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Kobayashi N. Optimization of flip angle and radiofrequency pulse phase to maximize steady-state magnetization in three-dimensional missing pulse steady-state free precession. NMR IN BIOMEDICINE 2024; 37:e5112. [PMID: 38299770 PMCID: PMC11078623 DOI: 10.1002/nbm.5112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 12/07/2023] [Accepted: 01/09/2024] [Indexed: 02/02/2024]
Abstract
Missing pulse (MP) steady-state free precession (SSFP) is a magnetic resonance imaging (MRI) pulse sequence that is highly tolerant to the magnetic field inhomogeneity. In this study, optimal flip angle and radiofrequency (RF) phase scheduling in three-dimensional (3D) MP-SSFP is introduced to maximize the steady-state magnetization while keeping broadband excitation to cover widely distributed frequencies generated by inhomogeneous magnetic fields. Numerical optimization based on extended phase graph (EPG) simulation was performed to maximize the MP-SSFP steady-state magnetization. To limit the specific absorption rate (SAR) associated with the broadband excitation in 3D MP-SSFP, SAR constraint was introduced in the numerical optimization. Optimized flip angle and RF phase settings were experimentally tested by introducing a linear inhomogeneous magnetic field in a range of 10-20 mT/m and using a phantom with known T1/T2 relaxation and diffusion parameters at 3 T. The experimental results were validated through comparisons with EPG simulation. Image contrasts and molecular diffusion effects were investigated in in vivo human brain imaging with 3D MP-SSFP with the optimal flip angle and RF phase settings. In the phantom measurements, the optimal flip angle and RF phase settings improved the MP-SSFP steady-state magnetization/signal-to-noise ratio by up to 41% under the fixed SAR conditions, which matched well with EPG simulation results. In vivo brain imaging with the optimal RF pulse settings provided T2-like image contrasts. Diffusion effects were relatively minor with the linear inhomogeneous field of 10-20 mT/m for white and gray matter, but cerebrospinal fluid showed conspicuous signal intensity attenuation as the linear inhomogeneous field increased. Numerical optimization achieved significant improvement in the steady-state magnetization in MP-SSFP compared with the RF pulse settings used in previous studies. The proposed flip angle and RF phase optimization is promising to improve 3D MP-SSFP image quality for MRI in inhomogeneous magnetic fields.
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Affiliation(s)
- Naoharu Kobayashi
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota, USA
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Özdemir S, Ilicak E, Zapp J, Schad LR, Zöllner FG. Feasibility of undersampled spiral trajectories in MREPT for fast conductivity imaging. Magn Reson Med 2024; 91:1567-1575. [PMID: 38044757 DOI: 10.1002/mrm.29952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 10/09/2023] [Accepted: 11/13/2023] [Indexed: 12/05/2023]
Abstract
PURPOSE To investigate spiral-based imaging including trajectories with undersampling as a fast and robust alternative for phase-based magnetic resonance electrical properties tomography (MREPT) techniques. METHODS Spiral trajectories with various undersampling ratios were prescribed to acquire images from an experimental phantom and a healthy volunteer at 3T. The non-Cartesian acquisitions were reconstructed using SPIRiT, and conductivity maps were derived using phase-based cr-MREPT. The resulting maps were compared between different sampling trajectories. Additionally, a conductivity map was obtained using a Cartesian balanced SSFP acquisition from the volunteer to comparatively demonstrate the robustness of the proposed method. RESULTS The phantom and volunteer results illustrate the benefits of the spiral acquisitions. Specifically, undersampled spiral acquisitions display improved robustness against field inhomogeneity artifacts and lowered SD values with shortened readout times. Furthermore, average of conductivity values measured for the cerebrospinal fluid with the spiral acquisitions were 1.703 S/m, indicating a close agreement with the theoretical values of 1.794 S/m. CONCLUSION A spiral-based acquisition framework for conductivity imaging with and without undersampling is presented. Overall, spiral-based acquisitions improved robustness against field inhomogeneity artifacts, while achieving whole head coverage with multiple averages in less than a minute.
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Affiliation(s)
- Safa Özdemir
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Efe Ilicak
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Jascha Zapp
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Lothar R Schad
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Frank G Zöllner
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
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Assländer J, Gultekin C, Mao A, Zhang X, Duchemin Q, Liu K, Charlson RW, Shepherd TM, Fernandez-Granda C, Flassbeck S. Rapid quantitative magnetization transfer imaging: Utilizing the hybrid state and the generalized Bloch model. Magn Reson Med 2024; 91:1478-1497. [PMID: 38073093 DOI: 10.1002/mrm.29951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 10/30/2023] [Accepted: 11/14/2023] [Indexed: 02/03/2024]
Abstract
PURPOSE To explore efficient encoding schemes for quantitative magnetization transfer (qMT) imaging with few constraints on model parameters. THEORY AND METHODS We combine two recently proposed models in a Bloch-McConnell equation: the dynamics of the free spin pool are confined to the hybrid state, and the dynamics of the semi-solid spin pool are described by the generalized Bloch model. We numerically optimize the flip angles and durations of a train of radio frequency pulses to enhance the encoding of three qMT parameters while accounting for all eight parameters of the two-pool model. We sparsely sample each time frame along this spin dynamics with a three-dimensional radial koosh-ball trajectory, reconstruct the data with subspace modeling, and fit the qMT model with a neural network for computational efficiency. RESULTS We extracted qMT parameter maps of the whole brain with an effective resolution of 1.24 mm from a 12.6-min scan. In lesions of multiple sclerosis subjects, we observe a decreased size of the semi-solid spin pool and longer relaxation times, consistent with previous reports. CONCLUSION The encoding power of the hybrid state, combined with regularized image reconstruction, and the accuracy of the generalized Bloch model provide an excellent basis for efficient quantitative magnetization transfer imaging with few constraints on model parameters.
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Affiliation(s)
- Jakob Assländer
- Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA
- Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, NYU School of Medicine, New York, New York, USA
| | - Cem Gultekin
- Courant Institute of Mathematical Sciences, New York University, New York, New York, USA
| | - Andrew Mao
- Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA
- Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, NYU School of Medicine, New York, New York, USA
- Vilcek Institute of Graduate Biomedical Sciences, NYU School of Medicine, New York, New York, USA
| | - Xiaoxia Zhang
- Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA
- Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, NYU School of Medicine, New York, New York, USA
| | - Quentin Duchemin
- Laboratoire d'analyse et de mathématiques appliquées, Université Gustave Eiffel, Champs-sur-Marne, France
| | - Kangning Liu
- Center for Data Science, New York University, New York, New York, USA
| | - Robert W Charlson
- Department of Neurology, NYU School of Medicine, New York, New York, USA
| | - Timothy M Shepherd
- Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA
| | - Carlos Fernandez-Granda
- Courant Institute of Mathematical Sciences, New York University, New York, New York, USA
- Center for Data Science, New York University, New York, New York, USA
| | - Sebastian Flassbeck
- Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA
- Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, NYU School of Medicine, New York, New York, USA
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4
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Gao C, Ming Z, Nguyen KL, Pang J, Bedayat A, Dale BM, Zhong X, Finn JP. Ferumoxytol-Enhanced Cardiac Cine MRI Reconstruction Using a Variable-Splitting Spatiotemporal Network. J Magn Reson Imaging 2024. [PMID: 38436994 DOI: 10.1002/jmri.29295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Revised: 01/29/2024] [Accepted: 01/31/2024] [Indexed: 03/05/2024] Open
Abstract
BACKGROUND Balanced steady-state free precession (bSSFP) imaging is commonly used in cardiac cine MRI but prone to image artifacts. Ferumoxytol-enhanced (FE) gradient echo (GRE) has been proposed as an alternative. Utilizing the abundance of bSSFP images to develop a computationally efficient network that is applicable to FE GRE cine would benefit future network development. PURPOSE To develop a variable-splitting spatiotemporal network (VSNet) for image reconstruction, trained on bSSFP cine images and applicable to FE GRE cine images. STUDY TYPE Retrospective and prospective. SUBJECTS 41 patients (26 female, 53 ± 19 y/o) for network training, 31 patients (19 female, 49 ± 17 y/o) and 5 healthy subjects (5 female, 30 ± 7 y/o) for testing. FIELD STRENGTH/SEQUENCE 1.5T and 3T, bSSFP and GRE. ASSESSMENT VSNet was compared to VSNet with total variation loss, compressed sensing and low rank methods for 14× accelerated data. The GRAPPA×2/×3 images served as the reference. Peak signal-to-noise-ratio (PSNR), structural similarity index (SSIM), left ventricular (LV) and right ventricular (RV) end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) were measured. Qualitative image ranking and scoring were independently performed by three readers. Latent scores were calculated based on scores of each method relative to the reference. STATISTICS Linear mixed-effects regression, Tukey method, Fleiss' Kappa, Bland-Altman analysis, and Bayesian categorical cumulative probit model. A P-value <0.05 was considered statistically significant. RESULTS VSNet achieved significantly higher PSNR (32.7 ± 0.2), SSIM (0.880 ± 0.004), rank (2.14 ± 0.06), and latent scores (-1.72 ± 0.22) compared to other methods (rank >2.90, latent score < -2.63). Fleiss' Kappa was 0.52 for scoring and 0.61 for ranking. VSNet showed no significantly different LV and RV ESV (P = 0.938) and EF (P = 0.143) measurements, but statistically significant different (2.62 mL) EDV measurements compared to the reference. CONCLUSION VSNet produced the highest image quality and the most accurate functional measurements for FE GRE cine images among the tested 14× accelerated reconstruction methods. LEVEL OF EVIDENCE 3 TECHNICAL EFFICACY: Stage 1.
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Affiliation(s)
- Chang Gao
- Department of Physics and Biology in Medicine, University of California Los Angeles, Los Angeles, California, USA
- Department of Radiological Sciences, University of California Los Angeles, Los Angeles, California, USA
| | - Zhengyang Ming
- Department of Physics and Biology in Medicine, University of California Los Angeles, Los Angeles, California, USA
- Department of Radiological Sciences, University of California Los Angeles, Los Angeles, California, USA
| | - Kim-Lien Nguyen
- Department of Physics and Biology in Medicine, University of California Los Angeles, Los Angeles, California, USA
- Department of Radiological Sciences, University of California Los Angeles, Los Angeles, California, USA
- Division of Cardiology, University of California Los Angeles and VA Greater Los Angeles Healthcare System, Los Angeles, California, USA
| | - Jianing Pang
- MR R&D Collaborations, Siemens Medical Solutions USA, Inc., Chicago, Illinois, USA
| | - Arash Bedayat
- Department of Radiological Sciences, University of California Los Angeles, Los Angeles, California, USA
| | - Brian M Dale
- MR R&D Collaborations, Siemens Medical Solutions USA, Inc., Cary, North Carliona, USA
| | - Xiaodong Zhong
- MR R&D Collaborations, Siemens Medical Solutions USA, Inc., Los Angeles, California, USA
| | - J Paul Finn
- Department of Physics and Biology in Medicine, University of California Los Angeles, Los Angeles, California, USA
- Department of Radiological Sciences, University of California Los Angeles, Los Angeles, California, USA
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He T, Zur Y, Montrazi ET, Frydman L. Phase-Incremented Steady-State Free Precession as an Alternate Route to High-Resolution NMR. J Am Chem Soc 2024; 146:3615-3621. [PMID: 38291738 PMCID: PMC10870713 DOI: 10.1021/jacs.3c12954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 01/20/2024] [Accepted: 01/22/2024] [Indexed: 02/01/2024]
Abstract
Pulsed Fourier transform nuclear magnetic resonance (FT-NMR) has reigned supreme in high-resolution, high-field spectroscopy─particularly when targeting complex liquid-state samples involving multiple sharp peaks spread over large spectral bandwidths. It is known, however, that if spectral resolution is not a must, the FT-based approach is not necessarily the optimal route for maximizing NMR sensitivity: if T2 ≈ T1, as often found in solutions, Carr's steady-state free-precession (SSFP) approach can in principle provide a superior signal-to-noise ratio per √(acquisition_time) (SNRt). A rapid train of pulses will then lead to a transverse component that reaches up to 50% of the thermal equilibrium magnetization, provided that pulses are applied at repetition times TR ≪ T2, T1, and that a single suitable offset is involved. It is generally assumed that having to deal with multiple chemical shifts deprives SSFP from its advantages. The present study revisits this assumption by introducing an approach whereby arbitrarily short SSFP-derived free induction decays (FIDs) can deliver high-resolution spectra, without suffering from peak broadenings or phase distortions. To achieve discrimination among nearby frequencies, signals arising from a series of regularly phase-increased excitation pulses are collected. Given SSFP's amplitude and phase sensitivity to the spins' offset, this enables the resolution of sites according to their chemical shift position. In addition, the extreme fold-over associated with SSFP acquisitions is dealt with by a customized discrete FT of the interpulse time-domain signal. Solution-state 13C NMR spectra which compare well with FT-NMR data in terms of sensitivity, bandwidth, and resolution can then be obtained.
