The Experts below are selected from a list of 100479 Experts worldwide ranked by ideXlab platform
Robert R. Edelman - One of the best experts on this subject based on the ideXlab platform.
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dynamic quantitative nonenhanced magnetic resonance angiography of the abdominal aorta and lower extremities using cine fast interrupted steady state in combination with arterial spin labeling a feasibility study
Journal of Cardiovascular Magnetic Resonance, 2019Co-Authors: Emily A Aherne, Robert R. Edelman, Ioannis Koktzoglou, Benjamin B LindAbstract:Cine fast interrupted steady-state in combination with arterial spin labeling is a recently described nonenhanced magnetic resonance angiography (MRA) technique that relies on bolus tracking for time-resolved digital subtraction angiography-like displays of blood Flow patterns. We evaluated the feasibility of applying this technique to display in-Plane Flow patterns in two regions: the abdominal aorta and lower extremity peripheral arteries. We performed an institutional review board-approved study in healthy subjects and patients. In 7 healthy subjects, in-Plane Flow was imaged at 4 stations ranging from the lower legs to the aorto-iliac bifurcation (junction of the distal thigh and upper calf, mid-thigh, junction of the upper thigh and pelvis, upper pelvis). In 5 healthy subjects and 6 patients without abdominal aortopathy, images were acquired through the suprarenal abdominal aorta. Ten patients with known peripheral arterial disease and two patients with stable disease of the abdominal aorta were also evaluated. Peak velocity was compared at each of the 4 stations for cine fast interrupted steady-state in combination with arterial spin labeling and two-dimensional cine phase contrast in patients with normal vessels. In-Plane Flow patterns were well visualized in all peripheral arterial stations and in the abdominal aorta, providing a high quality display of hemodynamic patterns along extensive lengths of the vessels. There was very strong positive correlation (r = 0.952, P < 0.05) and excellent agreement (intraclass correlation coefficient, 0.935; 95% confidence interval, 0.812–0.972) between peak Flow velocities measured by cine fast interrupted steady-state in combination with arterial spin labeling and two-dimensional cine phase contrast. In 10 patients with peripheral artery disease and 2 patients with aortic pathology, cine fast interrupted steady-state in combination with arterial spin labeling provided a visual demonstration of abnormal hemodynamics. This feasibility study suggests that cine fast interrupted steady-state in combination with arterial spin labeling provides an efficient, high quality and physiologically accurate display of in-Plane Flow patterns over extensive lengths of the lower extremity peripheral arteries, which can be difficult to achieve using other MRA techniques.
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Cardiovascular cine imaging and Flow evaluation using Fast Interrupted Steady-State (FISS) magnetic resonance
Journal of Cardiovascular Magnetic Resonance, 2018Co-Authors: Robert R. Edelman, Ali Serhal, Amit Pursnani, Jianing Pang, Ioannis KoktzoglouAbstract:Background Existing cine imaging techniques rely on balanced steady-state free precession (bSSFP) or spoiled gradient-echo readouts, each of which has limitations. For instance, with bSSFP, artifacts occur from rapid through-Plane Flow and off-resonance effects. We hypothesized that a prototype cine technique, radial fast interrupted steady-state (FISS) , could overcome these limitations. The technique was compared with standard cine bSSFP for cardiac function, coronary artery conspicuity, and aortic valve morphology. Given its advantageous properties, we further hypothesized that the cine FISS technique, in combination with arterial spin labeling (ASL), could provide an alternative to phase contrast for visualizing in-Plane Flow patterns within the aorta and branch vessels. Main body The study was IRB-approved and subjects provided consent. Breath-hold cine FISS and bSSFP were acquired using similar imaging parameters. There was no significant difference in biPlane left ventricular ejection fraction or cardiac image quality between the two techniques. Compared with cine bSSFP, cine FISS demonstrated a marked decrease in fat signal which improved conspicuity of the coronary arteries, while suppression of through-Plane Flow artifact on thin-slice cine FISS images improved visualization of the aortic valve. Banding artifacts in the subcutaneous tissues were reduced. In healthy subjects, dynamic Flow patterns were well visualized in the aorta, coronary and renal arteries using cine FISS ASL, even when the slice was substantially thicker than the vessel diameter. Conclusion Cine FISS demonstrates several benefits for cardiovascular imaging compared with cine bSSFP, including better suppression of fat signal and reduced artifacts from through-Plane Flow and off-resonance effects. The main drawback is a slight (~ 20%) decrease in temporal resolution. In addition, preliminary results suggest that cine FISS ASL provides a potential alternative to phase contrast techniques for in-Plane Flow quantification, while enabling an efficient, visually-appealing, semi-projective display of blood Flow patterns throughout the course of an artery and its branches.
Ioannis Koktzoglou - One of the best experts on this subject based on the ideXlab platform.
