Experimental determination of dosimetry parameters for Sinko 125I seed source using a modified polystyrene phantom

Successful treatment for permanent implant brachytherapy is based on accurate measurement of dosimetry parameters for the seed sources. Literature describes the application of various types of phantom to determine the AAPM TG-43 dosimetry parameters for permanent implant seeds. Previously we created a new type of phantom used to measure the dosimetry parameters of a high dose-rate Ir-192 source. In this study, we modified the phantom to suit to a common type of I-125 seed source (Sinko BT-125-1). The dose-rate constant, radial dose function and anisotropy function of this source were measured in detail and compared with the published values of other similar in-design I-125 seed sources. The experimental results exhibit fairly small measurement uncertainties and good self-consistency. The modified phantom is demonstrated on the measurement of dosimetry parameters for the Sinko BT-125-1 I-125 seed, however, it could easily be used for similar measurements of other permanent implantation seed sources.