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Affiliation(s)
- Tian He
- Department
of Chemical and Biological Physics, Weizmann
Institute, 7610001 Rehovot, Israel
- Department
of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Yuval Zur
- Insightec
Ltd, 3903203 Tirat Carmel, Israel
| | - Elton T. Montrazi
- Department
of Chemical and Biological Physics, Weizmann
Institute, 7610001 Rehovot, Israel
| | - Lucio Frydman
- Department
of Chemical and Biological Physics, Weizmann
Institute, 7610001 Rehovot, Israel
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Vu BTD, Jones BC, Lee H, Kamona N, Deshpande RS, Wehrli FW, Rajapakse CS. Six-minute, in vivo MRI quantification of proximal femur trabecular bone 3D microstructure. Bone 2023; 177:116900. [PMID: 37714503 DOI: 10.1016/j.bone.2023.116900] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 08/29/2023] [Accepted: 09/12/2023] [Indexed: 09/17/2023]
Abstract
BACKGROUND Assessment of proximal femur trabecular bone microstructure in vivo by magnetic resonance imaging has recently been validated for acquiring information independent of bone mineral density in osteoporotic patients. However, the requisite signal-to-noise ratio (SNR) and resolution for interrogation of the trabecular microstructure at this anatomical location prolongs the scan duration and renders the imaging protocol clinically infeasible. Parallel imaging and compressed sensing (PICS) techniques can reduce the scan duration of the imaging protocol without substantially compromising image quality. The present work investigates the limits of acceleration for a commonly used PICS technique, ℓ1-ESPIRiT, for the purpose of quantifying measures of trabecular bone microarchitecture. Based on a desired error tolerance, a six-minute, prospectively accelerated variant of the imaging protocol was developed and assessed for intersession reproducibility and agreement with the longer reference scan. PURPOSE To investigate the limits of acceleration for MRI-based trabecular bone quantification by parallel imaging and compressed sensing reconstruction, and to develop a prototypical imaging protocol for assessing the proximal femur microstructure in a clinically practical scan time. METHODS Healthy participants (n = 11) were scanned by a 3D balanced steady-state free precession (bSSFP) sequence satisfying the Nyquist criterion with a scan duration of about 18 min. The raw data were retrospectively undersampled and reconstructed to mimic various acceleration factors ranging from 2 to 6. Trabecular volumes-of-interest in four major femoral regions (greater trochanter, intertrochanteric region, femoral neck, and femoral head) were analyzed and six relevant measures of trabecular bone microarchitecture (bone volume fraction, surface-to-curve ratio, erosion index, elastic modulus, trabecular thickness, plates-to-rods ratio) were obtained for images of all accelerations. To assess agreement, median percent error and intraclass correlation coefficients (ICCs) were computed using the fully-sampled data as reference. Based on this analysis, a prospectively 3-fold accelerated sequence with a duration of about 6 min was developed and the analysis was repeated. RESULTS A prospective acceleration factor of 3 demonstrated comparable performance in reproducibility and absolute agreement to the fully-sampled scan. The median CoV over all image-derived metrics was generally <6 % and ICCs >0.70. Also, measurements from prospectively 3-fold accelerated scans demonstrated in general median percent errors of <7 % and ICCs >0.70. CONCLUSION The present work proposes a method to make in vivo quantitative assessment of proximal femur trabecular microstructure with a clinically practical scan duration of about 6 min.
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Affiliation(s)
- Brian-Tinh Duc Vu
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, 1 Founders Building, 3400 Spruce St, Philadelphia, PA 19104, United States of America; Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, 210 South 33(rd) St, Philadelphia, PA 19104, United States of America.
| | - Brandon C Jones
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, 1 Founders Building, 3400 Spruce St, Philadelphia, PA 19104, United States of America; Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, 210 South 33(rd) St, Philadelphia, PA 19104, United States of America
| | - Hyunyeol Lee
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, 1 Founders Building, 3400 Spruce St, Philadelphia, PA 19104, United States of America; School of Electronics Engineering, Kyungpook National University, 80 Daehakro, Bukgu, Daegu 41566, South Korea
| | - Nada Kamona
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, 1 Founders Building, 3400 Spruce St, Philadelphia, PA 19104, United States of America; Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, 210 South 33(rd) St, Philadelphia, PA 19104, United States of America
| | - Rajiv S Deshpande
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, 1 Founders Building, 3400 Spruce St, Philadelphia, PA 19104, United States of America; Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, 210 South 33(rd) St, Philadelphia, PA 19104, United States of America
| | - Felix W Wehrli
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, 1 Founders Building, 3400 Spruce St, Philadelphia, PA 19104, United States of America
| | - Chamith S Rajapakse
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, 1 Founders Building, 3400 Spruce St, Philadelphia, PA 19104, United States of America; Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 3400 Spruce St, Philadelphia, PA 19104, United States of America
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Rossi GMC, Mackowiak ALC, Açikgöz BC, Pierzchała K, Kober T, Hilbert T, Bastiaansen JAM. SPARCQ: A new approach for fat fraction mapping using asymmetries in the phase-cycled balanced SSFP signal profile. Magn Reson Med 2023; 90:2348-2361. [PMID: 37496187 DOI: 10.1002/mrm.29813] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 06/19/2023] [Accepted: 07/12/2023] [Indexed: 07/28/2023]
Abstract
PURPOSE To develop SPARCQ (Signal Profile Asymmetries for Rapid Compartment Quantification), a novel approach to quantify fat fraction (FF) using asymmetries in the phase-cycled balanced SSFP (bSSFP) profile. METHODS SPARCQ uses phase-cycling to obtain bSSFP frequency profiles, which display asymmetries in the presence of fat and water at certain TRs. For each voxel, the measured signal profile is decomposed into a weighted sum of simulated profiles via multi-compartment dictionary matching. Each dictionary entry represents a single-compartment bSSFP profile with a specific off-resonance frequency and relaxation time ratio. Using the results of dictionary matching, the fractions of the different off-resonance components are extracted for each voxel, generating quantitative maps of water and FF and banding-artifact-free images for the entire image volume. SPARCQ was validated using simulations, experiments in a water-fat phantom and in knees of healthy volunteers. Experimental results were compared with reference proton density FFs obtained with 1 H-MRS (phantoms) and with multiecho gradient-echo MRI (phantoms and volunteers). SPARCQ repeatability was evaluated in six scan-rescan experiments. RESULTS Simulations showed that FF quantification is accurate and robust for SNRs greater than 20. Phantom experiments demonstrated good agreement between SPARCQ and gold standard FFs. In volunteers, banding-artifact-free quantitative maps and water-fat-separated images obtained with SPARCQ and ME-GRE demonstrated the expected contrast between fatty and non-fatty tissues. The coefficient of repeatability of SPARCQ FF was 0.0512. CONCLUSION SPARCQ demonstrates potential for fat quantification using asymmetries in bSSFP profiles and may be a promising alternative to conventional FF quantification techniques.
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Affiliation(s)
- Giulia M C Rossi
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Translational Imaging Center, Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Adèle L C Mackowiak
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Translational Imaging Center, Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Berk Can Açikgöz
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Translational Imaging Center, Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
| | - Katarzyna Pierzchała
- CIBM Center for Biomedical Imaging, Lausanne, Switzerland
- Animal Imaging and Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Tobias Kober
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
- Advanced Clinical Imaging Technology, Siemens Healthineers International AG, Lausanne, Switzerland
- LTS5, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Tom Hilbert
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
- Advanced Clinical Imaging Technology, Siemens Healthineers International AG, Lausanne, Switzerland
- LTS5, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Jessica A M Bastiaansen
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Translational Imaging Center, Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
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Chen Z, Hua S, Gao J, Chen Y, Gong Y, Shen Y, Tang X, Emu Y, Jin W, Hu C. A dual-stage partially interpretable neural network for joint suppression of bSSFP banding and flow artifacts in non-phase-cycled cine imaging. J Cardiovasc Magn Reson 2023; 25:68. [PMID: 37993824 PMCID: PMC10666342 DOI: 10.1186/s12968-023-00988-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 11/12/2023] [Indexed: 11/24/2023] Open
Abstract
PURPOSE To develop a partially interpretable neural network for joint suppression of banding and flow artifacts in non-phase-cycled bSSFP cine imaging. METHODS A dual-stage neural network consisting of a voxel-identification (VI) sub-network and artifact-suppression (AS) sub-network is proposed. The VI sub-network provides identification of artifacts, which guides artifact suppression and improves interpretability. The AS sub-network reduces banding and flow artifacts. Short-axis cine images of 12 frequency offsets from 28 healthy subjects were used to train and test the dual-stage network. An additional 77 patients were retrospectively enrolled to evaluate its clinical generalizability. For healthy subjects, artifact suppression performance was analyzed by comparison with traditional phase cycling. The partial interpretability provided by the VI sub-network was analyzed via correlation analysis. Generalizability was evaluated for cine obtained with different sequence parameters and scanners. For patients, artifact suppression performance and partial interpretability of the network were qualitatively evaluated by 3 clinicians. Cardiac function before and after artifact suppression was assessed via left ventricular ejection fraction (LVEF). RESULTS For the healthy subjects, visual inspection and quantitative analysis found a considerable reduction of banding and flow artifacts by the proposed network. Compared with traditional phase cycling, the proposed network improved flow artifact scores (4.57 ± 0.23 vs 3.40 ± 0.38, P = 0.002) and overall image quality (4.33 ± 0.22 vs 3.60 ± 0.38, P = 0.002). The VI sub-network well identified the location of banding and flow artifacts in the original movie and significantly correlated with the change of signal intensities in these regions. Changes of imaging parameters or the scanner did not cause a significant change of overall image quality relative to the baseline dataset, suggesting a good generalizability. For the patients, qualitative analysis showed a significant improvement of banding artifacts (4.01 ± 0.50 vs 2.77 ± 0.40, P < 0.001), flow artifacts (4.22 ± 0.38 vs 2.97 ± 0.57, P < 0.001), and image quality (3.91 ± 0.45 vs 2.60 ± 0.43, P < 0.001) relative to the original cine. The artifact suppression slightly reduced the LVEF (mean bias = -1.25%, P = 0.01). CONCLUSIONS The dual-stage network simultaneously reduces banding and flow artifacts in bSSFP cine imaging with a partial interpretability, sparing the need for sequence modification. The method can be easily deployed in a clinical setting to identify artifacts and improve cine image quality.
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Affiliation(s)
- Zhuo Chen
- National Engineering Research Center of Advanced Magnetic Resonance Technologies for Diagnosis and Therapy, School of Biomedical Engineering, Shanghai Jiao Tong University, 415 S Med-X Center, 1954 Huashan Road, Shanghai, 200030, China
| | - Sha Hua
- Department of Cardiovascular Medicine, Heart Failure Center, Ruijin Hospital Lu Wan Branch, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Juan Gao
- National Engineering Research Center of Advanced Magnetic Resonance Technologies for Diagnosis and Therapy, School of Biomedical Engineering, Shanghai Jiao Tong University, 415 S Med-X Center, 1954 Huashan Road, Shanghai, 200030, China
| | - Yanjia Chen
- Department of Cardiovascular Medicine, Heart Failure Center, Ruijin Hospital Lu Wan Branch, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yiwen Gong
- Department of Cardiovascular Medicine, Heart Failure Center, Ruijin Hospital Lu Wan Branch, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yiwen Shen
- Department of Cardiovascular Medicine, Heart Failure Center, Ruijin Hospital Lu Wan Branch, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xin Tang
- National Engineering Research Center of Advanced Magnetic Resonance Technologies for Diagnosis and Therapy, School of Biomedical Engineering, Shanghai Jiao Tong University, 415 S Med-X Center, 1954 Huashan Road, Shanghai, 200030, China
| | - Yixin Emu
- National Engineering Research Center of Advanced Magnetic Resonance Technologies for Diagnosis and Therapy, School of Biomedical Engineering, Shanghai Jiao Tong University, 415 S Med-X Center, 1954 Huashan Road, Shanghai, 200030, China
| | - Wei Jin
- Department of Cardiovascular Medicine, Heart Failure Center, Ruijin Hospital Lu Wan Branch, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chenxi Hu
- National Engineering Research Center of Advanced Magnetic Resonance Technologies for Diagnosis and Therapy, School of Biomedical Engineering, Shanghai Jiao Tong University, 415 S Med-X Center, 1954 Huashan Road, Shanghai, 200030, China.
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Han PK, Marin T, Zhuo Y, Ouyang J, El Fakhri G, Ma C. Arterial spin labeled perfusion imaging with balanced steady-state free precession readout and radial sampling. Magn Reson Imaging 2023; 102:126-132. [PMID: 37187264 PMCID: PMC10524790 DOI: 10.1016/j.mri.2023.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 04/19/2023] [Accepted: 05/09/2023] [Indexed: 05/17/2023]
Abstract
PURPOSE To develop an arterial spin labeling (ASL) perfusion imaging method with balanced steady-state free precession (bSSFP) readout and radial sampling for improved SNR and robustness to motion and off-resonance effects. METHODS An ASL perfusion imaging method was developed with pseudo-continuous arterial spin labeling (pCASL) and bSSFP readout. Three-dimensional (3D) k-space data were collected in segmented acquisitions following a stack-of-stars sampling trajectory. Multiple phase-cycling technique was utilized to improve the robustness to off-resonance effects. Parallel imaging with sparsity-constrained image reconstruction was used to accelerate imaging or increase the spatial coverage. RESULTS ASL with bSSFP readout showed higher spatial and temporal SNRs of the gray matter perfusion signal compared to those from spoiled gradient-recalled acquisition (SPGR). Cartesian and radial sampling schemes showed similar spatial and temporal SNRs, regardless of the imaging readout. In case of severe B0 inhomogeneity, single-RF phase incremented bSSFP acquisitions showed banding artifacts. These artifacts were significantly reduced when multiple phase-cycling technique (N = 4) was employed. The perfusion-weighted images obtained by the Cartesian sampling scheme showed respiratory motion-related artifacts when a high segmentation number was used. The perfusion-weighted images obtained by the radial sampling scheme did not show these artifacts. Whole brain perfusion imaging was feasible in 1.15 min or 4.6 min for cases without and with phase-cycling (N = 4), respectively, using the proposed method with parallel imaging. CONCLUSIONS The developed method allows non-invasive perfusion imaging of the whole-brain with relatively high SNR and robustness to motion and off-resonance effects in a practically feasible imaging time.
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Affiliation(s)
- Paul Kyu Han
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States; Department of Radiology, Harvard Medical School, Boston, MA, United States
| | - Thibault Marin
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States; Department of Radiology, Harvard Medical School, Boston, MA, United States
| | - Yue Zhuo
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States; Department of Radiology, Harvard Medical School, Boston, MA, United States
| | - Jinsong Ouyang
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States; Department of Radiology, Harvard Medical School, Boston, MA, United States
| | - Georges El Fakhri
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States; Department of Radiology, Harvard Medical School, Boston, MA, United States
| | - Chao Ma
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States; Department of Radiology, Harvard Medical School, Boston, MA, United States.
