Accuracy and precision of computer-simulated tissue temperatures in individual human intracranial tumours treated with interstitial hyperthermia.

Accurate knowledge of tissue temperature is necessary for effective delivery of clinical hyperthermia in the treatment of malignant tumours. This report compares computer-predicted versus measured intratumoral temperatures in 11 human subjects with intracranial tumours, treated with a conceptually simple 'conductive' interstitial hyperthermia system. Interstitial hyperthermia was achieved by the use of parallel arrays of implanted, electrically heated catheters. The tissue was warmed by thermal conduction and blood convection. Simulation of intratumoral temperatures was achieved by solving a modified bioheat transfer equation on a digital computer using a finite difference method. Comparison of intratumoral temperatures from simulations and measured values differed by about +/- 0.75 degrees C. Further analysis of computed temperature distributions between catheters revealed a rapidly computable relationship between the local minimum tumour temperature and nearby catheter power and temperature that accounts for effects of varying blood flow. These findings suggest that 'on-line' prediction and control of local minimum tumour temperatures are feasible with the conductive interstitial technique.