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Dyverfeldt P, Ebbers T, Länne T. Pulse wave velocity with 4D flow MRI: systematic differences and age-related regional vascular stiffness. Magn Reson Imaging 2014; 32:1266-71. [PMID: 25171817 DOI: 10.1016/j.mri.2014.08.021] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 08/11/2014] [Accepted: 08/13/2014] [Indexed: 11/24/2022]
Abstract
PURPOSE The objective of this study was to compare multiple methods for estimation of PWV from 4D flow MRI velocity data and to investigate if 4D flow MRI-based PWV estimation with piecewise linear regression modeling of travel-distance vs. travel time is sufficient to discern age-related regional differences in PWV. METHODS 4D flow MRI velocity data were acquired in 8 young and 8 older (age: 23±2 vs. 58±2 years old) normal volunteers. Travel-time and travel-distance were measured throughout the aorta and piecewise linear regression was used to measure global PWV in the descending aorta and regional PWV in three equally sized segments between the top of the aortic arch and the renal arteries. Six different methods for extracting travel-time were compared. RESULTS Methods for estimation of travel-time that use information about the whole flow waveform systematically overestimate PWV when compared to methods restricted to the upslope-portion of the waveforms (p<0.05). In terms of regional PWV, a significant interaction was found between age and location (p<0.05). The age-related differences in regional PWV were greater in the proximal compared to distal descending aorta. CONCLUSION Care must be taken as different classes of methods for the estimation of travel-time produce different results. 4D flow MRI-based PWV estimation with piecewise linear regression modeling of travel-distance vs. travel time can discern age-related differences in regional PWV well in line with previously reported data.
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Affiliation(s)
- 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; Division of Media and Information Technology, Department of Science and Technology/Swedish e-Science Research Centre (SeRC), Linköping University, Linköping, Sweden
| | - Toste Länne
- 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 Cardiovascular Surgery, Linköping University Hospital, County Council of Östergötland, Linköping, Sweden
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2
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Parczyk M, Herold V, Klug G, Bauer WR, Rommel E, Jakob PM. Regional in vivo transit time measurements of aortic pulse wave velocity in mice with high-field CMR at 17.6 Tesla. J Cardiovasc Magn Reson 2010; 12:72. [PMID: 21134260 PMCID: PMC3014910 DOI: 10.1186/1532-429x-12-72] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Accepted: 12/06/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Transgenic mouse models are increasingly used to study the pathophysiology of human cardiovascular diseases. The aortic pulse wave velocity (PWV) is an indirect measure for vascular stiffness and a marker for cardiovascular risk. RESULTS This study presents a cardiovascular magnetic resonance (CMR) transit time (TT) method that allows the determination of the PWV in the descending murine aorta by analyzing blood flow waveforms. Systolic flow pulses were recorded with a temporal resolution of 1 ms applying phase velocity encoding. In a first step, the CMR method was validated by pressure waveform measurements on a pulsatile elastic vessel phantom. In a second step, the CMR method was applied to measure PWVs in a group of five eight-month-old apolipoprotein E deficient (ApoE(-/-)) mice and an age matched group of four C57Bl/6J mice. The ApoE(-/-) group had a higher mean PWV (PWV = 3.0 ± 0.6 m/s) than the C57Bl/6J group (PWV = 2.4 ± 0.4 m/s). The difference was statistically significant (p = 0.014). CONCLUSIONS The findings of this study demonstrate that high field CMR is applicable to non-invasively determine and distinguish PWVs in the arterial system of healthy and diseased groups of mice.
