Thermal management solutions for medical ultrasonic transducers subjected to energetic modes

Abstract

Increasing use of energetic modes in modern ultrasonography has made efficient thermal management mandatory in medical transducers design. In this work, efficiency of different thermal conduction paths (central, peripheral, both), as well as different heat ways out (probe nose, whole probe body housing, cable braid shield) are investigated. Starting from a typical acoustic design for a 2,8 MHz phased array, 6 mock-ups are derived, using an acoustical stack either optimized for acoustical or thermal performances. Basically, each mock-up explores a particular thermal path, using passive solutions such as thermal fin, highly conductive backing (135 W/m/K), layers (85 W/m/K), resin (2.9W/m/K), etc. Thermal performances are then assessed in air, following a measurement protocol based on IEC60601-2-37. A heating burst is sent during 10 mins. at high PRF, while an IR camera records the temperature progress at the surface of the transducer. Owing to acoustic performances differences between both stacks, driving voltage is tuned to allow comparison either at a fixed MI or a same active power. IR frames are then processed to extract, for each mock-up, the hot spot profile during the heating stage. Further analysis of its dynamic provides insight on the impact of the different thermal solutions investigated.