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Lee J, Gupta AN, Ma LE, Scott MB, Mason OR, Wu E, Thomas JD, Markl M. Valvular regurgitation flow jet assessment using in vitro 4D flow MRI: Implication for mitral regurgitation. Magn Reson Med 2021; 87:1923-1937. [PMID: 34783383 DOI: 10.1002/mrm.29082] [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: 06/25/2021] [Revised: 10/01/2021] [Accepted: 10/25/2021] [Indexed: 11/11/2022]
Abstract
PURPOSE The purpose of this study was to evaluate the accuracy of four-dimensional (4D) flow MRI for direct assessment of peak velocity, flow volume, and momentum of a mitral regurgitation (MR) flow jets using an in vitro pulsatile jet flow phantom. We systematically investigated the impact of spatial resolution and quantification location along the jet on flow quantities with Doppler ultrasound as a reference for peak velocity. METHODS Four-dimensional flow MRI data of a pulsatile jet through a circular, elliptical, and 3D-printed patient-specific MR orifice model was acquired with varying spatial resolution (1.5-5 mm isotropic voxel). Flow rate and momentum of the jet were quantified at various axial distances (x = 0-50 mm) and integrated over time to calculate Voljet and MTIjet . In vivo assessment of Voljet and MTIjet was performed on 3 MR patients. RESULTS Peak velocities were comparable to Doppler ultrasound (3% error, 1.5 mm voxel), but underestimated with decreasing spatial resolution (-40% error, 5 mm voxel). Voljet was similar to regurgitant volume (RVol) within 5 mm, and then increased linearly with the axial distance (19%/cm) because of flow entrainment. MTIjet remained steady throughout the jet (2%/cm) as theoretically predicted. Four and 9 voxels across the jet were required to measure flow volume and momentum-time-integral within 10% error, respectively. CONCLUSION Four-dimensional flow MRI detected accurate peak velocity, flow rate, and momentum for in vitro MR-mimicking flow jets. Spatial resolution significantly impacted flow quantitation, which otherwise followed predictions of flow entrainment and momentum conservation. This study provides important preliminary information for accurate in vivo MR assessment using 4D flow MRI.
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Affiliation(s)
- Jeesoo Lee
- Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Aakash N Gupta
- Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Liliana E Ma
- Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Michel B Scott
- Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - O'Neil R Mason
- Division of Cardiology, Northwestern Memorial Hospital, Chicago, Illinois, USA
| | - Erik Wu
- Division of Cardiology, Northwestern Memorial Hospital, Chicago, Illinois, USA
| | - James D Thomas
- Division of Cardiology, Northwestern Memorial Hospital, Chicago, Illinois, USA
| | - Michael Markl
- Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA.,Department of Biomedical Engineering, Northwestern University, McCormick School of Engineering, Evanston, Illinois, USA
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Blanken CPS, Westenberg JJM, Aben JP, Bijvoet GP, Chamuleau SAJ, Boekholdt SM, Nederveen AJ, Leiner T, van Ooij P, Planken RN. Quantification of Mitral Valve Regurgitation from 4D Flow MRI Using Semiautomated Flow Tracking. Radiol Cardiothorac Imaging 2020; 2:e200004. [PMID: 33778618 DOI: 10.1148/ryct.2020200004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 06/23/2020] [Accepted: 06/26/2020] [Indexed: 11/11/2022]
Abstract
Purpose To compare the accuracy of semiautomated flow tracking with that of semiautomated valve tracking in the quantification of mitral valve (MV) regurgitation from clinical four-dimensional (4D) flow MRI data obtained in patients with mild, moderate, or severe MV regurgitation. Materials and Methods The 4D flow MRI data were retrospectively collected from 30 patients (21 men; mean age, 61 years ± 10 [standard deviation]) who underwent 4D flow MRI from 2006 to 2016. Ten patients had mild MV regurgitation, nine had moderate MV regurgitation, and 11 had severe MV regurgitation, as diagnosed by using semiquantitative echocardiography. The regurgitant volume (Rvol) across the MV was obtained using three methods: indirect quantification of Rvol (RvolINDIRECT), semiautomated quantification of Rvol using valve tracking (RvolVALVE), and semiautomated quantification of Rvol using flow tracking (RvolFLOW). A second observer repeated the measurements. Aortic valve flow was quantified as well to test for intervalve consistency. The Wilcoxon signed rank test, orthogonal regression, Bland-Altman analysis, and coefficients of variation were used to assess agreement among measurements and between observers. Results RvolFLOW was higher (median, 24.8 mL; interquartile range [IQR], 14.3-45.7 mL) than RvolVALVE (median, 9.9 mL; IQR, 6.0-16.9 mL; P < .001). Both RvolFLOW and RvolVALVE differed significantly from RvolINDIRECT (median, 19.1 mL; IQR, 4.1-47.5 mL; P = .03). RvolFLOW agreed more with RvolINDIRECT (ŷ = 0.78x + 12, r = 0.88) than with RvolVALVE (ŷ = 0.16x + 8.1, r = 0.53). Bland-Altman analysis revealed underestimation of RvolVALVE in severe MV regurgitation. Interobserver agreement was excellent for RvolFLOW (r = 0.95, coefficient of variation = 27%) and moderate for RvolVALVE (r = 0.72, coefficient of variation = 57%). Orthogonal regression demonstrated better intervalve consistency for flow tracking (ŷ = 1.2x - 13.4, r = 0.82) than for valve tracking (ŷ = 2.7x - 92.4, r = 0.67). Conclusion Flow tracking enables more accurate 4D flow MRI-derived MV regurgitation quantification than valve tracking in terms of agreement with indirect quantification and intervalve consistency, particularly in severe MV regurgitation.Supplemental material is available for this article.© RSNA, 2020.
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Affiliation(s)
- Carmen P S Blanken
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - Jos J M Westenberg
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - Jean-Paul Aben
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - Geertruida P Bijvoet
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - Steven A J Chamuleau
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - S Matthijs Boekholdt
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - Aart J Nederveen
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - Tim Leiner
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - Pim van Ooij
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - R Nils Planken
- Departments of Radiology and Nuclear Medicine (C.P.S.B., A.J.N., P.v.O., R.N.P.) and Cardiology (S.M.B.), Amsterdam University Medical Centers, Location Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands (J.J.M.W.); Department of Research and Development, Pie Medical Imaging BV, Maastricht, the Netherlands (J.P.A.); and Departments of Cardiology (G.P.B., S.A.J.C.) and Radiology (T.L.), University Medical Center Utrecht, Utrecht, the Netherlands
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Jacobs KG, Chan FP, Cheng JY, Vasanawala SS, Maskatia SA. 4D flow vs. 2D cardiac MRI for the evaluation of pulmonary regurgitation and ventricular volume in repaired tetralogy of Fallot: a retrospective case control study. Int J Cardiovasc Imaging 2020; 36:657-669. [PMID: 31894524 DOI: 10.1007/s10554-019-01751-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 12/14/2019] [Indexed: 11/26/2022]
Abstract
Lengthy exams and breath-holding limit the use of pediatric cardiac MRI (CMR). 3D time-resolved flow MRI (4DF) is a free-breathing, single-sequence exam that obtains magnitude (anatomic) and phase contrast (PC) data. We compare the accuracy of gadobenate dimeglumine-enhanced 4DF on a 1.5 T magnet to 2D CMR in children with repaired tetralogy of Fallot (rTOF) to measure pulmonary net flow (PNF) as a reflection of pulmonary regurgitation, forward flow (FF) and ventricular volumetry. Thirty-four consecutive cases were included. 2D PCs were obtained at the valve level. Using 4DF, we measured PNF at the valve and at the main and branch pulmonary arteries. PNF measured at the valve by 4DF demonstrated the strongest correlation (r = 0.87, p < 0.001) and lowest mean difference (3.5 ± 9.4 mL/beat) to aortic net flow (ANF). Semilunar FF and stroke volume of the respective ventricle demonstrated moderate-strong correlation by 4DF (r = 0.66-0.81, p < 0.001) and strong correlation by 2D (r = 0.81-0.84, p < 0.001) with similar correlations and mean differences between techniques (p > 0.05). Ventricular volumes correlated strongly between 2D and 4DF (r = 0.75-0.96, p < 0.001), though 4DF overestimated right ventricle volumes by 11.8-19.2 mL/beat. Inter-rater reliability was excellent for 2D and 4DF volumetry (ICC = 0.91-0.99). Ejection fraction moderately correlated (r = 0.60-0.75, p < 0.001) with better reliability by 4DF (ICC: 0.80-0.85) than 2D (ICC: 0.69-0.89). 4DF exams were shorter than 2D (9 vs. 71 min, p < 0.001). 4DF provides highly reproducible and accurate measurements of flow with slight overestimation of RV volumes compared to 2D in pediatric rTOF. 4DF offers important advantages in this population with long-term monitoring needs.
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Affiliation(s)
- Kimberley G Jacobs
- Department of Pediatrics, Stanford University School of Medicine, Palo Alto, CA, USA.