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Affiliation(s)
- Marco Parczyk
- Julius-Maximilians-Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, Am Hubland, 97074 Würzburg, Germany
| | - Volker Herold
- Julius-Maximilians-Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, Am Hubland, 97074 Würzburg, Germany
| | - Gert Klug
- Julius-Maximilians-Universität Würzburg, Medizinische Klinik und Poliklinik I, Oberdürrbacher Straße 6, 97080 Würzburg, Germany
| | - Wolfgang R Bauer
- Julius-Maximilians-Universität Würzburg, Medizinische Klinik und Poliklinik I, Oberdürrbacher Straße 6, 97080 Würzburg, Germany
| | - Eberhard Rommel
- Julius-Maximilians-Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, Am Hubland, 97074 Würzburg, Germany
| | - Peter M Jakob
- Julius-Maximilians-Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, Am Hubland, 97074 Würzburg, Germany
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3
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Markl M, Wallis W, Brendecke S, Simon J, Frydrychowicz A, Harloff A. Estimation of global aortic pulse wave velocity by flow-sensitive 4D MRI. Magn Reson Med 2010; 63:1575-82. [PMID: 20512861 DOI: 10.1002/mrm.22353] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The aim of this study was to determine the value of flow-sensitive four-dimensional MRI for the assessment of pulse wave velocity as a measure of vessel compliance in the thoracic aorta. Findings in 12 young healthy volunteers were compared with those in 25 stroke patients with aortic atherosclerosis and an age-matched normal control group (n = 9). Results from pulse wave velocity calculations incorporated velocity data from the entire aorta and were compared to those of standard methods based on flow waveforms at only two specific anatomic landmarks. Global aortic pulse wave velocity was higher in patients with atherosclerosis (7.03 +/- 0.24 m/sec) compared to age-matched controls (6.40 +/- 0.32 m/sec). Both were significantly (P < 0.001) increased compared to younger volunteers (4.39 +/- 0.32 m/sec). Global aortic pulse wave velocity in young volunteers was in good agreement with previously reported MRI studies and catheter measurements. Estimation of measurement inaccuracies and error propagation analysis demonstrated only minor uncertainties in measured flow waveforms and moderate relative errors below 16% for aortic compliance in all 46 subjects. These results demonstrate the feasibility of pulse wave velocity calculation based on four-dimensional MRI data by exploiting its full volumetric coverage, which may also be an advantage over standard two-dimensional techniques in the often-distorted route of the aorta in patients with atherosclerosis.
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Affiliation(s)
- Michael Markl
- Department of Radiology, Medical Physics, University Hospital, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
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4
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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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5
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Dowsey AW, Keegan J, Lerotic M, Thom S, Firmin D, Yang GZ. Motion-compensated MR valve imaging with COMB tag tracking and super-resolution enhancement. Med Image Anal 2007; 11:478-91. [PMID: 17804277 DOI: 10.1016/j.media.2007.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Revised: 06/30/2007] [Accepted: 07/17/2007] [Indexed: 10/23/2022]
Abstract
Understanding the morphology and function of heart valves is important to the study of underlying causes of heart failure. Existing techniques such as those based on echocardiography are limited by the relatively low signal-to-noise ratio (SNR), attenuation artefacts, and restricted access. The alternative of cardiovascular MR imaging offers versatility and accuracy in 3D localisation, but is hampered by large movements of the valves throughout the cardiac cycle. This paper presents a motion-compensated adaptive imaging approach for MR valve imaging. To illustrate its clinical potential, 3D motion of the aortic valve plane is first captured through a single breath-hold COMB tag pre-scan and then tracked in real-time with an automatic method based on multi-resolution image registration. Motion-compensated coverage of the aortic valve is then acquired prospectively, thus allowing its clear 3D reconstruction and visualisation. To provide isotropic voxel coverage of the imaging volume, retrospective projection onto convex sets (POCS) super-resolution enhancement is applied to the slice-select direction. In vivo results demonstrate the effectiveness of the proposed motion-compensation and super-resolution schemes for depicting the structure of the valve leaflets throughout the cardiac cycle. The proposed method fundamentally changes the way MR imaging is performed by transforming it from a spatially to materially localised imaging method. This also has important implications for quantifying blood flow and myocardial perfusion, as well as tracking anatomy and function of the heart.
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Affiliation(s)
- Andrew W Dowsey
- Institute of Biomedical Engineering, Imperial College London SW7 2AZ, UK.
