Estimating average dielectric properties for microwave breast imaging using focal quality metrics

Abstract

Confocal Microwave Imaging algorithms synthetically focus backscattered radar signals to create an image of the breast. Spatial focusing is achieved by delaying the received signals by the round-trip propagation delay to the voxels of interest. A key component in calculating propagation time is a good estimate of the average dielectric properties of the breast, because the accuracy of the reconstructed image varies significantly with the value of average dielectric properties used. This paper investigates the use of focal quality metrics to estimate the optimal average dielectric properties to use to reconstruct an image of the breast. Focal quality metrics have long been used to find optimally focused images in microscopy and camera systems without prior knowledge of the imaged object's location or texture. In this paper, five common focusing algorithms from autofocus and shape-from-focus applications are compared to investigate whether these focal quality metrics can be used to estimate the patient-specific average dielectric properties.