Tissue photothermal effect based on photoacoustic temperature feedback control

Hotothermal therapy (PTT) is an alternative to surgery, which is commonly used to treat tumors in intracavitary organs. PTT involves heating the diseased tissue with radiation energy, resulting in tumor necrosis. In order to improve the safety and effectiveness of PT, it is necessary to monitor the tissue temperature in real time and regulate the laser power during PTT. Photoacoustic imaging (PAI) is a non-invasive and non-ionizing imaging method with high resolution and high accuracy. Due to the dependence of the thermal expansion coefficient on temperature, the Grüneisen parameter is linearly proportional to temperature, and the variation of the amplitude of the photoacoustic signal is related to the variation of the Grüneisen parameter. In this study, we propose a system for laser dose regulation with photoacoustic signal temperature feedback based on PID algorithm. The pulsed laser is irradiated on the sample surface, the ultrasonic probe receives the photoacoustic signal generated by the sample, and the photoacoustic signal is collected by the oscilloscope and transmitted to the computer, which generates the corresponding command to the heating laser according to the signal and changes the output power of the heating laser. The experimental results show that this method can effectively control the photothermal damage range.