Abstract
The ultrasonic attenuation (As) and the propagation velocity (Vs) in the human coronary artery (CA) intima were measured to evaluate the progression of atherosclerosis of CA wall using acoustic microscopy. We used an ultrasonic tissue characterization system with a scanning acoustic microscope (HSAM-500S, 450MHz). CA specimens were obtained by autopsy from 52 patients and cut into rings 4 microns thick. Based on the pathological findings in the intima with an optical microscope, we classified them into 3 groups: normal (21 specimens), early stages of sclerosis (24 specimens), and advanced stages of sclerosis (7 specimens). The relationships between age and As, and age and Vs were not statistically significant. Significantly, As was lower in the early stage (1.7±0.6dB), and higher in the advanced stage (5.4±0.8dB) than in normal (2.5±0.5dB), while Vs was slower in the early stage (1, 611.9±53.0m/s), and faster in the advanced stage (2, 031.4±145.0m/s) than in normal (1, 757.8±90.4m/s). In summary, both As and Vs were not significantly affected by age, but were mainly influenced by pathological atherosclerotic change. In addition, both parameters showed non-linear change as compared with the optical findings of CA. Because PV is proportional to the square root of the elastic modules, As is faster in harder tissue. We therefore concluded that CA intima in optically defined early stages of disease showed an initial softening as compared with normal tissue, and this was followed by increasing hardening in the advanced stage as a result of progressing fibrosis and calcification.