- Lucile Packard Children's Hospital, 725 Welch Rd, Room G71, MC 5906, Palo Alto, CA, 94304, USA.
| | - Frandics P Chan
- Department of Pediatrics, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Joseph Y Cheng
- Department of Pediatrics, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Shreyas S Vasanawala
- Divisions of Pediatric Radiology and Cardiovascular Imaging, Department of Radiology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Shiraz A Maskatia
- Department of Pediatrics, Stanford University School of Medicine, Palo Alto, CA, USA
- Divisions of Pediatric Cardiology and Cardiovascular Imaging, Department of Pediatrics, Stanford University School of Medicine, Palo Alto, CA, USA
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Ha H, Kvitting JP, Dyverfeldt P, Ebbers T. 4D Flow MRI quantification of blood flow patterns, turbulence and pressure drop in normal and stenotic prosthetic heart valves. Magn Reson Imaging 2019; 55:118-127. [PMID: 30266627 DOI: 10.1016/j.mri.2018.09.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 09/10/2018] [Accepted: 09/24/2018] [Indexed: 11/17/2022]
Affiliation(s)
- Hojin Ha
- Department of Mechanical and Biomedical Engineering, Kangwon National University, Chuncheon, Republic of Korea; Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.
| | - John Peder Kvitting
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden; Department of Cardiothoracic Surgery, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Petter Dyverfeldt
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - Tino Ebbers
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
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Havsteen I, Ohlhues A, Madsen KH, Nybing JD, Christensen H, Christensen A. Are Movement Artifacts in Magnetic Resonance Imaging a Real Problem?-A Narrative Review. Front Neurol 2017; 8:232. [PMID: 28611728 PMCID: PMC5447676 DOI: 10.3389/fneur.2017.00232] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Accepted: 05/12/2017] [Indexed: 12/29/2022] Open
Abstract
Movement artifacts compromise image quality and may interfere with interpretation, especially in magnetic resonance imaging (MRI) applications with low signal-to-noise ratio such as functional MRI or diffusion tensor imaging, and when imaging small lesions. High image resolution has high sensitivity to motion artifacts and often prolongs scan time that again aggravates movement artifacts. During the scan fast imaging techniques and sequences, optimal receiver coils, careful patient positioning, and instruction may minimize movement artifacts. Physiological noise sources are motion from respiration, flow and pulse coupled to cardiac cycles, from the swallowing reflex and small spontaneous head movements. Par example, in resting-state functional MRI spontaneous neuronal activity adds 1–2% of signal change, even under optimal conditions signal contributions from physiological noise remain a considerable fraction hereof. Movement tracking during imaging may allow for prospective correction or postprocessing steps separating signal and noise.
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Affiliation(s)
- Inger Havsteen
- Department of Radiology, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark
| | - Anders Ohlhues
- Department of Clinical Engineering Diagnostic Imaging Section, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Kristoffer H Madsen
- Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
| | - Janus Damm Nybing
- Department of Radiology, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark
| | - Hanne Christensen
- Department of Neurology, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark
| | - Anders Christensen
- Department of Radiology, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark
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A novel method for evaluating enhancement using gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid in the hepatobiliary phase of magnetic resonance imaging. Clin Imaging 2016; 40:1112-1117. [DOI: 10.1016/j.clinimag.2016.07.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 06/19/2016] [Accepted: 07/05/2016] [Indexed: 02/06/2023]
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7
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Improvement in visualization of carotid artery uniformity using silent magnetic resonance angiography. Radiol Phys Technol 2016; 10:113-120. [DOI: 10.1007/s12194-016-0375-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 08/29/2016] [Accepted: 08/30/2016] [Indexed: 11/25/2022]
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8
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Kang CK, Park CA, Lee DS, Lee YB, Park CW, Kim YB, Cho ZH. Velocity measurement of microvessels using phase-contrast magnetic resonance angiography at 7 Tesla MRI. Magn Reson Med 2015; 75:1640-6. [PMID: 25980462 DOI: 10.1002/mrm.25600] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Revised: 12/10/2014] [Accepted: 12/12/2014] [Indexed: 01/26/2023]
Abstract
PURPOSE The purpose of this study was to measure the velocity and direction of blood flow in microvessels, such as lenticulostriate arteries (LSAs), using PC MRA. METHODS Eleven healthy subjects were scanned with 7 Tesla (T) MRI. Three velocity encoding (VENC) values of 15, 50, and 100 cm/s were tested for detecting the flow velocity in LSAs. The flow directions in Circle of Willis (CoW) were also examined with images obtained by the proposed method. Three subjects were also scanned with 3T MRI to determine the possibility of velocity measurement in LSAs. Difference between 3T and 7T was quantitatively analyzed in terms of signal-to-noise ratio and velocities in vessels and static tissues. RESULTS In 7T MRI, use of VENC = 15 cm/s provided great visualization and velocity measurements in small and slow flowing vessels, such as the LSAs. The mean of peak velocities in LSAs was 9.61 ± 1.78 cm/s. The results obtained with low VENC also clearly depicted the directions of flow in CoW, especially in posterior communicating arteries. However, 3T MRI could not detect the velocity of blood flow in LSAs. CONCLUSION This study demonstrated the potential for measuring the velocity and direction of blood flow in the targeted microvessels using an appropriate VENC and 7T MRI.
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Affiliation(s)
- Chang-Ki Kang
- Neuroscience Research Institute, Gachon University, Incheon, Korea.,Department of Radiological Science, Gachon University, Incheon, Korea
| | - Chan-A Park
- Bioimaging Research Team, Korea Basic Science Institute, Chungcheongbuk-do, Korea
| | - David Soobin Lee
- Department of Biomedical Engineering and Center for Imaging Science, Johns Hopkins University, Baltimore, Maryland, USA
| | - Yeong-Bae Lee
- Department of Neurology, Gachon University Gil Hospital, Gachon University, Incheon, Korea
| | - Cheol-Wan Park
- Neuroscience Research Institute, Gachon University, Incheon, Korea
| | - Young-Bo Kim
- Neuroscience Research Institute, Gachon University, Incheon, Korea.,Department of Neurosurgery, Gachon University Gil Hospital, Gachon University, Incheon, Korea
| | - Zang-Hee Cho
- Department of Radiological Sciences, University of California, Irvine, California, USA
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Koktzoglou I, Giri S, Piccini D, Grodzki DM, Flanagan O, Murphy IG, Gupta N, Collins JD, Edelman RR. Arterial spin labeled carotid MR angiography: A phantom study examining the impact of technical and hemodynamic factors. Magn Reson Med 2015; 75:295-301. [PMID: 25684192 DOI: 10.1002/mrm.25611] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 12/17/2014] [Accepted: 12/18/2014] [Indexed: 11/07/2022]
Abstract
PURPOSE To quantify the accuracy of three-dimensional (3D) radial arterial spin labeled (ASL) magnetic resonance angiography (MRA) using vascular models of carotid stenosis. METHODS Eight vascular models were imaged at 1.5 Tesla using pulsatile flow waveforms at rates found in the internal carotid arteries (100-400 mL/min). The impacts of the 3D ASL imaging readout (fast low angle shot (FLASH) versus balanced steady-state free precession (bSSFP)), ultrashort echo time imaging using a pointwise encoding time reduction with radial acquisition (PETRA), and model stenosis severity on the accuracy of vascular model display at the location of stenosis were quantified. Accuracy was computed vis-à-vis a reference bSSFP volume acquired under no flow. Comparisons were made with standard-of-care contrast-enhanced MRA (CEMRA) and Cartesian time-of-flight (TOF) MRA protocols. RESULTS For 50% and 70% stenoses, CEMRA was most accurate (respective accuracies of 81.7% and 78.6%), followed by ASL FLASH (75.7% and 71.8%), ASL PETRA (69.6% and 70.6%), 3D TOF (66.6% and 57.1%), ASL bSSFP (68.7% and 51.2%), and 2D TOF (65.1% and 50.6%). CONCLUSION Flow phantom imaging studies show that ASL MRA can improve the display of hemodynamically significant carotid arterial stenosis compared with TOF MRA, with FLASH and ultrashort echo time readouts being most accurate.
