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

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-dimensional/M-mode echocar-diographic 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 stEEI 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 +-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 facilitated clinical tissue characterization with ultrasonic backscatter.