A Real-Time Integrated Backscatter Measurement System for Quantitative Cardiac Tissue Characterization

Abstmct-To quantify integrated backscatter of ultrasound for realtime tissue characterization of myocardium in vivo an analog system that is used in conjunction with a two-dimensionaliM-mode echocardingraphic imager was developed and evaluated. The system measures the energy contained in a portion of the received rf signal from a selected myocardial segment with a CdS acoustoelectric detector. A standard substitution technique is used to calibrate the system relative to a stainless steel reflector. Integrated backscatter is sampled at 5 ms intervals, its time-variation recorded and simultaneously integrated to yield the time-averaged integrated backscatter. Both time-varying and time-averaged integrated backscatter are displayed in real-time. Timeaveraged integrated backscatter in five dogs was -54 f 2.4 dB (SD). Cyclic variations during the cardiac cycle ranged from 5-10 dB. Both the time-averaged and time-varying features of integrated backscatter are consistent with values obtained with earlier measurement systems that required off-line analysis of data. The real-time data acquisition system developed should facilitate clinical tissue characterization with ultrasonic backscatter.