Comparison between thermal strain and acoustic radiation force imaging methods for estimation of heat source distribution of high-intensity focused ultrasound

In high-intensity focused ultrasound treatment, targeting its focal region prior to the thermal coagulation is required for the safety and efficacy of the treatment because the size and position of the thermally effective focal zone depend on the acoustic properties of the tissue. Acoustic radiation force impulse imaging can estimate the focal region from the displacement caused by ARF which stems from ultrasonic attenuation. Thermal strain (TS) imaging is another targeting method, which is based on temperature rise caused by tissue absorption. In this study, the TS imaging and temperature measurement by thermocouple were conducted for the same location, and a linear relationship between the TS and temperature rise was confirmed. In addition, the differences of the distribution depending upon the physical phenomena such as the thermo-acoustic lens effect and the effect of acoustic reflection were observed by comparing two imaging methods.