Different degrees of atherosclerosis detected by backscattered ultrasound: An in vitro study on fixed human aortic walls

Abstract

The aim of the study was to establish whether ultrasonic backscattered signals may characterize the atherosclerotic process, providing a quantitative assessment of severity. Measurements on aortic specimens were made in vitro by a transducer acting as transmitter and receiver. Two different indices were measured, one based on peak amplitude value (Vmax) and the other on fast Fourier transform (FFT) analysis of ultrasonic reflected signal (IBI). Two hundred fixed aortic wall specimens (50 normal, 50 fatty streaks, 50 fibrofatty, and 50 calcific) were first characterized ultrasonically and then pathologically, both macroscopically (before ultrasonic study) and histologically (after it). Differentiation of normal, fibrofatty and calcific specimens was achieved using Vmax. Values obtained in fatty streaks overlapped with normal wall but significantly differed from values of fibrofatty and calcific subsets. The results with IBI were similar except that the difference between normal and fibrofatty specimens was not statistically significant. Such changes in acoustic behavior of atherosclerotic walls could be due to increased deposition of highly echogenic biological materials, such as collagen, cholesterol crystals (in fibrofatty specimens), and calcium salts (in calcific ones). Therefore, backscattered signals appear to provide in vitro simple parameters indicative of changes in the arterial wall structure due to the atherosclerotic process.

In Vivo Quantitative Tissue Characterization of Human Coronary Arterial Plaques by Use of Integrated Backscatter Intravascular Ultrasound and Comparison With Angioscopic Findings

“…10,13 Several studies have documented that formalin fixation does not significantly affect the morphology and quantitative echo character of plaque tissue of human aortic walls. 5,14 This fact was also confirmed in the present study. Because the IB values of saline are similar to those of uniformly flowing blood, 15 the IB values of each category obtained from the autopsy study by use of saline were used in the in vivo study.…”

Tissue Characterization of Coronary Plaques Comparison of Integrated Backscatter Intravascular Ultrasound With Virtual Histology Intravascular Ultrasound

“…Several studies have documented that formalin fixation does not significantly affect the quantitative echo character of plaque tissue from human aortic walls. 13,14 In addition, we previously confirmed that the IB values of arteries with a constant pressure before fixation were similar to those of non-pressured arteries after fixation at the same site in a comparison of 50 cross-sections of 10 coronary arteries obtained at autopsy from 5 cadavers. 12 In that study, the Bland-Altman plot showed that the differences between the IB values of pressured arteries before fixation and nonpressured arteries after fixation were within 2 standard deviations of the mean difference; there was also an excellent correlation between the 2 methods (r=0.99, p<0.001).…”

A Histological and Clinical Comparison of New and Conventional Integrated Backscatter Intravascular Ultrasound (IB-IVUS)

“…It is possible that the fixation process by removing free water might have altered tissue characteristics; however, it has previously been shown that formalin fixation does not significantly affect the quantitative echo characteristics of plaque tissue from human aortic walls. 27,34, 35 Finally, our cohort was comprised of patients with stable atherosclerotic coronary artery disease. Patients with acute coronary syndromes were not studied because of the inability of IB-IVUS to differentiate thrombus at its different stages of evolution from other plaque constituents.…”