Real time breast microwave radar image reconstruction using circular holography: a study of experimental feasibility

The purpose of this paper is to assess the experimental feasibility of a novel breast microwave radar reconstruction approach, circular holography, using realistic experimental datasets recorded using a preclinical experimental setup. The performance of this approach was quantitatively evaluated by calculating the signal to noise ratio, contrast to noise ratio, spatial accuracy, and reconstruction time.

Six datasets were recorded, three corresponding to fatty cases and three containing synthetic dense tissue structures. Five of these datasets contained an 8 mm inclusion that emulated a malignant lesion. The data were acquired from synthetic phantoms that mimic the dielectric properties of breast tissues in the 1-6 GHz range using a custom experimental breast microwave radar system. The spatial accuracy and signal to noise ratio of the reconstructed was calculated for all the reconstructed images. The contrast to noise ratio of the reconstructed images corresponding to the datasets containing fibroglandular tissue regions was determined. This was done to evaluate the ability of the circular holographic method to provide images in which the responses from tumors can be distinguished from adjacent dense tissue structures. The execution time required to form the images was also measured to evaluate the data throughput of the holographic approach.

For all the reconstructed datasets, the location of the synthetic tumors in the experimental setup was consistent with its position in the reconstructed image. The average spatial error was 2.2 mm, which is less than half the spatial resolution of the data acquisition system. The average signal to noise ratio of the reconstructed images containing an artificial malignant lesion was 8.5 dB, while the average contrast to noise ratio was 6.7 dB. The reconstructed images presented no artifacts. The average execution time of the images formed using the proposed approach was 5 ms, which is six orders of magnitude faster than current state of the art breast microwave radar (BMR) reconstruction algorithms.

The results show that circular holography is capable of forming accurate images with signal to noise levels higher than 8 dB in quasi real time. Compared to BMR reconstruction algorithms tested on datasets containing dense tissue structures, the holographic approach generated images of similar spatial accuracy with higher signal to noise ratios and an acceleration factor of one order of magnitude.