Feedback interstitial diode laser (805 nm) thermotherapy system: ex vivo evaluation and mathematical modeling with one and four-fibers

Lasers Surg Med. 1998;22(2):86-96. doi: 10.1002/(sici)1096-9101(1998)22:2<86::aid-lsm4>;2-s.


Background and objective: In this study a newly developed microprocessor controlled power regulation and thermometry system integrated with a diode laser (805 nm wavelength) was evaluated with respect to temperature distribution, effectiveness of regulation, and ability to predict temperature distributions by computer simulation.

Study design/materials and methods: Experiments were performed in ground bovine muscle using either a single laser fiber or four-fibers. The target temperature at one (feedback) thermistor, placed 5 mm from one of the laser fibers, was set to 50 degrees C and was maintained by means of stepwise power regulation. The temperature distribution was monitored using multiple thermistor probes. A numerical model based on the bioheat equation was used to calculate the temperature distributions.

Results: Temperature regulation was excellent with a tendency towards better regulation in the four-fiber than in the single-fiber experiments. Agreement between calculated and measured temperatures was good. The coagulated (> 55 degrees C) and hyperthermic (> 45 degrees C) volumes were 6 and 10-11 times larger, respectively, with four-fibers than with a single fiber.

Conclusion: It is concluded that the stepwise power regulation system was efficient in maintaining a stable target temperature. The results indicate that the system can produce lesion volumes adequate for treating a relatively large tumor in a single session and that computer simulation may be useful for predicting temperature distribution.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cattle
  • Computer Simulation
  • Hyperthermia, Induced / instrumentation*
  • Lasers*
  • Models, Theoretical
  • Muscle, Skeletal / surgery