Treatment planning for MRI-guided laser-induced interstitial thermotherapyof brain tumors - The role of blood perfusion

MR techniques have been demonstrated to allow a reliable monitoring of lase r-induced interstitial thermotherapy (LITT). However, an adequate on-line c ontrol of this coagulation technique requires an exact therapy planning. Th e latter is mandatory to interpret the MR-monitoring data correctly to guar antee a precise laser irradiation. Moreover, it is a prerequisite for onlin e decisions if modifications of the therapeutic regimen are required. In th is work, we present a new simulation technique for LITT planning. The model accounts for the specific geometry of the treatment site, the exact config uration of the applicator, and the optical and thermal properties of the ti ssue, including changes during the heating process. The simulation results were compared with MR scans of laser-induced lesions in three patients with World Health Organization (WHO) grade II astrocytoma, Special interest was directed toward the role of blood perfusion, which was studied parametrica lly, Good agreement between the simulation results and the MR data was foun d if the appropriate blood perfusion rates were taken into account. Thus, t he model can generate valid therapy plans allowing a precise on-line contro l of laser irradiation using MR techniques. Neglecting adequate perfusion p arameters resulted in substantial errors with respect to the prediction of the final laser lesion.