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6
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Keegan J, Gatehouse PD, Prasad SK, Firmin DN. Improved turbo spin-echo imaging of the heart with motion-tracking. J Magn Reson Imaging 2007; 24:563-70. [PMID: 16878314 DOI: 10.1002/jmri.20655] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To improve dark-blood and short tau inversion recovery (STIR) prepared turbo spin-echo (TSE) imaging of the heart, particularly in the basal short-axis plane where cardiac misregistration between the preparation and imaging phases is high. MATERIALS AND METHODS In the first approach (tracked), the basal short-axis plane was labeled and tracked over the cardiac cycle. The slice-selective 180 degrees dark-blood and STIR preparation pulses were then independently positioned on the appropriately timed labeled images. In the second approach (offset), the preparation pulses were output in the same orientation as the imaging plane, but with a user-defined slice offset that was derived from the labeled data. Both approaches were compared with the standard untracked dark-blood STIR TSE sequence (7-mm slice thickness) in 10 healthy volunteers. RESULTS For typical preparation slice thicknesses, tracked and offset TSE images were superior to the untracked images (both P < 0.01). For the more mobile right ventricle (RV), the image quality of the tracked images was superior to that of the offset images (P < 0.05). CONCLUSION Tracking the through-plane motion of the heart between preparation and imaging phases improves the quality of thin-slice basal short-axis TSE images, particularly for the more mobile RV.
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Affiliation(s)
- Jennifer Keegan
- Cardiovascular Magnetic Resonance Unit, Royal Brompton Hospital, London, United Kingdom.
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7
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Yu HY, Peng HH, Wang JL, Wen CY, Tseng WYI. Quantification of the pulse wave velocity of the descending aorta using axial velocity profiles from phase-contrast magnetic resonance imaging. Magn Reson Med 2006; 56:876-83. [PMID: 16947380 DOI: 10.1002/mrm.21034] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The pulse wave velocity (PWV) of aortic blood flow is considered a surrogate for aortic compliance. A new method using phase-contrast (PC)-MRI is presented whereby the spatial and temporal profiles of axial velocity along the descending aorta can be analyzed. Seventeen young healthy volunteers (the YH group), six older healthy volunteers (the OH group), and six patients with coronary artery disease (the CAD group) were studied. PC-MRI covering the whole descending aorta was acquired, with velocity gradients encoding the in-plane velocity. From the corrected axial flow velocity profiles, PWV was determined from the slope of an intersecting line between the presystolic and early systolic phases. Furthermore, the aortic elastic modulus (Ep) was derived from the ratio of the brachial pulse pressure to the strain of the aortic diameter. The PWV increased from YH to OH to CAD (541 +/- 94, 808 +/- 184, 1121 +/- 218 cm/s, respectively; P = 0.015 between YH and OH; P = 0.023 between OH and CAD). There was a high correlation between PWV and Ep (r = 0.861, P < 0.001). Multivariate analysis showed that age and CAD were independent risk factors for an increase in the PWV. Compared to existing methods, our method requires fewer assumptions and provides a more intuitive and objective way to estimate the PWV.
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Affiliation(s)
- Hsi-Yu Yu
- Institute of Biomedical Engineering, College of Engineering, National Taiwan University Hospital, Taipei, Taiwan
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8
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Dowsey AW, Keegan J, Lerotic M, Thom S, Firmin D, Yang GZ. Motion-Compensated MR Valve Imaging with COMB Tag Tracking and Super-Resolution Enhancement. ACTA ACUST UNITED AC 2006; 9:364-71. [PMID: 17354793 DOI: 10.1007/11866763_45] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
MR imaging of the heart valve leaflets is a challenging problem due to their large movements throughout the cardiac cycle. This paper presents a motion-compensated imaging approach with COMB tagging for valve imaging. It involves an automatic method for tracking the full 3D motion of the valve plane so as to provide a motion-tracked acquisition scheme. Super-resolution enhancement is then applied to the slice-select direction so that the partial volume effect is minimised. In vivo results have shown that in terms of slice positioning, the method has equivalent accuracy to that of a manual approach whilst being quicker and more consistent. The use of multiple parallel COMB tags will permit adaptive imaging that follows tissue motion. This will have significant implications for quantification of myocardial perfusion and tracking anatomy, functions that are traditionally difficult in MRI.
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Affiliation(s)
- Andrew W Dowsey
- Royal Society / Wolfson Foundation Medical Image Computing Laboratory, Department of Computing, Imperial College London, UK.
