Abstract 5730: Dosimetric properties of a new thermobrachytherapy seed with ferromagnetic core for treatment of solid tumors

Abstract

Abstract Studies of the curative effects of hyperthermia and radiation therapy on treatment of cancer show a strong evidence of a synergistic enhancement when both radiation and hyperthermia modalities are applied simultaneously. Varieties of tissue heating approaches developed up to date still fail to overcome such essential limitations as an inadequate temperature control, temperature non-uniformity, and prolonged time delay between hyperthermia and radiation treatments. We propose a new self-regulating Thermobrachytherapy seed, which serves as a source of both radiation and heat for concurrent administration of brachytherapy and hyperthermia. The proposed seed is based on the BEST Seed Model 2301-I125, where tungsten marker core and the air gap are replaced with a ferromagnetic material. The ferromagnetic core 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. We present the Monte Carlo study of dose rate constant and the other TG-43 radiation characteristic factors for the proposed seed. For the thermal characteristics, we studied a model consisting of 16 seeds placed in the central region of a cylindrical water phantom using a finite-element partial differential equation solver package “COMSOL Multiphysics”. The modeling result shows that temperature of the thermoseed surface rises rapidly and stays constant around TC of the ferromagnetic material. The amount of heat produced by the ferromagnetic core is sufficient to raise the temperature of the surrounding volume to the therapeutic range. The volume of the therapeutic temperature range increases with increase of frequency or magnetic field strength. These studies demonstrate that an optimal isothermal distribution can be achieved on a target volume to match with the radiation isodose distribution for the seed configuration by tuning frequency and intensity of the alternating magnetic field. The proposed combination seed model has a high potential for implementation of concurrent brachytherapy and hyperthermia. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5730. doi:1538-7445.AM2012-5730