Ultrasonic power measurement by calorimetric method using water as heating material: Investigation on thermal effects other than ultrasound

摘要

This study shows the ultrasonic power measurement method for HITU (High Intensity Therapeutic Ultrasound) by calorimetric method using water as heating material. RFB (Radiation Force Balance) method has been widely used for the ultrasonic power measurement. Recently, high-power ultrasonic has been used in medical filed such as HITU equipment. RFB, however, is difficult to measure the high ultrasound power because of some problems such as the thermal damaged of the targets. Therefore, we have started to develop a precise measurement technique of ultrasonic power by calorimetric method for high ultrasonic power standard alternatives to RFB. In this paper, we investigated the effects of heat generation of ultrasonic transducer, heat loss of water vessel, and dissolved oxygen level of water on calorimetric method. As the results, excessively high ultrasonic power was measured owing to effect of heat generation of the transducer. And, relative standard deviation of measured values by calorimetric method was decreased from 20% to 5% by using the vessel covered with thermal insulator. Finally, radiation conductance calculated from ultrasonic power measured by calorimetric method used degassed water was about 6% smaller than those of saturated water.