Recently, laser-induced interstitial thermotherapy (LITT) has been investigated and considered a minimally invasive treatment method to achieve deep coagulation in prostate tumor. However, excessive heating in the target region adversely affects the adjacent healthy tissue, possibly leading to thermal injury to critical organs such as urethra, sphincter, erectile nerves, and bowel. The aim of the current study was to develop a pulse-processing model to predict and manage the temperature development and thermal coagulation region during LITT-prostate cancer treatment. A CW 532-nm laser beam was expanded and then focused on the fiber connector by using a combination of concave and convex lens. A shutter was placed in-between the two lens, and all cycle parameters including exposure, delay, and duty cycle were driven by using a control system in conjunction with LabView software. The 5-W 532 nm laser system connected with the pulse–processing model was employed with a diffusing applicator to thermally coagulate liver tissue. The cyclic parameters were divided into three sequential periods: CW mode, pulse-processing mode, and laser-off mode. The results showed that after 15-s irradiation, the local tissue temperature achieved 70 °C. Based on optical and thermal properties of the tissue, the pulse-processing mode with a duty cycle of 70% (exposure time = 350-ms vs. delay time = 150-ms) was calculated and used in the experiment. Due to the pulse-processing mode, the surface temperature was initially maintained at 70 °C for 60 s with a steady-state error of less than 2 °C. The proposed pulse-processing model can be a feasible tool to provide the optimal therapeutic conditions for the LITT-prostate cancer treatment.
Van Gia Truong, Van Nam Tran, and Hyun Wook Kang, "Investigations on pulse-processing model for diffuser-assisted LITT on prostate cancer," Proc. SPIE 10852, Therapeutics and Diagnostics in Urology 2019, 1085204 (Presented at SPIE BiOS: February 02, 2019; Published: 26 February 2019); https://doi.org/10.1117/12.2507164.
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