In vitro experiment using porcine artery for evaluation of ultrasonic measurement of arterial luminal surface profile.

Abstract

In early-stage atherosclerosis, the luminal surface of the arterial wall becomes rough because of detachment of endothelial cells and degeneration of the internal elastic layer. Therefore, it would be useful if minute luminal surface roughness of the carotid arterial wall, which occurs in the early stage of atherosclerosis, could be measured noninvasively with ultrasound. The injured luminal surface is believed to have roughness of a few hundred micrometers. However, in conventional ultrasonography, the axial resolution of a B-mode image depends on the ultrasonic wavelength (150μm at ultrasonic center frequency of 10MHz) because a B-mode image is constructed using the amplitude of the RF echo signal. Therefore, such surface roughness cannot be measured accurately from a conventional B-mode image. Recently, we successfully measured such minute surface profile transcutaneously using the phase shift of an ultrasonic echo from the carotid arterial wall. In our previous validation experiment, a silicone phantom with minute surface roughness of 10-20μm was measured. However, the feasibility of our proposed method has never been validated using biological tissues. In the present study, luminal surface roughness of a porcine artery was measured and the result was evaluated by comparing it with the result measured using a stylus profilometer. The root mean squared difference between the surface roughness measured by ultrasound and the stylus profilometer was 10.5μm. This result proves that our proposed method can be used to measure minute surface roughness of biological tissue.