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9
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Lee KJ, Wild JM, Griffiths PD, Paley MNJ. Simultaneous multislice imaging with slice-multiplexed RF pulses. Magn Reson Med 2005; 54:755-60. [PMID: 16155891 DOI: 10.1002/mrm.20643] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A method for simultaneous multislice imaging is presented that uses a multislice RF pulse that imparts a different linear phase profile to each slice. During readout, slices are unaliased by using extra slice-select gradient lobes, which rephase and dephase individual slices one at a time. Compared to other simultaneous slice methods, this method avoids distortion by slice-select gradients, and does not require extra views or additional hardware. However, because one echo per slice is required, the method requires a longer read period. This can cause non-ideal rephasing of the individual slices due to susceptibility gradients, which manifests itself as crosstalk between slices. There is also a concomitant increase in the minimum TR of the sequence. The method is demonstrated with phantom and in vivo images using gradient-echo and spin-echo versions.
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Affiliation(s)
- K J Lee
- Academic Unit of Radiology, University of Sheffield, UK.
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10
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Galea D, Lauzon ML, Drangova M. Peak velocity determination using fast Fourier velocity encoding with minimal spatial encoding. Med Phys 2002; 29:1719-28. [PMID: 12201419 DOI: 10.1118/1.1494829] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
For quantitative peak velocity determination, a technique was developed that uses Fourier velocity encoding (FVE) for the fast acquisition of images of velocity with no spatial encoding other than slice selection. The technique produces images of velocity versus temporal frequency. In applications where the quantity of interest is the peak velocity and in-plane spatial localization is not required, high SNR images are produced with reduced sensitivity to errors due to slice thickness and motion. The technique was validated using steady and pulsatile flow in a straight tube, and compared to both phase contrast measurements and numerical models using steady flow in a 50% and a 75% cosinusoidal stenosis phantom. Results show that for slices as large as 2 cm and/or undergoing periodic motion, FVE can accurately measure the peak velocity in cases where a distribution of velocities exist.
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Affiliation(s)
- Daniela Galea
- Robarts Research Institute, and Department of Medical Biophysics, University of Western Ontario, London, Canada
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11
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Khir AW, O'Brien A, Gibbs JS, Parker KH. Determination of wave speed and wave separation in the arteries. J Biomech 2001; 34:1145-55. [PMID: 11506785 DOI: 10.1016/s0021-9290(01)00076-8] [Citation(s) in RCA: 166] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Considering waves in the arteries as infinitesimal wave fronts rather than sinusoidal wavetrains, the change in pressure across the wave front, dP, is related to the change in velocity, dU, that it induces by the "water hammer" equation, dP=+/-rhocdU, where rho is the density of blood and c is the local wave speed. When only unidirectional waves are present, this relationship corresponds to a straight line when P is plotted against U with slope rhoc. When both forward and backward waves are present, the PU-loop is no longer linear. Measurements in latex tubes and systemic and pulmonary arteries exhibit a linear range during early systole and this provides a way of determining the local wave speed from the slope of the linear portion of the loop. Once the wave speed is known, it is also possible to separate the measured P and U into their forward and backward components. In cases where reflected waves are prominent, this separation of waves can help clarify the pattern of waves in the arteries throughout the cardiac cycle.
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Affiliation(s)
- A W Khir
- Physiological Flow Studies Group, Department of Biological and Medical Systems, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK
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12
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Kraft KA, Itskovich VV, Fei DY. Rapid measurement of aortic wave velocity: in vivo evaluation. Magn Reson Med 2001; 46:95-102. [PMID: 11443715 DOI: 10.1002/mrm.1164] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A 1D MR sequence has been developed for determining aortic flow wave velocity (WV), a metric of arterial compliance, within a single cardiac cycle. Studies were carried out on the thoracic aortas of 10 normal volunteers. Correlative WV data were also acquired from each subject using a conventional phase-velocity 2D mapping technique. Aortic WV in this cohort was found to range from 411 to 714 cm/s and was highly correlated (R = 0.95) between the two methods. Peak blood velocity was also measured using both methods and found to agree closely. The reproducibility of WV measurements using the rapid 1D method averaged 7.6%, which is comparable or better than that achieved using existing noninvasive techniques. Magn Reson Med 46:95-102, 2001.
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Affiliation(s)
- K A Kraft
- Department of Radiology, Virginia Commonwealth University, 1101 East Marshall St., Richmond, VA 23298-0072, USA.
