds, Leeds, United Kingdom
| | - Derek Magee
- School of Computing, University of Leeds, Leeds, United Kingdom
| | - Robin Damion
- School of Physics and Astronomy, University of Leeds, Leeds, United Kingdom
| | - Ruth K. Wilcox
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, United Kingdom
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Nielsen JF, Noll DC. Improved spoiling efficiency in dynamic RF-spoiled imaging by ghost phase modulation and temporal filtering. Magn Reson Med 2015; 75:2388-93. [PMID: 26153387 DOI: 10.1002/mrm.25843] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 06/18/2015] [Accepted: 06/22/2015] [Indexed: 11/11/2022]
Abstract
PURPOSE Radiofrequency-spoiled steady-state sequences offer rapid data acquisition with T1- or T2*-weighting. The spoiler gradients in these sequences must be large enough to suppress ghost artifacts, and are chosen empirically. However, certain factors such as the need to minimize gradient first moments or acoustic noise can limit the spoiler size and, hence, the ability to suppress ghosts. We present an acquisition and preprocessing strategy for improved spoiling efficiency in conventional and echo-shifted dynamic radiofrequency-spoiled 3D imaging. THEORY AND METHODS By requiring each time-frame in a dynamic imaging sequence to contain a particular (restricted) number of total radiofrequency shots, the ghost signal can be made to alternate in sign every other frame. The ghost is then suppressed by Fourier transforming along the temporal dimension, and removing the Nyquist frequency in preprocessing (similar to UNFOLD). The method works for both Cartesian and non-Cartesian imaging. RESULTS We demonstrate improved ghost suppression with the proposed approach, for both conventional and echo-shifted spoiled gradient echo imaging in stationary phantoms and in vivo. Cartesian echo-shifted spoiled gradient echo imaging produces two ghosts shifted in opposite directions, both of which are suppressed with our method. CONCLUSION For a given spoiler gradient area, the proposed approach substantially suppresses the ghost signal in both conventional and echo-shifted dynamic radiofrequency-spoiled imaging. Magn Reson Med 75:2388-2393, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Jon-Fredrik Nielsen
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Douglas C Noll
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
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Wang Y, Liu T. Quantitative susceptibility mapping (QSM): Decoding MRI data for a tissue magnetic biomarker. Magn Reson Med 2015; 73:82-101. [PMID: 25044035 PMCID: PMC4297605 DOI: 10.1002/mrm.25358] [Citation(s) in RCA: 550] [Impact Index Per Article: 61.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 06/13/2014] [Accepted: 06/18/2014] [Indexed: 01/03/2023]
Abstract
In MRI, the main magnetic field polarizes the electron cloud of a molecule, generating a chemical shift for observer protons within the molecule and a magnetic susceptibility inhomogeneity field for observer protons outside the molecule. The number of water protons surrounding a molecule for detecting its magnetic susceptibility is vastly greater than the number of protons within the molecule for detecting its chemical shift. However, the study of tissue magnetic susceptibility has been hindered by poor molecular specificities of hitherto used methods based on MRI signal phase and T2* contrast, which depend convolutedly on surrounding susceptibility sources. Deconvolution of the MRI signal phase can determine tissue susceptibility but is challenged by the lack of MRI signal in the background and by the zeroes in the dipole kernel. Recently, physically meaningful regularizations, including the Bayesian approach, have been developed to enable accurate quantitative susceptibility mapping (QSM) for studying iron distribution, metabolic oxygen consumption, blood degradation, calcification, demyelination, and other pathophysiological susceptibility changes, as well as contrast agent biodistribution in MRI. This paper attempts to summarize the basic physical concepts and essential algorithmic steps in QSM, to describe clinical and technical issues under active development, and to provide references, codes, and testing data for readers interested in QSM.
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Affiliation(s)
- Yi Wang
- Radiology, Weill Medical College of Cornell UniversityNew York, New York, USA
- Biomedical Engineering, Cornell UniversityIthaca, New York, USA
- Biomedical Engineering, Kyung Hee UniversitySeoul, South Korea
| | - Tian Liu
- MedImageMetric, LLCNew York, New York, USA
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Sukstanskii AL, Yablonskiy DA. On the role of neuronal magnetic susceptibility and structure symmetry on gradient echo MR signal formation. Magn Reson Med 2014; 71:345-53. [PMID: 23382087 PMCID: PMC3657601 DOI: 10.1002/mrm.24629] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 11/20/2012] [Accepted: 12/15/2012] [Indexed: 12/13/2022]
Abstract
PURPOSE Phase images obtained by gradient-recalled echo (GRE) MRI provide new contrast in the brain that is distinct from that obtained with conventional T1-weighted and T2-weighted images. The results are especially intriguing in white matter where both signal amplitude and phase display anisotropic properties. However, the biophysical origins of these phenomena are not well understood. The goal of this article is to provide a comprehensive theory of GRE signal formation based on a realistic model of neuronal structure. METHODS We use Maxwell equations to find the distribution of magnetic field induced by myelin sheath and axon. We account for both anisotropy of neuronal tissue "magnetic micro-architecture" and anisotropy of myelin sheath magnetic susceptibility. RESULTS Model describes GRE signal comprising of three compartments-axonal, myelin, and extracellular. Both axonal and myelin water signals have frequency shifts that are affected by the magnetic susceptibility anisotropy of long molecules forming lipid bilayer membranes. These parts of frequency shifts reach extrema for axon oriented perpendicular to the magnetic field and are zeros in a parallel case. Myelin water signal is substantially non-monoexponential. CONCLUSIONS Both, anisotropy of neuronal tissue "magnetic micro-architecture" and anisotropy of myelin sheath magnetic susceptibility, are important for describing GRE signal phase and magnitude.
