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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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Fu J, Lin Z, Zhang B, Song L, Qin N, Qiu J, Yang M, Zou Y. Magnetic Resonance Imaging in Atherosclerotic Renal Artery Stenosis: The Update and Future Directions from Interventional Perspective. KIDNEY DISEASES (BASEL, SWITZERLAND) 2024; 10:23-31. [PMID: 38322626 PMCID: PMC10843188 DOI: 10.1159/000534499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 08/23/2023] [Indexed: 02/08/2024]
Abstract
Background Atherosclerotic renal artery stenosis (ARAS) is a condition where the renal arteries become narrowed due to atherosclerosis, leading to reduced blood flow to the kidneys and various renal complications. The effectiveness of interventional treatments, such as renal artery angioplasty and stenting, remains debated, making patient selection for these procedures challenging. Summary This review focuses on the diagnosis and management of ARAS, with a particular emphasis on the potential role of functional magnetic resonance imaging (MRI) in evaluating renal function and mechanisms. By summarizing current diagnostic approaches and outcomes of interventional treatments, the review highlights the importance of informed clinical decision-making in ARAS management. Functional MRI emerges as a promising noninvasive tool to assess renal function, aiding in patient stratification and treatment planning. Key Messages The efficacy of interventional treatments for ARAS requires further investigation and careful patient selection. Functional MRI holds promise as a noninvasive means to assess renal function and mechanisms, potentially guiding more effective clinical decisions in ARAS management. Advancing research in diagnostic methods, particularly functional MRI, can enhance our understanding and improve the treatment outcomes for ARAS patients.
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Affiliation(s)
- Jia Fu
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
| | - Zhiyong Lin
- Department of Radiology, Peking University First Hospital, Beijing, China
| | - Bihui Zhang
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
| | - Li Song
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
| | - Naishan Qin
- Department of Radiology, Peking University First Hospital, Beijing, China
| | - Jianxing Qiu
- Department of Radiology, Peking University First Hospital, Beijing, China
| | - Min Yang
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
| | - Yinghua Zou
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
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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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Abo Seada S, Price AN, Hajnal JV, Malik SJ. Minimum TR radiofrequency-pulse design for rapid gradient echo sequences. Magn Reson Med 2021; 86:182-196. [PMID: 33586800 DOI: 10.1002/mrm.28705] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 11/07/2022]
Abstract
PURPOSE A framework to design radiofrequency (RF) pulses specifically to minimize the TR of gradient echo sequences is presented, subject to hardware and physiological constraints. METHODS Single-band and multiband (MB) RF pulses can be reduced in duration using variable-rate selective excitation (VERSE) VERSE for a range of flip angles; however, minimum-duration pulses do not guarantee minimum TR because these can lead to a high specific absorption rate (SAR). The optimal RF pulse is found by meeting spatial encoding, peripheral nerve stimulation (PNS) and SAR constraints. A TR reduction for a range of designs is achieved and an application of this in an MB cardiac balanced steady-state free-precession (bSSFP) experiment is presented. Gradient imperfections and their imaging effects are also considered. RESULTS Sequence TR with low-time bandwidth product (TBP) pulses, as used in bSSFP, was reduced up to 14%, and the TR when using high TBP pulses, as used in slab-selective imaging, was reduced by up to 72%. A breath-hold cardiac exam was reduced by 46% using both MB and the TR-optimal framework. The importance of RF-based correction of gradient imperfections is demonstrated. PNS was not a practical limitation. CONCLUSION The TR-optimal framework designs RF pulses for a range of pulse parameters, specifically to minimize sequence TR.
