[Clinical implications of ultrasonic tissue characterization for atherosclerotic carotid intima-media].

: Current imaging modalities, such as ultrasonic tissue characterization, have enabled accurate determination of the composition of atherosclerotic plaque of excised aortic tissue. The aim of this study is to compare integrated backscatter (IBS) echo signals of the intima-media complex of human carotid arteries between young and elderly subjects, and to evaluate the ability of ultrasonic tissue characterization. We compared the difference in ultrasonic parameters between the carotid arteries of young healthy subjects (n = 27, 25 +/- 1 y.o.) and elderly subjects (n = 55, 75 +/- 4 y.o.). Intima-media thickness (IMT) and calibrated IBS value (C-IBS: Tissue IBS-vessel lumen IBS value) were measured. The IMT values of young and elderly subjects were 0.54 +/- 0.03 and 1.08 +/- 0.07 mm, respectively (p < 0.01). C-IBS of elderly subjects (11.7 +/- 0.8 dB) was significantly higher than that of young subjects (6.9 +/- 0.7 dB). Significantly wider standard deviation of C-IBS value in each individual was observed in elderly subjects (mean +/- SE of individual standard deviation in C-IBS: 4.2 +/- 0.9 dB) compared with that in young subjects (1.7 +/- 0.3 dB). This might reflect varied composition of atherosclerotic plaques in elderly subjects. IBS analysis would become a promising method to distinguish plaque composition quantitatively and to assess the stability of plaques in clinical setting.