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Garetier M, Rousset J, Makki K, Brochard S, Rousseau F, Salem DB, Borotikar B. Assessment and comparison of image quality between two real-time sequences for dynamic MRI of distal joints at 3.0 Tesla. Acta Radiol 2023; 64:1093-1102. [PMID: 35616984 DOI: 10.1177/02841851221101889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Real-time sequences allow functional evaluation of various joint structures during a continuous motion and help understand the pathomechanics of underlying musculoskeletal diseases. PURPOSE To assess and compare the image quality of the two most frequently used real-time sequences for joint dynamic magnetic resonance imaging (MRI), acquired during finger and ankle joint motion. MATERIAL AND METHODS A real-time dynamic acquisition protocol, including radiofrequency (RF)-spoiled and balanced steady-state free precession (bSSFP) sequences, optimized for temporal resolution with similar spatial resolution, was performed using a 3.0-T MRI scanner on 10 fingers and 12 ankles from healthy individuals during active motion. Image quality criteria were evaluated on each time frame and compared between these two sequences. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were determined and compared from regions of interest placed on cortical bone, tendon, fat, and muscle. Visualization of anatomical structures and overall image quality appreciation were rated by two radiologists using a 0-10 grading scale. RESULTS Mean CNR was significantly higher with bSSFP sequence compared to RF-spoiled sequence. The grading score was in the range of 5-9.3 and was significantly higher with RF-spoiled sequence for bone and joint evaluation and overall image appreciation on the two joints. The standard deviation for SNR, CNR, and grading score during motion was smaller with RF-spoiled sequence for both the joints. The inter-reader reliability was excellent (>0.75) for evaluating anatomical structures in both sequences. CONCLUSION A RF-spoiled real-time sequence is recommended for the in vivo clinical evaluation of distal joints on a 3.0-T MRI scanner.
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Affiliation(s)
- Marc Garetier
- Department of Radiology, Military Teaching Hospital Clermont-Tonnerre, Brest, France
- Department of Radiology, University Hospital Morvan, Brest, France
- Laboratory of Medical Information Processing (LATIM), INSERM-UMR 1101, Brest, France
| | - Jean Rousset
- Department of Radiology, Military Teaching Hospital Clermont-Tonnerre, Brest, France
| | - Karim Makki
- INRIA Fluminance, Rennes, France
- 56498IFPEN, Rueil-Malmaison, France
| | - Sylvain Brochard
- Laboratory of Medical Information Processing (LATIM), INSERM-UMR 1101, Brest, France
- Department of Physical and Medical Rehabilitation, University Hospital Morvan, Brest, France
- Department of Paediatric Physical and Medical Rehabilitation, Fondation Ildys, Brest, France
- University of Western Brittany (UBO), Brest, France
| | - François Rousseau
- Laboratory of Medical Information Processing (LATIM), INSERM-UMR 1101, Brest, France
- 52826IMT Atlantique, UBL, Brest, France
| | - Douraïed Ben Salem
- Laboratory of Medical Information Processing (LATIM), INSERM-UMR 1101, Brest, France
- University of Western Brittany (UBO), Brest, France
- Department of Radiology, University Hospital La Cavale Blanche, Brest, France
| | - Bhushan Borotikar
- Laboratory of Medical Information Processing (LATIM), INSERM-UMR 1101, Brest, France
- Symbiosis Centre for Medical Image Analysis, 29630Symbiosis International University, Pune, India
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11
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Hoff MN, Xiang QS, Cross NM, Hippe D, Andre JB. Motion resilience of the balanced steady-state free precession geometric solution. Magn Reson Med 2022; 89:192-204. [PMID: 36093906 DOI: 10.1002/mrm.29438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 07/26/2022] [Accepted: 08/11/2022] [Indexed: 11/06/2022]
Abstract
PURPOSE Many MRI sequences are sensitive to motion and its associated artifacts. The linearized geometric solution (LGS), a balanced steady-state free precession (bSSFP) off-resonance signal demodulation technique, is evaluated with respect to motion artifact resilience. THEORY AND METHODS The mechanism and extent of LGS motion artifact resilience is examined in simulated, flow phantom, and in vivo clinical imaging. Motion artifact correction capabilities are decoupled from susceptibility artifact correction when feasible to permit controlled analysis of motion artifact correction when comparing the LGS with standard and phase-cycle-averaged (complex sum) bSSFP imaging. RESULTS Simulations reveal that the LGS demonstrates motion artifact reduction capabilities similar to standard clinical bSSFP imaging techniques, with slightly greater resilience in high SNR regions and for shorter-duration motion. Flow phantom experiments assert that the LGS reduces shorter-duration motion artifact error by ∼24%-65% relative to the complex sum, whereas reconstructions exhibit similar error reduction for constant motion. In vivo analysis demonstrates that in the internal auditory canal/orbits, the LGS was deemed to have less artifact in 24%/49% and similar artifact in 76%/51% of radiological assessments relative to the complex sum, and the LGS had less artifact in 97%/81% and similar artifact in 3%/16% of assessments relative to standard bSSFP. Only 2 of 63 assessments deemed the LGS inferior to either complex sum or standard bSSFP in terms of artifact reduction. CONCLUSION The LGS provides sufficient bSSFP motion artifact resilience to permit robust elimination of susceptibility artifacts, inspiring its use in a wide variety of applications.
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Affiliation(s)
- Michael N Hoff
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
| | - Qing-San Xiang
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Nathan M Cross
- Department of Radiology, University of Washington, Seattle, Washington, USA
| | - Daniel Hippe
- Clinical Biostatistics, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | - Jalal B Andre
- Department of Radiology, University of Washington, Seattle, Washington, USA
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12
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Ilicak E, Ozdemir S, Schad LR, Weis M, Schoenberg SO, Zöllner FG, Zapp J. Phase-cycled balanced SSFP imaging for non-contrast-enhanced functional lung imaging. Magn Reson Med 2022; 88:1764-1774. [PMID: 35608220 DOI: 10.1002/mrm.29302] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 04/11/2022] [Accepted: 04/25/2022] [Indexed: 11/09/2022]
Abstract
PURPOSE To introduce phase-cycled balanced SSFP (bSSFP) acquisition as an alternative in Fourier decomposition MRI for improved robustness against field inhomogeneities. METHODS Series 2D dynamic lung images were acquired in 5 healthy volunteers at 1.5 T and 3 T using bSSFP sequence with multiple RF phase increments and compared with conventional single RF phase increment acquisitions. The approach was evaluated based on functional map homogeneity analysis, while ensuring image and functional map quality by means of SNR and contrast-to-noise ratio analyses. RESULTS At both field strengths, functional maps obtained with phase-cycled acquisitions displayed improved robustness against local signal losses compared with single-phase acquisitions. The coefficient of variation (mean ± SD, across volunteers) measured in the ventilation maps resulted in 29.7 ± 2.6 at 1.5 T and 37.5 ± 3.1 at 3 T for phase-cycled acquisitions, compared with 39.9 ± 5.2 at 1.5 T and 49.5 ± 3.7 at 3 T for single-phase acquisitions, indicating a significant improvement ( p < 0.05 $$ p<0.05 $$ ) in ventilation map homogeneity. CONCLUSIONS Phase-cycled bSSFP acquisitions improve robustness against field inhomogeneity artifacts and significantly improve ventilation map homogeneity at both field strengths. As such, phase-cycled bSSFP may serve as a robust alternative in lung function assessments.
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Affiliation(s)
- Efe Ilicak
- Computer Assisted Clinical Medicine, Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Safa Ozdemir
- Computer Assisted Clinical Medicine, Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Lothar R Schad
- Computer Assisted Clinical Medicine, Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Meike Weis
- Department of Clinical Radiology and Nuclear Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Stefan O Schoenberg
- Department of Clinical Radiology and Nuclear Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Frank G Zöllner
- Computer Assisted Clinical Medicine, Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Jascha Zapp
- Computer Assisted Clinical Medicine, Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
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Kim KH, Seo S, Do WJ, Luu HM, Park SH. Varying undersampling directions for accelerating multiple acquisition magnetic resonance imaging. NMR IN BIOMEDICINE 2022; 35:e4572. [PMID: 34114253 DOI: 10.1002/nbm.4572] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 05/27/2021] [Accepted: 05/27/2021] [Indexed: 06/12/2023]
Abstract
In this study, we propose a new sampling strategy for efficiently accelerating multiple acquisition MRI. The new sampling strategy is to obtain data along different phase-encoding directions across multiple acquisitions. The proposed sampling strategy was evaluated in multicontrast MR imaging (T1, T2, proton density) and multiple phase-cycled (PC) balanced steady-state free precession (bSSFP) imaging by using convolutional neural networks with central and random sampling patterns. In vivo MRI acquisitions as well as a public database were used to test the concept. Based on both visual inspection and quantitative analysis, the proposed sampling strategy showed better performance than sampling along the same phase-encoding direction in both multicontrast MR imaging and multiple PC-bSSFP imaging, regardless of sampling pattern (central, random) or datasets (public, retrospective and prospective in vivo). For the prospective in vivo applications, acceleration was performed by sampling along different phase-encoding directions at the time of acquisition with a conventional rectangular field of view, which demonstrated the advantage of the proposed sampling strategy in the real environment. Preliminary trials on compressed sensing (CS) also demonstrated improvement of CS with the proposed idea. Sampling along different phase-encoding directions across multiple acquisitions is advantageous for accelerating multiacquisition MRI, irrespective of sampling pattern or datasets, with further improvement through transfer learning.
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Affiliation(s)
- Ki Hwan Kim
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Sunghun Seo
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Won-Joon Do
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Huan Minh Luu
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Sung-Hong Park
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
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14
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Tendler BC, Hanayik T, Ansorge O, Bangerter-Christensen S, Berns GS, Bertelsen MF, Bryant KL, Foxley S, van den Heuvel MP, Howard AFD, Huszar IN, Khrapitchev AA, Leonte A, Manger PR, Menke RAL, Mollink J, Mortimer D, Pallebage-Gamarallage M, Roumazeilles L, Sallet J, Scholtens LH, Scott C, Smart A, Turner MR, Wang C, Jbabdi S, Mars RB, Miller KL. The Digital Brain Bank, an open access platform for post-mortem imaging datasets. eLife 2022; 11:e73153. [PMID: 35297760 PMCID: PMC9042233 DOI: 10.7554/elife.73153] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 03/17/2022] [Indexed: 11/13/2022] Open
Abstract
Post-mortem magnetic resonance imaging (MRI) provides the opportunity to acquire high-resolution datasets to investigate neuroanatomy and validate the origins of image contrast through microscopy comparisons. We introduce the Digital Brain Bank (open.win.ox.ac.uk/DigitalBrainBank), a data release platform providing open access to curated, multimodal post-mortem neuroimaging datasets. Datasets span three themes-Digital Neuroanatomist: datasets for detailed neuroanatomical investigations; Digital Brain Zoo: datasets for comparative neuroanatomy; and Digital Pathologist: datasets for neuropathology investigations. The first Digital Brain Bank data release includes 21 distinctive whole-brain diffusion MRI datasets for structural connectivity investigations, alongside microscopy and complementary MRI modalities. This includes one of the highest-resolution whole-brain human diffusion MRI datasets ever acquired, whole-brain diffusion MRI in fourteen nonhuman primate species, and one of the largest post-mortem whole-brain cohort imaging studies in neurodegeneration. The Digital Brain Bank is the culmination of our lab's investment into post-mortem MRI methodology and MRI-microscopy analysis techniques. This manuscript provides a detailed overview of our work with post-mortem imaging to date, including the development of diffusion MRI methods to image large post-mortem samples, including whole, human brains. Taken together, the Digital Brain Bank provides cross-scale, cross-species datasets facilitating the incorporation of post-mortem data into neuroimaging studies.
