The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Vivek Muthurangu - One of the best experts on this subject based on the ideXlab platform.
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real time assessment of right and left ventricular volumes and function in children using high spatiotemporal resolution spiral bssfp with compressed sensing
Journal of Cardiovascular Magnetic Resonance, 2018Co-Authors: Jennifer A Steeden, Grzegorz T Kowalik, Oliver Tann, Marina Hughes, Kristian H Mortensen, Vivek MuthuranguAbstract:Real-time cardiovascular magnetic resonance (CMR) assessment of ventricular volumes and function enables data acquisition during free-breathing. The requirement for high spatiotemporal resolution in children necessitates the use of highly accelerated imaging techniques. A novel real-time balanced steady state free precession (bSSFP) spiral sequence reconstructed using Compressed Sensing (CS) was prospectively validated against the breath-hold clinical standard for assessment of ventricular volumes in 60 children with congenital heart disease. Qualitative image scoring, quantitative image quality, as well as evaluation of biventricular volumes was performed. Standard BH and real-time measures were compared using the paired t-test and agreement for volumetric measures were evaluated using Bland Altman analysis. Acquisition time for the entire short axis stack (~ 13 slices) using the spiral real-time technique was ~ 20 s, compared to ~ 348 s for the standard breath hold technique. Qualitative scores reflected more residual aliasing artefact (p < 0.001) and lower Edge Definition (p < 0.001) in spiral real-time images than standard breath hold images, with lower quantitative Edge sharpness and estimates of image contrast (p < 0.001). There was a small but statistically significant (p < 0.05) overestimation of left ventricular (LV) end-systolic volume (1.0 ± 3.5 mL), and underestimation of LV end-diastolic volume (− 1.7 ± 4.6 mL), LV stroke volume (− 2.6 ± 4.8 mL) and LV ejection fraction (− 1.5 ± 3.0%) using the real-time technique. We also observed a small underestimation of right ventricular stroke volume (− 1.8 ± 4.9 mL) and ejection fraction (− 1.4 ± 3.7%) using the real-time imaging technique. No difference in inter-observer or intra-observer variability were observed between the BH and real-time sequences. Real-time bSSFP imaging using spiral trajectories combined with a compressed sensing reconstruction showed good agreement for quantification of biventricular metrics in children with heart disease, despite slightly lower image quality. This technique holds the potential for free breathing data acquisition, with significantly shorter scan times in children.
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real time assessment of right and left ventricular volumes and function in children using high spatiotemporal resolution spiral bssfp with compressed sensing
arXiv: Medical Physics, 2018Co-Authors: Jennifer A Steeden, Grzegorz T Kowalik, Oliver Tann, Marina Hughes, Kristian H Mortensen, Vivek MuthuranguAbstract:Background: Real-time (RT) assessment of ventricular volumes and function enables data acquisition during free-breathing. However, in children the requirement for high spatiotemporal resolution requires accelerated imaging techniques. In this study, we implemented a novel RT bSSFP spiral sequence reconstructed using Compressed Sensing (CS) and validated it against the breath-hold (BH) reference standard for assessment of ventricular volumes in children with heart disease. Methods: Data was acquired in 60 children. Qualitative image scoring and evaluation of ventricular volumes was performed by 3 clinical cardiac MR specialists. 30 cases were reassessed for intra-observer variability, and the other 30 cases for inter-observer variability. Results: Spiral RT images were of good quality, however qualitative scores reflected more residual artefact than standard BH images and slightly lower Edge Definition. Quantification of Left Ventricular (LV) and Right Ventricular (RV) metrics showed excellent correlation between the techniques with narrow limits of agreement. However, we observed small but statistically significant overestimation of LV end-diastolic volume, underestimation of LV end-systolic volume, as well as a small overestimation of RV stroke volume and ejection fraction using the RT imaging technique. No difference in inter-observer or intra-observer variability were observed between the BH and RT sequences. Conclusions: Real-time bSSFP imaging using spiral trajectories combined with a compressed sensing reconstruction is feasible. The main benefit is that it can be acquired during free breathing. However, another important secondary benefit is that a whole ventricular stack can be acquired in ~20 seconds, as opposed to ~6 minutes for standard BH imaging. Thus, this technique holds the potential to significantly shorten MR scan times in children.
Tom Baer - One of the best experts on this subject based on the ideXlab platform.