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Affiliation(s)
- Ioannis Koktzoglou
- Department of Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA.,The University of Chicago Pritzker School of Medicine, Chicago, Illinois, USA
| | | | - Davide Piccini
- Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Switzerland.,Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
| | | | - Oisin Flanagan
- Department of Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA.,Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Ian G Murphy
- Department of Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA.,Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - NavYash Gupta
- The University of Chicago Pritzker School of Medicine, Chicago, Illinois, USA.,Department of Surgery, Division of Vascular Surgery, NorthShore University HealthSystem, Evanston, Illinois, USA
| | - Jeremy D Collins
- Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Robert R Edelman
- Department of Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA.,Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
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10
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Kadbi M, Negahdar M, Cha JW, Traughber M, Martin P, Stoddard MF, Amini AA. 4D UTE flow: a phase-contrast MRI technique for assessment and visualization of stenotic flows. Magn Reson Med 2014; 73:939-50. [PMID: 24604617 DOI: 10.1002/mrm.25188] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 01/22/2014] [Accepted: 02/02/2014] [Indexed: 11/10/2022]
Abstract
PURPOSE Inaccuracy of conventional four-dimensional (4D) flow MR imaging in the presence of random unsteady and turbulent blood flow distal to a narrowing has been an important challenge. Previous investigations have revealed that shorter echo times (TE) decrease the errors, leading to more accurate flow assessments. METHODS In this study, as part of a 4D flow acquisition, an Ultra-Short TE (UTE) method was adopted. UTE works based on a center-out radial k-space trajectory that inherently has a short TE. By employing free induction decay sampling starting from read-out gradient ramp-up, and by combining the refocusing lobe of the slice select gradient with the bipolar flow encoding gradient, TEs of ≈1 msec may be achieved. RESULTS Both steady and pulsatile flow regimes, and in each case a range of Reynolds numbers, were studied in an in-vitro model. Flow assessment at low and medium flow rates demonstrated a good agreement between 4D UTE and conventional 4D flow techniques. However, 4D UTE flow significantly outperformed conventional 4D flow, at high flow rates for both steady and pulsatile flow regimes. Feasibility of the method in one patient with Aortic Stenosis was also demonstrated. CONCLUSION For both steady and pulsatile high flow rates, the measured flow distal to the stenotic narrowing using conventional 4D flow revealed more than 20% error compared to the ground-truth flow. This error was reduced to less than 5% using the 4D UTE flow technique.
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Affiliation(s)
- Mo Kadbi
- Electrical and Computer Engineering Department, University of Louisville, Louisville, Kentucky, USA
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Kadbi M, Wang H, Negahdar M, Warner L, Traughber M, Martin P, Amini AA. A novel phase-corrected 3D cine ultra-short te (UTE) phase-contrast MRI technique. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2012:77-81. [PMID: 23365836 DOI: 10.1109/embc.2012.6345875] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Phase-contrast (PC) MRI is a non-invasive technique to assess cardiovascular blood flow. However, this technique is not accurate for instance at the carotid bifurcation due to turbulent and disturbed blood flow in atherosclerotic disease. Flow quantification using conventional PC MRI distal to stenotic vessels suffers from intravoxel dephasing and flow artifacts. Previous studies have shown that short echo time (TE) potentially decreases the phase errors. In this work, a novel 3D cine UTE-PC imaging method is designed to measure the blood velocity in the carotid bifurcation using a UTE center-out radial trajectory and short TE time compared to standard PC MRI sequences. With a new phase error correction technique based on autocorrelation method, the proposed 3D cine UTE-PC has the potential to achieve high accuracy for quantification and visualization of velocity jet distal to a stenosis. Herein, we test the feasibility of the method in determining accurate flow waveforms in normal volunteers.
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Affiliation(s)
- Mo Kadbi
- Medical Imaging Lab, Dept. of Electrical and Computer Engineering, University of Louisville, Louisville, KY, United States.
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12
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In vivo validation of numerical prediction for turbulence intensity in an aortic coarctation. Ann Biomed Eng 2011; 40:860-70. [PMID: 22016327 DOI: 10.1007/s10439-011-0447-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 10/13/2011] [Indexed: 10/16/2022]
Abstract
This paper compares numerical predictions of turbulence intensity with in vivo measurement. Magnetic resonance imaging (MRI) was carried out on a 60-year-old female with a restenosed aortic coarctation. Time-resolved three-directional phase-contrast (PC) MRI data was acquired to enable turbulence intensity estimation. A contrast-enhanced MR angiography (MRA) and a time-resolved 2D PCMRI measurement were also performed to acquire data needed to perform subsequent image-based computational fluid dynamics (CFD) modeling. A 3D model of the aortic coarctation and surrounding vasculature was constructed from the MRA data, and physiologic boundary conditions were modeled to match 2D PCMRI and pressure pulse measurements. Blood flow velocity data was subsequently obtained by numerical simulation. Turbulent kinetic energy (TKE) was computed from the resulting CFD data. Results indicate relative agreement (error ≈10%) between the in vivo measurements and the CFD predictions of TKE. The discrepancies in modeled vs. measured TKE values were within expectations due to modeling and measurement errors.
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13
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Barker AJ, Staehle F, Bock J, Jung BA, Markl M. Analysis of complex cardiovascular flow with three-component acceleration-encoded MRI. Magn Reson Med 2011; 67:50-61. [DOI: 10.1002/mrm.22974] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 03/18/2011] [Accepted: 04/04/2011] [Indexed: 11/06/2022]
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14
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Petersson S, Dyverfeldt P, Gårdhagen R, Karlsson M, Ebbers T. Simulation of phase contrast MRI of turbulent flow. Magn Reson Med 2011; 64:1039-46. [PMID: 20574963 DOI: 10.1002/mrm.22494] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Phase contrast MRI is a powerful tool for the assessment of blood flow. However, especially in the highly complex and turbulent flow that accompanies many cardiovascular diseases, phase contrast MRI may suffer from artifacts. Simulation of phase contrast MRI of turbulent flow could increase our understanding of phase contrast MRI artifacts in turbulent flows and facilitate the development of phase contrast MRI methods for the assessment of turbulent blood flow. We present a method for the simulation of phase contrast MRI measurements of turbulent flow. The method uses an Eulerian-Lagrangian approach, in which spin particle trajectories are computed from time-resolved large eddy simulations. The Bloch equations are solved for each spin for a frame of reference moving along the spins trajectory. The method was validated by comparison with phase contrast MRI measurements of velocity and intravoxel velocity standard deviation (IVSD) on a flow phantom consisting of a straight rigid pipe with a stenosis. Turbulence related artifacts, such as signal drop and ghosting, could be recognized in the measurements as well as in the simulations. The velocity and the IVSD obtained from the magnitude of the phase contrast MRI simulations agreed well with the measurements.
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Affiliation(s)
- Sven Petersson
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
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15
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Flow assessment through four heart valves simultaneously using 3-dimensional 3-directional velocity-encoded magnetic resonance imaging with retrospective valve tracking in healthy volunteers and patients with valvular regurgitation. Invest Radiol 2010; 44:669-75. [PMID: 19724233 DOI: 10.1097/rli.0b013e3181ae99b5] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES To validate 3-dimensional (3D) 3-directional velocity-encoded (VE) magnetic resonance imaging (MRI) for flow assessment through all 4 heart valves simultaneously with retrospective valve-tracking during off-line analysis in healthy volunteers and in patients with valvular regurgitation. MATERIAL AND METHODS Three-dimensional 3-directional VE MRI was performed in 22 healthy volunteers and in 29 patients with ischemic cardiomyopathy who were suspected of valvular regurgitation and net flow volumes through the 4 heart valves were compared. Furthermore, the analysis was repeated for each valve in 10 healthy volunteers and in 10 regurgitant valves to assess intra- and interobserver agreement for assessment of respectively net flow volumes and regurgitation fraction. RESULTS In healthy volunteers, the average net flow volume through the mitral valve, tricuspid valve, aortic valve, and pulmonary valve was 85 +/- 20 mL, 85 +/- 21 mL, 83 +/- 19 mL, 82 +/- 21 mL, respectively. Strong correlations between net flow volumes through the 4 heart valves were observed (intraclass correlation coefficients [ICC] 0.93-0.95) and the coefficient of variance (CV) was small (6%-9%). The repeated analysis by the same observer and by a second observer yielded good agreement for measurement of net flow volumes (ICC: 0.93-0.99 and CV: 3%-7%). Strong correlations between the net flow volumes through the 4 heart valves were also observed in the patients with valvular regurgitation (ICC: 0.85-0.95 and CV: 7%-18%). The average net flow volume through the mitral valve, tricuspid valve, aortic valve, and pulmonary valve was 63 +/- 20 mL, 63 +/- 20 mL, 63 +/- 20 mL, 63 +/- 20 mL, respectively. Furthermore, the intra- and interobserver agreement for assessment of regurgitation fraction was good (ICC: 0.86 and 0.85, CV: 12% and 13%). CONCLUSIONS Flow assessment using 3D 3-directional VE MR with retrospective valve-tracking during off-line analysis enables accurate quantification of net flow volumes through 4 heart valves within a single acquisition in healthy volunteers and in patients with valvular regurgitation.
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16
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Mariappan YK, Glaser KJ, Manduca A, Ehman RL. Cyclic motion encoding for enhanced MR visualization of slip interfaces. J Magn Reson Imaging 2009; 30:855-63. [PMID: 19787735 DOI: 10.1002/jmri.21914] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To develop and test a magnetic resonance imaging-based method for assessing the mechanical shear connectivity across tissue interfaces with phantom experiments and in vivo feasibility studies. MATERIALS AND METHODS External vibrations were applied to phantoms and tissue and the differential motion on either side of interfaces within the media was mapped onto the phase of the MR images using cyclic motion encoding gradients. The phase variations within the voxels of functional slip interfaces reduced the net magnitude signal in those regions, thus enhancing their visualization. A simple two-compartment model was developed to relate this signal loss to the intravoxel phase variations. In vivo studies of the abdomen and forearm were performed to visualize slip interfaces in healthy volunteers. RESULTS The phantom experiments demonstrated that the proposed technique can assess the functionality of shear slip interfaces and they provided experimental validation for the theoretical model developed. Studies of the abdomen showed that the slip interface between the small bowel and the peritoneal wall can be visualized. In the forearm, this technique was able to depict the slip interfaces between the functional compartments of the extrinsic forearm muscles. CONCLUSION Functional shear slip interfaces can be visualized sensitively using cyclic motion encoding of externally applied tissue vibrations.
