Development of an implantable quartz thermosensor for organ temperature monitoring using ultrasonic detection

A rod-shaped capsule (diameter 2 mm, length 7 mm) containing a quartz crystal resonator was developed for use in an implantable organ temperature sensor (thermosensor). Temperature is percutaneously determined on the basis of changes in resonant frequency with a surface probe emitting a 40 kHz ultrasonic wave. Animal liver and kidney temperatures was determined experimentally using implanted thermosensors, and human intragastric temperature was measured noninvasively by swallowing a sensor-mounted Silastic tubing.