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solid freeform fabrication of aqueous alumina poly vinyl alcohol gelcasting suspensions
Journal of the American Ceramic Society, 2004Co-Authors: Sherry L Morissette, Jennifer A Lewis, Joseph Cesarano, D Dimos, Tom BaerAbstract:Solid freeform fabrication of aqueous alumina–poly(vinyl alcohol) (Al2O3–PVA) gel-casting suspensions was conducted using a computer-controlled extrusion apparatus fitted with a two-nozzle delivery system. The impact of casting parameters on the shear rate profiles experienced during deposition was evaluated via conventional flow analysis and computer simulations. In addition, the influence of these parameters on line resolution/uniformity, printability, and as-cast component properties was studied using laser profilometry, optical microscopy, and scanning electron microscopy. Continuous printablity was achieved for tip diameters ranging from 0.254 to 1.370 mm for all mixing rates and suspension compositions studied. Printed lines were uniform with good Edge Definition, and line dimensions were independent of mixing rate for these process conditions. The Al2O3 volume fraction (φAl2O3) in the as-deposited layers depended on casting conditions and cross-linking agent concentration, where (φAl2O3 increased with decreased tip diameter and increased cross-linking agent concentration. The free-formed Al2O3 components exhibited uniform particle packing, with minimal macrodefects (e.g., slumping or staircasing) and no discernable microdefects (e.g., bubbles or cracking).
James D Thomas - One of the best experts on this subject based on the ideXlab platform.
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qualitative and quantitative effects of harmonic echocardiographic imaging on endocardial Edge Definition and side lobe artifacts
Journal of The American Society of Echocardiography, 2000Co-Authors: David N Rubin, Naji Yazbek, Mario J Garcia, William J Stewart, James D ThomasAbstract:Abstract Harmonic imaging is a new ultrasonographic technique that is designed to improve image quality by exploiting the spontaneous generation of higher frequencies as ultrasound propagates through tissue. We studied 51 difficult-to-image patients with blinded side-by-side cineloop evaluation of endocardial border Definition by harmonic versus fundamental imaging. In addition, quantitative intensities from cavity versus wall were compared for harmonic versus fundamental imaging. Harmonic imaging improved left ventricular endocardial border delineation over fundamental imaging (superior: harmonic=71.1%, fundamental=18.7%; similar: 10.2%; P P P (J Am Soc Echocardiogr 2000;13:1012-8.)
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qualitative and quantitative effects of harmonic echocardiographic imaging on endocardial Edge Definition and side lobe artifacts
Journal of The American Society of Echocardiography, 2000Co-Authors: David N Rubin, Naji Yazbek, Mario J Garcia, William J Stewart, James D ThomasAbstract:Harmonic imaging is a new ultrasonographic technique that is designed to improve image quality by exploiting the spontaneous generation of higher frequencies as ultrasound propagates through tissue. We studied 51 difficult-to-image patients with blinded side-by-side cineloop evaluation of endocardial border Definition by harmonic versus fundamental imaging. In addition, quantitative intensities from cavity versus wall were compared for harmonic versus fundamental imaging. Harmonic imaging improved left ventricular endocardial border delineation over fundamental imaging (superior: harmonic = 71.1%, fundamental = 18.7%; similar: 10.2%; P <.001). Quantitative analysis of 100 wall/cavity combinations demonstrated brighter wall segments and more strikingly darker cavities during harmonic imaging (cavity intensity on a 0 to 255 scale: fundamental = 15.6 +/- 8.6; harmonic = 6.0 +/- 5.3; P <.0001), which led to enhanced contrast between the wall and cavity (1.89 versus 1.19, P <.0001). Harmonic imaging reduces side-lobe artifacts, resulting in a darker cavity and brighter walls, thereby improving image contrast and endocardial delineation.
Jennifer A Steeden - One of the best experts on this subject based on the ideXlab platform.
