Fundamental, formational, and practical challenges in microwave inverse scattering for medical imaging of the breast

Microwave frequency electromagnetic illumination is widely investigated for application to medical imaging. In particular, the breast is an excellent candidate for microwave medical imaging research given the application's technical viability and epidemiological relevance. From a technical perspective, waves scattered from the fibroglandular tissue structures are measurable with practical hardware, due to the accessibility of the breast to multi-view illumination and the relatively low loss of the adipose tissue which comprises much of the interior. From a public health perspective, since breast cancer has the highest morbidity and second highest mortality rates among women, any improvements over the current screening and detection methodologies may have a significant impact. Microwave imaging has the potential to address several shortcomings in contemporary medical imaging technology: the illumination is low-power and non-ionizing, the hardware comparatively portable and inexpensive, and the microwave frequency dielectric contrast between malignant and normal tissue provides a physical basis for tumor detection.;Investigations by the research community into the clinical utility of microwave images of the breast have been largely inconclusive. Challenges have been encountered including insufficient image resolution, uncertain sensitivity and specificity of tumor detection, and stringent requirements on measurement and modeling accuracies. Our research objective is to further the understanding of the fundamental limitations and potential imaging performance of microwave breast imaging. State-of-the-art numerical breast phantoms, realistic in both anatomical structure and physical properties, are used to ensure faithful simulations of clinical data. Phantoms with varied density of healthy fibroglandular tissue are studied to reveal modest imaging performance with potential for density assessment. Phantoms with contrast-enhanced tumors are imaged differentially to show the measurable perturbation of the scattering data by exogenous agents. A method of analysis of the scattering data is implemented to estimate an upper-bound on image quality relative to various design and error considerations. The totality of this research suggests that optimal design of measurement systems and further development of imaging methods may lead to clinically relevant microwave images of the breast.