Ultrasonic Tissue Characterization of Atherosclerosis by a Speed-of-Sound

Abstract—We have been developing a scanning acoustic microscope (SAM) system for medicine and biology featur-ing quantitative measurement of ultrasonic parameters of soft tissues. In the present study, we propose a new concept sound speed microscopy that can measure the thickness and speed of sound in the tissue using fast Fourier transform of a single pulsed wave instead of burst waves used in con-ventional SAM systems. Two coronary arteries were frozen and sectioned approximately 10 m in thickness. They were mounted on glass slides without cover slips. The scanning time of a frame with 300 300 pixels was 90 s and two-dimensional distribution of speed of sound was obtained. The speed of sound was 1680 30 m/s in the thickened intima with collagen fiber, 1520 8 m/s in the lipid de-position underlying the fibrous cap, and 1810 25 m/s in a calcified lesion in the intima. These basic measurements will help in the understanding of echo intensity and pattern in intravascular ultrasound images. I