Session S21.5

A Computational Tool for Quantitative Assessment of Peripheral Arteries in Ultrasound Images

M Higa*, PE Pilon, SG Lage, MA Gutierrez

University of São Paulo
São Paulo, Brazil

Ultrasound signals have been extensively used in clinic sites, by exploiting Doppler effect to measure vascular blood velocity and flow, among other parameters. Typically, a spectrum of frequencies related to the different velocities of the blood cells is presented as a curve of velocity vs. time. This information is very important because it can be used to reveal relationships between the frequency spectral pattern along the cardiac cycle and the presence of a cardiovascular disease, which can be observed in the vascular ultrasound exams.
Thus, in order to facilitate this type of study in clinical protocols involving hundreds of patients, a computational tool has been developed to process and extract quantitative data from spectral display of Doppler images, completely independent of the commercial ultrasound system used to acquire them. After calibration and selection of the region of interest defined by the user, the algorithm automatically detects the baseline and the spectrum envelope. Then, it computes the mean peak velocity and the velocity-time integral (VTI). In addition, if B-Mode images are available, an artery-wall interface detection module determines the vessel diameter and the blood flow can be obtained. Image processing techniques, such as Connected Components, Gaussian and Median filters were applied to improve the robustness of the envelope detection.
A comparative analysis between a commercial ultrasound system operated by a specialist and the present methodology included 1 to 4 systolic peak velocities and respective VTI along one cardiac cycle of 7 spectral displays of common carotid artery, 7 of brachial artery under basal condition, 9 of brachial in the reactive hyperemic response, and 7 echocardiography exams. Preliminary results using linear regression showed high correlation for both, peak velocity (r 0.99, p <0.01, 93 samples) and VTI (r 0.90, p <0.01, 93 samples), while Bland-Altman analysis points to small bias (-0.04 m/s and 9.5 cm, respectively). These findings indicate the viability of this tool. Furthermore, due to its user friendly graphical interface, it can be easily used by the clinicians for their large-scale studies of cardiovascular diseases based on Doppler ultrasound images.

(Abstract Control Number: 193)