Dose uniformity in MECS interstitial hyperthermia: the impact of longitudinal control in model anatomies

Abstract

The quality of temperature distributions that can be generated with the multi-electrode current source (MECS) interstitial hyperthermia system, which allows 3D control of the spatial SAR distribution, has been investigated. For the investigations, computer models of idealized anatomies were used. These anatomical models did not contain discrete vessels. Binary-media anatomies, containing media interfaces oriented parallel, perpendicular or oblique with respect to the long axis of the implant, represent simple anatomies which can be encountered in the clinic. The implant volume was about 40 cm3. A seven-catheter hexagonal implant geometry with a nearest-neighbor distance of 15 mm was used. In each interstitial probe between one and four electrodes with a diameter 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 conductivity 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 satisfactory, with T10-T90 of the order of 2-3 K. Treatment planning must ensure that the placement of the current source electrodes is compatible with the media configuration.

Comparison of temperature distributions in interstitial hyperthermia: experiments in bovine tongues versus generic simulations

“…For an adequate hyperthermia treatment, a homogeneous tumour temperature distribution as well as a sufficiently high temperature is needed. Tissue heterogeneities (Van der Koijk et al 1996) and especially large blood vessels (Lagendijk 1990, Roemer 1990) affect the temperature homogeneity. Treatment planning can help to diminish these temperature heterogeneities, requiring modelling of the thermal behaviour of the vasculature (Lagendijk et al 1993).…”

Temperature simulations in tissue with a realistic computer generated vessel network

“…Considering that Baish (1994) found that the statistics of the temperature distribution are insensitive to the exact organization of the vasculature, accurate predictions of tissue thermal behaviour using computer generated networks should be possible. For the comparison of various designs in hyperthermia heating equipment, thermal modelling of realistic generic vessel networks has already been proven to be useful (Van der Koijk et al 1996;Van Wieringen et al 1998).…”

Determination and validation of the actual 3D temperature distribution during interstitial hyperthermia of prostate carcinoma

“…The simulated anatomy is assumed to be homogeneous and the tissue heterogeneity of the capsula, for instance, is not taken into account and no discrete vasculature included in the modelling. Both phenomena can yield temperature heterogeneity in MECS interstitial hyperthermia as shown by Van der Koijk et al (1996. Furthermore, the perfusion level in the simulations is assumed to be homogeneous.…”