Experimental determination of the dosimetric characteristics for the I-Plant model 3600 125I brachytherapy source

The dosimetric characteristics for a new brachytherapy seed source (I-Plant model 3600) were measured using LiF thermoluminescent dosimeters and appropriate phantom materials in conformance with the methodology and guidance provided by the AAPM Task Group 43. The I-Plant model 3600 is the successor to the I-Plant model 3500. The major difference between these sources is that the model 3600 contains a leaded-glass core to provide radio-opacity (while the model 3500 contains a silver core), which does not produce spectral contamination upon neutron activation. The dose rate constant lambda for the model 3600 was determined to be 1.00 Gy h(-1) U(-1) (with a 6% overall relative standard deviation), compared to 1.01 cGy h(-1) U(-1) reported for the model 3500 in previous studies. The remaining dosimetric characteristics also are similar for both sources.