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dynamic quantitative nonenhanced magnetic resonance angiography of the abdominal aorta and lower extremities using cine fast interrupted steady state in combination with arterial spin labeling a feasibility study
Journal of Cardiovascular Magnetic Resonance, 2019Co-Authors: Emily A Aherne, Robert R. Edelman, Ioannis Koktzoglou, Benjamin B LindAbstract:Cine fast interrupted steady-state in combination with arterial spin labeling is a recently described nonenhanced magnetic resonance angiography (MRA) technique that relies on bolus tracking for time-resolved digital subtraction angiography-like displays of blood Flow patterns. We evaluated the feasibility of applying this technique to display in-Plane Flow patterns in two regions: the abdominal aorta and lower extremity peripheral arteries. We performed an institutional review board-approved study in healthy subjects and patients. In 7 healthy subjects, in-Plane Flow was imaged at 4 stations ranging from the lower legs to the aorto-iliac bifurcation (junction of the distal thigh and upper calf, mid-thigh, junction of the upper thigh and pelvis, upper pelvis). In 5 healthy subjects and 6 patients without abdominal aortopathy, images were acquired through the suprarenal abdominal aorta. Ten patients with known peripheral arterial disease and two patients with stable disease of the abdominal aorta were also evaluated. Peak velocity was compared at each of the 4 stations for cine fast interrupted steady-state in combination with arterial spin labeling and two-dimensional cine phase contrast in patients with normal vessels. In-Plane Flow patterns were well visualized in all peripheral arterial stations and in the abdominal aorta, providing a high quality display of hemodynamic patterns along extensive lengths of the vessels. There was very strong positive correlation (r = 0.952, P < 0.05) and excellent agreement (intraclass correlation coefficient, 0.935; 95% confidence interval, 0.812–0.972) between peak Flow velocities measured by cine fast interrupted steady-state in combination with arterial spin labeling and two-dimensional cine phase contrast. In 10 patients with peripheral artery disease and 2 patients with aortic pathology, cine fast interrupted steady-state in combination with arterial spin labeling provided a visual demonstration of abnormal hemodynamics. This feasibility study suggests that cine fast interrupted steady-state in combination with arterial spin labeling provides an efficient, high quality and physiologically accurate display of in-Plane Flow patterns over extensive lengths of the lower extremity peripheral arteries, which can be difficult to achieve using other MRA techniques.
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Cardiovascular cine imaging and Flow evaluation using Fast Interrupted Steady-State (FISS) magnetic resonance
Journal of Cardiovascular Magnetic Resonance, 2018Co-Authors: Robert R. Edelman, Ali Serhal, Amit Pursnani, Jianing Pang, Ioannis KoktzoglouAbstract:Background Existing cine imaging techniques rely on balanced steady-state free precession (bSSFP) or spoiled gradient-echo readouts, each of which has limitations. For instance, with bSSFP, artifacts occur from rapid through-Plane Flow and off-resonance effects. We hypothesized that a prototype cine technique, radial fast interrupted steady-state (FISS) , could overcome these limitations. The technique was compared with standard cine bSSFP for cardiac function, coronary artery conspicuity, and aortic valve morphology. Given its advantageous properties, we further hypothesized that the cine FISS technique, in combination with arterial spin labeling (ASL), could provide an alternative to phase contrast for visualizing in-Plane Flow patterns within the aorta and branch vessels. Main body The study was IRB-approved and subjects provided consent. Breath-hold cine FISS and bSSFP were acquired using similar imaging parameters. There was no significant difference in biPlane left ventricular ejection fraction or cardiac image quality between the two techniques. Compared with cine bSSFP, cine FISS demonstrated a marked decrease in fat signal which improved conspicuity of the coronary arteries, while suppression of through-Plane Flow artifact on thin-slice cine FISS images improved visualization of the aortic valve. Banding artifacts in the subcutaneous tissues were reduced. In healthy subjects, dynamic Flow patterns were well visualized in the aorta, coronary and renal arteries using cine FISS ASL, even when the slice was substantially thicker than the vessel diameter. Conclusion Cine FISS demonstrates several benefits for cardiovascular imaging compared with cine bSSFP, including better suppression of fat signal and reduced artifacts from through-Plane Flow and off-resonance effects. The main drawback is a slight (~ 20%) decrease in temporal resolution. In addition, preliminary results suggest that cine FISS ASL provides a potential alternative to phase contrast techniques for in-Plane Flow quantification, while enabling an efficient, visually-appealing, semi-projective display of blood Flow patterns throughout the course of an artery and its branches.
Che Sun - One of the best experts on this subject based on the ideXlab platform.
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geometric structure of pseudo Plane quadratic Flows
Physics of Fluids, 2017Co-Authors: Che SunAbstract:Quadratic Flows have the unique property of uniform strain and are commonly used in turbulence modeling and hydrodynamic analysis. While previous applications focused on two-dimensional homogeneous fluid, this study examines the geometric structure of three-dimensional quadratic Flows in stratified fluid by solving a steady-state pseudo-Plane Flow model. The complete set of exact solutions reveals that steady quadratic Flows have an invariant conic type in the non-rotating frame and a non-rotatory vertical structure in the rotating frame. Three baroclinic solutions with vertically non-aligned formulation disprove an earlier conjecture. All elliptic and hyperbolic solutions, except for the inertial ones, exhibit vertical concentricity. The rich geometry of quadratic Flows stands in contrast to the depleted geometry of high-degree polynomial Flows. A paradox in the steady solutions of shallow-water reduced-gravity models is also explained.