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Affiliation(s)
- Samy Abo Seada
- School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom
| | - Anthony N Price
- School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom
| | - Joseph V Hajnal
- School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom
| | - Shaihan J Malik
- School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom
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Demirel OB, Weingärtner S, Moeller S, Akçakaya M. Improved simultaneous multislice cardiac MRI using readout concatenated k-space SPIRiT (ROCK-SPIRiT). Magn Reson Med 2021; 85:3036-3048. [PMID: 33566378 DOI: 10.1002/mrm.28680] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 12/21/2020] [Accepted: 12/22/2020] [Indexed: 01/31/2023]
Abstract
PURPOSE To develop and evaluate a simultaneous multislice (SMS) reconstruction technique that provides noise reduction and leakage blocking for highly accelerated cardiac MRI. METHODS ReadOut Concatenated k-space SPIRiT (ROCK-SPIRiT) uses the concept of readout concatenation in image domain to represent SMS encoding, and performs coil self-consistency as in SPIRiT-type reconstruction in an extended k-space, while allowing regularization for further denoising. The proposed method is implemented with and without regularization, and validated on retrospectively SMS-accelerated cine imaging with three-fold SMS and two-fold in-plane acceleration. ROCK-SPIRiT is compared with two leakage-blocking SMS reconstruction methods: readout-SENSE-GRAPPA and split slice-GRAPPA. Further evaluation and comparisons are performed using prospectively SMS-accelerated cine imaging. RESULTS Results on retrospectively three-fold SMS and two-fold in-plane accelerated cine imaging show that ROCK-SPIRiT without regularization significantly improves on existing methods in terms of PSNR (readout-SENSE-GRAPPA: 33.5 ± 3.2, split slice-GRAPPA: 34.1 ± 3.8, ROCK-SPIRiT: 35.0 ± 3.3) and SSIM (readout-SENSE-GRAPPA: 84.4 ± 8.9, split slice-GRAPPA: 85.0 ± 8.9, ROCK-SPIRiT: 88.2 ± 6.6 [in percentage]). Regularized ROCK-SPIRiT significantly outperforms all methods, as characterized by these quantitative metrics (PSNR: 37.6 ± 3.8, SSIM: 94.2 ± 4.1 [in percentage]). The prospectively five-fold SMS and two-fold in-plane accelerated data show that ROCK-SPIRiT and regularized ROCK-SPIRiT have visually improved image quality compared with existing methods. CONCLUSION The proposed ROCK-SPIRiT technique reduces noise and interslice leakage in accelerated SMS cardiac cine MRI, improving on existing methods both quantitatively and qualitatively.
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Affiliation(s)
- Omer Burak Demirel
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, USA.,Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Sebastian Weingärtner
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, USA.,Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA.,Department of Imaging Physics, Delft University of Technology, Delft, the Netherlands
| | - Steen Moeller
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Mehmet Akçakaya
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, USA.,Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
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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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Bian W, Kerr AB, Tranvinh E, Parivash S, Zahneisen B, Han MH, Lock CB, Goubran M, Zhu K, Rutt BK, Zeineh MM. MR susceptibility contrast imaging using a 2D simultaneous multi-slice gradient-echo sequence at 7T. PLoS One 2019; 14:e0219705. [PMID: 31314813 PMCID: PMC6636815 DOI: 10.1371/journal.pone.0219705] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 06/29/2019] [Indexed: 12/15/2022] Open
Abstract
Purpose To develop a 7T simultaneous multi-slice (SMS) 2D gradient-echo sequence for susceptibility contrast imaging, and to compare its quality to 3D imaging. Methods A frequency modulated and phase cycled RF pulse was designed to simultaneously excite multiple slices in multi-echo 2D gradient-echo imaging. The imaging parameters were chosen to generate images with susceptibility contrast, including T2*-weighted magnitude/phase images, susceptibility-weighted images and quantitative susceptibility/R2* maps. To compare their image quality with 3D gradient-echo imaging, both 2D and 3D imaging were performed on 11 healthy volunteers and 4 patients with multiple sclerosis (MS). The signal to noise ratio (SNR) in gray and white matter and their contrast to noise ratio (CNR) was simulated for the 2D and 3D magnitude images using parameters from the imaging. The experimental SNRs and CNRs were measured in gray/white matter and deep gray matter structures on magnitude, phase, R2* and QSM images from volunteers and the visibility of MS lesions on these images from patients was visually rated. All SNRs and CNRs were compared between the 2D and 3D imaging using a paired t-test. Results Although the 3D magnitude images still had significantly higher SNRs (by 13.0~17.6%), the 2D magnitude and QSM images generated significantly higher gray/white matter or globus pallidus/putamen contrast (by 13.3~87.5%) and significantly higher MS lesion contrast (by 5.9~17.3%). Conclusion 2D SMS gradient-echo imaging can serve as an alternative to often used 3D imaging to obtain susceptibility-contrast-weighted images, with an advantage of providing better image contrast and MS lesion sensitivity.
