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Arn L, van Heeswijk RB, Stuber M, Bastiaansen JAM. A robust broadband fat-suppressing phaser T 2 -preparation module for cardiac magnetic resonance imaging at 3T. Magn Reson Med 2021; 86:1434-1444. [PMID: 33759208 DOI: 10.1002/mrm.28785] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 03/01/2021] [Accepted: 03/04/2021] [Indexed: 12/25/2022]
Abstract
PURPOSE Designing a new T2 -preparation (T2 -Prep) module to simultaneously provide robust fat suppression and efficient T2 preparation without requiring an additional fat-suppression module for T2 -weighted imaging at 3T. METHODS The tip-down radiofrequency (RF) pulse of an adiabatic T2 -Prep module was replaced by a custom-designed RF-excitation pulse that induces a phase difference between water and fat, resulting in a simultaneous T2 preparation of water signals and the suppression of fat signals at the end of the module (a phaser adiabatic T2 -Prep). Numerical simulations and in vitro and in vivo electrocardiogram (ECG)-triggered navigator-gated acquisitions of the human heart were performed. Blood, myocardium, and fat signal-to-noise ratios and right coronary artery vessel sharpness were compared against previously published adiabatic T2 -Prep approaches. RESULTS Numerical simulations predicted an increased fat-suppression bandwidth and decreased sensitivity to transmit magnetic field inhomogeneities using the proposed approach while preserving the water T2 -Prep capabilities. This was confirmed by the tissue signals acquired in the phantom and the in vivo images, which show similar blood and myocardium signal-to-noise ratio, contrast-to-noise ratio, and significantly reduced fat signal-to-noise ratio compared with the other methods. As a result, the right coronary artery conspicuity was significantly increased. CONCLUSION A novel fat-suppressing T2 -Prep method was developed and implemented that showed robust fat suppression and increased vessel sharpness compared with conventional techniques while preserving its T2 -Prep capabilities.
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Affiliation(s)
- Lionel Arn
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Ruud B van Heeswijk
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Matthias Stuber
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.,Center for Biomedical Imaging, Lausanne, Switzerland
| | - Jessica A M Bastiaansen
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
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Zeng DY, Baron CA, Malavé MO, Kerr AB, Yang PC, Hu BS, Nishimura DG. Combined T 2 -preparation and multidimensional outer volume suppression for coronary artery imaging with 3D cones trajectories. Magn Reson Med 2020; 83:2221-2231. [PMID: 31691350 PMCID: PMC7047567 DOI: 10.1002/mrm.28057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 10/08/2019] [Accepted: 10/09/2019] [Indexed: 11/07/2022]
Abstract
PURPOSE To develop a modular magnetization preparation sequence for combined T2 -preparation and multidimensional outer volume suppression (OVS) for coronary artery imaging. METHODS A combined T2 -prepared 1D OVS sequence with fat saturation was defined to contain a 90°-60 180°60 composite nonselective tip-down pulse, two 180°Y hard pulses for refocusing, and a -90° spectral-spatial sinc tip-up pulse. For 2D OVS, 2 modules were concatenated, selective in X and then Y. Bloch simulations predicted robustness of the sequence to B0 and B1 inhomogeneities. The proposed sequence was compared with a T2 -prepared 2D OVS sequence proposed by Luo et al, which uses a spatially selective 2D spiral tip-up. The 2 sequences were compared in phantom studies and in vivo coronary artery imaging studies with a 3D cones trajectory. RESULTS Phantom results demonstrated superior OVS for the proposed sequence compared with the Luo sequence. In studies on 15 healthy volunteers, the proposed sequence had superior image edge profile acutance values compared with the Luo sequence for the right (P < .05) and left (P < .05) coronary arteries, suggesting superior vessel sharpness. The proposed sequence also had superior signal-to-noise ratio (P < .05) and passband-to-stopband ratio (P < .05). Reader scores and reader preference indicated superior coronary image quality of the proposed sequence for both the right (P < .05) and left (P < .05) coronary arteries. CONCLUSION The proposed sequence with concatenated 1D spatially selective tip-ups and integrated fat saturation has superior image quality and suppression compared with the Luo sequence with 2D spatially selective tip-up.
