Novel laser system and laser irradiation method reduced the risk of carbonization during laser interstitial thermotherapy: Assessed by MR temperaturemeasurement

Background and Objective: To establish laser interstitial thermotherapy (LI TT) for intracranial tumors, the authors investigated a method to regulate localized temperature generated by interstitial laser irradiation using mag netic resonance (MR) temperature mapping. Study Design/Materials and Methods: A diode laser system and six different types of optical-fiber system were developed for LITT. The characteristics of temperature profiles produced by each laser-fiber system were investigat ed with MR temperature measurement (the water proton chemical technique), a nd differences in the temperature profile induced by two laser-irradiation methods (continuous and intermittent) were observed. Results: All fiber systems with the exception of the diffuse-projection fib er system, created a spherical temperature profile. Carbonization sometimes occurred around the bare-end fiber tip upon high power laser irradiation. The diffuse-projection fiber system produced a cylindrical temperature dist ribution, and the temperature profile showed a more gradual temperature ele vation than the bare-end fiber. No carbonization occurred at the tip of the diffuse-projection fiber system. In addition, the utilization of the inter mittent irradiation method also increased temperature gradually. Fiber-syst em modification and intermittent irradiation reduced laser-beam intensity a nd the risk of carbonization. Conclusion: The use of a diffuse-projection fiber system which intermittent ly transmits a reduced intensity laser beam is an effective tool to regulat e temperature during LITT using MR temperature measurement. (C) 2001 Wiley- Liss, Inc.