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Affiliation(s)
- Wei Bian
- Department of Biomedical Engineering, School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu, China
| | - Adam B. Kerr
- Department of Electrical Engineering, Stanford University, Palo Alto, CA, United States of America
| | - Eric Tranvinh
- Department of Radiology, Stanford University, Palo Alto, CA, United States of America
| | - Sherveen Parivash
- Department of Radiology, Stanford University, Palo Alto, CA, United States of America
| | - Benjamin Zahneisen
- Department of Radiology, Stanford University, Palo Alto, CA, United States of America
| | - May H. Han
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Palo Alto, CA, United States of America
| | - Christopher B. Lock
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Palo Alto, CA, United States of America
| | - Maged Goubran
- Department of Radiology, Stanford University, Palo Alto, CA, United States of America
| | - Kongrong Zhu
- Department of Electrical Engineering, Stanford University, Palo Alto, CA, United States of America
| | - Brian K. Rutt
- Department of Radiology, Stanford University, Palo Alto, CA, United States of America
| | - Michael M. Zeineh
- Department of Radiology, Stanford University, Palo Alto, CA, United States of America
- * E-mail:
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Abo Seada S, Price AN, Schneider T, Hajnal JV, Malik SJ. Multiband RF pulse design for realistic gradient performance. Magn Reson Med 2019; 81:362-376. [PMID: 30277267 PMCID: PMC6334175 DOI: 10.1002/mrm.27411] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/29/2018] [Accepted: 05/29/2018] [Indexed: 11/07/2022]
Abstract
PURPOSE Simultaneous multi-slice techniques are reliant on multiband RF pulses, for which conventional design strategies result in long pulse durations, lengthening echo-times so lowering SNR for spin-echo imaging, and lengthening repetition times for gradient echo sequences. Pulse durations can be reduced with advanced RF pulse design methods that use time-variable selection gradients. However, the ability of gradient systems to reproduce fast switching pulses is often limited and can lead to image artifacts when ignored. We propose a time-efficient pulse design method that inherently produces gradient waveforms with lower temporal bandwidth. METHODS Efficient multiband RF pulses with time-variable gradients were designed using time-optimal VERSE. Using VERSE directly on multiband pulses leads to gradient waveforms with high temporal bandwidth, whereas VERSE applied first to singleband RF pulses and then modulated to make them multiband, significantly reduces this. The relative performance of these approaches was compared using simulation and experimental measurements. RESULTS Applying VERSE before multiband modulation was successful at removing out-of-band slice distortion. This effectively removes the need for high frequency modulation in the gradient waveform while preserving the benefit of time-efficiency inherited from VERSE. CONCLUSION We propose a time-efficient RF pulse design that produces gradient pulses with lower temporal bandwidth, reducing image artifacts associated with finite temporal bandwidth of gradient systems.