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Affiliation(s)
- David Y Zeng
- Department of Electrical Engineering, Stanford University, Stanford, California
| | - Corey A Baron
- Department of Electrical Engineering, Stanford University, Stanford, California
- Department of Medical Biophysics, Western University, London, Canada
| | - Mario O Malavé
- Department of Electrical Engineering, Stanford University, Stanford, California
| | - Adam B Kerr
- Department of Electrical Engineering, Stanford University, Stanford, California
| | - Phillip C Yang
- Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California
| | - Bob S Hu
- Department of Electrical Engineering, Stanford University, Stanford, California
- Department of Cardiology, Palo Alto Medical Foundation, Palo Alto, California
| | - Dwight G Nishimura
- Department of Electrical Engineering, Stanford University, Stanford, California
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Coristine AJ, Chaptinel J, Ginami G, Bonanno G, Coppo S, van Heeswijk RB, Piccini D, Stuber M. Improved respiratory self-navigation for 3D radial acquisitions through the use of a pencil-beam 2D-T 2 -prep for free-breathing, whole-heart coronary MRA. Magn Reson Med 2018; 79:1293-1303. [PMID: 28568961 PMCID: PMC5931377 DOI: 10.1002/mrm.26764] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 05/01/2017] [Accepted: 05/03/2017] [Indexed: 12/26/2022]
Abstract
PURPOSE In respiratory self-navigation (SN), signal from static structures, such as the chest wall, may complicate motion detection or introduce post-correction artefacts. Suppressing signal from superfluous tissues may therefore improve image quality. We thus test the hypothesis that SN whole-heart coronary magnetic resonance angiography (MRA) will benefit from an outer-volume suppressing 2D-T2 -Prep and present both phantom and in vivo results. METHODS A 2D-T2 -Prep and a conventional T2 -Prep were used prior to a free-breathing 3D-radial SN sequence. Both techniques were compared by imaging a home-built moving cardiac phantom and by performing coronary MRA in nine healthy volunteers. Reconstructions were performed using both a reference-based and a reference-independent approach to motion tracking, along with several coil combinations. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared, along with vessel sharpness (VS). RESULTS In phantoms, using the 2D-T2 -Prep increased SNR by 16% to 53% and mean VS by 8%; improved motion tracking precision was also achieved. In volunteers, SNR increased by an average of 29% to 33% in the blood pool and by 15% to 25% in the myocardium, depending on the choice of reconstruction coils and algorithm, and VS increased by 34%. CONCLUSION A 2D-T2 -Prep significantly improves image quality in both phantoms and volunteers when performing SN coronary MRA. Magn Reson Med 79:1293-1303, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- A. J. Coristine
- Department of BioMedical Engineering, Case Western Reserve University (CWRU), Cleveland, Ohio, USA
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
| | - J. Chaptinel
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
| | - G. Ginami
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
| | - G. Bonanno
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
| | - S. Coppo
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
| | - R. B. van Heeswijk
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
| | - D. Piccini
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
- Advanced Clinical Imaging Technology, Siemens Healthcare, Lausanne, Switzerland
| | - M. Stuber
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
- CardioVascular Magnetic Resonance (CVMR) research centre, Centre for BioMedical Imaging (CIBM), Lausanne, VD, Switzerland
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Jang A, Wu X, Auerbach EJ, Garwood M. Designing 3D selective adiabatic radiofrequency pulses with single and parallel transmission. Magn Reson Med 2018; 79:701-710. [PMID: 28497465 PMCID: PMC5682242 DOI: 10.1002/mrm.26720] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 03/23/2017] [Accepted: 03/24/2017] [Indexed: 11/11/2022]
Abstract
PURPOSE To introduce a method of designing single and parallel transmit (pTx) 3D adiabatic π pulses for inverting and refocusing spins that are insensitive to transmit B1 ( B1+) inhomogeneity. THEORY AND METHODS A 3D adiabatic pulse is created by replacing each piece-wise constant element (or sub-pulse) of an adiabatic full passage (AFP) by a 2D selective pulse. In this study, the parent AFP is an HS1 and each sub-pulse is a 2D pulse derived from a jinc function designed using a spiral k-trajectory. Spatial selectivity in the third direction is achieved by blipping the slab-selective gradient between sub-pulses, yielding a rectangular slab profile identical to that of the parent AFP. The slew-rate limited sub-pulse can be undersampled utilizing pTx, thus shortening the overall pulse width. Simulations and experiments demonstrate the quality of spatial selectivity and adiabaticity achievable. RESULTS The 3D adiabatic pulse inverts and refocus spins in a sharply demarcated cylindrical volume. When stepping RF amplitude, an adiabatic threshold is observed above which the flip angle remains π. Experimental results demonstrate that pTx is an effective means to significantly improve pulse performance. CONCLUSION A method of designing 3D adiabatic pulses insensitive to B1 inhomogeneity has been developed. pTx can shorten these pulses while retaining their adiabatic character. Magn Reson Med 79:701-710, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Albert Jang
