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


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.


CONCLUSIONS
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.
Ivarsson
K
K
Department of Surgery, Lund University, Sweden.
Olsrud
J
J
Sturesson
C
C
Möller
P H
PH
Persson
B R
BR
Tranberg
K G
KG
D000818:Animals; D002417:Cattle; D003198:Computer Simulation; D006979:Hyperthermia, Induced / Q000295:instrumentation*; D007834:Lasers; D008962:Models, Theoretical; D018482:Muscle, Skeletal / Q000601:surgery