Evaluation of Local Pulse Wave Velocity using an Image Free Ultrasound Technique

Abstract

Pulse wave velocity (PWV) measured over small arterial sections provide localized elastic characteristics, which helps assessment of the subtle progressions of various cardiovascular diseases. Several ultrasound-based techniques that are reported, require high frame rate imaging for performing accurate measurements of local PWV. In this work, an image free ultrasound method for evaluation of local PWV is proposed. The technique uses a novel dual element ultrasound probe for simultaneous capturing of A-scan frames (frame rate = 10 kHz) from two arterial sites located 35 mm apart. Our clinically validated ARTSENS technology was used to obtain high fidelity of distension waveforms by processing the acquired frames. The high frame rate acquisition enabled measurement of pulse transit time with a resolution of 0.1 ms for reliable evaluation of local PWV. The functionality of the developed prototype system was initially verified by conducting experiments on physiological flow-phantom setup. The phantom study results demonstrated that the proposed system could reliably perform local PWV measurements over short arterial segments. The performance of the measurement system was further validated by an in-vivo studied conducted on a pool of 10 young healthy subjects. The mean local PWV measured from the carotid artery for all subjects was 4.8±0.8 The prototype system could perform reliable and repeatable local PWV measurements on both phantom and human subjects over continuous cardiac cycles with the coefficient of variation less than 2.6% and 5% respectively. The proposed image-free ultrasound measurement method greatly eliminates the complexity and computational overhead associated with processing images or 2D RF data acquired at high frame rates.