Evaluation of a Novel Thermobrachytherapy Seed for Concurrent Administration of Brachytherapy and Magnetically Mediated Hyperthermia in Treatment of Solid Tumors

Concurrent hyperthermia and radiation therapy in treatment of cancer show a strong evidence of a synergistic enhancement. We designed a new self-regulating Thermo-Brachytherapy seed, which serves as a source of both radiation and heat for concurrent administration of brachytherapy and hyperthermia. The Thermo-Brachytherapy seed has a core of ferromagnetic material which produces heat when subjected to alternating electro-magnetic (EM) field and effectively shuts off after reaching the Curie temperature (TC) of the ferromagnetic material thus realizing the temperature self-regulation. For the thermal characteristics, we considered a model consisting of one seed as well as an array of 16 seeds placed in the central region of a cylindrical water phantom. Isodose distributions of these models were computed using MCNP5 Monte Carlo simulation technique. The modeling for the isothermal distribution computations performed using a finite-element partial differential equation solver package COMSOL Multiphysics. It is shown that by changing frequency and intensity of the alternating applied magnetic field, we can obtain desired isothermal distribution within the target volume. Adjustment of these two parameters allows one to match the desired isosurface dose distribution with an optimized isothermal distribution achieving optimal treatment in both modalities. We also demonstrate that the effect of tissue cooling down due to the blood perfusion could be compensated by adjusting the externally applied magnetic field parameters. In this paper, parameters effecting radiation and thermal distribution on this proposed new seed will be presented.