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Affiliation(s)
- Benjamin C Tendler
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Taylor Hanayik
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Olaf Ansorge
- Division of Clinical Neurology, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Sarah Bangerter-Christensen
- Division of Clinical Neurology, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | | | - Mads F Bertelsen
- Centre for Zoo and Wild Animal Health, Copenhagen ZooFrederiksbergDenmark
| | - Katherine L Bryant
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Sean Foxley
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
- Department of Radiology, University of ChicagoChicagoUnited States
| | - Martijn P van den Heuvel
- Department of Complex Trait Genetics, Centre for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, Vrije Universiteit AmsterdamAmsterdamNetherlands
- Department of Child Psychiatry, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit AmsterdamAmsterdamNetherlands
| | - Amy FD Howard
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Istvan N Huszar
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Alexandre A Khrapitchev
- Medical Research Council Oxford Institute for Radiation Oncology, University of OxfordOxfordUnited Kingdom
| | - Anna Leonte
- Division of Clinical Neurology, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Paul R Manger
- School of Anatomical Sciences, Faculty of Health Sciences, University of the WitwatersrandJohannesburgSouth Africa
| | - Ricarda AL Menke
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Jeroen Mollink
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Duncan Mortimer
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Menuka Pallebage-Gamarallage
- Division of Clinical Neurology, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Lea Roumazeilles
- Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, University of OxfordOxfordUnited Kingdom
| | - Jerome Sallet
- Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, University of OxfordOxfordUnited Kingdom
- Stem Cell and Brain Research Institute, Université Lyon 1, INSERMBronFrance
| | - Lianne H Scholtens
- Department of Complex Trait Genetics, Centre for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, Vrije Universiteit AmsterdamAmsterdamNetherlands
| | - Connor Scott
- Division of Clinical Neurology, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Adele Smart
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
- Division of Clinical Neurology, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Martin R Turner
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
- Division of Clinical Neurology, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Chaoyue Wang
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Saad Jbabdi
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
| | - Rogier B Mars
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
- Donders Institute for Brain, Cognition and Behaviour, Radboud University NijmegenNijmegenNetherlands
| | - Karla L Miller
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of OxfordOxfordUnited Kingdom
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Keskin K, Yilmaz U, Cukur T. Constrained Ellipse Fitting for Efficient Parameter Mapping With Phase-Cycled bSSFP MRI. IEEE TRANSACTIONS ON MEDICAL IMAGING 2022; 41:14-26. [PMID: 34351856 DOI: 10.1109/tmi.2021.3102852] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Balanced steady-state free precession (bSSFP) imaging enables high scan efficiency in MRI, but differs from conventional sequences in terms of elevated sensitivity to main field inhomogeneity and nonstandard [Formula: see text]-weighted tissue contrast. To address these limitations, multiple bSSFP images of the same anatomy are commonly acquired with a set of different RF phase-cycling increments. Joint processing of phase-cycled acquisitions serves to mitigate sensitivity to field inhomogeneity. Recently phase-cycled bSSFP acquisitions were also leveraged to estimate relaxation parameters based on explicit signal models. While effective, these model-based methods often involve a large number of acquisitions (N ≈ 10-16), degrading scan efficiency. Here, we propose a new constrained ellipse fitting method (CELF) for parameter estimation with improved efficiency and accuracy in phase-cycled bSSFP MRI. CELF is based on the elliptical signal model framework for complex bSSFP signals; and it introduces geometrical constraints on ellipse properties to improve estimation efficiency, and dictionary-based identification to improve estimation accuracy. CELF generates maps of [Formula: see text], [Formula: see text], off-resonance and on-resonant bSSFP signal by employing a separate [Formula: see text] map to mitigate sensitivity to flip angle variations. Our results indicate that CELF can produce accurate off-resonance and banding-free bSSFP maps with as few as N = 4 acquisitions, while estimation accuracy for relaxation parameters is notably limited by biases from microstructural sensitivity of bSSFP imaging.
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Avanesov M, Weinrich JM, Sinn M, Lenz A, von Düring F, Salamon J, Henes FO, Schönnagel BP, Adam G, von Kodolitsch Y, Bannas P. Intraindividual comparison of 1.5 T and 3 T non-contrast MR angiography for monitoring of aortic root diameters in Marfan patients. Int J Cardiol 2021; 337:119-126. [PMID: 33933510 DOI: 10.1016/j.ijcard.2021.04.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 04/12/2021] [Accepted: 04/26/2021] [Indexed: 10/21/2022]
Abstract
BACKGROUND Reproducible aortic diameter measurements are crucial for assessment of aortic growth and aneurysm formation in patients with Marfan syndrome. The objective of this study was to perform an intraindividual comparison of aortic measurements at 1.5 T and 3 T using non-contrast magnetic resonance angiography (MRA) in pre-surgical and post-surgical Marfan patients. METHODS Forty consecutive Marfan patients were retrospectively evaluated by ECG-gated 2D balanced steady-state free precession (bSSFP) MRA at 1.5 T and 3 T after 363 ± 58 days. 24 patients were before and 16 patients after aortic root surgery. Two readers independently measured aortic diameters at seven aortic levels and rated the image quality/image artifacts (1 = poor/severe, 4 = excellent/none). Contrast-to-noise ratio (CNR) and signal intensity slopes between aortic lumen and vessel walls were semiautomatically determined. RESULTS In pre-surgical Marfan patients, interobserver agreement of aortic root diameter measurements was significantly higher at 3 T compared to 1.5 T (p < 0.05). In post-surgical Marfan patients, image quality and artifacts were significantly worse at 3 T compared to 1.5 T (p < 0.05). CNR was higher at 3 T compared to 1.5 T at all aortic levels. Significantly steeper slopes of signal intensity curves were observed at 3 T at all aortic levels (p < 0.001). CONCLUSIONS In pre-surgical Marfan patients, non-contrast MRA provides higher reproducibility of aortic diameter measurements at 3 T compared to 1.5 T. In post-surgical Marfan patients, metallic implants result in significantly worse imaging artifacts and reduced image quality at 3 T compared to 1.5 T. Therefore, we propose to monitor the thoracic aorta with non-contrast MRA at 3 T in pre-surgical Marfan patients and at 1.5 T in post-surgical Marfan patients.
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Affiliation(s)
- Maxim Avanesov
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany.
| | - Julius Matthias Weinrich
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Martin Sinn
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Alexander Lenz
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Felicia von Düring
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Johannes Salamon
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Frank-Oliver Henes
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Björn Peter Schönnagel
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Gerhard Adam
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Yskert von Kodolitsch
- Department of General and Interventional Cardiology, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Peter Bannas
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
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Jang YI, Sim JY, Yang JR, Kwon NK. The Optimal Selection of Mother Wavelet Function and Decomposition Level for Denoising of DCG Signal. SENSORS 2021; 21:s21051851. [PMID: 33800862 PMCID: PMC7961558 DOI: 10.3390/s21051851] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 03/03/2021] [Accepted: 03/03/2021] [Indexed: 11/16/2022]
Abstract
The aim of this paper is to find the optimal mother wavelet function and wavelet decomposition level when denoising the Doppler cardiogram (DCG), the heart signal obtained by the Doppler radar sensor system. To select the best suited mother wavelet function and wavelet decomposition level, this paper presents the quantitative analysis results. Both the optimal mother wavelet and decomposition level are selected by evaluating signal-to-noise-ratio (SNR) efficiency of the denoised signals obtained by using the wavelet thresholding method. A total of 115 potential functions from six wavelet families were examined for the selection of the optimal mother wavelet function and 10 levels (1 to 10) were evaluated for the choice of the best decomposition level. According to the experimental results, the most efficient selections of the mother wavelet function are "db9" and "sym9" from Daubechies and Symlets families, and the most suitable decomposition level for the used signal is seven. As the evaluation criterion in this study rates the efficiency of the denoising process, it was found that a mother wavelet function longer than 22 is excessive. The experiment also revealed that the decomposition level can be predictable based on the frequency features of the DCG signal. The proposed selection of the mother wavelet function and the decomposition level could reduce noise effectively so as to improve the quality of the DCG signal in information field.
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Affiliation(s)
| | | | - Jong-Ryul Yang
- Correspondence: (J.-R.Y.); (N.K.K.); Tel.: +82-53-810-2495 (J.-R.Y.); +82-53-3095 (N.K.K.)
| | - Nam Kyu Kwon
- Correspondence: (J.-R.Y.); (N.K.K.); Tel.: +82-53-810-2495 (J.-R.Y.); +82-53-3095 (N.K.K.)
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Zidan MA, Almansor N. Presence of vascular loop in patients with audio-vestibular symptoms: is it a significant finding? Evaluation with 3-tesla MRI 3D constructive interference steady state (CISS) sequence. THE EGYPTIAN JOURNAL OF RADIOLOGY AND NUCLEAR MEDICINE 2020. [DOI: 10.1186/s43055-020-00238-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Lally PJ, Matthews PM, Bangerter NK. Unbalanced SSFP for super-resolution in MRI. Magn Reson Med 2020; 85:2477-2489. [PMID: 33201538 PMCID: PMC8972796 DOI: 10.1002/mrm.28593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 09/18/2020] [Accepted: 10/20/2020] [Indexed: 11/13/2022]
Abstract
Purpose: To achieve rapid, low specific absorption rate (SAR) super-resolution imaging by exploiting the characteristic magnetization off-resonance profile in SSFP. Theory and Methods: In the presented technique, low flip angle unbalanced SSFP imaging is used to acquire a series of images at a low nominal resolution that are then combined in a super-resolution strategy analogous to non-linear structured illumination microscopy. This is demonstrated in principle via Bloch simulations and synthetic phantoms, and the performance is quantified in terms of point-spread function (PSF) and SNR for gray and white matter from field strengths of 0.35T to 9.4T. A k-space reconstruction approach is proposed to account for B0 effects. This was applied to reconstruct super-resolution images from a test object at 9.4T. Results: Artifact-free super-resolution images were produced after incorporating sufficient preparation time for the magnetization to approach the steady state. High-resolution images of a test object were obtained at 9.4T, in the presence of considerable B0 inhomogeneity. For gray matter, the highest achievable resolution ranges from 3% of the acquired voxel dimension at 0.35T, to 9% at 9.4T. For white matter, this corresponds to 3% and 10%, respectively. Compared to an equivalent segmented gradient echo acquisition at the optimal flip angle, with a fixed TR of 8 ms, gray matter has up to 34% of the SNR at 9.4T while using a ×10 smaller flip angle. For white matter, this corresponds to 29% with a ×11 smaller flip angle. Conclusion: This approach achieves high degrees of super-resolution enhancement with minimal RF power requirements.
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Affiliation(s)
- Peter J Lally
- Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Paul M Matthews
- Department of Brain Sciences, Imperial College London, London, United Kingdom.,UK Dementia Research Institute Centre at Imperial College London, London, United Kingdom
| | - Neal K Bangerter
- Department of Bioengineering, Imperial College London, London, United Kingdom
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Mehan WA, Buch K, Brasz MF, Simonis FFJ, MacDonald S, Rincon S, Kirsch JE, Caruso P. Balanced Steady-State Free Precession Techniques Improve Detection of Residual Germ Cell Tumor for Treatment Planning. AJNR Am J Neuroradiol 2020; 41:898-903. [PMID: 32354710 PMCID: PMC7228177 DOI: 10.3174/ajnr.a6540] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 03/16/2020] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Identification of a partial/complete chemotherapy response in pediatric patients with intracranial germ cell tumors is clinically important for radiation treatment and management. Partial/complete response is conventionally determined on postcontrast MR imaging sequences. The purpose of this study was to assess the diagnostic utility of a balanced steady-state free precession sequence as an adjunct to standard MR imaging sequences for the detection of residual tumor in pediatric patients on postchemoreduction pre-radiation planning MR imaging. MATERIALS AND METHODS This was a retrospective study of pediatric patients with intracranial germ cell tumors undergoing postchemotherapy, preradiotherapy MR imaging. Patients underwent 1.5T or 3T MR imaging with pre- and postcontrast T1WIs, T2WIs, and a balanced steady-state free precession sequence. Two neuroradiologists independently reviewed standard MR imaging sequences without the balanced steady-state free precession sequence, then with the balanced steady-state free precession sequence 1 week later. Assessment for partial/complete response was determined using Response Assessment in Neuro-Oncology criteria. A 5-point Likert scale scored the diagnostic confidence of the neuroradiologist rating each study without/with the balanced steady-state free precession sequence. Rates of residual disease concordance and diagnostic confidence levels without/with the balanced steady-state free precession sequence were calculated. RESULTS Thirty-nine patients were included with 31 males and 8 females (mean age, 14.15 ± 4.26 years). Thirty-one patients had single-site disease; 8 patients had multisynchronous disease (47 sites in total). Compared to review of the standard MR sequences alone, the addition of the balanced steady state free precession sequence resulted in higher rates of tumor partial response categorization and greater diagnostic confidence levels (P < .001, P < .001). CONCLUSIONS The balanced steady-state free precession sequence improves detection of residual chemotherapy-reduced intracranial germ cell tumors and increases diagnostic confidence of the neuroradiologist. The balanced steady-state free precession sequence may be an important adjunct to the standard MR imaging protocol for radiation planning.
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Affiliation(s)
- W A Mehan
- From the Departments of Radiology (W.A.M, Jr., K.B., S.R., J.E.K., P.C.)
| | - K Buch
- From the Departments of Radiology (W.A.M, Jr., K.B., S.R., J.E.K., P.C.)
| | - M F Brasz
- and Magnetic Detection and Imaging (M.F.B., F.F.J.S.), TechMed Centre, University of Twente, Enschede, the Netherlands
| | - F F J Simonis
- and Magnetic Detection and Imaging (M.F.B., F.F.J.S.), TechMed Centre, University of Twente, Enschede, the Netherlands
| | - S MacDonald
- and Radiation Oncology (S.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - S Rincon
- From the Departments of Radiology (W.A.M, Jr., K.B., S.R., J.E.K., P.C.)
| | - J E Kirsch
- From the Departments of Radiology (W.A.M, Jr., K.B., S.R., J.E.K., P.C.)
| | - P Caruso
- From the Departments of Radiology (W.A.M, Jr., K.B., S.R., J.E.K., P.C.)
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21
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Bıyık E, Keskin K, Uh Dar S, Koç A, Çukur T. Factorized sensitivity estimation for artifact suppression in phase-cycled bSSFP MRI. NMR IN BIOMEDICINE 2020; 33:e4228. [PMID: 31985879 DOI: 10.1002/nbm.4228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 10/08/2019] [Accepted: 10/25/2019] [Indexed: 06/10/2023]
Abstract
OBJECTIVE Balanced steady-state free precession (bSSFP) imaging suffers from banding artifacts in the presence of magnetic field inhomogeneity. The purpose of this study is to identify an efficient strategy to reconstruct banding-free bSSFP images from multi-coil multi-acquisition datasets. METHOD Previous techniques either assume that a naïve coil-combination is performed a priori resulting in suboptimal artifact suppression, or that artifact suppression is performed for each coil separately at the expense of significant computational burden. Here we propose a tailored method that factorizes the estimation of coil and bSSFP sensitivity profiles for improved accuracy and/or speed. RESULTS In vivo experiments show that the proposed method outperforms naïve coil-combination and coil-by-coil processing in terms of both reconstruction quality and time. CONCLUSION The proposed method enables computationally efficient artifact suppression for phase-cycled bSSFP imaging with modern coil arrays. Rapid imaging applications can efficiently benefit from the improved robustness of bSSFP imaging against field inhomogeneity.