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13
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Abstract
The utility of a one-dimensional magnetic resonance (MR) sequence to rapidly and accurately measure wave velocity in vivo was evaluated. Studies were conducted in the thoracic aortas of 20 healthy subjects of varying age, and the MR method was validated in a compliant tube model. Aortic wave velocity ranged from 3.8 to 9.7 m/sec and demonstrated a positive correlation with subjects' age. Peak blood velocity ranged from 47 to 125 cm/sec and exhibited a strong negative correlation with subjects' age.
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Affiliation(s)
- V V Itskovich
- Department of Biomedical Engineering, Medical College of Virginia of Virginia Commonwealth University, 1101 E Marshall St, Rm B3-020, Richmond, VA 23298-0072, USA
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14
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Nesbitt E, Schmidt-Trucksäss A, Il'yasov KA, Weber H, Huonker M, Laubenberger J, Keul J, Hennig J, Langer M. Assessment of arterial blood flow characteristics in normal and atherosclerotic vessels with the fast Fourier flow method. MAGMA (NEW YORK, N.Y.) 2000; 10:27-34. [PMID: 10697223 DOI: 10.1007/bf02613109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The purpose of this study was to scrutinize the ability of magnetic resonance imaging (MRI)-performed measurements to compare arterial flow patterns in patients with peripheral arterial occlusive disease (PAOD), healthy volunteers (HV) and endurance athletes (EA). MRI blood flow data were partially repeated with Doppler ultrasound (DUS) with a view to a methodical comparison. Additionally, pulse wave velocity was assessed with the MUFF technique. For this purpose, MRI-performed flow measurements were performed in the common femoral artery in 21 patients with PAOD, in 34 HV and in 12 EA. The analysis included maximum flow velocities (MFV), velocity/time profile (VTP), pulse wave velocity (Vpulse), and vessel diameter (VD). In addition, MFV and VD were observed by DUS in most individuals. The results revealed a significant change regarding arterial blood flow characteristics in patients compared with HV and EA, with respect to the span between the peak positive and negative blood flow velocity in the femoral artery. The pulse wave velocity in patients was markedly elevated compared with healthy individuals. Furthermore, a complete, characteristic change in the VTP could be observed in patients. The methodical comparison between DUS and MRI showed a good correlation. Multi-slice Fourier flow data have indicated markedly increased pulse wave velocity in PAOD patients. Changes in the arterial blood flow can be clearly observed with MRI. In the future, this might offer a noninvasive possibility not only for the evaluation of the stage of the disease, but also for the detection of early, pre-clinical stages of atherosclerosis.
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Affiliation(s)
- E Nesbitt
- Department of Radiology, University Hospital of Freiburg, Germany
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15
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Yang GZ. Exploring in vivo blood flow dynamics. IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE : THE QUARTERLY MAGAZINE OF THE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY 1998; 17:64-72, 104. [PMID: 9604703 DOI: 10.1109/51.677171] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- G Z Yang
- Magnetic Resonance Unit, Royal Brompton Hospital, London.
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16
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Abstract
Several magnetic resonance imaging methods for measuring blood flow have greatly enhanced the capability of magnetic resonance imaging as a physiologic tool in cardiology. This article concentrates on phase-related techniques. Magnetic resonance velocity mapping is a flexible, robust, and accurate method of obtaining functional information in the cardiovascular system. It has the potential to contribute significantly to clinical decision making, and it should be a routine part of cardiovascular imaging whenever information on flow is required.
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Affiliation(s)
- R H Mohiaddin
- Magnetic Resonance Unit, Royal Brompton Hospital, Imperial College of Science, Technology and Medicine, National Heart and Lung Institute, London, United Kingdom
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17
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Kao YH, Wan X, MacFall JR. Simultaneous multislice acquisition with arterial-flow tagging (SMART) using echo planar imaging (EPI). Magn Reson Med 1998; 39:662-5. [PMID: 9543431 DOI: 10.1002/mrm.1910390422] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Arterial spin tagging techniques have been used to image tissue perfusion in MR without contrast injection or ionizing radiation. Currently, spin tagging studies are performed primarily using single-slice imaging sequences, which are time consuming. This note reports a multislice echo-planar arterial spin tagging technique (Simultaneous Multislice Acquisition with aRterial-flow Tagging, or "SMART"). Multiband RF encoding (Hadamard) is used to provide simultaneous multislice acquisition capability for spin tagging techniques (such as echo planar imaging signal targeting with alternating radio frequency and flow-sensitive alternative inversion recovery). The method is illustrated with a two-slice pulse sequence that was implemented using the FAIR technique to generate two perfusion weighted images simultaneously. Compared with single-slice sequences, this two-slice sequence provided similar image quality, signal-to-noise ratio, and twice the spatial coverage compared with the single-slice technique within the same scan time.
