Breast tissue composition and breast density measurements from ultrasound tomography

It is known that breast cancer risk is greater in women with higher breast densities. Currently, breast density is measured using mammographic percent density, defined as the ratio of fibroglandular to total breast area on a two dimensional mammogram. Alternatively, systems that use ultrasound tomography (UST) create tomographic sound speed images of the patient's breast. These volumetric images can be useful as a diagnostic aid because it is also known that sound speed of tissue is proportional to the density of the tissue. The purpose of this work is to expand on the comparisons of the two imaging modalities by introducing new ultrasound tomography measurements that separate and quantify the fatty and dense tissue distributions within the breast. A total of 249 patients were imaged using both imaging modalities. By using k-means clustering, correlations beyond the volume averaged sound speed of the ultrasound images and the mammographic percent density were investigated. Both the ultrasound and mammographic images were separated into dense and fatty regions. Various associations between the global breast properties as well as separate tissue components were found.