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Affiliation(s)
- Erdem Bıyık
- Department of Electrical Engineering, Stanford University, CA, USA
- Intelligent Data Analytics Research Program Department, Aselsan Research Center, Ankara, Turkey
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
| | - Kübra Keskin
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | - Salman Uh Dar
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | - Aykut Koç
- Intelligent Data Analytics Research Program Department, Aselsan Research Center, Ankara, Turkey
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | - Tolga Çukur
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
- Neuroscience Program at Sabuncu Brain Research Center, Bilkent University, Ankara, Turkey
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22
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Topping GJ, Hundshammer C, Nagel L, Grashei M, Aigner M, Skinner JG, Schulte RF, Schilling F. Acquisition strategies for spatially resolved magnetic resonance detection of hyperpolarized nuclei. MAGMA (NEW YORK, N.Y.) 2020; 33:221-256. [PMID: 31811491 PMCID: PMC7109201 DOI: 10.1007/s10334-019-00807-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 10/08/2019] [Accepted: 11/21/2019] [Indexed: 12/13/2022]
Abstract
Hyperpolarization is an emerging method in magnetic resonance imaging that allows nuclear spin polarization of gases or liquids to be temporarily enhanced by up to five or six orders of magnitude at clinically relevant field strengths and administered at high concentration to a subject at the time of measurement. This transient gain in signal has enabled the non-invasive detection and imaging of gas ventilation and diffusion in the lungs, perfusion in blood vessels and tissues, and metabolic conversion in cells, animals, and patients. The rapid development of this method is based on advances in polarizer technology, the availability of suitable probe isotopes and molecules, improved MRI hardware and pulse sequence development. Acquisition strategies for hyperpolarized nuclei are not yet standardized and are set up individually at most sites depending on the specific requirements of the probe, the object of interest, and the MRI hardware. This review provides a detailed introduction to spatially resolved detection of hyperpolarized nuclei and summarizes novel and previously established acquisition strategies for different key areas of application.
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Affiliation(s)
- Geoffrey J Topping
- Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Christian Hundshammer
- Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Luca Nagel
- Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Martin Grashei
- Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Maximilian Aigner
- Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Jason G Skinner
- Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | | | - Franz Schilling
- Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.
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23
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Godinez F, Scott G, Padormo F, Hajnal JV, Malik SJ. Safe guidewire visualization using the modes of a PTx transmit array MR system. Magn Reson Med 2019; 83:2343-2355. [PMID: 31722119 PMCID: PMC7048617 DOI: 10.1002/mrm.28069] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 10/16/2019] [Accepted: 10/16/2019] [Indexed: 02/06/2023]
Abstract
Purpose MRI‐guided cardiovascular intervention using standard metal guidewires can produce focal tissue heating caused by induced radiofrequency guidewire currents. It has been shown that safe operation is made possible by using parallel transmit radiofrequency coils driven in the null current mode, which does not induce radiofrequency currents and hence allows safe tissue visualization. We propose that the maximum current modes, usually considered unsafe, be used at very low power levels to visualize conductive wires, and we investigate pulse sequences best suited for this application. Methods Spoiled gradient echo, balanced steady‐state free precession, and turbo spin echo sequences were evaluated for their ability to visualize a conductive guidewire embedded in a gel phantom when run in maximum current modes at very low power level. Temperature at the guidewire tip was monitored for safety assessment. Results Excellent guidewire visualization could be achieved using maximum current modes excitation, with the turbo spin echo sequence giving the best image quality. Although turbo spin echo is usually considered to be a high‐power sequence, our method reduced all pulses to 1% amplitude (0.01% power), and heating was not detected. In addition, visualization of background tissue can be achieved using null current mode, also with no recorded heating at the guidewire tip even when running at 100% (reported) specific absorption rate. Conclusion Parallel transmit is a promising approach for both guidewire and tissue visualization using maximum and null current modes, respectively, for interventional cardiac MRI. Such systems can switch excitation mode instantaneously, allowing for flexible integration into interactive sequences.
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Affiliation(s)
- Felipe Godinez
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Greig Scott
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | | | - Joseph V Hajnal
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Shaihan J Malik
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
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24
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Datta A, Nishimura DG, Baron CA. Banding‐free balanced SSFP cardiac cine using frequency modulation and phase cycle redundancy. Magn Reson Med 2019; 82:1604-1616. [DOI: 10.1002/mrm.27815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 04/09/2019] [Accepted: 04/24/2019] [Indexed: 11/09/2022]
Affiliation(s)
- Anjali Datta
- Electrical Engineering Stanford University Stanford California
| | | | - Corey A. Baron
- Electrical Engineering Stanford University Stanford California
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25
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Neumann W, Pusch TP, Siegfarth M, Schad LR, Stallkamp JL. CT and MRI compatibility of flexible 3D-printed materials for soft actuators and robots used in image-guided interventions. Med Phys 2019; 46:5488-5498. [PMID: 31587313 DOI: 10.1002/mp.13852] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 08/12/2019] [Accepted: 09/26/2019] [Indexed: 01/09/2023] Open
Abstract
PURPOSE Three-dimensional (3D) printing allows for the fabrication of medical devices with complex geometries, such as soft actuators and robots that can be used in image-guided interventions. This study investigates flexible and rigid 3D-printing materials in terms of their impact on multimodal medical imaging. METHODS The generation of artifacts in clinical computer tomography (CT) and magnetic resonance (MR) imaging was evaluated for six flexible and three rigid materials, each with a cubical and a cylindrical geometry, and for one exemplary flexible fluidic actuator. Additionally, CT Hounsfield units (HU) were quantified for various parameter sets iterating peak voltage, x-ray tube current, slice thickness, and convolution kernel. RESULTS We found the image artifacts caused by the materials to be negligible in both CT and MR images. The HU values mainly depended on the elemental composition of the materials and applied peak voltage was ranging between 80 and 140 kVp. Flexible, nonsilicone-based materials were ranged between 51 and 114 HU. The voltage dependency was less than 29 HU. Flexible, silicone-based materials were ranged between 60 and 365 HU. The voltage-dependent influence was as large as 172 HU. Rigid materials ranged between -69 and 132 HU. The voltage-dependent influence was <33 HU. CONCLUSIONS All tested materials may be employed for devices placed in the field of view during CT and MR imaging as no significant artifacts were measured. Moreover, the material selection in CT could be based on the desired visibility of the material depending on the application. Given the wide availability of the tested materials, we expect our results to have a positive impact on the development of devices and robots for image-guided interventions.
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Affiliation(s)
- Wiebke Neumann
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
| | - Tim P Pusch
- Fraunhofer Institute for Manufacturing Engineering and Automation, Project Group for Automation in Medicine and Biotechnology, 68167, Mannheim, Germany
| | - Marius Siegfarth
- Fraunhofer Institute for Manufacturing Engineering and Automation, Project Group for Automation in Medicine and Biotechnology, 68167, Mannheim, Germany
| | - Lothar R Schad
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
| | - Jan L Stallkamp
- Fraunhofer Institute for Manufacturing Engineering and Automation, Project Group for Automation in Medicine and Biotechnology, 68167, Mannheim, Germany.,Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
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26
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Robb JS, Hu C, Peters DC. Interleaved, undersampled radial multiple-acquisition steady-state free precession for improved left atrial cine imaging. Magn Reson Med 2019; 83:1721-1729. [PMID: 31605555 DOI: 10.1002/mrm.28036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 08/31/2019] [Accepted: 09/20/2019] [Indexed: 11/10/2022]
Abstract
PURPOSE Balanced steady-state free precession (bSSFP) left atrial (LA) cine suffers from off-resonance artifacts, particularly in the pulmonary veins (PVs). Linear combination or multiple-acquisition SSFP (MA-SSFP) effectively removes banding but greatly increases scan time. We hypothesized that MA-SSFP with interleaved radial undersampling, where each phase-cycling is acquired with an interleaved set of radial projections, would improve image quality of LA cine with a small increase of scan time and streak artefacts. METHODS Undersampled radial MA-SSFP with and without interleaving was compared with fully sampled radial bSSFP by means of simulations, phantoms, and in vivo imaging. Ten healthy subjects were imaged on a 3T scanner, with bSSFP and MA-SSFP cine of the left atrium, and B0-mapping. Images were assessed (1 = worst, 5 = best) by 2 independent readers, with respect to 5 qualitative criteria and apparent signal-to-noise ratio. RESULTS In healthy subjects, off-resonance differed from the right inferior PVs to the LA cavity by 163 Hz ± 73 Hz at 3T. Compared with fully sampled radial bSSFP, interleaved radial MA-SSFP significantly improved image quality with respect to off-resonance artifacts (3.8 ± 0.6 versus 2.3 ± 1.0; P = 0.005), PV conspicuity (2.8 ± 1.0 versus 4.3 ± 0.5; P = 0.005), and the number of visualized PVs (1.7 ± 0.4 versus 0.9 ± 0.7; P = 0.008), although with greater streak artifacts (3.4 ± 0.4 versus 4.9 ± 0.2; P = 0.004) and lower measured apparent signal-to-noise ratio (24 ± 9 versus 69 ± 36; P = 0.002). Flow artifacts were similar. Interleaved radial MA-SSFP reduced streaking artifacts and increased apparent signal-to-noise ratio versus noninterleaved radial. CONCLUSIONS Interleaved radial MA-SSFP cine reduces banding artifacts with an acceptable increase of scan time and streak artifacts. The proposed technique improves the LA and PV visualization in bSSFP cine imaging.
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Affiliation(s)
| | - Chenxi Hu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.,Department of Radiology and Biomedical Imaging, Yale School of Medicine, Yale University, New Haven, Connecticut
| | - Dana C Peters
- Department of Radiology and Biomedical Imaging, Yale School of Medicine, Yale University, New Haven, Connecticut
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27
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Michael Gach H, Curcuru AN, Wittland EJ, Maraghechi B, Cai B, Mutic S, Green OL. MRI quality control for low-field MR-IGRT systems: Lessons learned. J Appl Clin Med Phys 2019; 20:53-66. [PMID: 31541542 PMCID: PMC6806483 DOI: 10.1002/acm2.12713] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 06/27/2019] [Accepted: 08/12/2019] [Indexed: 11/25/2022] Open
Abstract
Purpose To present lessons learned from magnetic resonance imaging (MRI) quality control (QC) tests for low‐field MRI‐guided radiation therapy (MR‐IGRT) systems. Methods MRI QC programs were established for low‐field MRI‐60Co and MRI‐Linac systems. A retrospective analysis of MRI subsystem performance covered system commissioning, operations, maintenance, and quality control. Performance issues were classified into three groups: (a) Image noise and artifact; (b) Magnetic field homogeneity and linearity; and (c) System reliability and stability. Results Image noise and artifacts were attributed to room noise sources, unsatisfactory system cabling, and broken RF receiver coils. Gantry angle‐dependent magnetic field inhomogeneities were more prominent on the MRI‐Linac due to the high volume of steel shielding in the gantry. B0 inhomogeneities measured in a 24‐cm spherical phantom were <5 ppm for both MR‐IGRT systems after using MRI gradient offset (MRI‐GO) compensation on the MRI‐Linac. However, significant signal dephasing occurred on the MRI‐Linac while the gantry was rotating. Spatial integrity measurements were sensitive to gradient calibration and vulnerable to shimming. The most common causes of MR‐IGRT system interruptions were software disconnects between the MRI and radiation therapy delivery subsystems caused by patient table, gantry, and multi‐leaf collimator (MLC) faults. The standard deviation (SD) of the receiver coil signal‐to‐noise ratio was 1.83 for the MRI‐60Co and 1.53 for the MRI‐Linac. The SD of the deviation from the mean for the Larmor frequency was 1.41 ppm for the MRI‐60Co and 1.54 ppm for the MRI‐Linac. The SD of the deviation from the mean for the transmitter reference amplitude was 0.90% for the MRI‐60Co and 1.68% for the MRI‐Linac. High SDs in image stability data corresponded to reports of spike noise. Conclusions There are significant technological challenges associated with implementing and maintaining MR‐IGRT systems. Most of the performance issues were identified and resolved during commissioning.
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Affiliation(s)
- H Michael Gach
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA.,Department of Radiology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA.,Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, 63110, USA
| | - Austen N Curcuru
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, 63110, USA
| | - Erin J Wittland
- Department of Radiation Oncology, Barnes Jewish Hospital, St. Louis, Missouri, 63110, USA
| | - Borna Maraghechi
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA
| | - Bin Cai
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA
| | - Sasa Mutic
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA
| | - Olga L Green
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA
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Shcherbakova Y, Bartels LW, Mandija S, Beld E, Seevinck PR, van der Voort van Zyp JRN, Kerkmeijer LGW, Moonen CTW, Lagendijk JJW, van den Berg CAT. Visualization of gold fiducial markers in the prostate using phase-cycled bSSFP imaging for MRI-only radiotherapy. ACTA ACUST UNITED AC 2019; 64:185001. [DOI: 10.1088/1361-6560/ab35c3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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29
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Gavazzi S, Shcherbakova Y, Bartels LW, Stalpers LJA, Lagendijk JJW, Crezee H, van den Berg CAT, van Lier ALHMW. Transceive phase mapping using the PLANET method and its application for conductivity mapping in the brain. Magn Reson Med 2019; 83:590-607. [PMID: 31483520 PMCID: PMC6900152 DOI: 10.1002/mrm.27958] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/25/2019] [Accepted: 07/30/2019] [Indexed: 12/23/2022]
Abstract
Purpose To demonstrate feasibility of transceive phase mapping with the PLANET method and its application for conductivity reconstruction in the brain. Methods Accuracy and precision of transceive phase (ϕ±) estimation with PLANET, an ellipse fitting approach to phase‐cycled balanced steady state free precession (bSSFP) data, were assessed with simulations and measurements and compared to standard bSSFP. Measurements were conducted on a homogeneous phantom and in the brain of healthy volunteers at 3 tesla. Conductivity maps were reconstructed with Helmholtz‐based electrical properties tomography. In measurements, PLANET was also compared to a reference technique for transceive phase mapping, i.e., spin echo. Results Accuracy and precision of ϕ± estimated with PLANET depended on the chosen flip angle and TR. PLANET‐based ϕ± was less sensitive to perturbations induced by off‐resonance effects and partial volume (e.g., white matter + myelin) than bSSFP‐based ϕ±. For flip angle = 25° and TR = 4.6 ms, PLANET showed an accuracy comparable to that of reference spin echo but a higher precision than bSSFP and spin echo (factor of 2 and 3, respectively). The acquisition time for PLANET was ~5 min; 2 min faster than spin echo and 8 times slower than bSSFP. However, PLANET simultaneously reconstructed T1, T2, B0 maps besides mapping ϕ±. In the phantom, PLANET‐based conductivity matched the true value and had the smallest spread of the three methods. In vivo, PLANET‐based conductivity was similar to spin echo‐based conductivity. Conclusion Provided that appropriate sequence parameters are used, PLANET delivers accurate and precise ϕ± maps, which can be used to reconstruct brain tissue conductivity while simultaneously recovering T1, T2, and B0 maps.