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minnesota, United States
- Department of Electrical and Computer Engineering, University of Minnesota, Minnesota, United States
- Department of Medicine, Cardiovascular Division, University of Minnesota, Minnesota, United States
| | - Xiaoping Wu
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minnesota, United States
| | - Edward J. Auerbach
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minnesota, United States
| | - Michael Garwood
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minnesota, United States
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Mooiweer R, Sbrizzi A, Raaijmakers AJ, van den Berg CA, Luijten PR, Hoogduin H. Combining a reduced field of excitation with SENSE-based parallel imaging for maximum imaging efficiency. Magn Reson Med 2017; 78:88-96. [PMID: 27633931 PMCID: PMC5484283 DOI: 10.1002/mrm.26346] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 06/23/2016] [Accepted: 06/24/2016] [Indexed: 12/27/2022]
Abstract
PURPOSE To show that a combination of parallel imaging using sensitivity encoding (SENSE) and inner volume imaging (IVI) combines the known benefits of both techniques. SENSE with a reduced field of excitation (rFOX) is termed rSENSE. THEORY AND METHODS The noise level in SENSE reconstructions is reduced by removing voxels from the unfolding process that are rendered silent by using rFOX. The silent voxels need to be identified beforehand, this is done by using rFOX in the coil sensitivity maps. In vivo experiments were performed at 7 Tesla using a 32-channel receive coil. RESULTS Good image quality could be obtained in vivo with rSENSE at acceleration factors that are higher than could be obtained using SENSE or IVI alone. With rSENSE we were also able to accelerate scans using an rFOX that was purposely designed to be imperfect or incompatible at all with IVI. CONCLUSION rSENSE has been demonstrated in vivo with two-dimensionally selective radiofrequency pulses. Besides allowing additional scan acceleration, it offers a greater robustness and flexibility than IVI. The proposed method can be used with other field strengths, anatomies and other rFOX techniques. Magn Reson Med 78:88-96, 2017. © 2016 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 Non Commercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
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Affiliation(s)
- Ronald Mooiweer
- Center for Image Sciences, University Medical Center UtrechtUtrechtThe Netherlands
| | - Alessandro Sbrizzi
- Center for Image Sciences, University Medical Center UtrechtUtrechtThe Netherlands
| | | | | | - Peter R. Luijten
- Center for Image Sciences, University Medical Center UtrechtUtrechtThe Netherlands
| | - Hans Hoogduin
- Center for Image Sciences, University Medical Center UtrechtUtrechtThe Netherlands
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Coristine AJ, Yerly J, Stuber M. A Cylindrical, Inner Volume Selecting 2D-T2-Prep Improves GRAPPA-Accelerated Image Quality in MRA of the Right Coronary Artery. PLoS One 2016; 11:e0163618. [PMID: 27736866 PMCID: PMC5063575 DOI: 10.1371/journal.pone.0163618] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 09/12/2016] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND Two-dimensional (2D) spatially selective radiofrequency (RF) pulses may be used to excite restricted volumes. By incorporating a "pencil beam" 2D pulse into a T2-Prep, one may create a "2D-T2-Prep" that combines T2-weighting with an intrinsic outer volume suppression. This may particularly benefit parallel imaging techniques, where artefacts typically originate from residual foldover signal. By suppressing foldover signal with a 2D-T2-Prep, image quality may therefore improve. We present numerical simulations, phantom and in vivo validations to address this hypothesis. METHODS A 2D-T2-Prep and a conventional T2-Prep were used with GRAPPA-accelerated MRI (R = 1.6). The techniques were first compared in numerical phantoms, where per pixel maps of SNR (SNRmulti), noise, and g-factor were predicted for idealized sequences. Physical phantoms, with compartments doped to mimic blood, myocardium, fat, and coronary vasculature, were scanned with both T2-Preparation techniques to determine the actual SNRmulti and vessel sharpness. For in vivo experiments, the right coronary artery (RCA) was imaged in 10 healthy adults, using accelerations of R = 1,3, and 6, and vessel sharpness was measured for each. RESULTS In both simulations and phantom experiments, the 2D-T2-Prep improved SNR relative to the conventional T2-Prep, by an amount that depended on both the acceleration factor and the degree of outer volume suppression. For in vivo images of the RCA, vessel sharpness improved most at higher acceleration factors, demonstrating that the 2D-T2-Prep especially benefits accelerated coronary MRA. CONCLUSION Suppressing outer volume signal with a 2D-T2-Prep improves image quality particularly well in GRAPPA-accelerated acquisitions in simulations, phantoms, and volunteers, demonstrating that it should be considered when performing accelerated coronary MRA.
