234 results on '"Velocity mapping"'
Search Results
102. Right ventricular function in patients after acute myocardial infarction assessed with phase contrast MR velocity mapping encoded in three directions
- Author
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Hein W. M. Kayser, Christianne S. J. Duchateau, Ernst E. van der Wall, Albert de Roos, and Rob J. van der Geest
- Subjects
medicine.medical_specialty ,Ventricular function ,business.industry ,Phase contrast microscopy ,Infarction ,medicine.disease ,law.invention ,medicine.anatomical_structure ,law ,Velocity mapping ,Ventricle ,Internal medicine ,medicine ,Cardiology ,Radiology, Nuclear Medicine and imaging ,In patient ,Myocardial infarction ,Systole ,business - Abstract
The purpose of the study was to assess global and regional myocardial function of the right ventricle (RV) with the use of phase contrast (PC) velocity mapping in patients after acute myocardial infarction. We examined 8 patients after acute myocardial wall infarction and 10 healthy volunteers for comparison. PC velocity mapping was performed in a single midventricular short-axis slice with velocity encoding in three different directions. RV displacement during systole in the through-plane direction differed significantly between patients and volunteers (P = 0.009). RV myocardial velocity in the through-plane and radial directions, evaluated at time of peak ejection rate, was significantly lower in patients than in healthy volunteers (P < 0.05). RV abnormalities may be detected in patients after acute myocardial infarction using PC velocity mapping with velocity encoding in three different directions. Owing to their short acquisition times and relatively easy postprocessing, PC techniques are time-efficient and promising tools for the evaluation of RV function. J. Magn. Reson. Imaging 2000;11:471–475. © 2000 Wiley-Liss, Inc.
- Published
- 2000
103. MR Evaluation Ex Vivo and In Vivo of a Covered Stent-Graft for Abdominal Aortic Aneurysms: Ferromagnetism, Heating, Artifacts, and Velocity Mapping
- Author
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Freddy Ståhlberg, Lena Engellau, Sara Brockstedt, Elna-Marie Larsson, Lars Norgren, Ulf Albrechtsson, and Johan Olsrud
- Subjects
Male ,medicine.medical_specialty ,Contrast Media ,Sensitivity and Specificity ,Heating ,Magnetics ,Aneurysm ,Coated Materials, Biocompatible ,Velocity mapping ,In vivo ,Suprarenal Aorta ,medicine.artery ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,cardiovascular diseases ,Vascular Patency ,Titanium ,Aorta ,medicine.diagnostic_test ,business.industry ,Magnetic resonance imaging ,equipment and supplies ,medicine.disease ,Spiral computed tomography ,Blood Vessel Prosthesis ,surgical procedures, operative ,cardiovascular system ,Female ,Stents ,Radiology ,Artifacts ,Tomography, X-Ray Computed ,business ,Blood Flow Velocity ,Magnetic Resonance Angiography ,Ex vivo ,Aortic Aneurysm, Abdominal - Abstract
Magnetic resonance imaging (MRI) safety was evaluated at 1.5 T in a covered nickel titanium stent-graft (Vanguard) used for endovascular treatment of abdominal aortic aneurysms (AAAs). Imaging artifacts were assessed on MRI with contrast-enhanced (CE) three-dimensional (3D) MR angiography (MRA) and spiral computed tomography (CT) in 10 patients as well as ex vivo. Velocity mapping was performed in the suprarenal aorta and femoral arteries in 14 patients before and after stent-graft placement. For comparison it was also performed in six healthy volunteers. No ferromagnetism or heating was detected. Metal artifacts caused minimal image distortion on MRI/MRA. The artifacts disturbed image evaluation on CT at the graft bifurcation and graft limb junction. No significant differences in mean flow were found in patients before and after stent-graft placement. Our study indicates that MRI at 1.5 T may be performed safely in patients with the (Vanguard) stent-graft. MRI/MRA provides diagnostic image information. Velocity mapping is not included in our routine protocol.
- Published
- 2000
104. Interleaved spiral cine coronary artery velocity mapping
- Author
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Peter D. Gatehouse, David N. Firmin, Guang-Zhong Yang, and Jennifer Keegan
- Subjects
Physics ,Reproducibility ,business.industry ,Hemodynamics ,Blood flow ,Scan time ,medicine.anatomical_structure ,Flow velocity ,Velocity mapping ,medicine ,Radiology, Nuclear Medicine and imaging ,Nuclear medicine ,business ,Spiral ,Artery - Abstract
Navigator-echo controlled interleaved spiral cine coronary-artery velocity maps were acquired in eight free-breathing volunteers. Good quality data were achieved in all subjects with phasic flow being clearly demonstrated. The improved efficiency of spiral k-space coverage compared to that of more conventional spin-warp techniques resulted in a mean scan time for 256 × 256 pixel-matrix studies of 94 sec (range 69 – 123 sec, SD = 20 sec), the navigator acceptance rate being typically 40–45%. Repeat scans in five subjects showed a high degree of reproducibility, with no significant differences occurring in the peak velocities (14.6 ± 1.4 cm/sec vs. 14.5 ± 1.5 cm/sec, P = ns) nor in the mean velocities measured over all cine phases (8.3 ± 2.1 cm/sec vs. 8.7 ± 1.6 cm/sec, P = ns). The potential benefits of using this sequence for assessing coronary blood flow and flow reserve are discussed. Magn Reson Med 43:787–792, 2000. © 2000 Wiley-Liss, Inc.
- Published
- 2000
105. Magnetic Resonance Imaging of Valvular Heart Disease
- Author
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Carsten Thomsen, Freddy Ståhlberg, and Lars Søndergaard
- Subjects
Mri techniques ,medicine.medical_specialty ,medicine.diagnostic_test ,business.industry ,valvular heart disease ,Hemodynamics ,Magnetic resonance imaging ,Integrated approach ,equipment and supplies ,Diagnostic tools ,medicine.disease ,Volume measurements ,Velocity mapping ,Internal medicine ,cardiovascular system ,medicine ,Cardiology ,Radiology, Nuclear Medicine and imaging ,cardiovascular diseases ,Radiology ,business - Abstract
The optimum management of patients with valvular heart diseases requires accurate and reproducible assessment of the valvular lesion and its hemodynamic consequences. Magnetic resonance imaging (MRI) techniques, such as volume measurements, signal-void phenomena, and velocity mapping, can be used in an integrated approach to gain qualitative and quantitative information on valvular heart disease as well as ventricular dimensions and functions. Thus, MRI may be advantageous to the established diagnostic tools in assessing the severity of valvular heart disease as well as monitoring the lesion and predicting the optimal timing for valvular surgery. This paper reviews the validation of these MRI techniques in assessing valvular heart disease and discusses some typical pitfalls of the techniques, including suggestions for solutions.J. Magn. Reson. Imaging 1999;10:627–638. © 1999 Wiley-Liss, Inc.
- Published
- 1999
106. Heart motion adapted cine phase-contrast flow measurements through the aortic valve
- Author
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Peter Boesiger, Erik Morre Pedersen, Sebastian Kozerke, and Markus B. Scheidegger
- Subjects
Physics ,Aortic valve ,medicine.diagnostic_test ,Cardiac cycle ,business.industry ,Heart motion ,Diastole ,Hemodynamics ,Magnetic resonance imaging ,Anatomy ,medicine.anatomical_structure ,Velocity mapping ,Circulatory system ,cardiovascular system ,medicine ,Radiology, Nuclear Medicine and imaging ,Nuclear medicine ,business - Abstract
A method for magnetic resonance cine velocity mapping through heart valves with adaptation of both slice offset and angulation according to the motion of the valvular plane of the heart is presented. By means of a subtractive labeling technique, basal myocardial markers are obtained and automatically extracted for quantification of heart motion at the valvular level. The captured excursion of the basal plane is used to calculate the slice offset and angulation of each required time frame for cine velocity mapping. Through-plane velocity offsets are corrected by subtracting velocities introduced by basal plane motion from the measured velocities. For evaluation of the method, flow measurements downstream from the aortic valve were performed both with and without slice adaptation in 11 healthy volunteers and in four patients with aortic regurgitation. Maximum through-plane motion at the aortic root level as calculated from the labeled markers averaged 8.9 mm in the volunteers and 6.5 mm in the patients. The left coronary root was visible in 2–4 (mean: 2.2) time frames during early diastole when imaging with a spatially fixed slice. Time frames obtained with slice adaptation did not contain the coronary roots. Motion correction increased the apparent regurgitant volume by 5.7 ± 0.4 ml for patients with clinical aortic regurgitation, for an increase of approximately 50%. The proposed method provides flow measurements with correction for through-plane motion perpendicular to the aortic root between the valvular annulus and the coronary ostia throughout the cardiac cycle. Magn Reson Med 42:970–978, 1999. © 1999 Wiley-Liss, Inc.