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Affiliation(s)
- Soraya Gavazzi
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Yulia Shcherbakova
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Lambertus W Bartels
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands.,Image Sciences Institute, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Lukas J A Stalpers
- Department of Radiotherapy, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Jan J W Lagendijk
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Hans Crezee
- Department of Radiotherapy, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Cornelis A T van den Berg
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands.,Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
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Feasibility of Diffusion Tensor and Morphologic Imaging of Peripheral Nerves at Ultra-High Field Strength. Invest Radiol 2019; 53:705-713. [PMID: 29979328 PMCID: PMC6221405 DOI: 10.1097/rli.0000000000000492] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Supplemental digital content is available in the text. Objectives The aim of this study was to describe the development of morphologic and diffusion tensor imaging sequences of peripheral nerves at 7 T, using carpal tunnel syndrome (CTS) as a model system of focal nerve injury. Materials and Methods Morphologic images were acquired at 7 T using a balanced steady-state free precession sequence. Diffusion tensor imaging was performed using single-shot echo-planar imaging and readout-segmented echo-planar imaging sequences. Different acquisition and postprocessing methods were compared to describe the optimal analysis pipeline. Magnetic resonance imaging parameters including cross-sectional areas, signal intensity, fractional anisotropy (FA), as well as mean, axial, and radial diffusivity were compared between patients with CTS (n = 8) and healthy controls (n = 6) using analyses of covariance corrected for age (significance set at P < 0.05). Pearson correlations with Bonferroni correction were used to determine association of magnetic resonance imaging parameters with clinical measures (significance set at P < 0.01). Results The 7 T acquisitions with high in-plane resolution (0.2 × 0.2mm) afforded detailed morphologic resolution of peripheral nerve fascicles. For diffusion tensor imaging, single-shot echo-planar imaging was more efficient than readout-segmented echo-planar imaging in terms of signal-to-noise ratio per unit scan time. Distortion artifacts were pronounced, but could be corrected during postprocessing. Registration of FA maps to the morphologic images was successful. The developed imaging and analysis pipeline identified lower median nerve FA (pisiform bone, 0.37 [SD 0.10]) and higher radial diffusivity (1.08 [0.20]) in patients with CTS compared with healthy controls (0.53 [0.06] and 0.78 [0.11], respectively, P < 0.047). Fractional anisotropy and radial diffusivity strongly correlated with patients' symptoms (r = −0.866 and 0.866, respectively, P = 0.005). Conclusions Our data demonstrate the feasibility of morphologic and diffusion peripheral nerve imaging at 7 T. Fractional anisotropy and radial diffusivity were found to be correlates of symptom severity.
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Senel LK, Kilic T, Gungor A, Kopanoglu E, Guven HE, Saritas EU, Koc A, Cukur T. Statistically Segregated k-Space Sampling for Accelerating Multiple-Acquisition MRI. IEEE TRANSACTIONS ON MEDICAL IMAGING 2019; 38:1701-1714. [PMID: 30640604 DOI: 10.1109/tmi.2019.2892378] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A central limitation of multiple-acquisition magnetic resonance imaging (MRI) is the degradation in scan efficiency as the number of distinct datasets grows. Sparse recovery techniques can alleviate this limitation via randomly undersampled acquisitions. A frequent sampling strategy is to prescribe for each acquisition a different random pattern drawn from a common sampling density. However, naive random patterns often contain gaps or clusters across the acquisition dimension that, in turn, can degrade reconstruction quality or reduce scan efficiency. To address this problem, a statistically segregated sampling method is proposed for multiple-acquisition MRI. This method generates multiple patterns sequentially while adaptively modifying the sampling density to minimize k-space overlap across patterns. As a result, it improves incoherence across acquisitions while still maintaining similar sampling density across the radial dimension of k-space. Comprehensive simulations and in vivo results are presented for phase-cycled balanced steady-state free precession and multi-echo [Formula: see text]-weighted imaging. Segregated sampling achieves significantly improved quality in both Fourier and compressed-sensing reconstructions of multiple-acquisition datasets.
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Küstner T, Bustin A, Jaubert O, Neji R, Prieto C, Botnar R. 3D Cartesian fast interrupted steady-state (FISS) imaging. Magn Reson Med 2019; 82:1617-1630. [PMID: 31197881 PMCID: PMC6772102 DOI: 10.1002/mrm.27830] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 04/24/2019] [Accepted: 05/07/2019] [Indexed: 11/11/2022]
Abstract
PURPOSE To enable intrinsic and efficient fat suppression in 3D Cartesian fast interrupted steady-state (FISS) acquisitions. METHODS A periodic interruption of the balanced steady-state free precession (bSSFP) readout train (FISS) has been previously proposed for 2D radial imaging. FISS modulates the bSSFP frequency response pattern in terms of shape, width and location of stop band (attenuated transverse magnetization). Depending on the FISS interruption rate, the stop band characteristic can be exploited to suppress the fat spectrum at 3.5 ppm, thus yielding intrinsic fat suppression. For conventional 2D Cartesian sampling, ghosting/aliasing artifacts along phase-encoding direction have been reported. In this work, we propose to extend FISS to 3D Cartesian imaging and report countermeasures for the previously observed ghosting/aliasing artifacts. Key parameters (dummy prepulses, spatial resolution, and interruption rate) are investigated to optimize fat suppression and image quality. FISS behavior is examined using extended phase graph simulations to recommend parametrizations which are validated in phantom and in vivo measurements on a 1.5T MRI scanner for 3 applications: upper thigh angiography, abdominal imaging, and free-running 5D CINE. RESULTS Using optimized parameters, 3D Cartesian FISS provides homogeneous and consistent fat suppression for all 3 applications. In upper thigh angiography, vessel structures can be recovered in FISS that are obscured in bSSFP. Fat suppression in free-running cardiac CINE resulted in less fat-related motion aliasing and yielded better image quality. CONCLUSION 3D Cartesian FISS is feasible and offers homogeneous intrinsic fat suppression for selected imaging parameters without the need for dedicated preparation pulses, making it a promising candidate for free-running fat-suppressed imaging.
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Affiliation(s)
- Thomas Küstner
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London, United Kingdom
| | - Aurélien Bustin
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London, United Kingdom
| | - Olivier Jaubert
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London, United Kingdom
| | - Radhouene Neji
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London, United Kingdom.,MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom
| | - Claudia Prieto
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London, United Kingdom.,Escuela de Ingeniería, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - René Botnar
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London, United Kingdom.,Escuela de Ingeniería, Pontificia Universidad Católica de Chile, Santiago, Chile
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Applications of Continuous Wave Free Precession Sequences in Low-Field, Time-Domain NMR. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9071312] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This review discusses the theory and applications of the Continuous Wave Free Precession (CWFP) sequence in low-field, time-domain nuclear magnetic resonance (TD-NMR). CWFP is a special case of the Steady State Free Precession (SSFP) regime that is obtained when a train of radiofrequency pulses, separated by a time interval Tp shorter than the effective transverse relaxation time (T2*), is applied to a sample. Unlike regular pulsed experiments, in the CWFP regime, the amplitude is not dependent on T1. Therefore, Tp should be as short as possible (limited by hardware). For Tp < 0.5 ms, thousands of scans can be performed per second, and the signal to noise ratio can be enhanced by more than one order of magnitude. The amplitude of the CWFP signal is dependent on T1/T2; therefore, it can be used in quantitative analyses for samples with a similar relaxation ratio. The time constant to reach the CWFP regime (T*) is also dependent on relaxation times and flip angle (θ). Therefore, T* has been used as a single shot experiment to measure T1 using a low flip angle (5°) or T2, using θ = 180°. For measuring T1 and T2 simultaneously in a single experiment, it is necessary to use θ = 90°, the values of T* and M0, and the magnitude of CWFP signal |Mss|. Therefore, CWFP is an important sequence for TD-NMR, being an alternative to the Carr-Purcell-Meiboom-Gill sequence, which depends only on T2. The use of CWFP for the improvement of the signal to noise ratio in quantitative and qualitative analyses and in relaxation measurements are presented and discussed.
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Van Ooteghem G, Dasnoy-Sumell D, Lambrecht M, Reychler G, Liistro G, Sterpin E, Geets X. Mechanically-assisted non-invasive ventilation: A step forward to modulate and to improve the reproducibility of breathing-related motion in radiation therapy. Radiother Oncol 2019; 133:132-139. [PMID: 30935569 DOI: 10.1016/j.radonc.2018.12.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 12/27/2018] [Accepted: 12/27/2018] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND PURPOSE When using highly conformal radiotherapy techniques, a stabilized breathing pattern could greatly benefit the treatment of mobile tumours. Therefore, we assessed the feasibility of Mechanically-assisted non-invasive ventilation (MANIV) on unsedated volunteers, and its ability to stabilize and modulate the breathing pattern over time. MATERIALS AND METHODS Twelve healthy volunteers underwent 2 sessions of dynamic MRI under 4 ventilation modes: spontaneous breathing (SP), volume-controlled mode (VC) that imposes regular breathing in physiologic conditions, shallow-controlled mode (SH) that intends to lower amplitudes while increasing the breathing rate, and slow-controlled mode (SL) that mimics end-inspiratory breath-holds. The last 3 modes were achieved under respirator without sedation. The motion of the diaphragm was tracked along the breathing cycles on MRI images and expressed in position, breathing amplitude, and breathing period for intra- and inter-session analyses. In addition, end-inspiratory breath-hold duration and position stability were analysed during the SL mode. RESULTS MANIV was well-tolerated by all volunteers, without adverse event. The MRI environment led to more discomfort than MANIV itself. Compared to SP, VC and SH modes improved the inter-session reproducibility of the amplitude (by 43% and 47% respectively) and significantly stabilized the intra- and inter-session breathing rate (p < 0.001). Compared to VC, SH mode significantly reduced the intra-session mean amplitude (36%) (p < 0.002), its variability (42%) (p < 0.001), and the intra-session baseline shift (26%) (p < 0.001). The SL mode achieved end-inspiratory plateaus lasting more than 10 s. CONCLUSION MANIV offers exciting perspectives for motion management. It improves its intra- and inter-session reproducibility and should facilitate respiratory tracking, gating or margin techniques for both photon and proton treatments.
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Affiliation(s)
- Geneviève Van Ooteghem
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Molecular Imaging, Radiotherapy and Oncology (MIRO), Brussels, Belgium; Cliniques Universitaires Saint Luc, Department of Radiation Oncology, Brussels, Belgium.
| | - Damien Dasnoy-Sumell
- Université Catholique de Louvain, ImagX-R, Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Louvain-La-Neuve, Belgium.
| | - Maarten Lambrecht
- University Hospitals Leuven Gasthuisberg, Department of Radiation Oncology, Leuven, Belgium; Katholieke Universiteit Leuven, Department of Oncology, Laboratory of Experimental Radiotherapy, Leuven, Belgium.
| | - Grégory Reychler
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Pôle de Pneumologie, ENT & Dermatologie, Brussels, Belgium.
| | - Giuseppe Liistro
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Pôle de Pneumologie, ENT & Dermatologie, Brussels, Belgium.
| | - Edmond Sterpin
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Molecular Imaging, Radiotherapy and Oncology (MIRO), Brussels, Belgium; Katholieke Universiteit Leuven, Department of Oncology, Laboratory of Experimental Radiotherapy, Leuven, Belgium.
| | - Xavier Geets
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Molecular Imaging, Radiotherapy and Oncology (MIRO), Brussels, Belgium; Cliniques Universitaires Saint Luc, Department of Radiation Oncology, Brussels, Belgium.
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Roeloffs V, Rosenzweig S, Holme HCM, Uecker M, Frahm J. Frequency-modulated SSFP with radial sampling and subspace reconstruction: A time-efficient alternative to phase-cycled bSSFP. Magn Reson Med 2018; 81:1566-1579. [PMID: 30357904 DOI: 10.1002/mrm.27505] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 07/05/2018] [Accepted: 08/03/2018] [Indexed: 11/11/2022]
Abstract
PURPOSE A novel subspace-based reconstruction method for frequency-modulated balanced steady-state free precession (fmSSFP) MRI is presented. In this work, suitable data acquisition schemes, subspace sizes, and efficiencies for banding removal are investigated. THEORY AND METHODS By combining a fmSSFP MRI sequence with a 3D stack-of-stars trajectory, scan efficiency is maximized as spectral information is obtained without intermediate preparation phases. A memory-efficient reconstruction routine is implemented by introducing the low-frequency Fourier transform as a subspace which allows for the formulation of a convex reconstruction problem. The removal of banding artifacts is investigated by comparing the proposed acquisition and reconstruction technique to phase-cycled bSSFP MRI. Aliasing properties of different undersampling schemes are analyzed and water/fat separation is demonstrated by reweighting the reconstructed subspace coefficients to generate virtual spectral responses in a post-processing step. RESULTS A simple root-of-sum-of-squares combination of the reconstructed subspace coefficients yields high-SNR images with the characteristic bSSFP contrast but without banding artifacts. Compared to Golden-Angle trajectories, turn-based sampling schemes were superior in minimizing aliasing across reconstructed subspace coefficients. Water/fat separated images of the human knee were obtained by reweighting subspace coefficients. CONCLUSIONS The novel subspace-based fmSSFP MRI technique emerges as a time-efficient alternative to phase-cycled bSFFP. The method does not need intermediate preparation phases, offers high SNR and avoids banding artifacts. Reweighting of the reconstructed subspace coefficients allows for generating virtual spectral responses with applications to water/fat separation.
