Simplified treatment planning for interstitial laser thermotherapy by disregarding light transport: a numerical study.
OBJECTIVE
The objective was to investigate the effect of light transport on the temperature distribution and the coagulated volume under conditions relevant to interstitial laser thermotherapy (ILT) of tumors in the human liver.


METHODS
Temperature distributions and coagulated volumes produced with a diffusing laser fiber or a conductive heat source, at equal output power, were numerically calculated for tissue with different optical penetration depths. Four irradiation times (5, 10, 20, and 30 min) were studied. A three-dimensional finite-element model was used to calculate the temperature distribution during heating with four conductive heat sources (no light emission). Results were compared with measured temperature distributions during laser irradiation in a gel phantom with known optical properties.


RESULTS
Numerical calculations showed that the influence of light transport on the coagulated volume was negligible in tissue with optical penetration depths below 3-4 mm at all studied irradiation times. The phantom experiment indicated good agreement with the calculated temperature distribution, both with a single diffusing laser fiber and with four fibers.


CONCLUSIONS
Light transport influences coagulated volumes only slightly under conditions presented in this work, which is relevant to ILT of tumors in the human liver.
Olsrud
J
J
Department of Radiation Physics, Lund University Hospital, SE-221 85 Lund, Sweden. johan.olsrud@mse.dll.se
Wirestam
R
R
Persson
B R
BR
Tranberg
K G
KG
D046508:Culture Techniques; D006358:Hot Temperature; D006801:Humans; D017075:Laser Coagulation / Q000379:methods*; D008027:Light; D008099:Liver / Q000473:pathology / Q000601:surgery; D008113:Liver Neoplasms / Q000175:diagnosis / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008954:Models, Biological; D019047:Phantoms, Imaging; D011467:Prostate / Q000473:pathology / Q000601:surgery; D012680:Sensitivity and Specificity