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Affiliation(s)
- Andrew J. Coristine
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
- CardioVascular Magnetic Resonance (CVMR) research centre, Centre for BioMedical Imaging (CIBM), Lausanne, VD, Switzerland
| | - Jerome Yerly
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
- CardioVascular Magnetic Resonance (CVMR) research centre, Centre for BioMedical Imaging (CIBM), Lausanne, VD, Switzerland
| | - Matthias Stuber
- Department of Radiology, University Hospital (CHUV) / University of Lausanne (UNIL), Lausanne, VD, Switzerland
- CardioVascular Magnetic Resonance (CVMR) research centre, Centre for BioMedical Imaging (CIBM), Lausanne, VD, Switzerland
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Addy NO, Ingle RR, Luo J, Baron CA, Yang PC, Hu BS, Nishimura DG. 3D image-based navigators for coronary MR angiography. Magn Reson Med 2016; 77:1874-1883. [PMID: 27174590 DOI: 10.1002/mrm.26269] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Revised: 04/13/2016] [Accepted: 04/17/2016] [Indexed: 01/22/2023]
Abstract
PURPOSE To develop a method for acquiring whole-heart 3D image-based navigators (iNAVs) with isotropic resolution for tracking and correction of localized motion in coronary magnetic resonance angiography (CMRA). METHODS To monitor motion in all regions of the heart during a free-breathing scan, a variable-density cones trajectory was designed to collect a 3D iNAV every heartbeat in 176 ms with 4.4 mm isotropic spatial resolution. The undersampled 3D iNAV data were reconstructed with efficient self-consistent parallel imaging reconstruction (ESPIRiT). 3D translational and nonrigid motion-correction methods using 3D iNAVs were compared to previous translational and nonrigid methods using 2D iNAVs. RESULTS Five subjects were scanned with a 3D cones CMRA sequence, accompanied by both 2D and 3D iNAVs. The quality of the right and left anterior descending coronary arteries was assessed on 2D and 3D iNAV-based motion-corrected images using a vessel sharpness metric and qualitative reader scoring. This assessment showed that nonrigid motion correction based on 3D iNAVs produced results that were noninferior to correction based on 2D iNAVs. CONCLUSION The ability to acquire isotropic-resolution 3D iNAVs every heartbeat during a CMRA scan was demonstrated. Such iNAVs enabled direct measurement of localized motion for nonrigid motion correction in free-breathing whole-heart CMRA. Magn Reson Med 77:1874-1883, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Nii Okai Addy
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - R Reeve Ingle
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Jieying Luo
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Corey A Baron
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Phillip C Yang
- Cardiovascular Medicine, Stanford University Medical Center, Stanford, California, USA
| | - Bob S Hu
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA.,Department of Cardiology, Palo Alto Medical Foundation, Palo Alto, California, USA
| | - Dwight G Nishimura
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
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Bano W, Feliciano H, Coristine AJ, Stuber M, van Heeswijk RB. On the accuracy and precision of cardiac magnetic resonance T 2 mapping: A high-resolution radial study using adiabatic T 2 preparation at 3 T. Magn Reson Med 2016; 77:159-169. [PMID: 26762815 DOI: 10.1002/mrm.26107] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 12/02/2015] [Accepted: 12/03/2015] [Indexed: 11/07/2022]
Abstract