- Published
- 1999
107. Vector analysis of the hemodynamics of atherogenesis in the human thoracic aorta using MR velocity mapping
- Author
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Teruhiko Toyo-oka, Fumitaka Nakamura, Junichi Nishikawa, Wee Soo Shin, Ryoichi Shimamoto, J.-I. Suzuki, T. Tomaru, and Toshiaki Nakajima
- Subjects
Adult ,Aortic arch ,Cardiac cycle ,Arteriosclerosis ,business.industry ,Healthy subjects ,Hemodynamics ,Aorta, Thoracic ,General Medicine ,Anatomy ,Wall shear ,Magnetic Resonance Imaging ,Flow velocity ,Velocity mapping ,medicine.artery ,Hemorheology ,medicine ,Humans ,Thoracic aorta ,Radiology, Nuclear Medicine and imaging ,business ,Blood Flow Velocity - Abstract
Our study was designed to assess the applicability of MR velocity mapping for vector analysis of the hemodynamics of atherogenesis.MR velocity mapping was used to measure axial and nonaxial elements and the length of the wall shear rate (a spatial gradient of near-wall flow velocity parallel to the vessel wall) vector at 16 time points per cardiac cycle at eight anatomic locations of the thoracic aorta in six healthy subjects. An oscillatory shear index (a ratio of blood flow volume in the recessive direction divided by the sum of blood flow volume in both dominant and recessive directions) was introduced for analysis of the degree of oscillation.The time-averaged length, axial element, and nonaxial element of the wall shear rate vector were 118+/-53 sec(-1), 106+/-55 sec(-1), and 33+/-23 sec(-1), respectively. The oscillatory shear index in the axial direction was 0.06+/-0.10 and that in the nonaxial direction was 0.07+/-0.13. At the inner wall of the distal portion of the aortic arch, the length of the wall shear rate was smallest (74+/-32 sec(-1)) and oscillation in the axial direction was largest (0.16+/-0.19).Vector analysis of the wall shear rate in the thoracic aorta was successfully done with MR velocity mapping in humans. MR velocity mapping can noninvasively evaluate the hemodynamics of atherogenesis induced by the complicated blood flow.
- Published
- 1998
108. Variability of splanchnic blood flow measurements using MR velocity mapping under fasting and post-prandial conditions - comparison with echo-Doppler
- Author
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Rik C. Schoemaker, Geert J. Lycklama à Nijeholt, Adam F. Cohen, K. Burggraaf, Leo J. Schultze Kool, Martin N. J. M. Wasser, and Albert de Roos
- Subjects
Adult ,Male ,medicine.medical_specialty ,Velocity mapping ,medicine.artery ,medicine ,Humans ,Splanchnic Circulation ,Superior mesenteric artery ,Echo doppler ,Reproducibility ,Hepatology ,medicine.diagnostic_test ,business.industry ,Ultrasonography, Doppler ,Magnetic resonance imaging ,Fasting ,Blood flow ,Postprandial Period ,Circulatory system ,cardiovascular system ,Radiology ,Splanchnic ,Nuclear medicine ,business ,Blood Flow Velocity ,Magnetic Resonance Angiography - Abstract
The aim was to study the reproducibility of magnetic resonance velocity mapping, when measuring portal vein and superior mesenteric artery blood flow, under fasting and post-prandial conditions. Magnetic resonance flow measurements for the portal vein were compared with echo-Doppler measurements in the right portal vein.Eight healthy volunteers were studied on two occasions, separated by 1 week. Blood flow in the portal vein and superior mesenteric artery was measured repeatedly under basal fasting conditions. On one occasion measurements were also made after a meal. Every magnetic resonance measurement was followed by an echo-Doppler measurement in the right portal vein. Correlations between flow values were calculated using Pearson's r. Variability components were assessed using ANOVA.Intra-individual variability was approximately 7% for portal vein flow measurements using magnetic resonance velocity mapping. This variability did not increase after 1 h, 1 week and after a meal. Values of flow measured in the portal vein and superior mesenteric artery using magnetic resonance velocity mapping correlated well (r = 0.80, p0.001). Fasting portal flow as measured with magnetic resonance velocity mapping was 1.2 l/min (range 0.96-1.6 l/min). Variability in echo-Doppler measurements was comparable to the variability of magnetic resonance velocity mapping, and flow measurements obtained with the two techniques correlated well (r = 0.74; p0.001).Magnetic resonance velocity mapping accurately measures blood flow in the portal vein with low variability and should be preferred when absolute flow values are necessary. Echo-Doppler measurement of the right portal vein has a low variability and can be used to study changes in flow.
- Published
- 1997
109. Surface acoustic wave velocity mapping of tissue samples using scanning laser Doppler velocimeter
- Author
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Yosuke Mizuno, Yukako Kato, Kentaro Nakamura, and Yuji Wada
- Subjects
Scanning Laser Doppler ,Materials science ,business.industry ,Acoustics ,Surface acoustic wave ,food and beverages ,Pork sample ,Laser Doppler velocimetry ,Optics ,Velocity mapping ,Acoustic Doppler velocimetry ,Laser scanning vibrometry ,business ,Laser Doppler vibrometer - Abstract
To estimate the distribution of the elastic constants over tissue samples, we measure the propagation velocities of the surface acoustic wave (SAW) at each point of the samples using a scanning laser Doppler velocimeter, which are displayed as two-dimensional maps. In a pork sample, the SAW velocity in fat is experimentally shown to be faster than that in lean meat, which is well recognized from the maps.
- Published
- 2013
110. The measurement of stroke volume by cine magnetic resonance imaging and phase contrast velocity mapping
- Author
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Takashi Tanimoto, Kumiko Hirata, Kohei Ishibashi, Takashi Yamano, Yasushi Ino, Tomoyuki Yamaguchi, Shingo Ota, Takashi Kubo, Takashi Akasaka, and Imanishi Toshio
- Subjects
lcsh:Diseases of the circulatory (Cardiovascular) system ,medicine.medical_specialty ,Short axis ,Phase contrast microscopy ,law.invention ,Nuclear magnetic resonance ,law ,Velocity mapping ,medicine.artery ,Ascending aorta ,medicine ,Left ventricular Stroke volume ,Radiology, Nuclear Medicine and imaging ,Medical physics ,cardiovascular diseases ,Angiology ,Medicine(all) ,Radiological and Ultrasound Technology ,medicine.diagnostic_test ,business.industry ,Magnetic resonance imaging ,Stroke volume ,lcsh:RC666-701 ,Poster Presentation ,cardiovascular system ,Cardiology and Cardiovascular Medicine ,business - Abstract
Background In the assessment of left ventricular stroke volume in cine magnetic resonance, drawing the endocardial contours in short axis slices are difficult at the 1 or 2 most basal slices due to systolic movement of the base towards the apex. The forward flow in the ascending aorta can be quantified using phase contrast velocity mapping. This study investigated which basal slices should be included
- Published
- 2013
111. Renal artery velocity mapping with MR imaging
- Author
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E. Schneider, Stephan E. Maier, Peter Boesiger, Kecheng Liu, Markus B. Scheidegger, and A. Bellinger
- Subjects
Adult ,Male ,medicine.medical_specialty ,Percutaneous ,Arteriosclerosis ,Magnetic Resonance Imaging, Cine ,Regurgitation (circulation) ,Kidney ,Renal Artery Obstruction ,Renal Artery ,Reference Values ,Velocity mapping ,medicine.artery ,Image Processing, Computer-Assisted ,medicine ,Fibromuscular Dysplasia ,Humans ,Radiology, Nuclear Medicine and imaging ,Renal artery ,Aged ,business.industry ,Abdominal aorta ,Blood flow ,Middle Aged ,Mr imaging ,Sagittal plane ,medicine.anatomical_structure ,Feasibility Studies ,Female ,Radiology ,business ,Angioplasty, Balloon ,Blood Flow Velocity ,Magnetic Resonance Angiography ,Follow-Up Studies - Abstract
An MR phase imaging sequence with a very short echo time was used to assess blood velocity and flow at the renal artery bifurcation. Cardiac-gated MR imaging data were obtained in six healthy subjects in sagittal planes adjacent to the abdominal aorta and transverse planes above and below the renal artery bifurcation. Average renal artery flow rate was 23.8 +/- 9 mL/sec. A strong individual variability was found for the velocity profiles in the abdominal aorta during end-systolic regurgitation. Flow rate was also determined in three patients with reduced renal artery blood flow. Two patients received therapy with percutaneous transluminal angioplasty. The successful outcome was documented with MR imaging. A reliable assessment of renal artery flow with MR phase imaging is feasible. Measurement of the velocity profiles yields valuable insights in the complicated flow regime at the renal artery bifurcation.
