Initial Experience with a Microwave Imaging System for Monitoring Temperature Change in an Animal Model

We are developing a microwave system for noninvasively monitoring temperature distributions in human tissue during thermal therapy. Central to our approach is a microwave antenna array and switching matrix which allows tomographic data collection over a wide range of frequencies (300 MHz 1 GHz). The measured field values are processed by a reconstruction algorithm that creates electrical property maps which vary with temperature and show changes in temperature as a function of time through difference imaging. Initial phantom investigations suggested that our imaging device was sufficiently sensitive to thermally induced electrical property changes to expand the studies to animal models. The results presented here are from our initial experiments conducted with a saline-coupled microwave imaging system on a 5-day old live piglet. The heating was accomplished using a heated tube of water surgically implanted in the piglet's abdomen. Fiber optic temperature sensors were inserted at various positions for comparison with recovered conductivity values and the entire experiment was performed in a CT scanner to facilitate localization of the probes with respect to the heating tube, piglet geometry and microwave antenna array.