Confocal microwave imaging for breast tumor detection: comparison of immersion liquids

Microwave imaging for breast cancer has been proposed as an alternative or complementary breast imaging technique. The physical basis for tumor detection with microwave imaging is the contrast in dielectric properties of normal and malignant breast tissue. One approach to active microwave imaging of the breast is confocal microwave imaging (CMI). CMI locates tumors using energy reflected from the breast after illumination by an ultra-wideband signal. In one configuration for CMI, a woman lies on her stomach with the breast naturally extending through a hole in the examination table. The illuminating antenna is positioned at a distance from the skin, and physically scanned to a number of locations. Both the antenna and breast are immersed in a low loss liquid for better matching. Previously, our investigations focussed on detection and localization of tumors in a 2D cross section of a simple breast model. We now present 3D localization of tumors achieved with 2 different immersions liquids, one similar to breast tissue and the other similar to skin. For both systems, a 6 mm diameter tumor is reliably detected and localized in 3D. The results do not indicate a clear advantage to selecting either liquid.