Ultrasound computed tomography for quantitative breast imaging

Ultrasound computer tomography is an emerging medical imaging modality with promising capabilities for breast cancer screening. It allows studying several acoustical properties of the tissues. The transmission modality of USCT provides maps of the speed of sound and the acoustic attenuation of the tissues. The mentioned properties offer high resolution and excellent contrast tissue representation. The levels of contrast in a speed of sound map are comparable to the ones obtained in a mammogram as this property is well correlated with the density in the tissues. On the other hand, the acoustic attenuation is expected to provide enhanced levels of contrast compared to mammography, due to a higher tissue type dependence, improving the detection of malignancies. This work presents preliminary results for acoustic attenuation and speed of sound reconstruction using a ray-tracing algorithm. We investigated experimental data from the acquisition of a tissue-mimicking phantom. The results were compared with an estimation of the X-ray attenuation coefficient (25 keV) of the phantom (information provided by mammography) to demonstrate the improvements in terms of contrast when acoustic attenuation maps are employed. Further tests are required, but these results show the potential of the USCT maps to identify malignant tissues in the breast.