Measurement of acoustic properties of tissues using ultrasonic tissue imaging system

Abstract

Acoustic properties of living tissues are an important parameter for quantitative estimation of the tissue structure. It is very important to determine the relationship between the physical and the chemical change of tissue structure and the change of acoustic properties. We have developed ultrasonic tissue imaging system (UTIS) to measure the special distribution of acoustic properties at frequencies form 3 MHz to 50 MHz. The speed and attenuation of sound were measured by the noncontact technique based on frequency-time analysis of a reflected pulse response. From rat tissues measurement, The speed of sound in normal tissues varied minimally between individuals and was not related to body weight or age. The relationship between speed of sound and density in normal, fatty and cirrhotic livers can be fitted well on the line which is estimated using the immiscible liquid model assuming a mixture of normal liver and fat tissues. We have also measured the distribution of acoustic properties in human tissues, and obtained relationship between the sound speed and the attenuation of tissue. These findings of the relationship between tissue structure and acoustic structure are used for development of a quantitative diagnosis technique.