Integrated microwave thermal imaging system with mechanically steerable HIFU therapy device

We are developing a microwave tomographic imaging system for non-invasive monitoring of temperature changes during thermal therapy, based on the known tissue conductivity temperature dependence. As with any monitoring system, the actual integration with a therapy device is a significant challenge. The combined high intensity focused ultrasound (HIFU)/microwave imaging approach is intriguing because the necessary characteristics for the microwave data gathering (highly EM attenuating coupling liquid) are not compromised by the HIFU requirements (low ultrasound attenuating coupling liquid) since the physics of the two wave propagations are quite different. We have previously reported results for a configuration for use in breast cancer treatment where the HIFU transducer was positioned within the array of coaxial support rods of the antennas which surrounded the breast while the ultrasound beam propagated towards the breast without being obstructed by the antennas. For our new implementation, we have positioned the heating device outside the antenna array and aimed the beam directly past the monopole antennas to the target tissue within. This configuration is particularly useful for various other anatomical sites where it is not possible to position the transducer inside the antenna array, such as for vital organs in the torso. Our initial results illustrate that the ultrasound beam is not significantly impaired by the presence of the microwave antennas and that the beam is readily steerable to desired locations. Additional dynamic experiments demonstrate good correlation between actual temperature rise and conductivity decreases in targeted positions. These results set the stage for actual animal experiments.