You can get temperature readings from a higher-frequency transducer. My old lab worked with HIFU and the transducer I used was a combination 1MHz and 20MHz coni

You can get temperature readings from a higher-frequency transducer. My old lab worked with HIFU and the transducer I used was a combination 1MHz and 20MHz conical transducer, where the inner high-frequency one was used for non-invasive temperature measurement. You get comparable results to implantable thermocouples.