Interstitial Laser-Induced Thermotherapy (LITT): Comparison of In-Vitro Irradiation Effects of Nd:YAG (1064 nm) and Diode (940 nm) Laser

Summary The Nd:YAG laser (1064 nm) is still the most commonly used laser system for interstitial LITT. However, high-power diode lasers are gaining a foothold in medical treatment by virtue of their compactness, reliability, and portability. This study investigates the feasibility of the 940 nm diode laser application for LITT procedures and enables a comparison of tissue effects using both laser systems. An in-vitro study was performed on porcine liver and muscle tissue using a bare fiber and a cooled, diffusely scattering applicator. Different power settings and exposure time combinations were chosen depending on the applicator type. Five applications were performed for each parameter combination. As a result, a clearly demarcated coagulation could be easily identified in each experiment. Carbonization effects were found to occur earlier in diode laser applications, while Nd:YAG laser applications allowed the use of higher power levels. The diode laser allows the creation of a certain volume of coagulation in a short period of time due to the lower optical penetration depth and this is usually accompanied by carbonization. Our results have shown that the 940 nm diode laser could be a possible alternative for the Nd:YAG laser especially in the interstitial treatment of pale tissue. Besides this it can be successfully applied even for the treatment of high absorbing tissue if small coagulation volumes are needed.