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17
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O'Brien KR, Gabriel RS, Greiser A, Cowan BR, Young AA, Kerr AJ. Aortic valve stenotic area calculation from phase contrast cardiovascular magnetic resonance: the importance of short echo time. J Cardiovasc Magn Reson 2009; 11:49. [PMID: 19925667 PMCID: PMC2785795 DOI: 10.1186/1532-429x-11-49] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2009] [Accepted: 11/19/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cardiovascular magnetic resonance (CMR) can potentially quantify aortic valve area (AVA) in aortic stenosis (AS) using a single-slice phase contrast (PC) acquisition at valve level: AVA = aortic flow/aortic velocity-time integral (VTI). However, CMR has been shown to underestimate aortic flow in turbulent high velocity jets, due to intra-voxel dephasing. This study investigated the effect of decreasing intra-voxel dephasing by reducing the echo time (TE) on AVA estimates in patients with AS. METHOD 15 patients with moderate or severe AS, were studied with three different TEs (2.8 ms/2.0 ms/1.5 ms), in the main pulmonary artery (MPA), left ventricular outflow tract (LVOT) and 0 cm/1 cm/2.5 cm above the aortic valve (AoV). PC estimates of stroke volume (SV) were compared with CMR left ventricular SV measurements and PC peak velocity, VTI and AVA were compared with Doppler echocardiography. CMR estimates of AVA obtained by direct planimetry from cine acquisitions were also compared with the echoAVA. RESULTS With a TE of 2.8 ms, the mean PC SV was similar to the ventricular SV at the MPA, LVOT and AoV0 cm (by Bland-Altman analysis bias +/- 1.96 SD, 1.3 +/- 20.2 mL/-6.8 +/- 21.9 mL/6.5 +/- 50.7 mL respectively), but was significantly lower at AoV1 and AoV2.5 (-29.3 +/- 31.2 mL/-21.1 +/- 35.7 mL). PC peak velocity and VTI underestimated Doppler echo estimates by approximately 10% with only moderate agreement. Shortening the TE from 2.8 to 1.5 msec improved the agreement between ventricular SV and PC SV at AoV0 cm (6.5 +/- 50.7 mL vs 1.5 +/- 37.9 mL respectively) but did not satisfactorily improve the PC SV estimate at AoV1 cm and AoV2.5 cm. Agreement of CMR AVA with echoAVA was improved at TE 1.5 ms (0.00 +/- 0.39 cm2) versus TE 2.8 (0.11 +/- 0.81 cm2). The CMR method which agreed best with echoAVA was direct planimetry (-0.03 cm2 +/- 0.24 cm2). CONCLUSION Agreement of CMR AVA at the aortic valve level with echo AVA improves with a reduced TE of 1.5 ms. However, flow measurements in the aorta (AoV 1 and 2.5) are underestimated and 95% limits of agreement remain large. Further improvements or novel, more robust techniques are needed in the CMR PC technique in the assessment of AS severity in patients with moderate to severe aortic stenosis.
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Affiliation(s)
- Kieran R O'Brien
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Ruvin S Gabriel
- Cardiology Department, Middlemore Hospital and University of Auckland, Auckland, New Zealand
| | | | - Brett R Cowan
- Centre for Advanced MRI, University of Auckland, Auckland, New Zealand
| | - Alistair A Young
- Department of Anatomy and Radiology, University of Auckland, Auckland, New Zealand
| | - Andrew J Kerr
- Cardiology Department, Middlemore Hospital and University of Auckland, Auckland, New Zealand
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18
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O'Brien KR, Myerson SG, Cowan BR, Young AA, Robson MD. Phase contrast ultrashort TE: A more reliable technique for measurement of high-velocity turbulent stenotic jets. Magn Reson Med 2009; 62:626-36. [PMID: 19488986 DOI: 10.1002/mrm.22051] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Kieran R O'Brien
- Bioengineering Institute, University of Auckland, Auckland, New Zealand.
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Abstract
Modern rapid magnetic resonance (MR) imaging techniques have led to widespread use of the modality in cardiac imaging. Despite this progress, many MR studies suffer from image degradation due to involuntary motion during the acquisition. This review describes the type and extent of the motion of the heart due to the cardiac and respiratory cycles, which create image artifacts. Methods of eliminating or reducing the problems caused by the cardiac cycle are discussed, including electrocardiogram gating, subject-specific acquisition windows, and section tracking. Similarly, for respiratory motion of the heart, techniques such as breath holding, respiratory gating, section tracking, phase-encoding ordering, subject-specific translational models, and a range of new techniques are considered.
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Affiliation(s)
- Andrew D Scott
- Cardiovascular Magnetic Resonance Unit, the Royal Brompton Hospital, London, England.
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20
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Shonai T, Carpenter JS, Lemieux SK, Harada K, Omori K, Kaneko N, Fukushima T. Improvement of vessel visibility in time-of-flight MR angiography of the brain. J Magn Reson Imaging 2008; 27:1362-70. [DOI: 10.1002/jmri.21371] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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21
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Prince MR. Is there replacement for percentage stenosis in characterizing occlusive vascular disease? Radiology 2007; 245:617-8. [PMID: 18024442 DOI: 10.1148/radiol.2453071331] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Characterization of vascular lesions on the basis of visual estimation of percentage stenosis is a valuable but limited procedure. In this issue, Lum et al (1) describe a fast, noninvasive four-dimensional MR method for accurate determination of pressure gradient maps, which correlate with direct pressure gradient measurements across vascular lesions in swine. This noninvasive determination of hemodynamic significance has potential to become a major advance in the diagnosis and management of vascular diseases, once it is verified in the clinical setting.
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Affiliation(s)
- Martin R Prince
- Department of Radiology, Weill Medical College of Cornell University, 525 E 68th St, New York, NY 10022, USA.
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Lorthois S, Stroud-Rossman J, Berger S, Jou LD, Saloner D. Numerical simulation of magnetic resonance angiographies of an anatomically realistic stenotic carotid bifurcation. Ann Biomed Eng 2005; 33:270-83. [PMID: 15868718 DOI: 10.1007/s10439-005-1730-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Magnetic Resonance Angiography (MRA) has become a routine imaging modality for the clinical evaluation of obstructive vascular disease. However, complex circulatory flow patterns, which redistribute the Magnetic Resonance (MR) signal in a complicated way, may generate flow artifacts and impair image quality. Numerical simulation of MRAs is a useful tool to study the mechanisms of artifactual signal production. The present study proposes a new approach to perform such simulations, applicable to complex anatomically realistic vascular geometries. Both the Navier-Stokes and the Bloch equations are solved on the same mesh to obtain the distribution of modulus and phase of the magnetization. The simulated angiography is subsequently constructed by a simple geometric procedure mapping the physical plane into the MRA image plane. Steady bidimensional numerical simulations of MRAs of an anatomically realistic severely stenotic carotid artery bifurcation are presented, for both time-of-flight and contrast-enhanced imaging modalities. These simulations are validated by qualitative comparison with flow phantom experiments performed under comparable conditions.
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Affiliation(s)
- Sylvie Lorthois
- Institut de Mécanique des Fluides de Toulouse, Groupe d'Etude sur les Milieux Poreux, Allés du Professeur Camille Soula, 31400 Toulouse Cedex, France.
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23
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Hyde DE, Fox AJ, Gulka I, Kalapos P, Lee DH, Pelz DM, Holdsworth DW. Internal Carotid Artery Stenosis Measurement. Stroke 2004; 35:2776-81. [PMID: 15514196 DOI: 10.1161/01.str.0000147037.12223.d5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
Clinical trials have shown that carotid endarterectomy reduces stroke risk in symptomatic individuals with severe internal carotid artery (ICA) stenosis. As a result of these trials, digital subtraction angiography (DSA) became a standard of reference for ICA stenosis diagnosis. Newer 3D techniques provide a larger number of views than DSA, which may influence the estimated degree of stenosis. We evaluate this possibility by directly comparing stenosis grades from 3D computed rotational angiography (CRA) and DSA.
Methods—
As a prospective diagnostic study, we performed CRA and DSA on 26 consecutive symptomatic patients. Only 1 angiographic procedure was performed on normal asymptomatic arteries, yielding 42 arteries for comparison. Four neuroradiologists graded the CRA maximum intensity projections (MIPs) and DSA images, according to the North American Symptomatic Carotid Endarterectomy Trial guidelines. CRA studies included a search for the narrowest view by evaluating 60 MIPs generated at 3° intervals and measurement of actual artery diameters. Artery diameters and stenosis grades were analyzed graphically; statistical significance was determined using a paired
t
test.
