Quest for the Vulnerable Atheroma: Carotid Stenosis and Diametric Strain--A Feasibility Study.

The Bernoulli effect may result in eruption of a vulnerable carotid atheroma, causing a stroke. We measured electrocardiography (ECG)-registered QRS intra-stenotic blood velocity and atheroma strain dynamics in carotid artery walls using ultrasonic tissue Doppler methods, providing displacement and time resolutions of 0.1 µm and 3.7 ms. Of 22 arteries, 1 had a peak systolic velocity (PSV) >280 cm/s, 4 had PSVs between 165 and 280 cm/s and 17 had PSVs <165 cm/s. Eight arteries with PSVs <65 cm/s and 4 of 9 with PSVs between 65 and 165 cm/s had normal systolic diametric expansion (0% and 7%) and corresponding systolic wall thinning. The remaining 10 arteries had abnormal systolic strain dynamics, 2 with diametric reduction (>-0.05 mm), 2 with extreme wall expansion (>0.1 mm), 2 with extreme wall thinning (>-0.1 mm) and 4 with combinations. Decreases in systolic diameter and/or extreme systolic arterial wall thickening may indicate imminent atheroma rupture.

Development of an interactive Coronary Doppler Vibrometry system for detection of coronary artery disease.

Coronary artery disease is a deadly and costly condition and represents an important public health issue globally. Coronary Doppler vibrometry (CDV), a new noninvasive coronary artery stenosis detection technique, showed encouraging results in our recent clinical study. However, the CDV system required lengthy offline data analysis, thus it did not provide any feedback during examination on the quality of data, not to mention analysis results. To overcome these limitations, we have developed a new CDV system that interactively performs acquisition, analysis and display of a complete data set while a subject is still on the examination table. Our system is based on a commercial ultrasound machine, and it will be a useful tool for CDV research and clinical studies in the future.

Reducing registration error in cross-beam vector doppler imaging with position sensor.

Various vector Doppler methods have been proposed in the last several decades to overcome the Doppler angle dependency in both conventional spectral Doppler and color Doppler by measuring both the speed and direction of blood flow. However, they have not been adopted for routine use because most of them require specialized hardware, which is not available in commercial ultrasound systems. An alternative approach (cross-beam method) that uses color Doppler images obtained from different steered beam angles is more feasible, but there is error in registering multiple color Doppler images because they are not acquired simultaneously. To alleviate this problem, we have evaluated a cross-beam vector Doppler system that registers spatially with a position sensor two color Doppler images from two different angles and temporally with ECG synchronization. The registration error was reduced to an average of 0.92 mm from 2.49 mm in 9 human subjects. Vector Doppler carotid artery images of a healthy subject and a patient with atherosclerotic plaques are also presented.

Continuous-wave Near-infrared Topography System and Its Clinical Application.

We developed a reflectance continuous-wave near-infrared spectroscopy topography system with multi-source and multi-detector sensor head. A single wavelength (808 nm) laser diode is used as the original light source. With different-measurement approach, we can reconstruct images representing the variety of cerebral blood volume in clinical applications. Phantom experiments have been taken to verify the performance of the system. We also took clinical experiments for brain activities research during acupunctures and have obtained some primarily results.