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Affiliation(s)
- Samy Abo Seada
- School of Biomedical Engineering & Imaging SciencesKing’s College London, King’s Health Partners, St Thomas’ HospitalLondonSE1 7EH
| | - Anthony N. Price
- School of Biomedical Engineering & Imaging SciencesKing’s College London, King’s Health Partners, St Thomas’ HospitalLondonSE1 7EH
| | | | - Joseph V. Hajnal
- School of Biomedical Engineering & Imaging SciencesKing’s College London, King’s Health Partners, St Thomas’ HospitalLondonSE1 7EH
| | - Shaihan J. Malik
- School of Biomedical Engineering & Imaging SciencesKing’s College London, King’s Health Partners, St Thomas’ HospitalLondonSE1 7EH
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Bilgic B, Kim TH, Liao C, Manhard MK, Wald LL, Haldar JP, Setsompop K. Improving parallel imaging by jointly reconstructing multi-contrast data. Magn Reson Med 2018; 80:619-632. [PMID: 29322551 PMCID: PMC5910232 DOI: 10.1002/mrm.27076] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 12/10/2017] [Accepted: 12/15/2017] [Indexed: 12/14/2022]
Abstract
PURPOSE To develop parallel imaging techniques that simultaneously exploit coil sensitivity encoding, image phase prior information, similarities across multiple images, and complementary k-space sampling for highly accelerated data acquisition. METHODS We introduce joint virtual coil (JVC)-generalized autocalibrating partially parallel acquisitions (GRAPPA) to jointly reconstruct data acquired with different contrast preparations, and show its application in 2D, 3D, and simultaneous multi-slice (SMS) acquisitions. We extend the joint parallel imaging concept to exploit limited support and smooth phase constraints through Joint (J-) LORAKS formulation. J-LORAKS allows joint parallel imaging from limited autocalibration signal region, as well as permitting partial Fourier sampling and calibrationless reconstruction. RESULTS We demonstrate highly accelerated 2D balanced steady-state free precession with phase cycling, SMS multi-echo spin echo, 3D multi-echo magnetization-prepared rapid gradient echo, and multi-echo gradient recalled echo acquisitions in vivo. Compared to conventional GRAPPA, proposed joint acquisition/reconstruction techniques provide more than 2-fold reduction in reconstruction error. CONCLUSION JVC-GRAPPA takes advantage of additional spatial encoding from phase information and image similarity, and employs different sampling patterns across acquisitions. J-LORAKS achieves a more parsimonious low-rank representation of local k-space by considering multiple images as additional coils. Both approaches provide dramatic improvement in artifact and noise mitigation over conventional single-contrast parallel imaging reconstruction. Magn Reson Med 80:619-632, 2018. © 2018 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Berkin Bilgic
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA
- Department of Radiology, Harvard Medical School, Boston, MA, USA
| | - Tae Hyung Kim
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA
- Signal and Image Processing Institute, University of Southern California, Los Angeles, CA, USA
| | - Congyu Liao
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA
- Center for Brain Imaging Science and Technology, Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Mary Kate Manhard
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA
- Department of Radiology, Harvard Medical School, Boston, MA, USA
| | - Lawrence L. Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA
- Department of Radiology, Harvard Medical School, Boston, MA, USA
- Harvard-MIT Health Sciences and Technology, MIT, Cambridge, MA, USA
| | - Justin P. Haldar
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA
- Signal and Image Processing Institute, University of Southern California, Los Angeles, CA, USA
| | - Kawin Setsompop
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA
- Department of Radiology, Harvard Medical School, Boston, MA, USA
- Harvard-MIT Health Sciences and Technology, MIT, Cambridge, MA, USA
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10
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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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11
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Martin T, Wang Y, Rashid S, Shao X, Moeller S, Hu P, Sung K, Wang DJJ. Highly Accelerated SSFP Imaging with Controlled Aliasing in Parallel Imaging and integrated-SSFP (CAIPI-iSSFP). INVESTIGATIVE MAGNETIC RESONANCE IMAGING 2017; 21:210-222. [PMID: 29520372 PMCID: PMC5839645 DOI: 10.13104/imri.2017.21.4.210] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 08/26/2017] [Accepted: 09/09/2017] [Indexed: 11/15/2022]
Abstract
PURPOSE To develop a novel combination of controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) with integrated SSFP (CAIPI-iSSFP) for accelerated SSFP imaging without banding artifacts at 3T. MATERIALS AND METHODS CAIPI-iSSFP was developed by adding a dephasing gradient to the balanced SSFP (bSSFP) pulse sequence with a gradient area that results in 2π dephasing across a single pixel. Extended phase graph (EPG) simulations were performed to show the signal behaviors of iSSFP, bSSFP, and RF-spoiled gradient echo (SPGR) sequences. In vivo experiments were performed for brain and abdominal imaging at 3T with simultaneous multi-slice (SMS) acceleration factors of 2, 3 and 4 with CAIPI-iSSFP and CAIPI-bSSFP. The image quality was evaluated by measuring the relative contrast-to-noise ratio (CNR) and by qualitatively assessing banding artifact removal in the brain. RESULTS Banding artifacts were removed using CAIPI-iSSFP compared to CAIPI-bSSFP up to an SMS factor of 4 and 3 on brain and liver imaging, respectively. The relative CNRs between gray and white matter were on average 18% lower in CAIPI-iSSFP compared to that of CAIPI-bSSFP. CONCLUSION This study demonstrated that CAIPI-iSSFP provides up to a factor of four acceleration, while minimizing the banding artifacts with up to a 20% decrease in the relative CNR.
