Dosimetric study of a new palladium seed

In this paper, the dosimetric parameters for a new palladium seed design: the InterSource(103,)(1) are presented as recommended by the AAPM in the TG-43 formalism. Measurements are made with LiF thermoluminescent dosimeters (size of 1mm(3)) in solid water phantoms WT1 to obtain the dose constant, the radial dose function and the anisotropy function. The TLD were calibrated at 6 MV and an energy correction factor of 1.40 has been applied. The same dose parameters are also obtained by Monte Carlo calculations (MCNP4B) in solid water and in liquid water. The calculated and the measured TG-43 functions for solid water are in excellent agreement. In WT1, the calculated dose rate constant is 0.657+/-1% and the measured value is 0.672+/-7%. The calculated value for water is 0.692+/-1%. The comparison with the previous study (Med. Phys. 27(5) (2000)) shows a very good agreement for the dose rate constant. The agreement for the radial function is poorer. For the measurements, it can be due to the difference of TLD settings. For the calculations the discrepancy could come from the different cross-section data utilized in the different Monte Carlo codes. In conclusion, the dosimetric functions for the new iodine seed InterSource(103) have been determined using the MCNP4B Monte Carlo code and TLD measurement in solid water WT1.