FEEDBACK INTERSTITIAL DIODE-LASER (805 NM) THERMOTHERAPY SYSTEM - EX-VIVO EVALUATION AND MATHEMATICAL-MODELING WITH ONE AND 4-FIBERS

Background and Objective: In this study a newly developed microprocess or controlled power regulation and thermometry system integrated with a diode laser (805 nm wavelength) was evaluated with respect to temper ature distribution, effectiveness of regulation, and ability to predic t temperature distributions by computer simulation. Study Design/Mater ials and Methods: Experiments were performed in ground bovine muscle u sing either a single laser fiber or four-fibers. The target temperatur e at one (feedback) thermistor, placed 5 mm from one of the laser fibe rs, was set to 50 degrees C and was maintained by means of stepwise po wer regulation. The temperature distribution was monitored using multi ple thermistor probes. A numerical model based on the bioheat equation was used to calculate the temperature distributions. Results: Tempera ture regulation was excellent with a tendency towards better regulatio n in the four-fiber than in the single-fiber experiments. Agreement be tween calculated and measured temperatures was good. The coagulated (> 55 degrees C) and hyperthermic (>45 degrees C) volumes were 6 and 10-1 1 times larger, respectively, with four-fibers than with a single fibe r. Conclusion: It is concluded that the stepwise power regulation syst em was efficient in maintaining a stable target temperature. The resul ts indicate that the system can produce lesion volumes adequate for tr eating a relatively large tumor in a single session and that computer simulation may be useful for predicting temperature distribution. (C) 1998 Wiley-Liss, Inc.