Author: Akire Trestrail ðĻâðŽ
Affiliation: University of Wisconsin ð
Purpose: To investigate the feasibility of using 125I as a HDR directional brachytherapy source.
Methods: Monte Carlo (MC) simulations were performed using the EGSnrc software toolkit. Dose rate distributions as a function of time were generated for the directional 125I source and compared to a reference 192Ir source. Relative dose distributions (RDD) were calculated on the central plane and normalized to 1 cm centered on the unshielded side of the source to evaluate dose distribution behavior. Furthermore, relevant TG-43 parameters were calculated for the source.
Results: Simulations revealed that a relatively low average energy of 28.5 keV emitted by 125I allows the source to be shielded with as little as 60 Ξm of gold. With a source diameter of 420 Ξm, and length of 1 cm, a pure cylindrical 125I source will have a dose rate after 3 months comparable to 192Ir. The source produces a range of angles 1630 wide that have an RDD âĨ 0.9, called the homogenous region (HR), and a range of angles 900 wide that have an RDD âĪ 0.15, called the shadow region (SR).
Conclusion: 125I is a feasible isotope for the development of a directional HDR brachytherapy source.