Development of a dual-mode microwave-ultrasound breast imaging system
This thesis reports on the development and testing of 2-D and 3-D ultrasound (US) breast imaging systems, as well as a novel integrated microwave-ultrasound breast imaging system that uses US-derived prior information to enhance microwave imaging (MWI). The dual-mode system is designed to overcome the challenges present in current breast cancer screening and diagnostic techniques, namely, the use of ionizing radiation, the dependence on a skilled clinician to perform the scan and painful compression of the breast during imaging. The USI systems presented herein utilize a stationary array of transceivers that surround the breast being imaged. Tissue-mimicking phantoms designed to have sound-speeds similar to real breast tissue were developed, and details of their design are reported. Reconstruction results for several 2-D and 3-D phantoms are shown, demonstrating the ability of our USI system to produce quantitative images of the speed of sound inside an object of interest. The integrated dual-mode system makes use of the new 3-D USI system along with an existing air-based MWI system. Features of the dual-mode design include the ability to obtain scattered field measurements for both imaging modalities with little to no movement of the breast, as well as not requiring the breast to be compressed, nor the use of an immersion medium. A workflow for dual-mode imaging has been developed, including the investigation of several techniques for producing and incorporating US-derived prior information into the MW finite-element method contrast source inversion algorithm. Data were obtained using each imaging modality as well as the integrated system for two simple dual-mode breast phantoms, and the resulting quantitative reconstructions shown. The impact of different types of prior information on the MW reconstructions is discussed. An improved ability for tumour-detection using a simple thresholding technique is demonstrated for the dual-mode system, as compared to either system on its own.
breast imaging, microwave imaging, ultrasound imaging, breast cancer, quantitative ultrasound imaging