A theoretical evaluation of the performance of the Dartmouth IMAAH system to heat cylindrical and ellipsoidal tumour models.

The Dartmouth interstitial microwave antenna array hyperthermia (IMAAH) system was evaluated based on its ability to heat idealized three-dimensional cylindrical and ellipsoidal tumour models with lengths between 2 and 16 cm. The evaluation was based on computer simulations of the three-dimensional temperature distributions produced by the explicit theoretical power deposition pattern of resonant dipole antenna arrays driven at 433, 915 and 2450 MHz. The theoretical calculations were performed using three-dimensional tumour models with constant thermal and dielectric tissue properties. Each 2 X 2 cm antenna array was evaluated on the basis of its ability to heat a specified tumour volume with various blood flow patterns. The bioheat transfer equation was solved in three dimensions using a Galerkin finite-element method. In general, under the conditions of this study, in all cases examined larger percentages of the ellipsoidal tumour volumes were heated to therapeutic temperatures (greater than or equal to 43 degrees C) than the cylindrical tumours. The 2450 MHz antenna array was the most effective at heating the shorter tumours, while the 433 MHz antenna array heated the longer tumours most effectively. The antennas driven at 915 MHz were most effective at heating the medium-length tumours, especially tumours with high blood flow. The results of this computerized comparative thermal dosimetry study provide information on the feasibility of modelling tumours as simple geometries, and serve to advance three-dimensional interstitial hyperthermia treatment planning.