Acoustic properties of atherosclerosis of human aorta obtained with high-frequency ultrasound

The ultrasonic properties of the tissue elements in the aorta were measured using a scanning acoustic microscope (SAM). Twelve autopsied aortas were formalin-fixed, frozen and sectioned at 10 μm thickness and mounted on glass slides for SAM investigation. A specially developed SAM system operating in the frequency range of 100-200 MHz was employed, and color- coded images of the two-dimensional (2-D) distributions of attenuation and sound speed were displayed. The region-of-interest (ROI) for attenuation and sound speed measurements was determined by comparison of optical and acoustic images. The average value of the slope of attenuation was 0.61 dB/mm/MHz and the sound speed was 1568 m/s in the normal intima; 2.5 dB/mm/MHz, 1760 m/s in the calcificated lesion; 1.7 dB/mm/MHz and 1677 m/s in the fibrosis; and 0.34 dB/mm/MHz, 1526 m/s in the fatty material, respectively. Acoustic microscopy provides the basic data for understanding the IVUS imaging of atherosclerosis, as well as on the pathological features of atherosclerosis.