- Published
- 1995
112. Magnetic resonance velocity mapping of normal human transmitral velocity profiles
- Author
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Kim H. Parker, Shinichi Fujimoto, Derek G. Gibson, and Raad H. Mohiaddin
- Subjects
Adult ,Male ,Adolescent ,Inflow ,Sensitivity and Specificity ,Ventricular Function, Left ,Nuclear magnetic resonance ,Velocity mapping ,Humans ,Medicine ,cardiovascular diseases ,Inflow velocity ,Analysis of Variance ,Jet (fluid) ,medicine.diagnostic_test ,business.industry ,Magnetic resonance imaging ,Middle Aged ,Magnetic Resonance Imaging ,Cross section (geometry) ,medicine.anatomical_structure ,Ventricle ,cardiovascular system ,Mitral Valve ,Early diastolic ,Atrial Function, Left ,Female ,Cardiology and Cardiovascular Medicine ,business ,Blood Flow Velocity ,circulatory and respiratory physiology - Abstract
We used magnetic resonance imaging (MRI) velocity mapping to assess the velocity profile of early diastolic mitral inflow in 11 normal subjects. Velocity maps of left ventricular inflow were obtained in the horizontal long axis of the left ventricle at the time of peak early diastolic filling. Velocity profile curves across the mitral inflow were obtained at 1-cm intervals from the mitral ring to 4 cm into the cavity. The jet width was 3.06 +/- 0.64 cm at the mitral ring level, increasing to 3.6 +/- 0.61 cm at 4 cm. The peak/mean velocity was 1.2 +/- 0.07 at the mitral ring and increased to around 1.4 at 3-4 cm from the mitral ring. The point at which the peak velocity was recorded at each level was skewed towards the septal side by 10%-13% of jet width from the center at the mitral ring and 2-4 cm from the ring. However, at a depth of 1 cm, corresponding to the mitral tip level, the peak velocity was at the center of the jet. The ratio of vertical and horizontal dimensions of the jet cross section was 1.11 +/- 0.05. Thus, the mitral inflow velocity profile is relatively flat at the mitral ring and tip level; the inflow jet cross section is effectively circular.
- Published
- 1995
113. Comparison between cine magnetic resonance velocity mapping and first-pass radionuclide angiocardiography for quantitating intracardiac shunts
- Author
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Constantinos Anagnostopoulos, Stefan P. Karwatowski, Robert Laney, Leopoldo Romeira, Jane Somerville, Raad H. Mohiaddin, and Richard Underwood
- Subjects
Adult ,Heart Septal Defects, Ventricular ,Male ,Adolescent ,Heart Septal Defects, Atrial ,Intracardiac injection ,Ventriculography, First-Pass ,Velocity mapping ,Humans ,Medicine ,Angiocardiography ,Child ,Radionuclide angiocardiography ,First pass ,medicine.diagnostic_test ,business.industry ,Heart Septal Defects ,Magnetic resonance imaging ,Middle Aged ,Evaluation Studies as Topic ,Female ,Congenital disease ,Cardiology and Cardiovascular Medicine ,business ,Nuclear medicine ,Magnetic Resonance Angiography ,Shunt (electrical) - Abstract
We conclude that first-pass radionuclide angio-cardiography has limited value when measuring Qp/Qs in our group of patients, and that magnetic resonance imaging with velocity mapping is an excellent alternative technique that should be considered, particularly in patients with complex congenital disease and right-to-left shunt, or when poor bolus quality is anticipated.
- Published
- 1995
114. The origin and significance of secondary flows in the aortic arch
- Author
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M. M. Black, Patricia V. Lawford, and D. R. Hose
- Subjects
Aortic arch ,Blood Volume ,Models, Cardiovascular ,Biomedical Engineering ,Aorta, Thoracic ,General Medicine ,Anatomy ,Mechanics ,Flow pattern ,Blood Viscosity ,Secondary flow ,Magnetic Resonance Imaging ,Transient flow ,Regional Blood Flow ,Velocity mapping ,Clinical evidence ,Pulsatile Flow ,medicine.artery ,Hemorheology ,medicine ,Humans ,Blood Flow Velocity ,Geology - Abstract
This paper comprises a study of the secondary flow patterns that can develop in the human aortic arch. Clinical evidence of these secondary flows has been obtained by Kilner et al. using magnatic resonance velocity mapping techniques. Some of their results are presented for comparison in this present paper. Four different Parametrk models of the aortic arch have been analysed using computational fluid dynamic techniques. Both steady and transient flow conditions have been considered and two different commercially available software packages were used, namely FIDAP and FLOTRAN. A satisfactory comparison of the theoretical analysis with the results, both in vivo and in vitro, obtained by Kilner et al. for their out-of-plane inlet model was found. The theoretical analysis can now be extended to anulyse the effect of different configurations and orientations of artificial aortic valves on the resulting aortic arch flow patterns.
- Published
- 1995
115. COMPARISON OF DIRECT AND INDIRECT MEASUREMENTS OF AORTIC VALVE REGURGITATION USING PHASE CONTRAST MAGNETIC RESONANCE VELOCITY MAPPING
- Author
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Matthew A. Harris, Gregory L. Fu, Marc S. Keller, Mark A. Fogel, and Kevin K. Whitehead
- Subjects
medicine.medical_specialty ,medicine.diagnostic_test ,business.industry ,Phase contrast microscopy ,Magnetic resonance imaging ,medicine.disease ,law.invention ,Nuclear magnetic resonance ,Velocity mapping ,law ,Internal medicine ,medicine ,Cardiology ,business ,Cardiology and Cardiovascular Medicine ,Aortic valve regurgitation - Published
- 2012
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116. A multi-center inter-manufacturer study of the temporal stability of phase-contrast velocity mapping background offset errors
- Author
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David N. Firmin, Peter D. Gatehouse, Karin Markenroth Bloch, Marijn P. Rolf, Martin J. Graves, Philip J. Kilner, Mark B.M. Hofman, Graves, Martin [0000-0003-4327-3052], Apollo - University of Cambridge Repository, Physics and medical technology, and ICaR - Heartfailure and pulmonary arterial hypertension
- Subjects
Cardiac output ,lcsh:Diseases of the circulatory (Cardiovascular) system ,Offset (computer science) ,Time Factors ,Phase contrast microscopy ,Whole body imaging ,Magnetic Resonance Imaging, Cine ,velocity offset error ,Imaging phantom ,law.invention ,Clinical study ,Magnetic resonance imaging ,Region of interest ,Velocity mapping ,law ,Predictive Value of Tests ,Image Interpretation, Computer-Assisted ,Medicine ,Humans ,Cardiac and Cardiovascular Systems ,Whole Body Imaging ,Radiology, Nuclear Medicine and imaging ,Simulation ,Medicine(all) ,Radiological and Ultrasound Technology ,business.industry ,Phantoms, Imaging ,Shunt flow ,Reproducibility of Results ,Regurgitation ,Equipment Design ,Geodesy ,Phase-contrast velocity mapping ,Europe ,Background ,Workshop Presentation ,Background Correction ,lcsh:RC666-701 ,Background velocity offset error ,Technical Notes ,business ,Cardiology and Cardiovascular Medicine - Abstract
Background Phase-contrast velocity images often contain a background or baseline offset error, which adds an unknown offset to the measured velocities. For accurate flow measurements, this offset must be shown negligible or corrected. Some correction techniques depend on replicating the clinical flow acquisition using a uniform stationary phantom, in order to measure the baseline offset at the region of interest and subtract it from the clinical study. Such techniques assume that the background offset is stable over the time of a patient scan, or even longer if the phantom scans are acquired later, or derived from pre-stored background correction images. There is no published evidence regarding temporal stability of the background offset. Methods This study assessed the temporal stability of the background offset on 3 different manufacturers’ scanners over 8 weeks, using a retrospectively-gated phase-contrast cine acquisition with fixed parameters and at a fixed location, repeated 5 times in rapid succession each week. A significant offset was defined as 0.6 cm/s within 50 mm of isocenter, based upon an accuracy of 10% in a typical cardiac shunt measurement. Results Over the 5 repeated cine acquisitions, temporal drift in the baseline offset was insignificant on two machines (0.3 cm/s, 0.2 cm/s), and marginally insignificant on the third machine (0.5 cm/s) due to an apparent heating effect. Over a longer timescale of 8 weeks, insignificant drift (0.4 cm/s) occurred on one, with larger drifts (0.9 cm/s, 0.6 cm/s) on the other machines. Conclusions During a typical patient study, background drift was insignificant. Extended high gradient power scanning with work requires care to avoid drift on some machines. Over the longer term of 8 weeks, significant drift is likely, preventing accurate correction by delayed phantom corrections or derivation from pre-stored background offset data.
