Clinical thermometry, using the 27 MHz multi-electrode current-source interstitial hyperthermia system in brain tumours

Background and purpose: In interstitial hyperthermia, temperature measureme nts are mainly performed inside heating applicators, and therefore, give th e maximum temperatures of a rather heterogeneous temperature distribution. The problem of how to estimate lesion temperatures using the multi-electrod e current-source interstitial hyperthermia (MECS-IHT) system in the brain w as studied. Materials and methods: Temperatures were measured within the electrodes and in an extra catheter at the edge of a 4 x 4 x 4.5 cm(3) glioblastoma multi forme resection cavity. From the temperature decays during a power-off peri od, information was obtained about local maximum and minimum tissue tempera tures. The significance of these data was examined through model calculatio ns. Results: Maximum tissue temperatures could be estimated roughly by switchin g off all electrodes for about 5 s. Model calculations showed that the mini mum tissue temperatures near a certain afterloading catheter correspond wel l with the temperature of the applicator inside, about 1 min after this app licator was switched off. Conclusions: Although the electrode temperatures read during heating are no t suitable to assess the temperature distribution, it is feasible to heat t he brain adequately using the MECS-IHT system with extra sensors outside th e electrodes and/or application of decay methods. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.