Local backscatter ultrasonic attenuation measurements in vitro (30 to 50 MHz) of the constituents of atherosclerotic plaques

Identification of the constituents of atherosclerotic plaques (lipids, extracellular matrix, calcifications) using backscattered ultrasound could provide a means for the objective characterization of lesions that could eventually be applied in vivo. Towards this goal, backscattered rf from 33 excised segments of human aorta were acquired using a 50 MHz center frequency acoustic backscatter microscope. Within selected regions of interest (ROI) of the plaque and the media of each scanned segment, the ultrasonic attenuation (30 to 50 MHz) was estimated using a multinarrow-band technique. The composition of each ROI was assessed by histology. Fourteen ROIs were studied from each of the following tissue groups: normal media in regions free of plaque, normal media beneath atherosclerotic plaque, dense collagen, and lipids. The attenuation measured in lipidic regions was higher than that measured in either dense collagen or normal media. The slope of attenuation was also elevated in the lipidic regions of the plaque. These preliminary results demonstrate that ultrasonic attenuation offers promise as a parameter for the characterization of the composition and structure of atherosclerotic plaques which could eventually be applied in vivo