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geometric structure of pseudo Plane quadratic Flows
arXiv: Fluid Dynamics, 2017Co-Authors: Che SunAbstract:Quadratic Flows have the unique property of uniform strain and are commonly used in turbulence modeling and hydrodynamic analysis. While previous application focused on two-dimensional homogeneous fluid, this study examines the geometric structure of three-dimensional quadratic Flows in stratified fluid by solving a steady-state pseudo-Plane Flow model. The complete set of exact solutions reveals that steady quadratic Flows have invariant conic type in non-rotating frame and non-rotatory vertical structure in rotating frame. Three baroclinic solutions with vertically non-aligned structure disprove an earlier conjecture. The rich topology of quadratic Flows stands in contrast to the depleted geometry of high-degree polynomial Flows. A paradox in the steady solutions of shallow-water reduced-gravity models is also explained.
Joachim Lotz - One of the best experts on this subject based on the ideXlab platform.
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real time phase contrast mri of cardiovascular blood Flow using undersampled radial fast low angle shot and nonlinear inverse reconstruction
NMR in Biomedicine, 2012Co-Authors: Arun A Joseph, Joachim Lotz, Klausdietmar Merboldt, Dirk Voit, Shuo Zhang, Martin Uecker, Jens FrahmAbstract:Velocity-encodedphase-contrast MRI ofcardiovascularblood Flowcommonlyreliesonelectrocardiogram-synchronized cine acquisitions of multiple heartbeats to quantitatively determine the Flow of an averaged cardiac cycle. Here, we present a new method for real-time phase-contrast MRI that combines Flow-encoding gradients with highly undersampled radial fast low-angle shot acquisitions and phase-sensitive image reconstructions by regularized nonlinear inversion. Apart from calibration studies using steady and pulsatile Flow, preliminary in vivo applications focused on through-Plane Flow in the ascending aorta of healthy subjects. With bipolar velocity-encoding gradients of alternating polarity that overlap the slice-refocusing gradient, the method yields Flow-encoded images with an in-Plane resolution of 1.8mm, section thickness of 6mm and measuring time at 3T of 24ms (TR/TE=3.44/2.76ms; flip angle, 10o; seven radial spokes per image). Accordingly, phase-contrast maps and corresponding velocity profiles achieve a temporal resolution of 48ms. The evaluated peak velocities, stroke volumes, Flow rates and respective variances over at least 20 consecutive heartbeats are in general agreement with literature data. Copyright © 2011 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this paper
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cardiovascular Flow measurement with phase contrast mr imaging basic facts and implementation
Radiographics, 2002Co-Authors: Joachim Lotz, Christian Meier, Andreas Leppert, Michael GalanskiAbstract:Phase-contrast magnetic resonance (MR) imaging is a well-known but undervalued method of obtaining quantitative information on blood Flow. Applications of this technique in cardiovascular MR imaging are expanding. According to the sequences available, phase-contrast measurement can be performed in a breath hold or during normal respiration. Prospective as well as retrospective gating techniques can be used. Common errors in phase-contrast imaging include mismatched encoding velocity, deviation of the imaging Plane, inadequate temporal resolution, inadequate spatial resolution, accelerated Flow and spatial misregistration, and phase offset errors. Flow measurements are most precise if the imaging Plane is perpendicular to the vessel of interest and Flow encoding is set to through-Plane Flow. The sequence should be repeated at least once, with a high encoding velocity used initially. If peak velocity has to be estimated, Flow measurement is repeated with an adapted encoding velocity. The overall error of a ...
Michael Galanski - One of the best experts on this subject based on the ideXlab platform.
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cardiovascular Flow measurement with phase contrast mr imaging basic facts and implementation
Radiographics, 2002Co-Authors: Joachim Lotz, Christian Meier, Andreas Leppert, Michael GalanskiAbstract:Phase-contrast magnetic resonance (MR) imaging is a well-known but undervalued method of obtaining quantitative information on blood Flow. Applications of this technique in cardiovascular MR imaging are expanding. According to the sequences available, phase-contrast measurement can be performed in a breath hold or during normal respiration. Prospective as well as retrospective gating techniques can be used. Common errors in phase-contrast imaging include mismatched encoding velocity, deviation of the imaging Plane, inadequate temporal resolution, inadequate spatial resolution, accelerated Flow and spatial misregistration, and phase offset errors. Flow measurements are most precise if the imaging Plane is perpendicular to the vessel of interest and Flow encoding is set to through-Plane Flow. The sequence should be repeated at least once, with a high encoding velocity used initially. If peak velocity has to be estimated, Flow measurement is repeated with an adapted encoding velocity. The overall error of a ...