Results—
The mean difference of 1.2% (CI, −18%, 21%) between CRA and DSA stenosis grades was not statistically significant (
P
=0.55). Agreement of the optimal CRA viewing angle was limited, with an interobserver variability of 24±13°. The interobserver variability of DSA and CRA stenosis grades, 9.1% (CI, 0%, 21%) and 9.4% (CI, 0%, 22%), respectively, was not significantly different (
P
=0.79).
Conclusion—
CRA provides stenosis grades equivalent to DSA, as well as absolute measurements, providing a comparison for newer 3D techniques.
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Affiliation(s)
- Derek E Hyde
- Robarts Research Institute, Imaging Research Laboratories, London, Ontario, Canada
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Keegan J, Gatehouse PD, John AS, Mohiaddin RH, Firmin DN. Breath-hold signal-loss sequence for the qualitative assessment of flow disturbances in cardiovascular MR. J Magn Reson Imaging 2004; 18:496-501. [PMID: 14508787 DOI: 10.1002/jmri.10373] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To develop a breath-hold segmented sequence which generates similar patterns of signal loss to a non-breath-hold, relatively long echo time, conventional gradient echo sequence for the qualitative assessment of valvular heart disease. MATERIALS AND METHODS Both velocity-sensitized and acceleration-sensitized segmented sequences were developed. The sensitivities were empirically adjusted to give similar degrees of signal loss to a conventional sequence. These sequences were compared with a conventional sequence in eight patients with flow disturbances and in four healthy subjects. RESULTS There was no significant difference in the extent of signal loss observed when using the breath-hold velocity- and acceleration-sensitized sequences developed and the conventional sequence (1862 mm(2), 1831 mm(2), and 1782 mm(2), respectively; P = ns). However, the image quality obtained was significantly better with the breath-hold sequences (both P < 0.01). Furthermore, the image quality achieved with the acceleration-sensitized sequence was significantly better than that achieved with the velocity-sensitized sequence (P < 0.01) where artifacts from beat-to-beat variations in blood-flow velocities were a frequent problem. CONCLUSION Signal loss in complex flow is best demonstrated using the breath-hold acceleration-sensitized sequence where the signal from both stationary and constant velocity material is rephased at the echo time.
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Affiliation(s)
- Jennifer Keegan
- Magnetic Resonance Unit, Royal Brompton and Harefield NHS Hospital Trust, London, UK.
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25
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Back MR, Rogers GA, Wilson JS, Johnson BL, Shames ML, Bandyk DF. Magnetic resonance angiography minimizes need for arteriography after inadequate carotid duplex ultrasound scanning. J Vasc Surg 2003; 38:422-30; discussion 431. [PMID: 12947246 DOI: 10.1016/s0741-5214(03)00794-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE We prospectively evaluated whether magnetic resonance angiography (MRA) enabled definition of cerebrovascular anatomy after indeterminate or inadequate results at duplex ultrasound scanning to facilitate patient selection for carotid endarterectomy (CEA) and for technical planning. METHODS After implementation of a protocol in October 1998 to minimize use of cerebral arteriography, MRA (arch/cervical two-dimensional and cranial three-dimensional time of flight technique) was performed in 138 consecutive patients with cerebrovascular occlusive disease and inconclusive duplex scans obtained by an ICAVL-approved laboratory. The ability of MRA to define anatomic features unresolved at duplex scanning was compared between categories of duplex scan inadequacies. Operative outcome was compared between patients requiring MRA before CEA (n = 66) and a concurrent cohort undergoing CEA on the basis of duplex scan results only (n = 69). RESULTS Incomplete imaging of the carotid bifurcation, because of high bifurcation, long (>3 cm) internal carotid artery (ICA) plaque, or calcific shadows, was the most common reason for inadequate duplex scans (n = 74, 53%), followed by borderline severe ICA disease (23.17%), suspected extracervical disease (supra-aortic trunk, vertebral, or intracranial, 22, 16%), ICA near- occlusion (12.9%), and diffuse recurrent stenosis (7.5%). MRA enabled resolution of duplex scan inadequacies in 95% of patients with disease confined to the carotid bifurcation, and 90% of all patients, but was least accurate for delineation of extracervical lesions (77%) and near-occlusions (75%). In 5 of 8 patients (6%) arteriography was performed to determine operability of ICA near-occlusion or extracervical lesions. Combined stroke and death rates after CEA were not statistically different (P =.3) between patients requiring MRA (3 of 66, 4.6%) and the concurrent group in whom MRA was performed solely on the basis of duplex results (1 of 69, 1.5%). However, intraoperative technical adjustments (anatomy that precluded shunt use, extended endarterectomy length, ICA shortening due to tortuosity) were planned in 71% of patients (12 of 17) with MRA-defined anatomy, but only 36% of patients (4 of 11) with long CEA on the basis of duplex results only (P =.08). CONCLUSION MRA replaces the need for cerebral arteriography in most patients after inadequate carotid duplex scanning. Delineation of cerebrovascular anatomy at MRA assists in determination of CEA candidacy and operative planning.
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Affiliation(s)
- Martin R Back
- Division of Vascular and Endovascular Surgery, University of South Florida College of Medicine, Tampa, FL 33606, USA.
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Chan JHM, Tsui EYK, Kwong KL, Poon WL, Yuen MK, Leung JOY, Lai WT, Yu CW, Wong KPC. 3D time of flight MR angiography: acquisition with small field of view and low phase encodes. Comput Med Imaging Graph 2003; 27:283-7. [PMID: 12631512 DOI: 10.1016/s0895-6111(02)00092-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The aim of the study was to evaluate and compare the image quality of the 3D TOF MRA acquired with a small FOV and low phase encodes with those MR angiographic images acquired with standard pulse sequence parameters. Twenty patients who were referred to our institution for MR imaging of the brain and strictly satisfied the selection criteria were included in this study. Apart from the routine protocol for MR imaging of the brain, 3D TOF MRA of the circle of Willis with a small FOV and a standard FOV were performed. The image quality of all MRA was evaluated by two independent observers who were blind to the pulse sequence parameters. From the standard FOV MRA, 22.5, 12.5, and 5% of the patients were graded as mild, moderate, and severe stenosis of the internal carotid artery, respectively. On the contrary, no apparent stenosis was observed from the small FOV MRA with low phase encodes. Regarding the reduction in MR artifacts and acquisition time achieved with the small FOV 3D TOF MRA with low phase encodes, this might be a useful MR angiographic technique to be used in routine clinical practice.
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Affiliation(s)
- J H M Chan
- Department of Diagnostic Radiology, Tuen Mun Hospital, Tsing Chung Koon Road, Tuen Mun, NT, Hong Kong, People's Republic of China.
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Elgersma OE, Wüst AF, Buijs PC, van Der Graaf Y, Eikelboom BC, Mali WP. Multidirectional depiction of internal carotid arterial stenosis: three-dimensional time-of-flight MR angiography versus rotational and conventional digital subtraction angiography. Radiology 2000; 216:511-6. [PMID: 10924579 DOI: 10.1148/radiology.216.2.r00au02511] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To evaluate whether and to what extent greater number of projection images obtained at three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography versus conventional digital subtraction angiography (DSA) causes overestimation of internal carotid arterial (ICA) stenosis. MATERIALS AND METHODS DSA (two or three projections), rotational angiography (16 or 32 projections), and 3D TOF MR angiography (12 projections) were performed in 47 stenotic ICAs of 38 symptomatic patients. Two observers independently measured maximum stenosis, and the mean differences among MR angiography, DSA, and rotational angiography were compared. RESULTS Three rotational and five MR angiograms were nondiagnostic. Seven MR angiograms of ICA stenoses showed a signal void and were excluded from analysis. On the remaining 32 angiograms, mean differences in maximum stenosis for observers 1 and 2, respectively, were 7% (95% CI: 3%, 12%) and 8% (95% CI: 3%, 13%) at MR angiography versus DSA and 2% (95% CI: -2%, 7%) and -1% (95% CI: -5%, 3%) at MR angiography versus rotational angiography. ICA stenosis was graded significantly higher at MR angiography versus DSA, whereas, it was not overestimated at MR angiography versus rotational angiography. The difference in maximum stenosis at MR angiography versus DSA was significantly different from that of MR angiography versus rotational angiography. CONCLUSION Apparent overestimation of ICA stenosis at 3D TOF MR angiography versus conventional DSA may be partly explained by the greater number of projection images available at 3D TOF MR angiography.