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Affiliation(s)
- Y H Kao
- Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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18
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Mohiaddin RH, Gatehouse PD, Henien M, Firmin DN. Cine MR Fourier velocimetry of blood flow through cardiac valves: comparison with Doppler echocardiography. J Magn Reson Imaging 1997; 7:657-63. [PMID: 9243384 DOI: 10.1002/jmri.1880070408] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Noninvasive measurement of blood flow velocity through the cardiac valves has important clinical applications. A wide variety of MR methods are available for flow measurement. The aim of this study was to investigate the ability of cine MR Fourier velocimetry to measure flow through healthy cardiac valves and to compare MR and Doppler peak velocity measurements. Ten healthy volunteers (age mean +/- SD, 24 +/- 4 years) without history of valvular disease were studied. Four of the subjects were females. In each subject, aortic, pulmonary, mitral, and tricuspid valves were evaluated with MR and Doppler imaging. A whole-body mobile MR machine was used, operating at .5-T with actively shielded magnetic field gradient coils on all three axes capable of 20 mT/m at a slew rate of 60 mT/ m/msec. The heart rate during MR and Doppler studies was not significantly different. The mean difference between the two studies was 2 beats/min, with a 95% confidence interval of -22 beats/min, +25 beats/ min. Peak systolic flow velocity in the aortic and pulmonary valves and peak diastolic flow velocity in the mitral and tricuspid valves measured with MRI and Doppler echocardiography correlated well. The mean difference between the two measurements (MR-Doppler) was 63 mm/sec, with a 95% confidence interval of -180 mm/sec, +310 mm/sec. The agreement between two observers interpreting the same MR velocity maps was close. The mean difference between their two measurements was 23 mm/sec, with a 95% confidence interval of -20 mm/sec, +60 mm/sec. There was no significant difference between MR and Doppler imaging or between the two MR observers. MR Fourier velocimetry has the necessary ease, reliability, and speed to measure blood flow through the cardiac valves, although measurement of late diastolic flow in the atrioventricular valves is limited. Measurement of peak blood velocity through the cardiac valves by this method showed satisfactory agreement with Doppler, but its clinical application for assessing diseased cardiac valves must be established.
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Affiliation(s)
- R H Mohiaddin
- Magnetic Resonance Unit, Royal Brompton Hospital, London, United Kingdom.
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19
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Kraft KA, Fatouros PP, Corwin FD, Fei DY. In Vitro Validation of Rapid MR Measurement of Wave Velocity. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1997; 126:103-109. [PMID: 9252279 DOI: 10.1006/jmre.1997.1148] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A one-dimensional time-of-flight MR sequence, having a total acquisition time of approximately 60 ms, has been employed to determine flow-wave propagation velocities for pulsatile flow in compliant latex tubes. The results were compared with those of two independent methods and were found to be in good agreement. An extension of the same MR method was used to test the validity of the "water-hammer" relationship as a means to assess pulse pressure. Very good agreement was found with direct manometric determinations of pulse pressure.
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Affiliation(s)
- KA Kraft
- Department of Radiology, Virginia Commonwealth University, Richmond, Virginia, 23298-0072
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Hardy CJ, Bolster BD, McVeigh ER, Iben IE, Zerhouni EA. Pencil excitation with interleaved fourier velocity encoding: NMR measurement of aortic distensibility. Magn Reson Med 1996; 35:814-9. [PMID: 8744007 PMCID: PMC2396293 DOI: 10.1002/mrm.1910350605] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/1995] [Accepted: 01/31/1996] [Indexed: 02/01/2023]
Abstract
A technique is presented for rapidly and noninvasively determining aortic distensibility, by NMR measurement of pulse-wave velocity in the aorta. A cylinder of magnetization is excited along the aorta, with Fourier-velocity encoding and readout gradients applied along the cylinder axis. Cardiac gating and data interleaving improve the effective time resolution to as high as 3 ms. Wave velocities are determined from the position of the foot of the flow wave in the velocity profiles. Evidence of helical flow distal to the aortic arch can be seen in normal subjects, while disturbed flow patterns are visible in patients with aneurysms and dissections.