- Published
- 2012
117. Retrogated spiral 3-directional myocardial phase velocity mapping in a single breath-hold
- Author
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Peter D. Gatehouse, David N. Firmin, Robin Simpson, and Jennifer Keegan
- Subjects
Medicine(all) ,lcsh:Diseases of the circulatory (Cardiovascular) system ,Radiological and Ultrasound Technology ,Cardiac cycle ,business.industry ,Single breath ,Bioinformatics ,Rapid assessment ,Workshop Presentation ,lcsh:RC666-701 ,Velocity mapping ,Myocardial motion ,Medicine ,High temporal resolution ,Radiology, Nuclear Medicine and imaging ,Phase velocity ,Cardiology and Cardiovascular Medicine ,business ,Spiral ,Biomedical engineering - Abstract
Background Myocardial phase velocity mapping studies have generally been acquired using Cartesian k-space coverage and respiratory gating [1,2]. Acquisition durations for high temporal resolution studies are therefore long and unpredictable and the use of navigators and prospective cardiac gating results in ‘dead-times’ in the cardiac cycle where imaging cannot be performed. We have developed a technique which combines highly efficient spiral k-space coverage with retrospective cardiac gating for 3D velocity mapping over the entire cardiac cycle within a breath-hold. The feasibility for rapid assessment of myocardial motion is demonstrated.
- Published
- 2012
118. Respiratory dependent stroke volume changes assessed by real time MR velocity mapping at 3 Tesla – A validation study
- Author
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H Esdorn, Peter Barth, Hermann Körperich, Wolfgang Burchert, G Uges, A Peterschröder, Kai Thorsten Laser, J Gieseke, and Deniz Kececioglu
- Subjects
Validation study ,Nuclear magnetic resonance ,business.industry ,Velocity mapping ,Medicine ,Radiology, Nuclear Medicine and imaging ,Stroke volume ,Respiratory system ,business - Published
- 2012
119. General Principles of Cardiac Magnetic Resonance Imaging
- Author
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Mark A. Fogel
- Subjects
Physics ,Clinical Practice ,Atrioventricular valve ,Nuclear magnetic resonance ,medicine.diagnostic_test ,Velocity mapping ,Cardiac magnetic resonance imaging ,Section (archaeology) ,Interventional magnetic resonance imaging ,medicine ,Magnetic resonance imaging - Abstract
A basic understanding of the underlying principles of cardiovascular magnetic resonance imaging (CMR) and methods used to form images is important if one is to successfully apply this technique in clinical practice or research and interpret it correctly. This section will provide a brief overview of the fundamentals and some techniques in CMR imaging. For more information, the reader is referred to the references in this chapter or the larger textbooks on fundamentals of magnetic resonance imaging as well as other chapters in this book [1].
- Published
- 2012
120. Velocity mapping of coronary artery blood flow
- Author
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Peter D. Gatehouse, Jennifer Keegan, David N. Firmin, and Donald B. Longmore
- Subjects
medicine.medical_specialty ,Radiological and Ultrasound Technology ,business.industry ,Biophysics ,Blood flow ,Imaging phantom ,Coronary arteries ,Normal volunteers ,medicine.anatomical_structure ,Velocity mapping ,Internal medicine ,Cardiology ,Medicine ,Radiology, Nuclear Medicine and imaging ,Phase velocity ,business ,Coronary flow ,Artery - Abstract
A segmentedk-space gradient-echo phase velocity mapping sequence has been developed for the measurement of through-plane and in-plane coronary artery blood flow velocity in a single breath-hold. The sequence was validated in phantom models representing stenosed and unste-nosed coronary arteries and also in the descending aortas of several normal volunteers. In-plane and through-planein vivo velocity maps of coronary arteries in normal subjects have been obtained and the problems associated with their acquisition are discussed.
- Published
- 1994
121. Functional evaluation in congenital and acquired heart disease
- Author
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Peter D. Gatehouse, J. Keegan, Donald B. Longmore, Guang Z. Yang, D. M. Firmin, and S. R. Underwood
- Subjects
medicine.medical_specialty ,Functional evaluation ,Radiological and Ultrasound Technology ,Heart disease ,Vascular disease ,Arterial disease ,business.industry ,Rapid imaging ,Biophysics ,Disease ,medicine.disease ,Health informatics ,Velocity mapping ,Internal medicine ,medicine ,Cardiology ,Radiology, Nuclear Medicine and imaging ,Intensive care medicine ,business - Abstract
Functional evaluation of the cardiovascular system using rapid imaging (spiral echo planar), chemical shift, and velocity mapping is capable of making the diagnosis in congenital and acquired cardiovascular disease which, between them, cause the largest number of deaths of any disease in the western world and massive morbidity and suffering. Furthermore, for the first time in the history of medicine, there is the opportunity to apply preventive measures to eardicate the epidemic of preventable arterial disease. There needs to be a change of emphasis and a switching of resources to apply to the most common diseases rather than to those which are most easily studied. There also needs to be proper training in cardiovascular MR, not so much for imagers as for cardiologists and experts in vascular disease.
- Published
- 1994
122. Assessment of regional left ventricular long-axis motion with MR velocity mapping in healthy subjects
- Author
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Martin St John Sutton, David N. Firmin, Guang Z. Yang, S. Richard Underwood, Donald B. Longmore, Stefan P. Karwatowski, and Raad H. Mohiaddin
- Subjects
Adult ,Male ,Systole ,Heart Ventricles ,Motion Pictures ,Diastole ,Ventricular Function, Left ,Velocity mapping ,Heart rate ,Image Processing, Computer-Assisted ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Aged ,Physics ,medicine.diagnostic_test ,business.industry ,Healthy subjects ,Magnetic resonance imaging ,Middle Aged ,Magnetic Resonance Imaging ,Myocardial Contraction ,Apex (geometry) ,medicine.anatomical_structure ,Evaluation Studies as Topic ,Ventricle ,Female ,Nuclear medicine ,business - Abstract
The pattern of left ventricular long-axis motion during early diastole was assessed with magnetic resonance (MR) velocity mapping in 31 healthy volunteers. Regional long-axis velocity varied with time and position around the ventricle. During systole, the base descended toward the apex. The greatest magnitude of long-axis velocity occurred during early diastole. The lateral wall had the highest velocity (140 mm/sec +/- 40 [mean +/- standard deviation]); the anterior and inferior walls had lower velocities (96 mm/sec +/- 27 and 92 mm/sec +/- 34, respectively). The inferoseptal area consistently had the lowest velocities (87 mm/sec +/- 40). Absolute values of peak early-diastolic velocity declined with age (r = -.64, P.001). Peak early-diastolic velocity was not dependent on heart rate (r = .014, P = .94). Regional variations in left ventricular wall motion were seen. MR velocity mapping is a useful technique for assessing regional left ventricular long-axis heart function.
- Published
- 1994
123. Genetic and entropy methods for laser process prediction
- Author
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S.Y. Lim and Chris Chatwin
- Subjects
Pulsed laser ,Materials processing ,Computer science ,Mechanical Engineering ,Evolutionary algorithm ,Laser ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Machining ,law ,Velocity mapping ,Continuous wave ,Entropy (information theory) ,Electrical and Electronic Engineering ,Algorithm ,Simulation - Abstract
Laser material processing can be modelled via an analytical or numerical approach. This article formulates two unconventional analytical approaches for the prediction of laser processing parameters. An evolutionary algorithm is used for the prediction of the optimal conditions for pulsed laser cutting. Continuous wave laser cutting is characterised by assuming a likelihood bias function, from which an optimal velocity mapping is obtained utilising the MAXENT concept. The mapping function serves as a topological guide to the prediction of cutting rates. Both prediction schemes give good agreement with experimental results.
- Published
- 1994
124. Carotid and vertebral artery blood flow in left- and right-handed healthy subjects measured with MR velocity mapping
- Author
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Hugo G. Bogren, Michael H. Buonocore, and Wei‐Zhong Gu
- Subjects
Adult ,Male ,medicine.medical_specialty ,Vertebral artery ,Functional Laterality ,Cerebral circulation ,Reference Values ,Velocity mapping ,medicine.artery ,Carotid artery disease ,Internal medicine ,Ascending aorta ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Common carotid artery ,Vertebral Artery ,business.industry ,Healthy subjects ,Blood flow ,medicine.disease ,Magnetic Resonance Imaging ,Carotid Arteries ,Cerebrovascular Circulation ,Cardiology ,Female ,business ,Blood Flow Velocity - Abstract
The goal of the study was to establish normal carotid artery flow rates in left-handed and right-handed individuals as a standard against which patients with carotid artery disease could be compared. Antegrade and retrograde flow were measured in the ascending aorta, in the right and left common, internal, and external carotid arteries, and in the vertebral arteries of 12 healthy subjects. Five subjects were right-handed, five left-handed, and two ambidextrous. Measured flow rates were as follows: common carotid arteries, 360-557 mL/min (mean [+/- standard deviation], 465 mL/min +/- 52); internal carotid arteries, 132-367 mL/min (mean, 265 mL/min +/- 60); external carotid arteries, 113-309 mL/min (mean, 186 mL/min +/- 51); vertebral arteries from 133-308 mL/min (mean, 244 mL/min +/- 43); and cerebral circulation, 546-931 mL/min (mean, 774 mL/min +/- 134). All right-handed subjects had higher flow rates in the left internal carotid artery than in the right, and all left-handed subjects had higher flow rates in the right internal carotid artery (P = .007). There were no significant differences in left and right common carotid artery flow rates between left- and right-handed subjects. The standard deviation of a single measurement was 5%. The flow rates were similar to those obtained previously with other techniques and could be used as a normal standard.
