Development of In Vivo Measurement System for Temperature Rise in Animal Tissue under Exposure to Ultrasound with Acoustic Radiation Force

Acoustic radiation force (ARF) has been recently used for the tissue elasticity measurement and imaging. On the other hand, it is predicted that the higher temperature rises occur. In vivo measurement of temperature rise in animal experiments is important, whereas the measurement using thermocouples have some problems such as position mismatch of a temperature measuring junction of thermocouple and a focal point of ultrasound and so on. Therefore, in vivo measurement system for solving the above problems was developed in this study. The feasibility of the developed system was verified by the experiments using a tissue mimicking materials (TMM), TMM with a bone mode, an extracted porcine liver and a bone of chicken. Moreover, relations between conditions of ultrasound irradiation and temperature rises were investigated using the system. These results showed that temperature rises at focus on the surface of bone may exceed an allowable temperature rise which WFUMB guideline recommends, even though the acoustic intensity is within the limits of acoustic output regulation in diagnostic ultrasound devices.