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Lee H, Sohn CH, Park J. Rapid hybrid encoding for high-resolution whole-brain fluid-attenuated imaging. NMR Biomed 2013; 26:1751-1761. [PMID: 24000143 DOI: 10.1002/nbm.3013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 05/28/2013] [Accepted: 07/16/2013] [Indexed: 06/02/2023]
Abstract
Single-slab three-dimensional (3D) turbo spin-echo (TSE) imaging combined with inversion recovery (IR), which employs short, spatially non-selective refocusing pulses and signal prescription based variable refocusing flip angles (VFA) to increase imaging efficiency, was recently introduced to produce fluid-attenuated brain images for lesion detection. Despite the advantages, the imaging efficiency in this approach still remains limited because a substantially long time of inversion is needed to selectively suppress the signal intensity of cerebrospinal fluid (CSF) while fully recovering that of brain tissues. The purpose of this work is to develop a novel, rapid hybrid encoding method for highly efficient whole-brain fluid-attenuated imaging. In each time of repetition, volumetric data are continuously encoded using the hybrid modular acquisition in a sequential fashion even during IR signal transition, wherein reversed fast imaging with steady-state free precession (PSIF) is employed to encode intermediate-to-high spatial frequency signals prior to CSF nulling, while VFA-TSE is used to collect low-to-intermediate spatial frequency signals afterwards. Gradient-induced spin de-phasing between a pair of neighboring radio-frequency (RF) pulses in both PSIF and TSE modules is kept identical to avoid the occurrence of multiple echoes in a single acquisition window. Additionally, a two-step, alternate RF phase-cycling scheme is employed in the low spatial frequency region to eliminate free induction decay induced edge artifacts. Numerical simulations of the Bloch equations were performed to evaluate signal evolution of brain tissues along the echo train while optimizing imaging parameters. In vivo studies demonstrate that the proposed technique produces high-resolution isotropic fluid-attenuated whole-brain images in a clinically acceptable imaging time with substantially high signal-to-noise ratio for white matter while retaining lesion conspicuity.
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Affiliation(s)
- Hoonjae Lee
- Biomedical Imaging and Engineering Lab, Department of Brain and Cognitive Engineering, Korea University, Seoul, Korea
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Neelavalli J, Mody S, Yeo L, Jella PK, Korzeniewski SJ, Saleem S, Katkuri Y, Bahado-Singh RO, Hassan SS, Haacke EM, Romero R, Thomason ME. MR venography of the fetal brain using susceptibility weighted imaging. J Magn Reson Imaging 2013; 40:949-57. [PMID: 24989457 DOI: 10.1002/jmri.24476] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 09/04/2013] [Indexed: 12/30/2022] Open
Abstract
PURPOSE To evaluate the feasibility of performing fetal brain magnetic resonance venography using susceptibility weighted imaging (SWI). MATERIALS AND METHODS After obtaining informed consent, pregnant women in the second and third trimester were imaged using a modified SWI sequence. Fetal SWI acquisition was repeated when fetal or maternal motion was encountered. The median and maximum number of times an SWI sequence was repeated was four and six respectively. All SWI image data were systematically evaluated by a pediatric neuroradiologist for image quality using an ordinal scoring scheme: 1. diagnostic; 2. diagnostic with artifacts; and 3. nondiagnostic. The best score in an individual fetus was used for further statistical analysis. Visibility of venous vasculature was also scored using a dichotomous variable. A subset of SWI data was re-evaluated by the first and independently by a second pediatric neuroradiologist. Kappa coefficients were computed to assess intra-rater and inter-rater reliability. RESULTS SWI image data from a total of 22 fetuses were analyzed. Median gestational age and interquartile range of the fetuses imaged were 32 (29.9-34.9) weeks. In 68.2% of the cases (n = 15), there was no artifact; 22.7% (n = 5) had minor artifacts and 9.1% (n = 2) of the data was of nondiagnostic quality. Cerebral venous vasculature was visible in 86.4% (n = 19) of the cases. Substantial agreement (Kappa = 0.73; 95% confidence interval 0.44-1.00)) was observed for intra-rater reliability and moderate agreement (Kappa = 0.48; 95% confidence interval 0.19-0.77) was observed for inter-rater reliability. CONCLUSION It is feasible to perform fetal brain venography in humans using SWI.