- Published
- 1994
125. NMR imaging of flow:mapping velocities inside microfluidic devices and sequence development
- Author
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Ahola, S. (Susanna)
- Subjects
NMR imaging ,nuclear magnetic resonance ,polarization ,velocity ,velocity mapping ,flow ,microfluidic devices ,remote detection ,propagators ,PHIP - Abstract
The subject of this thesis is flow imaging by methods based on the nuclear magnetic resonance (NMR) phenomenon. The thesis consists of three related topics: In the first one the feasibility of measuring velocity maps and distributions inside a microfluidic device by pulsed field gradient (PFG) NMR has been demonstrated. The second topic was to investigate microfluidic gas flow using a combination of a special detection technique and a powerful signal enhancement method. The third topic is related to the unambiguous determination of velocities under challenging experimental conditions and introduces a new, improved velocity imaging sequence. In the first part, well established imaging methods have been used to study water flow inside a micromixer. A surface coil matching the region of interest of the mixer was home built and used in the measurements in order to gain a better signal-to-noise ratio. Velocities inside the mixer have been measured by phase-encoding velocity, with unprecedented spatial resolution. Two dimensional NMR imaging and velocity maps revealed clogging and different manufacturing qualities of the mixers. In addition to the velocity maps, which display an average velocity for spins within one pixel, complete velocity distributions (so called average propagators) were measured. It was found that in the absence of spatial resolution in the third dimension, the propagator data can provide valuable insight to the flow system by revealing overlapping flow passages. The next topic was gas flow inside a microfluidic device. It was investigated by time-of-flight flow imaging. The measurement of the weak gas signal was enabled by the use of two signal enhancement techniques: remote detection NMR and parahydrogen induced polarization (PHIP). The results demonstrate that a very significant signal enhancement can be achieved by this technique. In the future it may enable the investigation of interesting chemical reactions inside microreactors. The third and last topic of the thesis deals with measuring flow by the so called multiecho sequences. When multiecho sequences are used in combination with phase encoding velocity, an error may be introduced: the multiecho sequence may produce a cumulative error to the phase of the magnetization, if it is sensitive to RF pulse imperfections. The problem has been elaborately explained and various solutions discussed, among the newly proposed one. Experimental results demonstrate the performance of the new velocity imaging sequence and show that the new sequence enables the unambiguous determination of velocities even in challenging experimental conditions resulting from inhomogeneous radio frequency fields of the measurement coils.
- Published
- 2011
126. Virtual Dye Angiography: flow visualization for MRI-guided interventions using endogenous contrast
- Author
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Anthony Z. Faranesh, John Andrew Derbyshire, Kanishka Ratnayaka, Michael S. Hansen, Robert J. Lederman, and Ashvin K George
- Subjects
Medicine(all) ,Flow visualization ,lcsh:Diseases of the circulatory (Cardiovascular) system ,Radiological and Ultrasound Technology ,medicine.diagnostic_test ,business.industry ,media_common.quotation_subject ,Steady-state free precession imaging ,Blood flow ,lcsh:RC666-701 ,Velocity mapping ,Arterial spin labeling ,Angiography ,medicine ,Oral Presentation ,Contrast (vision) ,Radiology, Nuclear Medicine and imaging ,Cardiology and Cardiovascular Medicine ,business ,Mri guided ,Biomedical engineering ,media_common - Abstract
Background Visualizing blood flow is important in MR-guided interventions (e.g. repairing structural heart defects). We introduce a method, called Virtual Dye Angiography (VDA), to visualize flow in a manner inspired by contrast-enhanced X-ray angiography. Slightly similar to arterial spin labeling, VDA saturates a localized region using multidimensional RF pulses. Unlike phase-contrast velocity mapping, which has unsuitably long acquisition times, VDA can be integrated into existing highcontrast, high-SNR SSFP imaging sequences with minimal modification.
- Published
- 2011
127. Pulmonary regurgitation in the late postoperative follow-up of tetralogy of Fallot. Volumetric quantitation by nuclear magnetic resonance velocity mapping
- Author
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Jan G.J. Chin, E. E. van der Wall, Jaap Ottenkamp, A. de Roos, and S A Rebergen
- Subjects
Adult ,Male ,medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,Adolescent ,Heart disease ,Regurgitation (circulation) ,Postoperative Complications ,Nuclear magnetic resonance ,Velocity mapping ,Physiology (medical) ,Internal medicine ,Pulmonary regurgitation ,medicine ,Humans ,In patient ,Postoperative Period ,Child ,Stroke ,Tetralogy of Fallot ,Blood Volume ,business.industry ,medicine.disease ,Pulmonary Valve Insufficiency ,medicine.anatomical_structure ,Pulmonary valve ,Cardiology ,Female ,Cardiology and Cardiovascular Medicine ,business ,Blood Flow Velocity ,Follow-Up Studies - Abstract
BACKGROUND Pulmonary regurgitation frequently occurs after surgical correction of tetralogy of Fallot. To date, reliable quantitation of pulmonary regurgitation has not been possible, and therefore the clinical significance of pulmonary regurgitation is controversial. Nuclear magnetic resonance (NMR) velocity mapping allows accurate measurement of volumetric flow. The feasibility and accuracy of NMR velocity mapping to quantify pulmonary regurgitation volumes are studied in patients after Fallot repair. METHODS AND RESULTS In 18 patients (mean age, 16.5 +/- 6.5 years), late (12.6 +/- 5.2 years) after Fallot surgery, forward and regurgitant volume flow was measured in the main pulmonary artery with NMR velocity mapping. To validate the measurements of pulmonary forward flow, right ventricular stroke volume was used as an internal reference standard. Pulmonary regurgitation volumes were compared with the differences between the corresponding right and left ventricular stroke volumes. Ventricular volumes were measured with a multisection gradient echo NMR method. In addition, the relation between pulmonary regurgitation and right ventricular volumes was studied. Measurements of pulmonary regurgitation volume with NMR velocity mapping closely corresponded with the tomographically determined volumes (r = .93). Forward pulmonary volume flow was nearly identical to right ventricular stroke volume (r = .98). Pulmonary regurgitation volume was significantly correlated with end-diastolic volume (r = .82, P < .0005), end-systolic volume (r = .63, P < .01), and stroke volume (r = .89, P < .0005) of the right ventricular but not with right ventricular ejection fraction (r = .41, P = NS). CONCLUSIONS NMR velocity mapping is an accurate method for the noninvasive, volumetric quantification of pulmonary regurgitation after surgical correction of tetralogy of Fallot.
- Published
- 1993
128. Adaptive optics imaging and TAURUS 2-D spectroscopy of galaxy cores
- Author
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Johan H. Knapen
- Subjects
Physics ,Star formation ,Near-infrared spectroscopy ,Astronomy ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Space and Planetary Science ,Velocity mapping ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Spectroscopy ,Adaptive optics ,Astrophysics::Galaxy Astrophysics - Abstract
Many barred galaxies show enhanced star formation activity in ring-like regions around their centres, at typical radii of 1–2 kpc. We show how kinematic (WHT TAURUS Fabry-Perot velocity mapping) and imaging (CFHT near infrared adaptive optics) observational tests, combined with dynamical modelling, can help in unravelling the dynamics and star formation properties of such circumnuclear regions. Our recent science-driven experience with adaptive optics and with TAURUS is discussed in relation to the future at ING.