PURPOSE The goal of this study was to characterize the accuracy and precision of cardiac T2 mapping as a function of different factors including low signal-to-noise ratio (SNR), imaging in systole, and off-resonance frequencies. METHODS Bloch equation and Monte Carlo simulations were used to determine the influence of SNR and the choice of T2 preparation echo time (TET2prep ) increments on the accuracy and precision of high-resolution radial cardiac T2 mapping at 3.0 T. Healthy volunteers were scanned to establish the difference in precision and inter- and intraobserver variability between T2 mapping in diastole and systole, as well as the effect of SNR and off-resonance frequencies on the accuracy of T2 maps. RESULTS The simulations demonstrated that a TET2prep increment of ∼0.75 times the T2 value of interest optimally increases the precision of the T2 fit. Systolic T2 maps were found to have a higher precision (P = 0.002), but similar inter- and intraobserver variability compared with diastolic T2 maps, whereas off-resonance frequencies beyond ± 100 Hz cause a significant decrease in both accuracy and precision (P < 0.05). CONCLUSION This evaluation of the accuracy and precision of cardiac T2 mapping characterizes the major vulnerabilities of the technique and will help guide protocol definition of studies that include T2 mapping. Magn Reson Med 77:159-169, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Wajiha Bano
- Cardiovascular Magnetic Resonance Research Center, Department of Radiology, University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Hélène Feliciano
- Cardiovascular Magnetic Resonance Research Center, Department of Radiology, University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Andrew J Coristine
- Cardiovascular Magnetic Resonance Research Center, Department of Radiology, University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Matthias Stuber
- Cardiovascular Magnetic Resonance Research Center, Department of Radiology, University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Ruud B van Heeswijk
- Cardiovascular Magnetic Resonance Research Center, Department of Radiology, University Hospital and University of Lausanne, Lausanne, Switzerland
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Luo J, Addy NO, Ingle RR, Hargreaves BA, Hu BS, Nishimura DG, Shin T. Combined outer volume suppression and T2 preparation sequence for coronary angiography. Magn Reson Med 2015; 74:1632-9. [PMID: 25521477 PMCID: PMC4470881 DOI: 10.1002/mrm.25575] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 11/10/2014] [Accepted: 11/14/2014] [Indexed: 12/25/2022]
Abstract
PURPOSE To develop a magnetization preparation sequence for simultaneous outer volume suppression (OVS) and T2 weighting in whole-heart coronary magnetic resonance angiography. METHODS A combined OVS and T2 preparation sequence (OVS-T2 Prep) was designed with a nonselective adiabatic 90° tipdown pulse, two adiabatic 180° refocusing pulses, and a 2D spiral -90° tipup pulse. The OVS-T2 Prep preserves the magnetization inside an elliptic cylinder with T2 weighting, while saturating the magnetization outside the cylinder. Its performance was tested on phantoms and on 13 normal subjects with coronary magnetic resonance angiography using 3D cones trajectories. RESULTS Phantom studies showed expected T2 -dependent signal amplitude in the spatial passband and suppressed signal in the spatial stopband. In vivo studies with full-field-of-view cones yielded a passband-to-stopband signal ratio of 3.18 ± 0.77 and blood-myocardium contrast-to-noise ratio enhancement by a factor of 1.43 ± 0.20 (P < 0.001). In vivo studies with reduced-field-of-view cones showed that OVS-T2 Prep well suppressed the aliasing artifacts, as supported by significantly reduced signal in the regions with no tissues compared to the images acquired without preparation (P < 0.0001). CONCLUSION OVS-T2 Prep is a compact sequence that can accelerate coronary magnetic resonance angiography by suppressing signals from tissues surrounding the heart while simultaneously enhancing the blood-myocardium contrast.
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Affiliation(s)
- Jieying Luo
- Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA
| | - Nii Okai Addy
- Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA
| | - R. Reeve Ingle
- Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA
| | | | - Bob S. Hu
- Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA
- Palo Alto Medical Foundation, Palo Alto, California, USA
| | - Dwight G. Nishimura
- Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA
| | - Taehoon Shin
- Diagnostic Radiology and Nuclear Medicine, University of Maryland, Baltimore, Maryland, USA
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