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Your search keyword '"Chee, A. J. Y."' showing total 29 results
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29 results on '"Chee, A. J. Y."'

2. Channel Count Reduction for Plane Wave Ultrasound Through Convolutional Neural Network Interpolation

Author

Xiao, Di, Yiu, Billy Y. S., Chee, Adrian J. Y., Yu, Alfred C. H., Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Karray, Fakhri, editor, Campilho, Aurélio, editor, and Yu, Alfred, editor

Published
2019
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20. Ultrasound vector projectile imaging for detection of altered carotid bifurcation hemodynamics during reductions in cardiac output.

Author

Au, Jason S., Yiu, Billy Y. S., So, Hélène, Chee, Adrian J. Y., Greaves, Danielle K., Hughson, Richard L., and Yu, Alfred C. H.

Subjects
CARDIAC output, INTERNAL carotid artery, HEMODYNAMICS, BLOOD flow, PROJECTILES, CAROTID artery
Abstract

Purpose: Complex blood flow is commonly observed in the carotid bifurcation, although the factors that regulate these patterns beyond arterial geometry are unknown. The emergence of high‐frame‐rate ultrasound vector flow imaging allows for noninvasive, time‐resolved analysis of complex hemodynamic behavior in humans, and it can potentially help researchers understand which physiological stressors can alter carotid bifurcation hemodynamics in vivo. Here, we seek to pursue the first use of vector projectile imaging (VPI), a dynamic form of vector flow imaging, to analyze the regulation of carotid bifurcation hemodynamics during experimental reductions in cardiac output induced via a physiological stressor called lower body negative pressure (LBNP). Methods: Seven healthy adults (age: 27 ± 4 yr, 4 men) underwent LBNP at −45 mmHg to simulate a postural hemodynamic response in a controlled environment. Using a research‐grade, high‐frame‐rate ultrasound platform, vector flow estimation in each subject's right carotid bifurcation was performed through a multi‐angle plane wave imaging (two transmission angles of 10° and −10°) formulation, and VPI cineloops were generated at a frame rate of 750 fps. Vector concentration was quantified by the resultant blood velocity vector angles within a region of interest; lower concentration indicated greater flow dispersion. Discrete concentration values during peak and late systole were compared across different segments of the carotid artery bifurcation before, and during, LBNP. Results: Vector projectile imaging revealed that external and internal carotid arteries exhibited regional hemodynamic changes during LBNP, which acted to reduce both the subject's cardiac output (Δ − 1.2 ± 0.5 L/min, −19%; P < 0.01) and peak carotid blood velocity (Δ − 6.30 ± 8.27 cm/s, −7%; P = 0.05). In these carotid artery branches, the vector concentration time trace before and during LBNP were observed to be different. The impact of LBNP on flow complexity in the two carotid artery branches showed variations between subjects. Conclusions: Using VPI, intuitive visualization of complex hemodynamic changes can be obtained in healthy humans subjected to LBNP. This imaging tool has potential for further applications in vascular physiology to identify and quantify complex hemodynamic features in humans during different physiological stressor tests that regulate hemodynamics. [ABSTRACT FROM AUTHOR]

Published
2020
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23. Preliminary investigation of an ultrasound method for estimating pressure changes in deep-positioned vessels.

Author

Duric, Neb, Heyde, Brecht, Olesen, Jacob Bjerring, Villagómez Hoyos, Carlos Armando, Traberg, Marie Sand, Chee, Adrian J. Y., Yiu, Billy Y. S., Ho, Chung Kit, Yu, Alfred C. H., Jensen, Jørgen Arendt, Duric, Neb, Heyde, Brecht, Olesen, Jacob Bjerring, Villagómez Hoyos, Carlos Armando, Traberg, Marie Sand, Chee, Adrian J. Y., Yiu, Billy Y. S., Ho, Chung Kit, Yu, Alfred C. H., and Jensen, Jørgen Arendt

Abstract

This paper presents a method for measuring pressure changes in deep-tissue vessels using vector velocity ultrasound data. The large penetration depth is ensured by acquiring data using a low frequency phased array transducer. Vascular pressure changes are then calculated from 2-D angle-independent vector velocity fields using a model based on the Navier-Stokes equations. Experimental scans are performed on a fabricated flow phantom having a constriction of 36% at a depth of 100 mm. Scans are carried out using a phased array transducer connected to the experimental scanner, SARUS. 2-D fields of angle-independent vector velocities are acquired using directional synthetic aperture vector flow imaging. The obtained results are evaluated by comparison to a 3-D numerical simulation model with equivalent geometry as the designed phantom. The study showed pressure drops across the constricted phantom varying from -40 Pa to 15 Pa with a standard deviation of 32%, and a bias of 25% found relative to the peak simulated pressure drop. This preliminary study shows that pressure can be estimated non-invasively to a depth that enables cardiac scans, and thereby, the possibility of detecting the pressure drops across the mitral valve.

Published
2016

26. High Sensitivity, Wearable, Piezoresistive Pressure Sensors Based on Irregular Microhump Structures and Its Applications in Body Motion Sensing

Author

Wang, Zongrong, primary, Wang, Shan, additional, Zeng, Jifang, additional, Ren, Xiaochen, additional, Chee, Adrian J. Y., additional, Yiu, Billy Y. S., additional, Chung, Wai Choi, additional, Yang, Yong, additional, Yu, Alfred C. H., additional, Roberts, Robert C., additional, Tsang, Anderson C. O., additional, Chow, Kwok Wing, additional, and Chan, Paddy K. L., additional

Published
2016
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29. Movie1.mp4

Author

Ho, Chung Kit, primary, Chee, Adrian J. Y., additional, Yiu, Billy Y. S., additional, Tsang, Anderson C. O., additional, Chow, Kwok Wing, additional, and Yu, Alfred C. H., additional

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