Simplified treatment planning for interstitial laser thermotherapy by disregarding light transport: A numerical study

Background and Objective The objective was to investigate the effect of lig ht transport on the temperature distribution and the coagulated volume unde r conditions relevant to interstitial laser thermotherapy (ILT) of tumors i n the human liver. Study Design/Materials and 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 a diffe rent optical penetration depths. Four irradiation times (5, 10, 20, and 30 min) were studied. A three-dimensional finite-element model was used to cal culate the temperature distribution during heating with four conductive hea t sources (no light emission). Results were compared with measured temperat ure distributions during laser irradiation in a gel phantom with known opti cal properties. Results: Numerical calculations showed that the influence of light transpor t on the coagulated volume was negligible in tissue with optical penetratio n depths below 3-4 mm at all studied irradiation times. The phantom experim ent indicated good agreement with the calculated temperature distribution, both with a single diffusing laser fiber and with four fibers. Conclusion: Light transport; influences coagulated volumes only slightly un der conditions presented in this work, which is relevant to ILT of tumors i n the human liver. (C) 1999 Wiley-Liss, Inc.