- Published
- 2001
129. Velocity mapping of coronary artery blood flow
- Author
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Keegan, Jennifer, Firmin, David, Gatehouse, Peter, and Longmore, Donald
- Published
- 1994
- Full Text
- View/download PDF
130. Short-echo-time magnetic resonance phase-shift velocity mapping for assessment of heart valve and great vessel stenoses: three years' experience
- Author
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Kilner, Philip J., Firmin, David N., Mohiaddin, Raad H., Sampson, Cynthia, and Underwood, S. Richard
- Published
- 1994
- Full Text
- View/download PDF
131. MR-based visualization and quantification of three-dimensional flow characteristics in the portal venous system
- Author
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Zoltan Csatari, Mathias Langer, Alex Frydrychowicz, Elisabeth Panther, Zoran Stankovic, Wulf Euringer, Simon Bauer, Peter Deibert, Wolfgang Kreisel, Michael Markl, and Maximilian Russe
- Subjects
Adult ,Liver Cirrhosis ,Male ,medicine.medical_specialty ,Portal venous system ,Hemodynamics ,Three dimensional flow ,Electrocardiography ,Imaging, Three-Dimensional ,Velocity mapping ,Image Processing, Computer-Assisted ,Medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Aged ,business.industry ,Portal Vein ,Respiration ,Velocity encoding ,Ultrasonography, Doppler ,Middle Aged ,Magnetic Resonance Imaging ,Visualization ,Venous hemodynamics ,Female ,Radiology ,business ,Respiratory navigator - Abstract
Purpose: To evaluate the feasibility of time-resolved flow-sensitive MRI for the three-dimensional (3D) visualization and quantification of normal and pathological portal venous (PV) hemodynamics. Materials and Methods: Portal venous hemodynamics were evaluated in 18 healthy volunteers and 5 patients with liver cirrhosis. ECG- and adaptive respiratory navigator gated flow-sensitive 4D MRI (time-resolved 3D MRI with three-directional velocity encoding) was performed on a 3 Tesla MR system (TRIO, Siemens, Germany). Qualitative flow analysis was achieved using 3D streamlines and time-resolved particle traces originating from seven emitter planes precisely placed at anatomical landmarks in the PV system. Quantitative analysis included retrospective extraction of regional peak and mean velocities and vessel area. Results were compared with standard 2D flow-sensitive MRI and to the reference standard Doppler ultrasound. Results: Qualitative flow analysis was successfully used in the entire PV system. Venous hemodynamics in all major branches in 17 of 18 volunteers and 3 of 5 patients were reliably depicted with good interobserver agreement (kappa = 0.62). Quantitative analysis revealed no significant differences and moderate agreement for peak velocities between 3D MR and 2D MRI (r = 0.46) and Doppler ultrasound (US) (r = 0.35) and for mean velocities between 3D and 2D MRI (r = 0.41). The PV area was significantly (P < 0.01) higher in 3D and 2D MRI compared with US. Conclusion: We successfully applied 3D MR velocity mapping in the PV system, providing a detailed qualitative and quantitative analysis of normal and pathological hemodynamics. J. Magn. Reson. Imaging 2010;32:466–475. © 2010 Wiley-Liss, Inc.
- Published
- 2010
132. Three-dimensional velocity mapping of thoracic aorta and supra-aortic arteries in Takayasu arteritis
- Author
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Tetsuro Sekine, Yuriko Suzuki, Ryo Takagi, Yasuo Amano, Marc Van Cauteren, and Shinichiro Kumita
- Subjects
Adult ,Diagnostic Imaging ,Male ,medicine.medical_specialty ,Systole ,Takayasu arteritis ,Contrast Media ,Aorta, Thoracic ,Imaging, Three-Dimensional ,Velocity mapping ,Internal medicine ,medicine.artery ,Image Processing, Computer-Assisted ,Medicine ,Thoracic aorta ,Humans ,Radiology, Nuclear Medicine and imaging ,Microscopy, Phase-Contrast ,Aged ,Aorta ,medicine.diagnostic_test ,business.industry ,Magnetic resonance imaging ,Magnetic Resonance Imaging ,Takayasu Arteritis ,Arterial flow ,Pulmonary artery ,Cardiology ,Female ,business - Abstract
Takayasu arteritis is an inflammatory disease of unknown etiology that involves the aorta, its major branches, and the pulmonary artery. We describe three patients with Takayasu arteritis who showed abnormal velocity profile of the thoracic aorta and supra-aortic arteries on time-resolved three-dimensional (3D) phase-contrast MR imaging and velocity mapping techniques. Compared with two comparative subjects, velocity reduction was observed in these arteries. The velocity reduction was prominent along the thickened arterial wall, even with normal luminal caliber, and the highest velocity was observed on the contralateral side. In one patient, the arterial flow velocity and its profile at systole were partly improved after the treatment. The time-resolved 3D velocity mapping visualized the changes in the blood velocity profile at systole in Takayasu arteritis.
- Published
- 2010
133. VORTEX FLOW FORMATION IN PATIENTS AFTER TETRALOGY OF FALLOT REPAIR WITH PULMONARY REGURGITATION UTILIZING 3-DIMENSIONAL PHASE ENCODED VELOCITY MAPPING - A CLUE TO POWER LOSS, POOR EXERCISE PERFORMANCE AND BETTER SURGERY
- Author
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Ajit P. Yoganathan, Elizabeth Goldmuntz, Matthew A. Harris, Kartik S. Sundareswaran, and Mark A. Fogel
- Subjects
medicine.medical_specialty ,Power loss ,business.industry ,medicine.disease ,Surgery ,Vortex ,Flow (mathematics) ,Velocity mapping ,Internal medicine ,Pulmonary regurgitation ,Exercise performance ,medicine ,Cardiology ,In patient ,business ,Cardiology and Cardiovascular Medicine ,Tetralogy of Fallot - Published
- 2010
- Full Text
- View/download PDF
134. Real-time NMR beam-directed velocity mapping. V-mode NMR
- Author
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J R Moore, M J Lizak, and Justin D. Pearlman
- Subjects
medicine.diagnostic_test ,business.industry ,Attenuation ,Aortic Valve Insufficiency ,Models, Cardiovascular ,Mode (statistics) ,Aorta, Thoracic ,Magnetic resonance imaging ,Blood flow ,Magnetic Resonance Imaging ,Models, Structural ,Nuclear magnetic resonance ,Flow (mathematics) ,Velocity mapping ,Physiology (medical) ,medicine ,Humans ,Cardiology and Cardiovascular Medicine ,Nuclear medicine ,business ,Blood Flow Velocity ,Beam (structure) ,Backflow - Abstract
BACKGROUND Currently available noninvasive techniques for measuring blood flow velocities are constrained by limited view orientations (Doppler ultrasound) or limited time resolution (magnetic resonance imaging, MRI). We describe an MRI technique for measuring flow velocities in real time at arbitrary orientations within a cylindrical volume or "beam": V-mode nuclear magnetic resonance (NMR). METHODS AND RESULTS The technique was implemented on a standard 1.5-T clinical NMR imager with no special hardware and was tested on phantoms and human volunteers. The beam can be fired at rates up to 60 times per second, allowing measurements on a time scale that is appropriate for ungated cardiac studies. In phantoms, steady flow velocities were measured with the beam aligned along the direction of flow, and the measured velocities correlated well with the actual velocities (r > 0.99). The radial distribution of velocities in phantoms under constant flow conditions was also determined. In humans, flow of blood in the descending aortas of normal and aortic insufficiency subjects was measured. Distinctive backflow of blood because of aortic insufficiency was readily apparent. CONCLUSIONS The V-mode NMR technique is capable of acquiring clinically relevant real-time blood flow information from any desired angle of view with no attenuation at bone or air-tissue interfaces.
- Published
- 1992
135. The velocity analysis of the complex piedmont region in the Tarim basin and the method of varying‐velocity mapping
- Author
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Yunhong Liu, Zhiyong Wang, and Yang Dexing
- Subjects
Velocity mapping ,Tarim basin ,Geomorphology ,Geology - Published
- 2009
136. Breathhold time-resolved three-directional MR velocity mapping of aortic flow in patients after aortic valve-sparing surgery
- Author
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Gert Reiter, Timothy J. Carroll, Xin Liu, James C. Carr, Aya Kino, Thomas G. Gleason, Karin E. Dill, and Peter Weale
- Subjects
Aortic valve ,Adult ,Gadolinium DTPA ,Male ,medicine.medical_specialty ,Aortic Valve Insufficiency ,Contrast Media ,Aortic aneurysm ,Blood Vessel Prosthesis Implantation ,Young Adult ,Aneurysm ,Imaging, Three-Dimensional ,Velocity mapping ,Internal medicine ,medicine.artery ,Ascending aorta ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,In patient ,Aorta ,Observer Variation ,business.industry ,Laminar flow ,Middle Aged ,medicine.disease ,Image Enhancement ,Surgery ,Aortic Aneurysm ,medicine.anatomical_structure ,Regional Blood Flow ,Aortic Valve ,Pulsatile Flow ,cardiovascular system ,Cardiology ,Female ,business ,Blood Flow Velocity ,Magnetic Resonance Angiography - Abstract
Purpose To evaluate the utility of breathhold time-resolved three-directional MR velocity mapping for quantifying the restoration of normal flow patterns in patients after aortic valve-sparing surgery. Materials and Methods Breathhold time-resolved three-directional MR velocity mapping was performed on 13 patients with aortic valve-sparing surgery. Ten healthy volunteers and 12 patients with ascending aortic aneurysm underwent the same MR examination for comparison. Aortic laminar flow, turbulent flow, and the presence of vortical flow in the sinuses of Valsalva were semiquantitatively assessed and statistically compared between the three groups of subjects. Results The average score of laminar flow in the ascending aorta for patients with surgery was not significantly different from that of volunteers (P = 0.210), but was significantly greater than that of patients with aneurysm (P < 0.01). The average score of turbulent flow in patients with surgery was significantly smaller than that of patients with aneurysm (P < 0.01). The presence of systolic vortical flow in the sinuses of Valsalva for patients with surgery was not significantly different from that of healthy volunteers (P = 0.405) and patients with aneurysm (P = 0.238). Conclusion Breathhold time-resolved three-directional MR velocity mapping allows for quantifying flow patterns in the aortic root and ascending aorta. Normal laminar flow in the ascending aorta and vortical flow in the sinuses of Valsalva can be restored in patients after aortic valve-sparing surgery. J. Magn. Reson. Imaging 2009;29:569–575. © 2009 Wiley-Liss, Inc.
