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Clinical thermometry, using the 27 MHz multi-electrode current-source interstitial hyperthermia system in brain
R S Kaatee1, P C Nowak, J van der Zee
1Division of Clinical Physics, Department of Radiotherapy, Daniel den Hoed Cancer Center, University Hospital Rotterdam, Groene Hilledijk 301, 3075 EA, The, Rotterdam, Netherlands.
Background And Purpose:
In interstitial hyperthermia, temperature measurements are mainly performed inside heating applicators, and therefore, give the maximum temperatures of a rather heterogeneous temperature distribution. The problem of how to estimate lesion temperatures using the multi-electrode current-source interstitial hyperthermia (MECS-IHT) system in the brain was 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 multiforme resection cavity. From the temperature decays during a power-off period, information was obtained about local maximum and minimum tissue temperatures. The significance of these data was examined through model calculations.
Results:
Maximum tissue temperatures could be estimated roughly by switching off all electrodes for about 5 s. Model calculations showed that the minimum tissue temperatures near a certain afterloading catheter correspond well with the temperature of the applicator inside, about 1 min after this applicator was switched off.
Conclusions:
Although the electrode temperatures read during heating are not suitable to assess the temperature distribution, it is feasible to heat the brain adequately using the MECS-IHT system with extra sensors outside the electrodes and/or application of decay methods.