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Affiliation(s)
- Thomas Martin
- Department of Radiological Sciences, University of California Los Angeles, California, USA
| | - Yi Wang
- Philips, MR Clinical Science NA, Florida, USA
| | - Shams Rashid
- Department of Radiological Sciences, University of California Los Angeles, California, USA
| | - Xingfeng Shao
- Laboratory of FMRI Technology (LOFT), Stevens Neuroimaging and Informatics Institute, University of Southern California, California, USA
| | - Steen Moeller
- Center of Magnetic Resonance Research, University of Minnesota, Minnesota, USA
| | - Peng Hu
- Department of Radiological Sciences, University of California Los Angeles, California, USA
| | - Kyunghyun Sung
- Department of Radiological Sciences, University of California Los Angeles, California, USA
| | - Danny JJ Wang
- Laboratory of FMRI Technology (LOFT), Stevens Neuroimaging and Informatics Institute, University of Southern California, California, USA
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12
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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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13
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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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14
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Hamilton J, Franson D, Seiberlich N. Recent advances in parallel imaging for MRI. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2017; 101:71-95. [PMID: 28844222 PMCID: PMC5927614 DOI: 10.1016/j.pnmrs.2017.04.002] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 04/09/2017] [Accepted: 04/17/2017] [Indexed: 05/22/2023]
Abstract
Magnetic Resonance Imaging (MRI) is an essential technology in modern medicine. However, one of its main drawbacks is the long scan time needed to localize the MR signal in space to generate an image. This review article summarizes some basic principles and recent developments in parallel imaging, a class of image reconstruction techniques for shortening scan time. First, the fundamentals of MRI data acquisition are covered, including the concepts of k-space, undersampling, and aliasing. It is demonstrated that scan time can be reduced by sampling a smaller number of phase encoding lines in k-space; however, without further processing, the resulting images will be degraded by aliasing artifacts. Nearly all modern clinical scanners acquire data from multiple independent receiver coil arrays. Parallel imaging methods exploit properties of these coil arrays to separate aliased pixels in the image domain or to estimate missing k-space data using knowledge of nearby acquired k-space points. Three parallel imaging methods-SENSE, GRAPPA, and SPIRiT-are described in detail, since they are employed clinically and form the foundation for more advanced methods. These techniques can be extended to non-Cartesian sampling patterns, where the collected k-space points do not fall on a rectangular grid. Non-Cartesian acquisitions have several beneficial properties, the most important being the appearance of incoherent aliasing artifacts. Recent advances in simultaneous multi-slice imaging are presented next, which use parallel imaging to disentangle images of several slices that have been acquired at once. Parallel imaging can also be employed to accelerate 3D MRI, in which a contiguous volume is scanned rather than sequential slices. Another class of phase-constrained parallel imaging methods takes advantage of both image magnitude and phase to achieve better reconstruction performance. Finally, some applications are presented of parallel imaging being used to accelerate MR Spectroscopic Imaging.
