Feasibility Study for Controlled Radiation Capsule for High Source Activity for Low Dose Radiation Brachytherapy

In this paper, we propose a new radiation capsule design to enable a high dose rate for a low energy radiation source Iodine-125, conventionally used for low dose radiation (LDR) brachytherapy to lower the radiation risk and reduce the treatment duration for cancer treatment. Conventional LDR has a dose rate of less than 2 Gy/day. The proposed capsule enables a high dose rate of 10 Gy/min or higher due to the ability to control the stoppage of the radiation. The release and stoppage of the radiation from the capsule is conducted by using an electromagnet that repels a permanent magnet, which controls the opening and closing of the window in the capsule. For feasibility of the new capsule design, simulations were conducted using TOPAS, which wraps and extends Geant4 simulation toolkit to make advanced Monte Carlo simulation of radiotherapy. Simulation results show that a 150-micron gold shielding blocks the radiation for a very high source activity of I-125. MATLAB is used to display the TOPAS results to compare the radiation intensity and beamwidth between a conventional LDR seed, the proposed capsule with a small 15 degree opening and a larger 120 degree opening.