Planning of hyperthermic treatment for malignant glioma using computer simulation

Interstitial hyperthermia was applied using a radiofrequency generator in the treatment of four malignant glioma patients who had especially deep seated brain tumours or were at high risk. Prior to heating tumours, treatment planning based on an accurate prediction of temperature distribution is essential. The present paper introduces a novel treatment planning method and discusses its clinical efficacy. The two-dimensional finite element method was used for simulation of temperature distribution, which was calculated using the bioheat transfer equation. This technique was applied to plan treatment. Temperature was measured at two points during heating and these values were compared with those estimated by the simulation. In addition, the area of the contrast enhanced (CE) rim on the pre-heating computed tomography (CT) image was compared with the low density area of the CE rim on the post-heating CT image, which was obtained within 2 months after heating. The optimal position and number of radiofrequency (RF) electrodes to include the outside of the CE rim in the simulated area above 42 degrees C contour could be easily determined using this planning system in all cases. The temperature estimated by the simulation was in good agreement with the actual values obtained (within 0.4 degrees C). The post-heating CT image revealed that the hyperthermic procedure described herein achieved more than an 80% low density area within the CE rim in all cases (mean 86.0%). These results demonstrate that this novel treatment planning method may prove to be a clinically valuable tool in the treatment of malignant glioma with RF electrodes.