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Affiliation(s)
- C J Hardy
- GE Corporate Research and Development Center, Schenectady, New York 12301, USA
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22
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Ravensbergen J, Tarnawski M, Vriens EM, Hillen B, Caro CG, Van Huffelen AC. New ways of performing in vivo flow velocity measurements in the basilar artery. Neuroradiology 1996; 38:1-5. [PMID: 8773265 DOI: 10.1007/bf00593204] [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: 02/02/2023]
Abstract
The basilar artery is the only large artery in which two flows merge, and this is reflected in the flow downstream. We report quantitative flow-velocity measurements with a phase-based MR technique, i.e. the Fourier velocity encoding method, in the basilar artery of a volunteer. To our knowledge, this has not previously been performed successfully. A comparison is made with the results of flow velocity measurements in the basilar artery with transcranial Doppler ultrasonography; the techniques agreed very well. Although Doppler ultrasonography is still most widely used, no information on the flow rate and the flow velocity distribution in the basilar artery can be provided. MR flow measurement techniques appear promising when detailed information on the flow velocity distribution and flow rate is needed.
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Affiliation(s)
- J Ravensbergen
- Centre for Biological and Medical Systems, Imperial College, London, UK
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23
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Abstract
An MR imaging method for measuring intravascular pressure variations is introduced. The technique is based on estimates of vascular compliance and vessel distension, which are obtained from a correlation of spatial and temporal velocity derivatives and measurements of the velocity gradient in the direction of flow, respectively. The accuracy of the technique was determined in vitro through a comparison of MR and transducer pressure measurements obtained in distensible vessel phantoms undergoing pulsatile flow. Results indicated that a root-mean-square error of 4-12% can be expected in phantoms covering a physiological range of compliance. In vivo feasibility was demonstrated by thoracic aorta pressure measurements, which produced pressure waveforms with an expected shape and magnitude.
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Affiliation(s)
- S N Urchuk
- Department of Medical Biophysics, University of Toronto, Ontario, Canada
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24
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Urchuk SN, Plewes DB. A velocity correlation method for measuring vascular compliance using MR imaging. J Magn Reson Imaging 1995; 5:628-34. [PMID: 8748478 DOI: 10.1002/jmri.1880050603] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A method for estimating vascular compliance using MR velocity imaging is presented. The technique combines an analysis of pulse propagation, based on spatially averaged equations of continuity and momentum, together with phase-contrast velocity measurements to estimate the compliance from a correlation of second-order spatial and temporal velocity derivatives. The technique can be applied in the presence of reflected flow waves and uses velocity data acquired throughout the entire cardiac cycle. The accuracy of the technique was assessed in distensible vessel phantoms spanning a physiological range of compliance through a comparison with compliance estimates obtained using high-resolution MR imaging and pressure transducers. The mean error of all measurements was found to be 0.04 +/- 0.02% per mm Hg, with the relative errors ranging from 1.2% to 46%. Error was found to decrease as the temporal sampling rate and/or image plane separation were increased. This suggests that an accurate hemodynamic evaluation of a vessel's elastic properties is feasible with MR velocity imaging techniques.
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Affiliation(s)
- S N Urchuk
- Department of Medical Biophysics, University of Toronto, Ontario, Canada
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25
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Bock M, Schad LR, Müller E, Lorenz WJ. Pulsewave velocity measurement using a new real-time MR-method. Magn Reson Imaging 1995; 13:21-9. [PMID: 7898277 DOI: 10.1016/0730-725x(94)00077-g] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A new, one-dimensional method for the measurement of pulsewave velocities using real-time magnetic resonance (MR) imaging is presented. The measurement sequence is essentially of a RACE-type (Real Time Acquisition and Evaluation) with interleaved acquisition in two not necessarily parallel slices. In each slice the blood flow velocity perpendicular to the slice orientation was monitored. From the relative time difference of blood flow activity and the slice distance, pulsewave velocities were calculated. With a time resolution of 13 ms an overall acquisition time of 3.3 s was achieved. A method for suppression of signal contributions from stationary tissue along the axis of projection is discussed on the basis of a simplified mathematical model. Preliminary volunteer studies show that pulsewave velocities in the range of 1-10 m/s can be measured with an uncertainty of about 0.6 m/s at a conventional 1.5 T imager with a gradient system of maximal 10 mT/m.
