DEVELOPMENT OF A NOVEL ULTRASOUND/PHOTOACOUSTIC TOMOGRAPHY SYSTEM FOR BREAST CANCER IMAGING USING FULL-RING ILLUMINATION MODE

Abstract

Breast cancer is a significant health problem, not only in the United States but globally. In the last year, breast cancer was the second leading cause of cancer deaths between women in the United States. In addition, the incidence rates of invasive and in situ female breast cancer increased in all age classes between 1975 and 2014. Early detection is a critical component in effectively managing this disease. One of the challenges of early detection of breast cancer lies in the availability and accuracy of diagnostic imaging. Several modalities for early detection are currently available and in use. One of the most widely used is the mammogram. However, this x-ray based diagnostic tool has several limitations, including low sensitivity to dense breast tissue, so there is a need for additional diagnostic tools, such as ultrasound (US) imaging or biopsies to complement the mammogram. The photoacoustic (PA) imaging modality has proven to be a reliable imaging technique that shares acquisition tools with the US modality. When used together, these modalities can provide molecular- and cellular-particular imaging of tumors. In addition, ultrasound tomography (UST) equipped with a ring US transducer has been shown in recent years to produce reliable results in imaging breast cancer. Significant advantages will be achieved by combining UST and PA tomography (PAT) into one complete and seamless US/PA tomography imaging modality, which will provide a valuable set of morphological and molecular data about the breast. However, the main challenge with any breast PAT lies in the accuracy of the acoustical receiver (transducer) and the effectiveness of the tissue (breast) illumination. In this Ph.D. thesis, I will explore a novel, omnidirectional full-ring illumination method designed to illuminate a specific cross-sectional slice of breast tissue using a combination of a ring US transducer and PAT, which is referred to US/PA tomography. Preliminary results, created from multiple studies on different tissue-mimicking phantoms by utilizing full-ring illumination, have shown a significant penetration depth in a targeted cross-sectional area irrespective of vertical depth. In addition, the full-ring illumination has shown a uniform PA signal in the targeted cross-sectional slice.