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Affiliation(s)
- O E Elgersma
- Departments of Radiology, University Hospital Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
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Toyoshima T, Nomura M, Nishikado A, Harada M, Nakaya Y, Ito S. Magnetic resonance coronary angiography in patients with ischemic heart disease: analysis of coronary arterial blood flow velocity pattern. JAPANESE HEART JOURNAL 2000; 41:153-64. [PMID: 10850531 DOI: 10.1536/jhj.41.153] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Only a few reports evaluating coronary arterial blood flow velocity patterns using magnetic resonance (MR) coronary angiography have appeared to date. This study reports an evaluation of coronary arterial blood flow velocity patterns in patients with ischemic heart disease and in healthy subjects using MR coronary angiography. The subjects consisted of 20 patients with ischemic heart disease (IHD group) and 20 normal healthy subjects (N group). Using the fCARD PC method, ECG-gated MR coronary angiography was performed using an anteroposterior opposing phased array coil. Regions of interest were placed on bilateral coronary arteries to measure coronary arterial blood flow velocity patterns. The IHD group was divided into two subgroups, based on the presence (MI group) or absence (AP group) of infarcted myocardium using 99m Tc-methoxyisobutylisonitrile (MIBI) myocardial scintigraphy. Average diastolic peak velocity (ADPV) was lower in the IHD group than in the N group. In addition, the diastolic / systolic velocity ratio (DSVR) was significantly lower in the MI group. Moreover, in the AP group, both the ADPV and DSVR values were significantly increased in those who had undergone percutaneous transluminal coronary angioplasty postoperatively. Different from the Doppler guidewire method, MR coronary angiography facilitates noninvasive evaluation of coronary arterial blood flow velocity. Therefore, these results indicate that MR coronary angiography represents a potentially useful technique for diagnosing lesions of coronary arteries and evaluating their functions. This noninvasive method can be expected to replace the invasive Doppler guidewire method in the near future with development of MR coronary angiography technology.
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Affiliation(s)
- T Toyoshima
- Second Department of Internal Medicine, University of Tokushima, Japan
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Westenberg JJ, van der Geest RJ, Wasser MN, Doornbos J, Pattynama PM, de Roos A, Vanderschoot J, Reiber JH. Stenosis quantification from post-stenotic signal loss in phase-contrast MRA datasets of flow phantoms and renal arteries. INTERNATIONAL JOURNAL OF CARDIAC IMAGING 1999; 15:483-93. [PMID: 10768743 DOI: 10.1023/a:1006329032742] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In this study a semi-automated and observer-independent algorithm for quantifying post-stenotic signal loss (PSL) in 3D phase-contrast (PC) magnetic resonance angiography (MRA) of patients with renal artery stenosis is presented. This algorithm was developed on MRA datasets of stenotic phantoms, which were included in a flow circuit with stationary flows. The length and the severity of the PSL (incorporating both length and degree of PSL) in the maximum intensity projections (MIPs) of MRA datasets were proposed for quantifying stenoses. The algorithm was tested in renal arteries of ten patients with renal artery stenosis and seven healthy volunteers. Digital subtraction angiography (DSA) was performed in the patients and served as the gold standard. Stenosis severity showed better correlation with the severity of the PSL than with the length, both for in vitro as in vivo. Spearman correlation coefficients (rS) showed statistically significant correlations between the severity of the PSL and parameters determined by DSA, i.e. percent diameter stenosis (rS = 0.90). The length of the PSL showed no correlation with the diameter stenosis (rS = 0.37).
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Affiliation(s)
- J J Westenberg
- Division of Image Processing, Leiden University Medical Center, The Netherlands
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30
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Westenberg JJ, Wasser MN, van der Geest RJ, Pattynama PM, de Roos A, Vanderschoot J, Reiber JH. Gadolinium contrast-enhanced three-dimensional MRA of peripheral arteries with multiple bolus injection: scan optimization in vitro and in vivo. INTERNATIONAL JOURNAL OF CARDIAC IMAGING 1999; 15:161-73. [PMID: 10453415 DOI: 10.1023/a:1006166330001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In this study, a scanning protocol was developed to image the arterial bed of the pelvis and both legs along their entire length in patients with peripheral arterial disease, using standard hard- and software. Three adjacent stations are acquired consecutively, with some small overlap; per station; one Gadolinium contrast bolus is administered. The scanning protocol was optimized in an in vitro phantom study. The optimal flip angle was found to be 50 degrees. Also, the optimal scan delay was chosen to be equal to the arrival time of the contrast bolus thereby minimizing artifacts. Three contrast bolus injections showed sufficient enhancement of the vessels after image subtraction. Finally, stenosis quantification by manual caliper was performed by five observers in the MRA images and correlated with the percent diameter reduction determined by quantitative angiography from corresponding X-ray images. The results of the MRA measurements were reproducible and intra- and inter-observer variabilities were statistically non-significant (p = 0.54 and p = 0.12, respectively). Stenosis quantification performed by four observers showed a good correlation with the X-ray derived values (rp > 0.90, p < 0.02); the results from one observer were not significantly correlated. Five patients with proven peripheral disease were investigated with this new MRA scanning protocol. The images were of good quality which allowed adequate clinical evaluation; the original diagnoses obtained from X-ray examinations, were confirmed with MRA. In conclusion, peripheral arterial disease can be evaluated adequately with this MR scanning protocol.
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Affiliation(s)
- J J Westenberg
- Division of Image Processing, Leiden University Medical Center, The Netherlands
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31
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Jara H, Yu BC, Caruthers SD, Melhem ER, Yucel EK. Voxel sensitivity function description of flow-induced signal loss in MR imaging: implications for black-blood MR angiography with turbo spin-echo sequences. Magn Reson Med 1999; 41:575-90. [PMID: 10204883 DOI: 10.1002/(sici)1522-2594(199903)41:3<575::aid-mrm22>3.0.co;2-w] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The conditions in which the image intensity of vessels transporting laminar flow is attenuated in black-blood MR angiography (BB-MRA) with turbo spin-echo (TSE) and conventional spin-echo (CSE) pulse sequences are investigated experimentally with a flow phantom, studied theoretically by means of a Bloch equation-voxel sensitivity function (VSF) formalism, and computer modeled. The experiments studied the effects of: a) flow velocity, b) imaging axes orientation relative to the flow direction, and c) phase encoding order of the TSE train. The formulated Bloch equation-VSF theory describes flow effects in two-dimensional (2D)- and 3D-Fourier transform magnetic resonance imaging. In this theoretical framework, the main attenuation mechanism instrumental to BB-MRA, i.e., transverse magnetization dephasing caused by flow in the presence of the imaging gradients, is described in terms of flow-induced distortions of the individual voxel sensitivity functions. The computer simulations predict that the intraluminal homogeneity and extent of flow-induced image intensity attenuation increase as a function of decreasing vessel diameter, in support of the superior image quality achieved with TSE-based BB-MRA in the brain.
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Affiliation(s)
- H Jara
- Boston University School of Medicine, Boston Medical Center, Massachusetts 02118, USA.
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32
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Hoogeveen RM, Bakker CJ, Viergever MA. MR digital subtraction angiography with asymmetric echo acquisition and complex subtraction: improved lumen and stenosis visualization. Magn Reson Imaging 1999; 17:305-11. [PMID: 10215487 DOI: 10.1016/s0730-725x(98)00164-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The use of complex subtraction in dynamic thick slab 2D MR digital subtraction angiography (MR-DSA) has been shown to eliminate partial volume effects, which are present if vessels cover a small fraction of the 2D slab. However, spin dephasing still results in a poor visualization of areas with complex flow. In this paper, it is shown that this can be overcome by using asymmetric echo (ASE) acquisition combined with complex subtraction. It is proven that an ASE acquisition does not destroy information necessary for complex subtraction if the subtraction is performed in k-space. As a consequence, the subtraction reconstruction is as reliable as the magnitude reconstruction of a single ASE data set. Experiments with ASE and complex subtraction show that flow voids near stenoses disappear, that the signal-to-noise ratio is improved and that temporal resolution is increased.
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Affiliation(s)
- R M Hoogeveen
- Department of Radiology, Image Sciences Institute, University Hospital Utrecht, The Netherlands.
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33
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Westenberg JJ, Wasser MN, van der Geest RJ, Pattynama PM, de Roos A, Vanderschoot J, Reiber JH. Scan optimization of gadolinium contrast-enhanced three-dimensional MRA of peripheral arteries with multiple bolus injections and in vitro validation of stenosis quantification. Magn Reson Imaging 1999; 17:47-57. [PMID: 9888398 DOI: 10.1016/s0730-725x(98)00152-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In this study, a T1-weighted three-dimensional (3D) spoiled gradient-echo scanning protocol was developed to image the complete arterial system of the pelvis and both legs along their entire length in patients with peripheral arterial disease. Three adjacent stations were to be acquired consecutively, with some overlap, to image the entire area of interest; per station one gadolinium (Gd) contrast bolus would be administered. In an in vitro phantom study, the scanning protocol was optimized. The optimal flip angle was found to be 50 degrees. Also, the optimal scan delay was chosen to be equal to the arrival time of the contrast bolus, thereby minimizing artifacts. Three contrast bolus injections showed sufficient enhancement of the vessels after image subtraction. Finally, stenosis quantification by manual caliper was performed by five observers in the magnetic resonance angiography (MRA) images and correlated with the percent diameter reduction determined by quantitative angiography from corresponding X-ray images. The MRA measurements were reproducible, and intra- and interobserver variabilities were statistically non-significant (p=0.54 and p=0.12, respectively). Stenosis quantification performed by four observers showed a good correlation with the X-ray-derived values (rp > 0.90, p < 0.02); the results from one observer were not significantly correlated. Five patients with proven peripheral disease were investigated with this new MRA scanning protocol, using standard hardware and software. The images were of good quality, which allowed adequate clinical evaluation; the original diagnoses obtained from X-ray examinations, were confirmed with MRA. In conclusion, peripheral arterial disease can be evaluated adequately with this magnetic resonance scanning protocol.
