Impact of Imprecision of the Time Delay on Imaging Result in Confocal Algorithm

The confocal microwave imaging (CMI) algorithm, which is used in radar imaging, has been applied to microwave medical imaging (MMI) [1, 2]. In MMI, the diseased region to be imaged has different electromagnetic characteristics from that of the surroundings. Time -domain MMI system often radiates an ultra-wideband pulse and then collect the backscatter signals with an antenna array. The time delay is then compensated for every unit in the array according to the time flight to each focal point within the region of interest. The compensated signals are finally summed to calculate the pixel value of each focal point. This process is repeated to achieve the value for all focal points in a 3D space to reconstruct the image. Since the method is only constrained in the time domain, the complexity is minimal, and an image can be obtained usually in few seconds. This paper discusses the robustness of CMI in MMI. Specifically, we analyzed the variation of image contrast as errors occur in the time-delay calculation. A simplified model of breast cancer detection was implemented to study the relationship between time-shift errors and the impact on images, quantitatively.