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Affiliation(s)
- Volkert Roeloffs
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany
| | - Sebastian Rosenzweig
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
| | - H Christian M Holme
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
| | - Martin Uecker
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
| | - Jens Frahm
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
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Matsumoto K, Yokota H, Mukai H, Masuda Y, Uno T, Miyati T. Merging images with different central frequencies reduces banding artifacts in balanced steady-state free precession magnetic resonance cisternography. J Appl Clin Med Phys 2018; 19:234-243. [PMID: 30288917 PMCID: PMC6236844 DOI: 10.1002/acm2.12468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 08/25/2018] [Accepted: 09/09/2018] [Indexed: 11/29/2022] Open
Abstract
Purpose The aim of this study was to evaluate the utility of merged balanced steady‐state free precession (bSSFP) magnetic resonance cisternography images. Materials and Methods Twenty ears of 10 healthy volunteers (six men, four women; mean age ± standard deviation, 26.7 ± 1.6 yr) and 10 patients (two men, eight women; mean age, 46.3 ± 10.9 yr) with neoplasm around the sella turcica were included. Two different devices (A and B) were used to confirm the versatility of our method for MR devices with different local magnetic field homogeneity. Images with different central frequencies (±10, ±20, ±30, ±40, and ±50 Hz) were merged with the maximum magnitude of corresponding pixels from the images acquired using both devices. Two neuroradiologists visually graded the image quality of 11 sites in the inner ear and three sites around the sella turcica (scale: 0–2) and compared the quality with that of the corresponding basic image (0 Hz). Results The image quality was better in merged images of the vestibule, superior semicircular canal (SCC), posterior SCC, and horizontal SCC (P = 0.005 to 0.020 mainly at ±40 and ±50 Hz on devices A and B), as well as in merged images of the sella turcica and right cavernous sinus (±50 Hz, P = 0.003 and 0.020 on device B, respectively), than it was in the corresponding basic images. Conclusions The maximum magnitude merging of images with different central frequencies makes it possible to reduce banding artifacts on bSSFP images without the need for special pulse sequences and image processing programs.
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Affiliation(s)
- Koji Matsumoto
- Department of Radiology, Chiba University Hospital, Chiba, Japan.,Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan
| | - Hajime Yokota
- Diagnostic Radiology and Radiation Oncology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Hiroki Mukai
- Diagnostic Radiology and Radiation Oncology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Yoshitada Masuda
- Department of Radiology, Chiba University Hospital, Chiba, Japan
| | - Takashi Uno
- Diagnostic Radiology and Radiation Oncology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Tosiaki Miyati
- Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan
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Parallel imaging compressed sensing for accelerated imaging and improved signal-to-noise ratio in MRI-based postimplant dosimetry of prostate brachytherapy. Brachytherapy 2018; 17:816-824. [DOI: 10.1016/j.brachy.2018.05.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 05/06/2018] [Accepted: 05/08/2018] [Indexed: 12/31/2022]
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Rashid S, Han F, Gao Y, Sung K, Cao M, Yang Y, Hu P. Cardiac balanced steady-state free precession MRI at 0.35 T: a comparison study with 1.5 T. Quant Imaging Med Surg 2018; 8:627-636. [PMID: 30211030 DOI: 10.21037/qims.2018.08.09] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Background While low-field MRI is disadvantaged by a reduced signal-to-noise ratio (SNR) compared to higher fields, it has a number of useful features such as decreased SAR and shorter T1, and has shown promise for diagnostic imaging. This study demonstrates the feasibility of cardiac balanced steady-state free precession (bSSFP) MRI at 0.35 T and compares cardiac bSSFP MRI images at 0.35 T with those at 1.5 T. Methods Cardiac images were acquired in 7 healthy volunteers using an ECG-gated bSSFP cine sequence on a 0.35 T superconducting MR system as well as a clinical 1.5 T system. Blood and myocardium SNR and contrast-to-noise ratio (CNR) were computed. Subjective image scoring was used to compare the image quality between 0.35 and 1.5 T. Results Cardiac images at 0.35 T were successfully acquired in all volunteers. While the 0.35 T images were noisier than those at 1.5 T, blood, myocardium and papillary muscles could be clearly delineated. At 0.35 T, bSSFP images were acquired at flip angles as high as 150°. Maximum CNR was achieved at 130°. Image quality scoring showed that while at lower flip angles, the 0.35 T images had poorer quality than the 1.5 T, but with flip angles of 110 and 130, the image quality at 0.35 T had scores similar to those at 1.5 T. Conclusions This study demonstrates that cardiac bSSFP imaging is highly feasible at 0.35 T.
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Affiliation(s)
- Shams Rashid
- Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Fei Han
- Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Yu Gao
- Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Physics and Biology in Medicine Inter-Departmental Program, University of California, Los Angeles, CA, USA
| | - Kyunghyun Sung
- Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Physics and Biology in Medicine Inter-Departmental Program, University of California, Los Angeles, CA, USA
| | - Minsong Cao
- Physics and Biology in Medicine Inter-Departmental Program, University of California, Los Angeles, CA, USA.,Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Yingli Yang
- Physics and Biology in Medicine Inter-Departmental Program, University of California, Los Angeles, CA, USA.,Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Peng Hu
- Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Physics and Biology in Medicine Inter-Departmental Program, University of California, Los Angeles, CA, USA
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Zarghami N, Khrapitchev AA, Perez-Balderas F, Soto MS, Larkin JR, Bau L, Sibson NR. Optimization of molecularly targeted MRI in the brain: empirical comparison of sequences and particles. Int J Nanomedicine 2018; 13:4345-4359. [PMID: 30100719 PMCID: PMC6064157 DOI: 10.2147/ijn.s158071] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Molecular MRI is an evolving field of research with strong translational potential. Selection of the appropriate MRI sequence, field strength and contrast agent depend largely on the application. The primary aims of the current study were to: 1) assess the sensitivity of different MRI sequences for detection of iron oxide particles in mouse brain; 2) determine the effect of magnetic field strength on detection of iron oxide particles in vivo; and 3) compare the sensitivity of targeted microparticles of iron oxide (MPIO) or ultra-small superparamagnetic iron oxide (USPIO) for detection of vascular cell adhesion molecule-1 (VCAM-1) in vivo. METHODS Mice were injected intrastriatally with interleukin 1β to induce VCAM-1 expression on the cerebral vasculature. Subsequently, animals were injected intravenously with either VCAM-MPIO or VCAM-USPIO and imaged 1 or 13 hours post-injection, respectively. MRI was performed at 4.7, 7.0, or 9.4 T, using three different T2*-weighted sequences: single gradient echo 3D (GE3D), multi-gradient echo 3D (MGE3D) and balanced steady-state free precession 3D (bSSFP3D). RESULTS MGE3D yielded the highest signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for the detection of iron oxide particles. All sequences showed a significant increase in SNR and CNR from 4.7 to 7.0 T, but no further improvement at 9.4 T. However, whilst targeted MPIO enabled sensitive detection of VCAM-1 expression on the cerebral vasculature, the long half-life (16.5 h vs 1.2 min) and lower relaxivity per particle (1.29×10-14 vs 1.18×10-9 Hz L/particle) of USPIO vs. MPIO rendered them impractical for molecular MRI. CONCLUSION These findings demonstrate clear advantages of MPIO compared to USPIO for molecularly-targeted MRI, and indicate that the MGE3D sequence is optimal for MPIO detection. Moreover, higher field strengths (7.0/9.4 T) showed enhanced sensitivity over lower field strengths (4.7 T). With the development of biodegradable MPIO, these agents hold promise for clinical translation.
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Affiliation(s)
- Niloufar Zarghami
- Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK,
| | - Alexandre A Khrapitchev
- Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK,
| | - Francisco Perez-Balderas
- Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK,
| | - Manuel Sarmiento Soto
- Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK,
| | - James R Larkin
- Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK,
| | - Luca Bau
- Institute of Biomedical Engineering, Department of Engineering Sciences, University of Oxford, Oxford, UK
| | - Nicola R Sibson
- Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK,
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Shen Y, Yan L, Shao X, Zhao B, Bai J, Lu W, Wang DJ. Improved sensitivity of cellular MRI using phase-cycled balanced SSFP of ferumoxytol nanocomplex-labeled macrophages at ultrahigh field. Int J Nanomedicine 2018; 13:3839-3852. [PMID: 30013339 PMCID: PMC6039059 DOI: 10.2147/ijn.s169860] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Purpose The purpose of this study was to investigate the feasibility and sensitivity of cellular magnetic resonance imaging (MRI) with ferumoxytol nanocomplex-labeled macrophages at ultrahigh magnetic field of 7 T. Materials and methods THP-1-induced macrophages were labeled using self-assembling heparin + protamine + ferumoxytol nanocomplexes which were injected into a gelatin phantom visible on both microscope and MRI. Susceptibility-weighted imaging (SWI) and balanced steady-state free precession (bSSFP) pulse sequences were applied at 3 and 7 T. The average, maximum intensity projection, and root mean square combined images were generated for phase-cycled bSSFP images. The signal-to-noise ratio and contrast-to-noise ratio (CNR) efficiencies were calculated. Ex vivo experiments were then performed using a formalin-fixed pig brain injected witĥ100 and ~1,000 labeled cells, respectively, at both 3 and 7 T. Results A high cell labeling efficiency (.90%) was achieved with heparin + protamine + ferumoxytol nanocomplexes. Less than 100 cells were detectable in the gelatin phantom at both 3 and 7 T. The 7 T data showed more than double CNR efficiency compared to the corresponding sequences at 3 T. The CNR efficiencies of phase-cycled bSSFP images were higher compared to those of SWI, and the root mean square combined bSSFP showed the highest CNR efficiency with minimal banding. Following co-registration of microscope and MR images, more cells (51/63) were detected by bSSFP at 7 T than at 3 T (36/63). On pig brain, botĥ100 and ~1,000 cells were detected at 3 and 7 T. While the cell size appeared larger due to blooming effects on SWI, bSSFP allowed better contrast to precisely identify the location of the cells with higher signal-to-noise ratio efficiency. Conclusion The proposed cellular MRI with ferumoxytol nanocomplex-labeled macrophages at 7 T has a high sensitivity to detect, 100 cells. The proposed method has great translational potential and may have broad clinical applications that involve cell types with a primary phagocytic phenotype.
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Affiliation(s)
- Yelong Shen
- Laboratory of FMRI Technology (LOFT), Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California (USC), Los Angeles, CA, USA, .,Shandong Medical Imaging Research Institute, School of Medicine, Shandong University, Jinan, Shangdong, China
| | - Lirong Yan
- Laboratory of FMRI Technology (LOFT), Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California (USC), Los Angeles, CA, USA,
| | - Xingfeng Shao
- Laboratory of FMRI Technology (LOFT), Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California (USC), Los Angeles, CA, USA,
| | - Bin Zhao
- Shandong Medical Imaging Research Institute, School of Medicine, Shandong University, Jinan, Shangdong, China
| | - Jinlun Bai
- Broad Center for Regenerative Medicine and Stem Cell Research, Keck School of Medicine, University of Southern California (USC), Los Angeles, CA, USA
| | - Wange Lu
- Broad Center for Regenerative Medicine and Stem Cell Research, Keck School of Medicine, University of Southern California (USC), Los Angeles, CA, USA
| | - Danny Jj Wang
- Laboratory of FMRI Technology (LOFT), Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California (USC), Los Angeles, CA, USA,
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Slawig A, Wech T, Ratz V, Neubauer H, Bley T, Köstler H. Frequency-modulated bSSFP for phase-sensitive separation of water and fat. Magn Reson Imaging 2018; 53:82-88. [PMID: 29902564 DOI: 10.1016/j.mri.2018.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 04/27/2018] [Accepted: 06/10/2018] [Indexed: 10/28/2022]
Abstract
Our study proposes the use of a frequency-modulated acquisition which suppresses banding artefacts in combination with a phase-sensitive water-fat separation algorithm. The performance of the phase-sensitive separation for standard bSSFP, complex sum combination thereof, and frequency-modulated bSSFP were compared in in vivo measurements of the upper and lower legs at 1.5 and 3 T. It is shown, that the standard acquisition suffered from banding artefacts and major swaps between tissues. The dual-acquisition bSSFP could alleviate banding artefacts and only minor swaps occurred, but it comes at the expense of a doubled acquisition. In the frequency-modulated acquisitions all banding artefacts and the associated phase jumps were eliminated and no swaps between tissues occurred. It therefore provides a means to robustly separate water and fat, in one single radial bSSFP scan, using the phase-sensitive approach, even in the presence of high field inhomogeneities.
