Construction of Pulse Echo Ultrasonic Test Equipment and Acquisition of Tissue Signature Data

摘要

Work is reported on the design, fabrication and testing of equipment to measure the interaction of ultrasound with small biological samples under conditions where the biological degradation of these samples is minimized. This equipment has also been used to measure these interaction parameters for various samples of tissue. Velocity, total attenuation, and scattering measurements can be made in rapid succession on a single sample. Absorption measurement require a swept burst of ultrasound over one-third of an octave and small tissue samples; therefore, they cannot be performed rapidly on the same sample. The method used for measuring absorption coefficients is a reverberation technique similar to one used in room acoustics. It calls for two measurements of the reverberation time, one with the chamber containing saline, and the other where some of the saline has been replaced by the tissue sample. The difference between these two measurements yields the rate of decay in the tissue. It appears that the greatest part of the attenuation of ultrasound by tissue is due to scattering, not absorption. Therefore, it should be expected that scattered signals are more likely to give more useful signatures than absorption measurements. The results of studies on tumorogenesis are reported. Also, tissue interactions having diagnostic importance are noted.