In the past our group has shown that the ultrasound power backscattered from subvolumes of in vitro tissue preparations is dependent on the temperature of the tissue.  The backscattered power tends to monotonically increase or decrease depending on the dominant type of scatterer within the subvolume.  We have extended this research to an in vivo system to test this hypothesis in living perfused tissue.  The animal system consisted of nude mice with implanted tumors (HT29 colon cancer line) on their hind quarters.  The mice were anesthetized with Ketamine Xylazine prior to being secured to a platform.  The platform and lower section of the mouse were submerged in a temperature controlled water bath filled with degassed water. The temperature of the mouse was measured with an implanted thermistor in a contralateral limb which had a similar implanted tumor and was similarly submerged in the water bath.  The transducer from a commercial laptop-based ultrasound system (Terason 2000, Teratech Corporation) was coupled to the target tumor through the water bath and images of the heated tumor were acquired at 0.5 ^oC increments from 37.0  to 45.0 ^oC.  These data are being analyzed in a manner similar to that used for data acquired from in vitro samples.  From these experiments we expect to learn the effects of perfusion and other physiological effects on our measure of the temperature dependence of backscattered ultrasound.  Thus far we have completed the experimental design and have run experiments on a sacrificed mouse and on a living mouse. We will report on the suitability of the experimental setup as well as analysis of the backscattered ultrasound.

Supported by NIH grant R21-CA90531