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real time assessment of right and left ventricular volumes and function in children using high spatiotemporal resolution spiral bssfp with compressed sensing
Journal of Cardiovascular Magnetic Resonance, 2018Co-Authors: Jennifer A Steeden, Grzegorz T Kowalik, Oliver Tann, Marina Hughes, Kristian H Mortensen, Vivek MuthuranguAbstract:Real-time cardiovascular magnetic resonance (CMR) assessment of ventricular volumes and function enables data acquisition during free-breathing. The requirement for high spatiotemporal resolution in children necessitates the use of highly accelerated imaging techniques. A novel real-time balanced steady state free precession (bSSFP) spiral sequence reconstructed using Compressed Sensing (CS) was prospectively validated against the breath-hold clinical standard for assessment of ventricular volumes in 60 children with congenital heart disease. Qualitative image scoring, quantitative image quality, as well as evaluation of biventricular volumes was performed. Standard BH and real-time measures were compared using the paired t-test and agreement for volumetric measures were evaluated using Bland Altman analysis. Acquisition time for the entire short axis stack (~ 13 slices) using the spiral real-time technique was ~ 20 s, compared to ~ 348 s for the standard breath hold technique. Qualitative scores reflected more residual aliasing artefact (p < 0.001) and lower Edge Definition (p < 0.001) in spiral real-time images than standard breath hold images, with lower quantitative Edge sharpness and estimates of image contrast (p < 0.001). There was a small but statistically significant (p < 0.05) overestimation of left ventricular (LV) end-systolic volume (1.0 ± 3.5 mL), and underestimation of LV end-diastolic volume (− 1.7 ± 4.6 mL), LV stroke volume (− 2.6 ± 4.8 mL) and LV ejection fraction (− 1.5 ± 3.0%) using the real-time technique. We also observed a small underestimation of right ventricular stroke volume (− 1.8 ± 4.9 mL) and ejection fraction (− 1.4 ± 3.7%) using the real-time imaging technique. No difference in inter-observer or intra-observer variability were observed between the BH and real-time sequences. Real-time bSSFP imaging using spiral trajectories combined with a compressed sensing reconstruction showed good agreement for quantification of biventricular metrics in children with heart disease, despite slightly lower image quality. This technique holds the potential for free breathing data acquisition, with significantly shorter scan times in children.
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real time assessment of right and left ventricular volumes and function in children using high spatiotemporal resolution spiral bssfp with compressed sensing
arXiv: Medical Physics, 2018Co-Authors: Jennifer A Steeden, Grzegorz T Kowalik, Oliver Tann, Marina Hughes, Kristian H Mortensen, Vivek MuthuranguAbstract:Background: Real-time (RT) assessment of ventricular volumes and function enables data acquisition during free-breathing. However, in children the requirement for high spatiotemporal resolution requires accelerated imaging techniques. In this study, we implemented a novel RT bSSFP spiral sequence reconstructed using Compressed Sensing (CS) and validated it against the breath-hold (BH) reference standard for assessment of ventricular volumes in children with heart disease. Methods: Data was acquired in 60 children. Qualitative image scoring and evaluation of ventricular volumes was performed by 3 clinical cardiac MR specialists. 30 cases were reassessed for intra-observer variability, and the other 30 cases for inter-observer variability. Results: Spiral RT images were of good quality, however qualitative scores reflected more residual artefact than standard BH images and slightly lower Edge Definition. Quantification of Left Ventricular (LV) and Right Ventricular (RV) metrics showed excellent correlation between the techniques with narrow limits of agreement. However, we observed small but statistically significant overestimation of LV end-diastolic volume, underestimation of LV end-systolic volume, as well as a small overestimation of RV stroke volume and ejection fraction using the RT imaging technique. No difference in inter-observer or intra-observer variability were observed between the BH and RT sequences. Conclusions: Real-time bSSFP imaging using spiral trajectories combined with a compressed sensing reconstruction is feasible. The main benefit is that it can be acquired during free breathing. However, another important secondary benefit is that a whole ventricular stack can be acquired in ~20 seconds, as opposed to ~6 minutes for standard BH imaging. Thus, this technique holds the potential to significantly shorten MR scan times in children.
Sherry L Morissette - One of the best experts on this subject based on the ideXlab platform.
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solid freeform fabrication of aqueous alumina poly vinyl alcohol gelcasting suspensions
Journal of the American Ceramic Society, 2004Co-Authors: Sherry L Morissette, Jennifer A Lewis, Joseph Cesarano, D Dimos, Tom BaerAbstract:Solid freeform fabrication of aqueous alumina–poly(vinyl alcohol) (Al2O3–PVA) gel-casting suspensions was conducted using a computer-controlled extrusion apparatus fitted with a two-nozzle delivery system. The impact of casting parameters on the shear rate profiles experienced during deposition was evaluated via conventional flow analysis and computer simulations. In addition, the influence of these parameters on line resolution/uniformity, printability, and as-cast component properties was studied using laser profilometry, optical microscopy, and scanning electron microscopy. Continuous printablity was achieved for tip diameters ranging from 0.254 to 1.370 mm for all mixing rates and suspension compositions studied. Printed lines were uniform with good Edge Definition, and line dimensions were independent of mixing rate for these process conditions. The Al2O3 volume fraction (φAl2O3) in the as-deposited layers depended on casting conditions and cross-linking agent concentration, where (φAl2O3 increased with decreased tip diameter and increased cross-linking agent concentration. The free-formed Al2O3 components exhibited uniform particle packing, with minimal macrodefects (e.g., slumping or staircasing) and no discernable microdefects (e.g., bubbles or cracking).