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Affiliation(s)
- Jesse Hamilton
- Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
| | - Dominique Franson
- Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
| | - Nicole Seiberlich
- Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; Radiology, University Hospitals Cleveland Medical Center, Cleveland, OH, USA.
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15
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Schmitter S, Moeller S, Wu X, Auerbach EJ, Metzger GJ, Van de Moortele PF, Uğurbil K. Simultaneous multislice imaging in dynamic cardiac MRI at 7T using parallel transmission. Magn Reson Med 2017; 77:1010-1020. [PMID: 26949107 DOI: 10.1002/mrm.26180] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 01/08/2016] [Accepted: 02/03/2016] [Indexed: 12/25/2022]
Abstract
PURPOSE Cardiac MRI at 7T suffers from contrast heterogeneity that can be mitigated with parallel transmission (pTX) and, when performed during breath-hold, from a limited number of slices that can be multiplied with multiband (MB) radiofrequency pulses by simultaneous excitation of multiple slices (SMS). The goal of this study was to apply both approaches simultaneously. METHODS Using a 16-channel transmit/receive body coil, pTX SMS was applied with/without CAIPIRINHA with a modified gradient echo cine sequence. Different calibration schemes were investigated for the slice-GRAPPA reconstruction kernels as a function of the cardiac cycle. RESULTS Excellent slice separation for MB = 2 was achieved with CAIPIRINHA, with slice leakage values below 3% for 99% of all voxels. A critical finding of this study was the variation of the MB leakage factor in the heart by as much as 30% throughout the cardiac cycle, which was reduced greatly when reconstruction kernels were calibrated on multiple cardiac phases. Acceptable results were still obtained when applying further acceleration with MB = 3 in combination with in-plane GRAPPA. In one case, two-spoke pulses were compared with one-spoke pulses, resulting as expected in improved homogeneity. CONCLUSION pTX SMS imaging at 7T can address contrast heterogeneity while allowing larger slice coverage in cardiac MRI performed under breath-hold. Magn Reson Med 77:1010-1020, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Sebastian Schmitter
- University of Minnesota, Department of Radiology, Center for Magnetic Resonance Research, Minneapolis, Minnesota, USA
| | - Steen Moeller
- University of Minnesota, Department of Radiology, Center for Magnetic Resonance Research, Minneapolis, Minnesota, USA
| | - Xiaoping Wu
- University of Minnesota, Department of Radiology, Center for Magnetic Resonance Research, Minneapolis, Minnesota, USA
| | - Edward J Auerbach
- University of Minnesota, Department of Radiology, Center for Magnetic Resonance Research, Minneapolis, Minnesota, USA
| | - Gregory J Metzger
- University of Minnesota, Department of Radiology, Center for Magnetic Resonance Research, Minneapolis, Minnesota, USA
| | | | - Kâmil Uğurbil
- University of Minnesota, Department of Radiology, Center for Magnetic Resonance Research, Minneapolis, Minnesota, USA
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16
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Ilicak E, Senel LK, Biyik E, Çukur T. Profile-encoding reconstruction for multiple-acquisition balanced steady-state free precession imaging. Magn Reson Med 2016; 78:1316-1329. [DOI: 10.1002/mrm.26507] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Revised: 09/02/2016] [Accepted: 09/21/2016] [Indexed: 11/12/2022]
Affiliation(s)
- Efe Ilicak
- Department of Electrical and Electronics Engineering; Bilkent University; Ankara Turkey
- National Magnetic Resonance Research Center (UMRAM); Bilkent University; Ankara Turkey
| | - Lutfi Kerem Senel
- Department of Electrical and Electronics Engineering; Bilkent University; Ankara Turkey
| | - Erdem Biyik
- Department of Electrical and Electronics Engineering; 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, Graduate School of Engineering and Science; Bilkent University; Ankara Turkey
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