Photo-/thermo-acoustic imaging and sensing for precision breast conserving surgery

Abstract

Breast cancer is the No.1 prevalent new cancer in female cancer now. Compared to mastectomy (removing the entire breast), breast-conserving surgery (only removing cancerous tissue), has become the preferred treatment for its better cosmetic outcome and patient healthcare. However, it is challenging for surgeons to accurately locate the tumor and completely remove it during the surgery. Consequently, it leads to prolonged surgical time and inadequate tumor margins, which requires a second operation. Currently, the reoperation rate in the U.S. is as high as 25%. This is due to the lack of intraoperative tumor margin assessment and accurate breast tumor localization tools inside the operating room (OR), making current lumpectomy far from precise. My thesis work aims to achieve precision lumpectomy through development of photo- and thermo-acoustic imaging and sensing techniques. To fulfill the first unmet need of high-speed intraoperative assessment of breast tumor margins, we developed a compact multimodal ultrasound and bond-selective photoacoustic imaging system to image the entire excised tissue in just 10 minutes. The system was validated at hospitals with fresh lumpectomy specimens from 66 patients, and it achieved a sensitivity of 85.5% and specificity of 90%, showing its potential for high-speed and accurate intraoperative assessment of breast tumor margins. Next, we addressed the second unmet need of fast and accurate breast tumor localization in the OR through development of a fiber optoacoustic guide (FOG). It resembles the current metal guide wire but broadcasts MHz ultrasound omnidirectional via photoacoustic effect and can achieve sub-mm tumor localization. With an augmented reality system, the obtained tumor location was projected as an intuitive visual guidance to minimize the interference to surgical workflow and achieve optimal surgical planning. A surgeon successfully deployed the FOG to excise a “pseudo tumor” in a female human cadaver. Lastly, to improve the patient flow and logistics in clinics with a wireless breast tumor localization tool, we developed a resonant ring antenna that converts microwave into ultrasound to realize a wireless acoustic beacon. As a proof-of-concept, the ring antenna demonstrated over 3 orders of improvement in conversion efficiency than a common contrast agent for thermo-acoustic imaging.