Digital Computer Simulation Study of a Real-Time Collection, Post-Processing Synthetic Focusing Ultrasound Cardiac Camera

Abstract

High resolution ultrasound images (90% of Rayleigh limit at all depths) were obtained by computer analysis of digitized (at 10 and 20 points per microsecond, 8 bits per point) signals detected with a 32 element lead zirconium titanate 3.0 MHz array. Every sixth element was used as a transmitter and pulsed 31 times while the signals from the remaining 31 elements were addressed sequentially by an analog switch and their signals digitized and recorded. Each pixel in the cross-sectional image was produced by calculating the inner product of a specific window function and the ensemble of digitized signals. Thus the array is mathematically focused optimally for each pixel in the image. The acquisition and storage of all received signals allows subsequent approximate calculation of spatial distributions of such parameters as reflection, index of refraction, attenuation, etc. The extension of these techniques through the use of a fast analog and digital computer interface to obtain realtime and stop-action imaging is treated. Examples of images produced by these algorithms, the time requirements of various algorithms as determined by the computation speeds of present and anticipated digital and analog processing hardware is presented. Supported in part by NIH research grants HT-4-2904, RR-7, and HL-04664. Also supported in part by a contract from the Office of Naval Research to E. M. Eyring, with whom S. A. Johnson was a part-time research associate.