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Affiliation(s)
- M Bock
- Forschungsschwerpunkt Radiologische Diagnostik und Therapie, Deutsches Krebsforschungszentrum (dkfz), Heidelberg, Germany
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26
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Abstract
Magnetic resonance angiography (MRA) has enjoyed enthusiastic success at many research institutions where it is now routinely used in place of invasive x-ray angiography (XRA) for a variety of applications. While the physical principles of MRA are well understood, there is still plenty of opportunity for growth in the coming years. Recent improvements in instrumentation have permitted more rapid acquisition and manipulation of larger data sets. Instruments in the future are sure to continue this trend as computer hardware becomes more capable and less expensive. New clinical applications will also expand the utility of MRA beyond its current use. MRA is already being used in peripheral vessels and it appears to have great potential in the abdomen. Research into MRA methods for coronary vessel imaging is also beginning to show intriguing results. In addition, preliminary research results suggest that interventional MRA may one day become a reality.
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Affiliation(s)
- C L Dumoulin
- General Electric Research and Development Center, Schenectady, N.Y. 12301, USA
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27
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Tarnawski M, Cybulski G, Doorly D, Dumoulin C, Darrow R, Caro C. Noninvasive determination of local wavespeed and distensibility of the femoral artery by comb-excited Fourier velocity-encoded magnetic resonance imaging: measurements on athletic and nonathletic human subjects. Heart Vessels 1994; 9:194-201. [PMID: 7961297 DOI: 10.1007/bf01746064] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The local distensibility of arteries is of interest because distensibility varies from artery to artery, may be altered by disease to different extents in different arteries, and may be modified by physiological or pharmacological means. Using magnetic resonance imaging (MRI) we have measured local arterial wavespeed in the femoral artery in healthy human subjects and calculated local arterial distensibility. We acquired 2-D coronal and sagittal MR phase contrast angiograms of the femoral artery. We used a novel imaging technique, comb-excited Fourier velocity-encoded MRI, to obtain simultaneous measurements of arterial blood velocity at two stations 14 cm apart on the femoral artery. The separation of the two stations divided by the delay between the onset of forward flow at the two stations was used to calculate the wavespeed. The measurements were made on 16 healthy men (8 athletes, 8 non-athletes) in the age range 20-30 years, who were scanned with the use of ECG gating and an extremity coil in a 1.5 Tesla scanner (GE Medical Systems, Milwaukee, WI). By systematically altering the delay between the R-wave and data acquisition, a temporal resolution of 2-4 ms was achieved. The onset of forward flow at each station was determined from a least-squares fit to the data for 30% of the maximum velocity during the cardiac cycle. Average femoral artery wavespeed was 7.7 m/s +/- 1.2 in the athletes and 11.5 m/s +/- 1.1 in the non-athletes (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Tarnawski
- Centre for Biological and Medical Systems, Imperial College, London, England
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28
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Hardy CJ, Bolster BD, McVeigh ER, Adams WJ, Zerhouni EA. A one-dimensional velocity technique for NMR measurement of aortic distensibility. Magn Reson Med 1994; 31:513-20. [PMID: 8015404 PMCID: PMC2570027 DOI: 10.1002/mrm.1910310507] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A technique is presented for rapidly and noninvasively determining aortic distensibility, by NMR measurement of wave velocity in the aorta. A two-dimensional NMR selective-excitation pulse is used to repeatedly excite a cylinder of magnetization in the aorta, with magnetization read out along the cylinder axis each time. A toggled bipolar flow-encoding pulse is applied prior to readout, to produce a non-dimensional phase-contrast flow image. Cardiac gating and data interleaving are employed to improve the effective time resolution to 2 ms. Wave velocities are determined from the slope of the leading edge of flow measured on the resulting M-mode velocity image. The technique is sensitive over a range of distensibilities from 10(-6) to 10(-3) m s2/kg. The average value in the descending thoracic aorta in seven normal subjects was found to be 4.8 x 10(-5) m s2/kg, with a significant inverse correlation with age.
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Affiliation(s)
- C J Hardy
- GE Corporate Research and Development Center, Schenectady, New York 12301
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