Monitoring of temperature distribution in tissues with optoacoustic technique in real time

To improve the safety and efficacy of thermal therapy, it is often necessary to map tissue temperature in real time with submillimeter spatial resolution in order to accurately control the boundaries of heated regions and minimize thermal damage to surrounding normal tissues. Current imaging modalities fail to monitor tissue temperature in real time with high resolution and accuracy. We propose to use optoacoustic technique for accurate, real-time monitoring of tissue temperature with high (submillimeter) spatial resolution. Our previous studies demonstrated that the efficiency of optoacoustic wave generation in tissues increases linearly with temperature during uniform heating. In this study, we induced temperature gradients in treated samples and monitor temperature distribution in tissue using optoacoustic technique. Fundamental harmonic of Q-switched Nd:YAG laser was used for optoacoustic wave generation and probing of tissue temperature while the tissue temperature was also monitored with a multi-sensor temperature probe inserted in the samples. Good agreement between optoacoustic data and the tissue temperature as recorded via the probe was demonstrated. The optoacoustic technique was capable of real-time temperature distribution monitoring with submillimeter resolution and high accuracy (one degree).