Improvement of Multi-Frequency Microwave Breast Imaging through Frequency Cycling and Tissue-Dependent Mapping

Two modifications of the Contrast Source Inversion (CSI) algorithm have been employed to improve resulting 2-D microwave images of the dielectric properties of synthetic breast models produced using a well-established frequency-hopping technique. First, while reconstructions from low-frequency data are often used as initial guesses for otherwise unstable higher-frequency inversions, an improvement in overall image quality can be observed when the imaginary part of the reconstructed low-frequency image is altered to reflect the identical tissue geometry as its real part when used as an initial guess during subsequent reconstructions. Second, in such frequency-hopping scenarios, rather than terminating reconstructions following inversions of the highest frequency data, “frequency cycling” (i.e., returning to the lowest frequency in the sequence) can be used to further improve reconstructions without loss of resolution or anatomical detail.