Poster — Wed Eve—16: Optoacoustic Detection of Tissue Thermal Damage

Minimally invasive thermal therapy has been investigated as an alternative treatment modality for solid tumours including breast, liver and prostate. Thermal therapy is typically delivered as a single‐fraction, stand‐alone therapy. It involves heating tissues to greater than 55 C over a period of a few minutes, which results in coagulative necrosis. It can potentially achieve highly conformal 3D coagulation volumes, exhibits sharp demarcation between treated and spared tissues, and tissue effects can be observed and thus potentially controlled in real time. This paper describes a new approach to guiding the progress of thermal therapy using optoacoustics, a technique which combines the high optical contrast and high resolution associated with near‐infrared optical imaging and ultrasound imaging, respectively. In this study, thermal lesions were induced in bovine liverex vivo via non‐contact single fiber laser heating at 810 nm. Optoacoustic signals were obtained using an optoacousticimaging system comprised of an Nd:YAG pumped Titanium‐Sapphire laser delivering 6 ns pulses and an annular array of 8, 4 MHz transducers. Optoacoustic signal increased up to 2.5 fold with heating times from 1 to 6 minutes. Furthermore, tissue coagulation was clearly visible in the optoacousticimages compared to the surrounding native tissue. The results demonstrate that optoacoustic signals are sensitive to changes in tissue optical and mechanical properties that occur when tissues are thermally damaged, and, hence, optoacousticimaging may be a suitable candidate for guiding thermal therapy delivery.