DOSE UNIFORMITY IN MECS INTERSTITIAL HYPERTHERMIA - THE IMPACT OF LONGITUDINAL CONTROL IN MODEL ANATOMIES

The quality of temperature distributions that can be generated with th e multielectrode current source (MECS) interstitial hyperthermia syste m, which allows 3D control of the spatial SAR distribution, has been i nvestigated. For the investigations, computer models of idealized anat omies were used. These anatomical models did not contain discrete vess els. Binary-media anatomies, containing media interfaces oriented para llel, perpendicular or oblique with respect to the long axis of the im plant, represent simple anatomies which can be encountered in the clin ic. The implant volume was about 40 cm(3). A seven-catheter hexagonal implant geometry with a nearest-neighbour distance of 15 mm was used. In each interstitial probe between one and four electrodes with a diam eter of 2.1 mm were placed along an 'active section' with a length of 50 mm. The electrode segments had lengths of 50, 20, 12 and 9 mm. This study shows that even with high contrasts in electrical and thermal c onductivity in the implant it remains possible to obtain satisfactory temperature distributions with the MECS system. Due to its 3D spatial control the temperature homogeneity in the implant can be made quite s atisfactory, with T-10 - T-90 of the order of 2-3 K. Treatment plannin g must ensure that the placement of the current source electrodes is c ompatible with the media configuration.