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Affiliation(s)
- J J Westenberg
- Division of Image Processing, Leiden University Medical Center, The Netherlands
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34
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Hoogeveen RM, Bakker CJ, Viergever MA. Limits to the accuracy of vessel diameter measurement in MR angiography. J Magn Reson Imaging 1998; 8:1228-35. [PMID: 9848733 DOI: 10.1002/jmri.1880080608] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
This work addresses the fundamental limits imposed by the MRI process on the accuracy with which vessel diameters and cross-sectional areas can be derived from time-of-flight (TOF) and phase-contrast (PC) MR source images. By means of simulations and in vitro experiments, it is demonstrated that, even in the absence of flow-related artifacts, severe inaccuracies in the determination of diameters or cross-sectional areas may occur solely because of the physical process of the MR image acquisition. Resolution and intraluminal saturation have strong effects on the vessel appearance and thus on the diameter estimation error. It is shown that low resolution leads to diameter overestimation or even underestimation and that intraluminal saturation causes severe underestimation, even for relatively low flip angles. Velocity and velocity encoding do not have a major influence on lumen appearance in PC images. Accurate diameter estimations can be attained only if lumen diameters constitute at least three pixels for both TOF and PC acquisitions, provided that intraluminal saturation is suppressed or avoided. Additionally, since the constitution of TOF and PC images is dissimilar, lumina should be analyzed differently to obtain accurate diameters and cross-sectional areas.
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Affiliation(s)
- R M Hoogeveen
- Department of Radiology, University Hospital Utrecht, The Netherlands
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35
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Westenberg JJ, van der Geest RJ, Wasser MN, Doornbos J, Pattynama PM, de Roos A, Vanderschoot J, Reiber JH. Objective stenosis quantification from post-stenotic signal loss in phase-contrast magnetic resonance angiographic datasets of flow phantoms and renal arteries. Magn Reson Imaging 1998; 16:249-60. [PMID: 9621966 DOI: 10.1016/s0730-725x(97)00298-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this study a semi-automated and observer-independent algorithm for quantifying post-stenotic signal loss (PSL) in three-dimensional phase-contrast (PC) magnetic resonance angiography (MRA) of patients with renal artery stenosis is presented. This algorithm was developed on MRA datasets of stenotic phantoms, included in a flow circuit with stationary flows. The length and the severity of the PSL (incorporating both the length and the degree of PSL) in the MRA datasets were proposed for quantifying the stenoses. The algorithm was tested in renal arteries; ten patients with renal artery stenosis and seven healthy volunteers were investigated. Digital subtraction angiography was performed in the patients and served as the gold standard. Stenosis severity showed better correlation with the severity of the PSL than with the length, both for in vitro and in vivo measurements. Spearman correlation coefficients (rs) showed statistically significant correlations between the severity of the PSL and parameters determined by digital subtraction angiography, i.e., percent diameter stenosis (rs = 0.90). The length of the PSL showed no correlation with the diameter stenosis (rs = 0.37). In conclusion, this study presents a semi-automated and observer-independent way of quantifying signal loss, and the severity of the PSL is proposed for quantifying stenoses, rather than the length of PSL.
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Affiliation(s)
- J J Westenberg
- Division of Image Processing, Leiden University Medical Centre, The Netherlands
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36
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Mustert BR, Williams DM, Prince MR. In vitro model of arterial stenosis: correlation of MR signal dephasing and trans-stenotic pressure gradients. Magn Reson Imaging 1998; 16:301-10. [PMID: 9621971 DOI: 10.1016/s0730-725x(97)00304-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE Turbulent flow just distal to stenoses causes signal loss (dephasing) on magnetic resonance angiography (MRA). This study correlates dephasing with trans-stenotic pressure gradients in an in vitro model of arterial stenosis. MATERIALS AND METHODS Three-dimensional (3D) phase contrast, 2D time-of-flight, and 3D spoiled gradient echo MRA with/without gadolinium and varied echo time were performed for a system consisting of a peristaltic perfusion pump and a silastic vessel with stenoses of varying caliber. Length and diameter of dephasing jets were measured, and volumes calculated at varying pressure gradients and echo times, then correlated with percentage cross-sectional area stenosis as measured by conventional angiography. RESULTS Dephasing occurred in all sequences at pressure gradients of > or =4 mmHg (1 mmHg = 133 Pa) and stenoses of greater than 70%, and varied directly with pressure gradient. The dephasing was greatest for 3D phase contrast (PC). Gadolinium did not diminish dephasing. CONCLUSIONS MRA signal dephasing at stenoses varies directly with pressure gradient. MRA may provide a non-invasive means for determining the hemodynamic significance of arterial stenoses.
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Affiliation(s)
- B R Mustert
- Department of Radiology, University Hospitals, University of Michigan, Ann Arbor 48109-0030, USA
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37
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Poutanen VP, Kivisaari R, Häkkinen AM, Savolainen S, Hekali P, Standertskjöld-Nordenstam CG. Multiphase segmented k-space velocity mapping in pulsatile flow waveforms. Magn Reson Imaging 1998; 16:261-70. [PMID: 9621967 DOI: 10.1016/s0730-725x(97)00279-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The aim of the present study was to obtain the precision of flow measurement in breath-hold segmented k-space flow sequences. The results are based on studies of pulsatile flow in a phantom tube. The ultimate purpose is to use these sequences to measure coronary flow. In abdominal and cardiothoracic magnetic resonance imaging the image quality is degraded due to respiratory motion. In the segmented k-space acquisition method, one obtains many phase-encoding steps or views per cardiac phase. This shortens imaging time in the order of phase-encoding lines and makes it possible to image in a single breath-hold, thereby eliminating respiratory artefacts and improving edge detection. With breath-hold multiframe cine flow images it is possible to evaluate flow in all abdominal and cardiothoracic areas, including the coronary arteries. Our study shows that velocity curves shift in time when the number of k-space ky-lines per segment (LPS) are varied; this shift is linear as a function of LPS. The mean velocity Vmean in the center of mass of the pulsatile peak is constant (Vmean = 40.1 +/- 2.9 cm/s) and time t = -10.1 x LPS + 268 (r = 0.993, p < 0.0001). Correlation between theoretical and experimental flow curves is also linear as a function of LPS: C = -0.977 * LPS (r = 0.987, p < 0.0001). It is concluded that velocity curves move with LPS and are smoothed when the breath-hold velocity mapping is used. The more LPS is gathered the more inaccurate results are. LPS 7 or more cannot be considered clinically relevant.
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Affiliation(s)
- V P Poutanen
- Department of Radiology, Helsinki University Central Hospital, Finland.
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38
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Weber-Fahr W, Meid T, Bock M, Bachert P, Turek S, Schad L. Untersuchung komplexer Strömungen mit MRA-Techniken und Vergleich mit theoretischen Strömungsanalysen. Z Med Phys 1998. [DOI: 10.1016/s0939-3889(15)70239-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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39
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Cheng HC, Chu WC, Chai JW. Convergent flow phenomenon mimics the appearance of venous thrombosis in gradient-echo images with or without the presence of a contrast agent. Magn Reson Imaging 1997; 15:863-7. [PMID: 9309617 DOI: 10.1016/s0730-725x(97)00025-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have observed signal voids at the junction of the renal vein and the inferior vena cava in the Spoiled Grass images. They mimicked the magnetic resonance appearance of an intraluminal thrombus with and without the presence of a contrast agent. The patency of the vessels was unveiled by fast Spoiled Grass sequence with reduced echo time as well as by Doppler ultrasound. Phantom studies revealed patterns of counterrotating vortices at the confluence. The cause of this image artifact was subsequently deduced as the intravoxel spin phase dispersion arising from the impinging flows of the renal vein and inferior vena cava. It is concluded that in regions where complex flow patterns reside, fast imaging sequences that reduce spin phase variations should always be conducted in addition to other routine sequences to exclude uncertainties in image interpretation.
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Affiliation(s)
- H C Cheng
- Institute of Biomedical Engineering, Yang Ming University, Taipei, Taiwan
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40
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Hoogeveen RM, Bakker CJ, Viergever MA. Phase-derivative analysis in MR angiography: reduced Venc dependency and improved vessel wall detection in laminar and disturbed flow. J Magn Reson Imaging 1997; 7:321-30. [PMID: 9090586 DOI: 10.1002/jmri.1880070212] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A problem of current MRA techniques is the inability to accurately depict the vascular anatomy, particularly in areas of disturbed flow. Various reasons, such as intravoxel phase dispersion, saturation, temporal variations, and maximum intensity projection (MIP) nonlinearity, cause a wrong delineation of vessel boundaries. A phase contrast (PC)-based postprocessing operation, the phase derivative (PhD), is introduced to detect phase fluctuations indicating flow. Two-dimensional and three-dimensional angiographic reconstruction algorithms are presented. Mathematical formulas are derived to predict the effect of sampling to flow profiles and the effect on the PhD of these profiles. Numerical, phantom, and preliminary in vivo experiments demonstrate that PhD images do not suffer from phase wraps and allow a velocity dynamic range extension only limited by a differential phase change. It is also shown that PhD MIPs produce higher signal-to-noise ratios than conventional PC angiograms and give a better impression of the anatomy of (stenotic) vessels and of their diameters for both laminar and disturbed flow.