- Published
- 2009
137. Effect of flow angle and flow profile on phase contrast flow measurements: overestimation at extreme angles and skewed profiles
- Author
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Matthew A. Harris, Matthew J. Gillespie, Mark A. Fogel, Ravi Doddasomayajula, and Kevin K. Whitehead
- Subjects
medicine.medical_specialty ,lcsh:Diseases of the circulatory (Cardiovascular) system ,Phase contrast microscopy ,Flow angle ,Pulsatile flow ,Regurgitation (circulation) ,Flow measurement ,law.invention ,law ,Velocity mapping ,medicine ,Radiology, Nuclear Medicine and imaging ,Medicine(all) ,Radiological and Ultrasound Technology ,Plane (geometry) ,business.industry ,Congenital Heart Disease ,Mechanics ,Straight Tube ,Flow (mathematics) ,lcsh:RC666-701 ,Pulsatile Flow ,Imaging Plane ,Oral Presentation ,Radiology ,Cardiology and Cardiovascular Medicine ,business ,human activities ,Flow Measurement - Abstract
Flow measurements derived from phase contrast velocity mapping (PC-MRI) have become an important part of pediatric cardiology, allowing accurate quantification of shunts, valve regurgitation, and cardiac output. Clinicians generally try to align the imaging plane orthogonal to flow. However, while flow velocities decrease by the cosine of the angle from orthogonal, the area should ideally increase by the same rate. There are situations in which it may be desirable to quantify flow in a vessel on an image that was not intended during the acquisition. In addition, in some flow regimes with highly skewed flow it is sometimes difficult to align the imaging plane with flow. Understanding the settings in which PC-MRI is accurate is important to the evaluation of congenital heart disease.
- Published
- 2009
138. Optical tweezers for velocity mapping in microfluidic channels
- Author
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Daniel Day, Jing Wu, and Min Gu
- Subjects
Physics::Fluid Dynamics ,Optics ,Materials science ,Optical tweezers ,Laser cutting ,business.industry ,Velocity mapping ,Microfluidic channel ,Laser Doppler velocimetry ,business ,Laser beams ,Computer Science::Other ,Computer Science::Information Theory - Abstract
We have successfully applied an optical tweezer for mapping the velocity profile in microfluidic channels. The velocity profiles for a straight and a u-shaped microfluidic channels were determined by direct measurment of the Stokes force.
- Published
- 2009
139. One-shot velocity mapping using multiple spin-echo EPI and its application to turbulent flow
- Author
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Katsumi Kose
- Subjects
Physics ,One shot ,Nuclear magnetic resonance ,Velocity mapping ,Turbulence ,General Engineering ,Spin echo - Published
- 1991
140. MR Phase-Shift Velocity Mapping of Mitral and Pulmonary Venous Flow
- Author
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Carla Manzara, Donald B. Longmore, Makoto Amanuma, Dudley J. Pennell, Raad H. Mohiaddin, and Philip J. Kilner
- Subjects
Adult ,Male ,medicine.medical_specialty ,Heart disease ,Systole ,Diastole ,Hemodynamics ,Venous flow ,Veins ,Pulmonary vein ,Reference Values ,Velocity mapping ,Internal medicine ,Mitral valve ,medicine ,Humans ,Mitral Valve Stenosis ,Radiology, Nuclear Medicine and imaging ,cardiovascular diseases ,Mitral flow ,business.industry ,Middle Aged ,medicine.disease ,Magnetic Resonance Imaging ,Myocardial Contraction ,Echocardiography, Doppler ,medicine.anatomical_structure ,Pulmonary Veins ,Regional Blood Flow ,cardiovascular system ,Cardiology ,Mitral Valve ,Female ,Radiology ,business ,Blood Flow Velocity - Abstract
Mitral and pulmonary venous flows are important indexes in the evaluation of left ventricular diastolic function and in the assessment of mitral valve disease. We used MR phase-shift velocity mapping to measure mitral and pulmonary venous flow velocity in 10 healthy volunteers and mitral flow velocity in 5 patients with mitral valve stenosis. Normal mitral flow shows two positive peaks: one during early ventricular diastole and the other during atrial contraction. Peak mitral flow velocity (mean +/- SD) in early diastole was 68 +/- 12 cm/s and during atrial contraction 39 +/- 10 cm/s. The ratio of peak mitral flow velocity in early diastole to that during atrial contraction was 1.9 +/- 0.6. In patients with mitral valve stenosis, the initial high flow velocity persisted through diastole. Peak mitral flow velocity of patients with mitral valve stenosis correlated well with values obtained from Doppler echocardiography. Pulmonary venous flow showed two positive peaks: one during ventricular systole and the other in ventricular diastole. A small backflow during atrial contraction was noticed. Peak systolic velocity in the right lower pulmonary vein was 47 +/- 11 cm/s, peak diastolic velocity was 40 +/- 9 cm/s, and peak backflow velocity was 14 +/- 3 cm/s. Magnetic resonance velocity mapping is a noninvasive technique for the evaluation of time-related flow velocity patterns and for quantitative measurement of mitral and pulmonary venous blood flow velocity.
- Published
- 1991
141. 1047 Time-resolved three-directional MR velocity mapping of aortic flow in patient follow-up after aortic valve-sparing surgery
- Author
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James C. Carr, Xin Liu, Karin E. Dill, Randall Ramsay, Gert Reiter, and Peter Weale
- Subjects
Medicine(all) ,Aortic valve ,lcsh:Diseases of the circulatory (Cardiovascular) system ,medicine.medical_specialty ,Radiological and Ultrasound Technology ,business.industry ,Aortic root ,Aortic flow ,Flow pattern ,Surgery ,medicine.anatomical_structure ,lcsh:RC666-701 ,Velocity mapping ,Internal medicine ,medicine.artery ,Ascending aorta ,cardiovascular system ,medicine ,Cardiology ,Radiology, Nuclear Medicine and imaging ,In patient ,Radiology ,Cardiology and Cardiovascular Medicine ,business ,Angiology - Abstract
Introduction Aortic valve-sparing operations have become a efficacious method for repairing aortic root aneurysm as it leaves native valvular structure in situ thus preserving the anatomy and function of native aortic valve. Cardiac MRI provides an accurate and comprehensive tool for the followup after aortic valve-sparing surgery. However, conventional phase-contrast MRI is unable to demonstrate the flow patterns in the aortic root and ascending aorta, which are highly associated with aortic valvular function. Recent studies demonstrated the feasibility of three-directional MR velocity mapping in visualization of aortic flow patterns.
- Published
- 2008
142. 1064 Evaluation of postoperative pulmonary regurgitation after surgical repair of tetralogy of Fallot: comparison between Doppler-echocardiography and MR velocity mapping
- Author
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Matthias Gutberlet, Janine Hoffmann, and Matthias Grothoff
- Subjects
Medicine(all) ,Surgical repair ,medicine.medical_specialty ,Radiological and Ultrasound Technology ,medicine.diagnostic_test ,business.industry ,Doppler echocardiography ,medicine.disease ,Velocity mapping ,Internal medicine ,Pulmonary regurgitation ,cardiovascular system ,medicine ,Cardiology ,Radiology, Nuclear Medicine and imaging ,In patient ,cardiovascular diseases ,Radiology ,Pulmonary Valve Insufficiency ,Cardiology and Cardiovascular Medicine ,business ,Tetralogy of Fallot ,Angiology - Abstract
Background Pulmonary regurgitation is a common finding in patients after correction of tetralogy of Fallot (TOF). Right ventricular impairment and even ventricular arrhythmia have been ascribed to pulmonary valve insufficiency (PI), which is therefore an important issue in follow-up examinations.
- Published
- 2008
143. Predictive K-PLSR Myocardial Contractility Modeling with Phase Contrast MR Velocity Mapping
- Author
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Qian Wu, Guang-Zhong Yang, Andrew Huntbatch, and Su-Lin Lee
- Subjects
business.industry ,Phase contrast microscopy ,Deformation (meteorology) ,Grid ,Field (computer science) ,Visualization ,law.invention ,Contractility ,law ,Velocity mapping ,Convergence (routing) ,Computer vision ,Artificial intelligence ,business ,Algorithm ,Mathematics - Abstract
With the increasing versatility of CMR, further understanding of intrinsic contractility of the myocardium can be achieved by performing subject-specific modeling by integrating structural and functional information available. The recent introduction of the virtual tagging framework allows for visualization of the localized deformation of the myocardium based on phase contrast myocardial velocity mapping. The purpose of this study is to examine the use of a non-linear, Kernel-Partial Least Squares Regression (K-PLSR) predictive motion modeling scheme for the virtual tagging framework. The method allows for the derivation of a compact non-linear deformation model such that the entire deformation field can be predicted by a limited number of control points. When applied to virtual tagging, the technique can be used to predictively guide the mesh refinement based on the motion of the coarse grid, thus greatly reducing the search space and increasing the convergence speed of the algorithm. The effectiveness and numerical accuracy of the proposed technique are assessed with both numerically simulated data sets and in vivo phase contrast CMR velocity mapping from a group of 7 subjects. The technique presented has a distinct advantage over the conventional mesh refinement scheme and brings CMR myocardial contractility analysis closer to routine clinical practice.