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Yablonskiy DA, Sukstanskii AL, Luo J, Wang X. Voxel spread function method for correction of magnetic field inhomogeneity effects in quantitative gradient-echo-based MRI. Magn Reson Med 2013; 70:1283-92. [PMID: 23233445 PMCID: PMC3604169 DOI: 10.1002/mrm.24585] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 10/29/2012] [Accepted: 11/14/2012] [Indexed: 11/10/2022]
Abstract
PURPOSE Macroscopic magnetic field inhomogeneities adversely affect different aspects of MRI images. In quantitative MRI when the goal is to quantify biological tissue parameters, they bias and often corrupt such measurements. The goal of this article is to develop a method for correction of macroscopic field inhomogeneities that can be applied to a variety of quantitative gradient-echo-based MRI techniques. METHODS We have reanalyzed a basic theory of gradient echo MRI signal formation in the presence of background field inhomogeneities and derived equations that allow for correction of magnetic field inhomogeneity effects based on the phase and magnitude of gradient echo data. We verified our theory by mapping effective transverse relaxation rate in computer simulated, phantom, and in vivo human data collected with multi-gradient echo sequences. RESULTS The proposed technique takes into account voxel spread function effects and allowed obtaining virtually free from artifacts effective transverse relaxation rate maps for all simulated, phantom and in vivo data except of the edge areas with very steep field gradients. CONCLUSION The voxel spread function method, allowing quantification of tissue specific effective transverse relaxation rate-related tissue properties, has a potential to breed new MRI biomarkers serving as surrogates for tissue biological properties similar to longitudinal and transverse relaxation rate constants widely used in clinical and research MRI.
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Affiliation(s)
- Dmitriy A Yablonskiy
- Department of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
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Garteiser P, Sahebjavaher RS, Ter Beek LC, Salcudean S, Vilgrain V, Van Beers BE, Sinkus R. Rapid acquisition of multifrequency, multislice and multidirectional MR elastography data with a fractionally encoded gradient echo sequence. NMR Biomed 2013; 26:1326-35. [PMID: 23712852 DOI: 10.1002/nbm.2958] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 03/08/2013] [Accepted: 03/08/2013] [Indexed: 05/16/2023]
Abstract
In MR elastography (MRE), periodic tissue motion is phase encoded using motion-encoding gradients synchronized to an externally applied periodic mechanical excitation. Conventional methods result in extended scan time for quality phase images, thus limiting the broad application of MRE in the clinic. For practical scan times, researchers have been relying on one-dimensional or two-dimensional motion-encoding, low-phase sampling and a limited number of slices, and artifact-prone, single-shot, echo planar imaging (EPI) readout. Here, we introduce a rapid multislice pulse sequence capable of three-dimensional motion encoding that is also suitable for simultaneously encoding motion with multiple frequency components. This sequence is based on a gradient-recalled echo (GRE) sequence and exploits the principles of fractional encoding. This GRE MRE pulse sequence was validated as capable of acquiring full three-dimensional motion encoding of isotropic voxels in a large volume within less than a minute. This sequence is suitable for monofrequency and multifrequency MRE experiments. In homogeneous paraffin phantoms, the eXpresso sequence yielded similar storage modulus values as those obtained with conventional methods, although with markedly reduced variances (7.11 ± 0.26 kPa for GRE MRE versus 7.16 ± 1.33 kPa for the conventional spin-echo EPI sequence). The GRE MRE sequence obtained better phase-to-noise ratios than the equivalent spin-echo EPI sequence (matched for identical acquisition time) in both paraffin phantoms and in vivo data in the liver (59.62 ± 11.89 versus 27.86 ± 3.81, 61.49 ± 14.16 versus 24.78 ± 2.48 and 58.23 ± 10.39 versus 23.48 ± 2.91 in the X, Y and Z components, respectively, in the case of liver experiments). Phase-to-noise ratios were similar between GRE MRE used in monofrequency or multifrequency experiments (75.39 ± 14.93 versus 86.13 ± 18.25 at 28 Hz, 71.52 ± 24.74 versus 86.96 ± 30.53 at 56 Hz and 95.60 ± 36.96 versus 61.35 ± 26.25 at 84Hz, respectively).
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Abstract
BACKGROUND AND PURPOSE A novel quantitative susceptibility mapping (QSM) processing technology has been developed to map tissue susceptibility property without blooming artifacts. We hypothesize that hematoma volume measurement on QSM is independent of imaging parameters, eliminating its echo time dependence on gradient echo MRI. METHODS Gradient echo MRI of 16 patients with intracerebral hemorrhage was processed with susceptibility-weighted imaging, R2* (=1/T2*) mapping, and QSM at various echo times. Hematoma volumes were measured from these images. RESULTS Linear regression of hematoma volume versus echo time showed substantial slopes for gradient echo magnitude (0.45±0.31 L/s), susceptibility-weighted imaging (0.52±0.46), and R2* (0.39±0.30) but nearly zero slope for QSM (0.01±0.05). At echo time=20 ms, hematoma volume on QSM was 0.80× that on gradient echo magnitude image (R2=0.99). CONCLUSIONS QSM can provide reliable measurement of hematoma volume, which can be performed rapidly and accurately using a semiautomated segmentation tool.
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Affiliation(s)
- Shuo Wang
- Department of Radiology, Weill Medical College of Cornell University, New York, NY 10022, USA
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