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Affiliation(s)
- R M Hoogeveen
- Imaging Center, University Hospital Utrecht, The Netherlands
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41
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Drangova M, Pelc NJ. Artifacts and signal loss due to flow in the presence of B(o) inhomogeneity. Magn Reson Med 1996; 35:126-30. [PMID: 8771030 DOI: 10.1002/mrm.1910350116] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
An in vitro study was performed to investigate the effects of B(o) inhomogeneity on magnetic resonance images of flow. Controlled inhomogeneity gradients (Gi) were applied and the magnitude of the artifacts produced was quantified for different echo delay times (TE). Both steady and pulsatile flows were examined. In the presence of an inhomogeneity gradient, signal loss is apparent if the flow is pulsatile and/or if the slice thickness is large. The signal loss increases with increasing TE and Gi. With pulsatile flow, ghosting artifacts are also generated. These increase in intensity with increasing TE and Gi. In vivo, field inhomogeneity due to susceptibility variations is large enough to produce these effects. Representative time-of-flight images obtained of a normal volunteer with two different TEs demonstrate the effect in vivo. Flow-related signal loss and artifacts, therefore, increase with increasing TE independent of the moments of the applied gradients.
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Affiliation(s)
- M Drangova
- Richard M. Lucas Center for MR Imaging and Spectroscopy, Department of Radiology, Stanford University, CA 94305-5488, USA
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42
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Ståhlberg F, Söndergaard L, Thomsen C. MR flow quantification with cardiovascular applications: a short overview. ACTA PAEDIATRICA (OSLO, NORWAY : 1992). SUPPLEMENT 1995; 410:49-56. [PMID: 8652916 DOI: 10.1111/j.1651-2227.1995.tb13844.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We present a short overview of the potential of magnetic resonance imaging (MRI) for quantification of flow in the cardiovascular system. The most widespread method for creation of MRI flow information utilized flow-sensitizing magnetic field gradients. Objects that move in the varying magnetic field introduced by such gradients change their precession frequency and therefore obtain a velocity-dependent offset phase angle. The exact phase behaviour for different types of gradients and motion patterns can be calculated and a very simple linear relationship is predicted by theory as well as confirmed in experiments between constant velocity and phase angle. Phase-sensitive flow MRI (velocity mapping) is frequently performed as a two-dimensional gradient-echo technique with flow sensitivity (flow encoding) in the through-plane direction, but other encoding directions are possible. Parameters that can be determined from a velocity map are linear velocity in each voxel, vessel area and flow rate. In the case of a stenotic vessel, the trans-stenotic pressure gradient can also be estimated. The velocity mapping method has been extensively used for cardiac flow studies in adult patient groups, e.g. for indirect measurements of coronary artery flow and for the study of aortic valve diseases. In children, the method has recently been used to determine shunt volumes in congenital heart disease. We conclude that flow investigation with MRI may in the future present a good alternative for the clinical evaluation of cardiovascular disorders.
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Affiliation(s)
- F Ståhlberg
- Department of Diagnostic Radiology, Lund University Hospital, Sweden
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43
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Clarke GD, Eckels R, Chaney C, Smith D, Dittrich J, Hundley WG, NessAiver M, Li HF, Parkey RW, Peshock RM. Measurement of absolute epicardial coronary artery flow and flow reserve with breath-hold cine phase-contrast magnetic resonance imaging. Circulation 1995; 91:2627-34. [PMID: 7743626 DOI: 10.1161/01.cir.91.10.2627] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND Noninvasive measurement of absolute coronary arterial flow and coronary flow reserve would be of considerable use in the diagnosis and management of patients with coronary artery disease. Phase-contrast magnetic resonance imaging (MRI) has been used to measure flow in a variety of vessels. The goal of the present study was to determine if MRI measurements of coronary artery flow in a single breath-hold can be used to determine flow reserve and the severity of pericardial stenosis. METHODS AND RESULTS In eight mongrel dogs, a closed chest model of partial left anterior descending coronary artery (LAD) occlusion was created. Coronary flows in the left circumflex artery (LCx) and LAD were measured at rest and during adenosine infusion using velocity-encoded, breath-hold MRI and perivascular ultrasound (US) flowmeters. MRI measurements of absolute coronary flow and coronary flow reserve were highly correlated with US (r = .96 and .94, respectively). Flow reserve measured in the constricted LAD was significantly lower than that in the unconstricted LCx by both US (P = .002) and MRI (P = .011). CONCLUSIONS MRI measurements of coronary flow and flow reserve were in good agreement with US measurements. In addition, MRI measurements of coronary flow reserve successfully discriminated stenotic from normal vessels. These results indicate that MRI is a useful method for the noninvasive assessment of coronary flow and stenosis.
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Affiliation(s)
- G D Clarke
- Department of Radiology, University of Texas Southwestern Medical Center at Dallas 75235-9071, USA
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44
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Chien D, Levin DL, Anderson CM. MR gradient echo imaging of intravascular blood oxygenation: T2* determination in the presence of flow. Magn Reson Med 1994; 32:540-5. [PMID: 7997123 DOI: 10.1002/mrm.1910320419] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The T2* relaxation time of blood varies with its oxygen saturation. To evaluate the feasibility of imaging intravascular blood oxygenation in humans using a conventional 1.5T MR system, we have implemented a method to measure T2* of blood despite the presence of pulsatile flow. The method was tested in a) stationary and flow phantoms, b) blood samples at different levels of oxygen saturation, and c) a human hypoxia model. Our results demonstrate the ability of cardiac-triggered, flow compensated gradient echo imaging to obtain reproducible T2* measurements of flowing blood in vivo.
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Affiliation(s)
- D Chien
- Department of Radiology, University of California-San Francisco
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45
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Tasciyan TA, Mitchell DG. Pulsatile flow artifacts in fast magnetization-prepared sequences. J Magn Reson Imaging 1994; 4:217-22. [PMID: 8180464 DOI: 10.1002/jmri.1880040221] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Fast magnetization-prepared magnetic resonance imaging sequences allow clinical acquisitions in about 1 second, with the preparation phase providing the desired contrast. Pulsatile flow artifacts, although reduced by rapid acquisition, can degrade image quality. The authors explore the causes of aortic pulsatile flow artifacts in inversion-recovery-prepared acquisitions of the abdomen, taking into consideration various parameters. The flow signal within an 8-mm-thick section was simulated and subsequently Fourier transformed to determine the location and extent of flow artifacts. Results of simulations were validated with abdominal images of human subjects. Recording all encodings within one cardiac cycle reduced pulsatile flow artifacts in nonsegmented acquisitions with sequential phase-encoding order, regardless of the location of magnetization preparation within the cardiac cycle. In segmented acquisitions, however, the sequential order always increased flow artifacts. To reduce the artifacts in short TI acquisitions, the magnetization should be prepared during diastole. In clinical acquisitions, flow artifacts were further reduced by modifying the phase-encoding scheme.
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Affiliation(s)
- T A Tasciyan
- Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA 19107
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46
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Ståhlberg F, Thomsen C, Söndergaard L, Henriksen O. Pulse sequence design for MR velocity mapping of complex flow: notes on the necessity of low echo times. Magn Reson Imaging 1994; 12:1255-62. [PMID: 7854031 DOI: 10.1016/0730-725x(94)90090-e] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Lowering of the echo time (TE) has been proposed as a way to reduce effects of phase dispersion in MR velocity mapping, because a low TE reduces sensitivity to higher-order motion terms while first-order velocity sensitivity is maintained. Methods of lowering TE involves the use of extreme gradient ramp times and gradient strengths as well as reduction of the duration of transmit/receive windows, the latter method causing decrements in image resolution. When reducing higher-order sensitivity, however, it is not the overall TE that is the critical parameter, but rather the time pattern of the gradients used in the experiment. Hence, changes in TE without subsequent variations in gradient pattern would, according to theory, not affect quantitative measurements of complex flow and vice versa. In this study, we experimentally demonstrate this relation and utilize the experience to create a sequence robust towards complex flow without sacrifices in image resolution. Our experimental observations show that variations in TE alone while maintaining the time course of the velocity-encoding gradient does not significantly affect measurements of through-plane average complex flow in the studied velocity range. A parameter that cannot be measured as accurately if TE is increased is the peak flow. A phase mapping sequence with prolonged TE from 3 ms to 5 ms but with short duration of the velocity-encoding (section-selective) gradient and improved in-plane resolution was demonstrated in vivo.
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Affiliation(s)
- F Ståhlberg
- Danish Center of Magnetic Resonance, Hvidovre Hospital, University of Copenhagen
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