- Published
- 2007
144. Blood velocity measurements using laser speckle imaging
- Author
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N.Y. Chou and L.W. Winchester
- Subjects
Materials science ,Blood velocity ,business.industry ,media_common.quotation_subject ,Laser Speckle Imaging ,Blood flow ,Laser ,law.invention ,Speckle pattern ,Optics ,law ,Velocity mapping ,medicine ,Contrast (vision) ,business ,media_common ,Iloprost ,medicine.drug - Abstract
Blood velocity measurements in the skin of pigs are reported. Measurements were obtained using laser speckle contrast analysis with a multiple scattering correction. Laser speckle contrast analysis is a rapid technique for obtaining a velocity mapping of perfused tissue. Measurements of blood velocity in pig skin were obtained using a laser and a monochrome digital camera. Blood velocities were measured in tissue prior to and after elevation of flaps. The effect of Iloprost and nitroglycerine on local blood velocity was also examined in nonexcised tissue.
- Published
- 2007
145. Velocity Mapping of Multiphoton Excited Molecules
- Author
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David H. Parker and David Chandler
- Subjects
Materials science ,Velocity mapping ,Excited state ,Molecule ,Atomic physics - Published
- 2007
146. NMR velocity mapping of gas flow around solid objects
- Author
-
Alexander Pines, Songi Han, and Kimberly L. Pierce
- Subjects
Physics::Fluid Dynamics ,Flow visualization ,Coherence time ,Classical mechanics ,Materials science ,Velocity mapping ,Low temperature combustion ,General Medicine ,Aerodynamics ,Hyperpolarization (physics) ,Velocimetry ,Wake ,Computational physics - Abstract
We present experimental visualizations of gas flow around solid blunt bodies by NMR imaging. NMR velocimetry is a model-free and tracer-free experimental means for quantitative and multi-dimensional flow visualization. Hyperpolarization of $^{129}\mathrm{Xe}$ provided sufficient NMR signal to overcome the low density of the dilute gas phase, and its long coherence time allows for true velocity vector mapping. In this study, the diverging gas flow around and wake patterns immediately behind a sphere could be vectorally visualized and quantified. In a similar experiment, the flow over an aerodynamic model airplane body revealed a less disrupted flow pattern.
- Published
- 2006
147. Time-Resolved 3-Dimensional Magnetic Resonance Velocity Mapping at 3 T Reveals Drastic Changes in Flow Patterns in a Partially Thrombosed Aortic Arch
- Author
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Jürgen Hennig, Andreas Harloff, Mathias Langer, Ernst Weigang, Alex Frydrychowicz, Michael Markl, and Friedhelm Beyersdorf
- Subjects
Aortic arch ,medicine.diagnostic_test ,Aortic lumen ,business.industry ,Magnetic resonance imaging ,Signal void ,Anatomy ,Flow pattern ,medicine.disease ,Magnetic resonance angiography ,Velocity mapping ,Physiology (medical) ,medicine.artery ,cardiovascular system ,medicine ,cardiovascular diseases ,Thrombus ,Cardiology and Cardiovascular Medicine ,business ,circulatory and respiratory physiology - Abstract
A 36-year-old female patient presented with recurrent arterial emboli of both arms and a suspected transient ischemic attack. Routine thoracic contrast-enhanced, 3D magnetic resonance angiography (CE-MRA) at 3 T was performed to rule out additional arterial thrombi. The resulting CE-MRA images and consecutive, curved, multiplanar reconstructions (Figure 1B and 1C) revealed a partially obstructing thrombus (as a signal void in the otherwise-bright aortic lumen) in the aortic arch and the proximal left subclavian artery. In contrast, maximum-intensity-projection analysis (Figure 1A) did not depict these findings, which mimicked normal aortic geometry. Figure 1. A, Inconspicuous CE maximum-intensity projection of MRA at 3-T field strength. No obvious cause for the concomitant …
- Published
- 2006
148. Kinematics analysis of a parallel machine tool based on genetic algorithms
- Author
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Yi Shi, Kui-Jing Zheng, Qingling Li, Yulei Hou, Yong-Sheng Zhao, and Jian-She Gao
- Subjects
Maxima and minima ,Matrix (mathematics) ,Theoretical computer science ,business.product_category ,Computer science ,Velocity mapping ,Numerical analysis ,Kinematics ,Workspace ,business ,Algorithm ,Expression (mathematics) ,Machine tool - Abstract
This paper presents the kinematics analysis of a novel 5-UPS/PRPU 5-degree-of-freedom parallel machine tool based on genetic algorithms. The characteristic of the parallel machine tool is described and the mathematic expression of the 5-UPS/PRPU parallel machine tool's velocity mapping matrix is derived. The genetic algorithms is introduced in the search of the singular configuration and the extrema of the kinematics performance of the parallel machine tool. The non-singular workspace of the parallel machine tool and the corresponding extrema of the kinematics performance evaluation indices are obtained. The numerical analysis results prove the effectiveness of the algorithm.
- Published
- 2006
149. DOPPLER-SELECTED TIME-OF-FLIGHT TECHNIQUE: A VERSATILE THREE-DIMENSIONAL VELOCITY MAPPING APPROACH
- Author
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Shih-Huang Lee and Kopin Liu
- Subjects
Physics ,symbols.namesake ,Velocity mapping ,Acoustics ,symbols ,Doppler effect - Published
- 2004
150. Flow volume and shunt quantification in pediatric congenital heart disease by real-time magnetic resonance velocity mapping: a validation study
- Author
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Jürgen Gieseke, Philipp Beerbaum, Hermann Esdorn, Hermann Körperich, Hans Meyer, Peter Barth, Romhild M. Hoogeveen, and Andreas Peterschröder
- Subjects
Heart Defects, Congenital ,Male ,Validation study ,Heart disease ,Hemodynamics ,Phase image ,Velocity mapping ,Physiology (medical) ,Coronary Circulation ,Medicine ,Humans ,Child ,Observer Variation ,medicine.diagnostic_test ,business.industry ,Echo-Planar Imaging ,Infant ,Reproducibility of Results ,Magnetic resonance imaging ,Stroke Volume ,Blood flow ,medicine.disease ,Child, Preschool ,Blood Circulation ,Female ,Cardiology and Cardiovascular Medicine ,Nuclear medicine ,business ,Shunt (electrical) ,Blood Flow Velocity - Abstract
Background— Flow quantification in real time by phase-contrast MRI (PC-MRI) may provide unique hemodynamic information in congenital heart disease, but available techniques have important limitations. We sought to validate a novel real-time magnetic resonance flow sequence in children. Methods and Results— In 14 pediatric patients (mean age 5.2±2.0 years) with cardiac left-to-right shunt, pulmonary (Q p ) and aortic (Q s ) flow rates were determined by nontriggered free-breathing real-time PC-MRI with single-shot echo-planar imaging combined with sensitivity encoding, which yielded 25 phase images per second at 2.7×2.7-mm in-plane resolution (field of view 30×34 cm 2 ). Over a 9.5-second period that included 2 to 5 respiratory cycles, 16.6±2.6 subsequent stroke volumes (range 13 to 22) were acquired in each vessel. Results were compared with conventional retrospectively ECG-gated PC-MRI. Mean Q p /Q s by conventional PC-MRI was 1.91±0.64, and it was 1.94±0.68 (mean±SD) by real-time PC-MRI. For blood flow rate through pulmonary artery and aorta, we found differences of 2% to 3% (Bland-Altman analysis), with lower limits of agreement of −11% to −13% (mean−2 SD) and upper limits of 18% to 19% (mean+2 SD), which demonstrated good agreement between both methods. Mean difference for Q p /Q s was 1%, with limits of agreement ranging between −18% and 22% (mean±2 SD). High repeatability but some flow overestimation was observed in vitro (pulsatile flow phantom) with real-time PC-MRI, whereas conventional PC-MRI was accurate. Beat-to-beat stroke-volume variation was 6.1±2.3% in vivo and 3.7±0.3% in vitro. Conclusions— Beat-to-beat quantification of pulmonary and aortic flows and hence left-to-right shunt within a few seconds is reliable by nontriggered real-time PC-MRI with echo-planar imaging and sensitivity encoding. Good spatial/temporal resolution and a large field of view may render the sequence valuable for multiple applications in congenital heart disease.
- Published
- 2004
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