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Affiliation(s)
- Anne Slawig
- University of Würzburg, Department of Diagnostic and Interventional Radiology, Oberdürrbacher Str. 6, 97080 Würzburg, Germany.
| | - Tobias Wech
- University of Würzburg, Department of Diagnostic and Interventional Radiology, Oberdürrbacher Str. 6, 97080 Würzburg, Germany
| | - Valentin Ratz
- University of Würzburg, Department of Diagnostic and Interventional Radiology, Oberdürrbacher Str. 6, 97080 Würzburg, Germany
| | - Henning Neubauer
- University of Würzburg, Department of Diagnostic and Interventional Radiology, Oberdürrbacher Str. 6, 97080 Würzburg, Germany; SRH Clinic of Radiology, Albert-Schweitzer-Str. 2, 98527 Suhl, Germany
| | - Thorsten Bley
- University of Würzburg, Department of Diagnostic and Interventional Radiology, Oberdürrbacher Str. 6, 97080 Würzburg, Germany
| | - Herbert Köstler
- University of Würzburg, Department of Diagnostic and Interventional Radiology, Oberdürrbacher Str. 6, 97080 Würzburg, Germany
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Kim MO, Hong T, Kim DH. Fast B1+ mapping using three consecutive RF pulses and balanced gradients for improved bSSFP imaging. Magn Reson Imaging 2018; 46:40-46. [DOI: 10.1016/j.mri.2017.10.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 10/27/2017] [Accepted: 10/31/2017] [Indexed: 10/18/2022]
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Kazakia GJ, Carballido-Gamio J, Lai A, Nardo L, Facchetti L, Pasco C, Zhang CA, Han M, Parrott AH, Tien P, Krug R. Trabecular bone microstructure is impaired in the proximal femur of human immunodeficiency virus-infected men with normal bone mineral density. Quant Imaging Med Surg 2018. [PMID: 29541618 DOI: 10.21037/qims.2017.10.10] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Background There is evidence that human immunodeficiency virus (HIV) infection and antiretroviral therapy (ART) are independent risk factors for osteoporosis and fracture which is not solely explained by changes in bone mineral density. Thus, we hypothesized that the assessment of trabecular microstructure might play an important role for bone quality in this population and might explain the increased fracture risk. In this study, we have assessed bone microstructure in the proximal femur using high-resolution magnetic resonance imaging (MRI) as well as in the extremities using high resolution peripheral quantitative computed tomography (HR-pQCT) in HIV-infected men and healthy controls and compared these findings to those based on areal bone mineral density (aBMD) derived from dual X-ray absorptiometry (DXA) which is the standard clinical parameter for the diagnosis of osteoporosis. Methods Eight HIV-infected men and 11 healthy age-matched controls were recruited and informed consent was obtained before each scan. High-resolution MRI of the proximal femur was performed using fully balanced steady state free precession (bSSFP) on a 3T system. Three volumes of interest at corresponding anatomic locations across all subjects were defined based on registrations of a common template. Four MR-based trabecular microstructural parameters were analyzed at each region: fuzzy bone volume fraction (f-BVF), trabecular number (Tb.N), thickness (Tb.Th), and spacing (Tb.Sp). In addition, the distal radius and distal tibia were imaged with HR-pQCT. Four HR-pQCT-based microstructural parameters were analyzed: trabecular bone volume fraction (BV/TV), Tb.N, Tb.Th, and Tb.Sp. Total hip and spine aBMD were determined from DXA. Results Microstructural bone parameters derived from MRI at the proximal femur and from HR-pQCT at the distal tibia showed significantly lower bone quality in HIV-infected patients compared to healthy controls. In contrast, DXA aBMD data showed no significant differences between HIV-infected patients and healthy controls. Conclusions Our results suggest that high-resolution imaging is a powerful tool to assess trabecular bone microstructure and can be used to assess bone health in HIV-infected men who show no differences to healthy males by DXA aBMD. Advances in MRI technology have made microstructural imaging at the proximal femur possible. Further studies in larger patient cohorts are clearly warranted.
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Affiliation(s)
- Galateia J Kazakia
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | | | - Andrew Lai
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Lorenzo Nardo
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Luca Facchetti
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Courtney Pasco
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Chiyuan A Zhang
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Misung Han
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Amanda Hutton Parrott
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Phyllis Tien
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Roland Krug
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
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Veldhoen S, Behzadi C, Lenz A, Henes FO, Rybczynski M, von Kodolitsch Y, Bley TA, Adam G, Bannas P. Non-contrast MR angiography at 1.5 Tesla for aortic monitoring in Marfan patients after aortic root surgery. J Cardiovasc Magn Reson 2017; 19:82. [PMID: 29084542 PMCID: PMC5661928 DOI: 10.1186/s12968-017-0394-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 10/09/2017] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Contrast-enhanced cardiovascular magnetic resonance angiography (CE-CMRA) is the established imaging modality for patients with Marfan syndrome requiring life-long annual aortic imaging before and after aortic root replacement. Contrast-free CMRA techniques avoiding side-effects of contrast media are highly desirable for serial imaging but have not been evaluated in the postoperative setup of Marfan patients. The purpose of this study was to assess the feasibility of non-contrast balanced steady-state free precession (bSSFP) magnetic resonance imaging for aortic monitoring of postoperative patients with Marfan syndrome. METHODS Sixty-four adult Marfan patients after aortic root replacement were prospectively included. Fourteen patients (22%) had a residual aortic dissection after surgical treatment of type A dissection. bSSFP imaging and CE-CMRA were performed at 1.5 Tesla. Two radiologists evaluated the images regarding image quality (1 = poor, 4 = excellent), artifacts (1 = severe, 4 = none) and aortic pathologies. Readers measured the aortic diameters at defined levels in both techniques. Statistics included observer agreement for image scoring and diameter measurements and ROC analyses for comparison of the diagnostic performance of bSSFP and CE-CMRA. RESULTS Both readers observed no significant differences in image quality between bSSFP and CE-CMRA and found a median image quality score of 4 for both techniques (all p > .05). No significant differences were found regarding the frequency of image artifacts in both sequences (all p > .05). Sensitivity and specificity for detection of aortic dissections was 100% for both readers and techniques. Compared to bSSFP imaging, CE-CMRA resulted in higher diameters (mean bias, 0.9 mm; p < .05). The inter-observer biases of diameter measurements were not significantly different (all p > .05), except for the distal graft anastomosis (p = .001). Using both techniques, the readers correctly identified a graft suture dehiscence with aneurysm formation requiring surgery. CONCLUSION Unenhanced bSSFP CMR imaging allows for riskless aortic monitoring with high diagnostic accuracy in Marfan patients after aortic root surgery.
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Affiliation(s)
- Simon Veldhoen
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Bavaria, Germany
| | - Cyrus Behzadi
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Alexander Lenz
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Frank Oliver Henes
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Meike Rybczynski
- Department of General and Interventional Cardiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Yskert von Kodolitsch
- Department of General and Interventional Cardiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Thorsten Alexander Bley
- Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Bavaria, Germany
| | - Gerhard Adam
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Peter Bannas
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Datta A, Cheng JY, Hargreaves BA, Baron CA, Nishimura DG. Mitigation of near-band balanced steady-state free precession through-plane flow artifacts using partial dephasing. Magn Reson Med 2017; 79:2944-2953. [PMID: 28994486 DOI: 10.1002/mrm.26957] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 09/11/2017] [Accepted: 09/14/2017] [Indexed: 11/07/2022]
Abstract
PURPOSE To mitigate artifacts from through-plane flow at the locations of steady-state stopbands in balanced steady-state free precession (SSFP) using partial dephasing. METHODS A 60° range in the phase accrual during a TR was created over the voxel by slightly unbalancing the slice-select dephaser. The spectral profiles of SSFP with partial dephasing for various constant flow rates and during pulsatile flow were simulated to determine if partial dephasing decreases through-plane flow artifacts originating near SSFP dark bands while maintaining on-resonant signal. Simulations were then validated in a flow phantom. Lastly, phase-cycled SSFP cardiac cine images were acquired with and without partial dephasing in six subjects. RESULTS Partial dephasing decreased the strength and non-linearity of the dependence of the signal at the stopbands on the through-plane flow rate. It thus mitigated hyper-enhancement from out-of-slice signal contributions and transient-related artifacts caused by variable flow both in the phantom and in vivo. In six volunteers, partial dephasing noticeably decreased artifacts in all of the phase-cycled cardiac cine datasets. CONCLUSION Partial dephasing can mitigate the flow artifacts seen at the stopbands in balanced SSFP while maintaining the sequence's desired signal. By mitigating hyper-enhancement and transient-related artifacts originating from the stopbands, partial dephasing facilitates robust multiple-acquisition phase-cycled SSFP in the heart. Magn Reson Med 79:2944-2953, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Anjali Datta
- Stanford University, David Packard Electrical Engineering 350 Serra Mall, Rm. 308, Stanford, California, USA
| | - Joseph Y Cheng
- Stanford University, David Packard Electrical Engineering 350 Serra Mall, Rm. 308, Stanford, California, USA
| | - Brian A Hargreaves
- Stanford University, David Packard Electrical Engineering 350 Serra Mall, Rm. 308, Stanford, California, USA
| | - Corey A Baron
- Stanford University, David Packard Electrical Engineering 350 Serra Mall, Rm. 308, Stanford, California, USA
| | - Dwight G Nishimura
- Stanford University, David Packard Electrical Engineering 350 Serra Mall, Rm. 308, Stanford, California, USA
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Biyik E, Ilicak E, Çukur T. Reconstruction by calibration over tensors for multi‐coil multi‐acquisition balanced SSFP imaging. Magn Reson Med 2017; 79:2542-2554. [DOI: 10.1002/mrm.26902] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 07/31/2017] [Accepted: 08/15/2017] [Indexed: 01/27/2023]
Affiliation(s)
- Erdem Biyik
- Department of Electrical and Electronics EngineeringBilkent UniversityAnkara Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent UniversityAnkara Turkey
| | - Efe Ilicak
- Department of Electrical and Electronics EngineeringBilkent UniversityAnkara Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent UniversityAnkara Turkey
| | - Tolga Çukur
- Department of Electrical and Electronics EngineeringBilkent UniversityAnkara Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent UniversityAnkara Turkey
- Neuroscience ProgramSabuncu Brain Research Center, Bilkent UniversityAnkara Turkey
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Hilbert T, Nguyen D, Thiran J, Krueger G, Kober T, Bieri O. True constructive interference in the steady state (trueCISS). Magn Reson Med 2017; 79:1901-1910. [DOI: 10.1002/mrm.26836] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 06/01/2017] [Accepted: 06/22/2017] [Indexed: 11/11/2022]
Affiliation(s)
- Tom Hilbert
- Advanced Clinical Imaging Technology (HC CEMEA SUI DI PI), Siemens Healthcare AGLausanne Switzerland
- LTS5, École Polytechnique Fédérale de LausanneLausanne Switzerland
- Department of RadiologyUniversity Hospital (CHUV)Lausanne Switzerland
| | - Damien Nguyen
- Division of Radiological PhysicsDepartment of Radiology, University Hospital Basel, University of BaselBasel Switzerland
- Department of Biomedical EngineeringUniversity of BaselBasel Switzerland
| | - Jean‐Philippe Thiran
- LTS5, École Polytechnique Fédérale de LausanneLausanne Switzerland
- Department of RadiologyUniversity Hospital (CHUV)Lausanne Switzerland
| | - Gunnar Krueger
- LTS5, École Polytechnique Fédérale de LausanneLausanne Switzerland
- Department of RadiologyUniversity Hospital (CHUV)Lausanne Switzerland
- Siemens Medical Solutions USABoston Massachusetts USA
| | - Tobias Kober
- Advanced Clinical Imaging Technology (HC CEMEA SUI DI PI), Siemens Healthcare AGLausanne Switzerland
- LTS5, École Polytechnique Fédérale de LausanneLausanne Switzerland
- Department of RadiologyUniversity Hospital (CHUV)Lausanne Switzerland
| | - Oliver Bieri
- Division of Radiological PhysicsDepartment of Radiology, University Hospital Basel, University of BaselBasel Switzerland
- Department of Biomedical EngineeringUniversity of BaselBasel Switzerland
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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 IN BIOMEDICINE 2017; 30:e3699. [PMID: 28187250 DOI: 10.1002/nbm.3699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 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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Shcherbakova Y, van den Berg CAT, Moonen CTW, Bartels LW. PLANET: An ellipse fitting approach for simultaneous T 1 and T 2 mapping using phase-cycled balanced steady-state free precession. Magn Reson Med 2017; 79:711-722. [PMID: 28543430 PMCID: PMC5811804 DOI: 10.1002/mrm.26717] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 03/23/2017] [Accepted: 03/26/2017] [Indexed: 11/09/2022]
Abstract
Purpose To demonstrate the feasibility of a novel, ellipse fitting approach, named PLANET, for simultaneous estimation of relaxation times T1 and T2 from a single 3D phase‐cycled balanced steady‐state free precession (bSSFP) sequence. Methods A method is presented in which the elliptical signal model is used to describe the phase‐cycled bSSFP steady‐state signal. The fitting of the model to the acquired data is reformulated into a linear convex problem, which is solved directly by a linear least squares method, specific to ellipses. Subsequently, the relaxation times T1 and T2, the banding free magnitude, and the off‐resonance are calculated from the fitting results. Results Maps of T1 and T2, as well as an off‐resonance and a banding free magnitude can be simultaneously, quickly, and robustly estimated from a single 3D phase‐cycled bSSFP sequence. The feasibility of the method was demonstrated in a phantom and in the brain of healthy volunteers on a clinical MR scanner. The results were in good agreement for the phantom, but a systematic underestimation of T1 was observed in the brain. Conclusion The presented method allows for accurate mapping of relaxation times and off‐resonance, and for the reconstruction of banding free magnitude images at realistic signal‐to‐noise ratios. Magn Reson Med 79:711–722, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
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Affiliation(s)
- Yulia Shcherbakova
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Cornelis A T van den Berg
- Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Chrit T W Moonen
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Lambertus W Bartels
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
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50
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Han PK, Park H, Park SH. DC artifact correction for arbitrary phase-cycling sequence. Magn Reson Imaging 2017; 38:21-26. [DOI: 10.1016/j.mri.2016.12.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Revised: 12/15/2016] [Accepted: 12/15/2016] [Indexed: 11/17/2022]
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