Determination of Dosimetric Parameters of the Second Model of Pd-103 Seed Manufactured at Agricultural, Medical and Industrial Research School

Introduction: The use of low energy isotopes such as 103 Pd in brachytherapy for the treatment of cancers such as prostate, eye, head, neck, breast and cervix is increasing. In this regard, different models of Pd- 103 seeds have been designed and manufactured at the Agricultural, Medical and Industrial Research School (AMIRS) of Atomic Energy Organization of Iran. In this research, the dosimetric parameters of the second model of Pd-103 seed manufactured at AMIRS have been calculated and measured. Materials and Methods: The dosimetric parameters of the second Pd-103 seed manufactured at AMIRS were determined according to TG-43U1 protocol using Monte Carlo calculations (MCNP4C computer code) and measurements performed using TLD-GR200A dosimeters in a Perspex phantom. The parameters include dose rate constant, geometry function, radial dose function, anisotropy function, anisotropy factor and anisotropy constant. Results: It was found that by using MCNP4C code the calculated dose rate constant in water and Perspex was 0.706±0.001 and 0.501±0.001 cGyh -1 U -1 , respectively. Using the calculated geometry function, the radial dose function and the anisotropy function were determined by experimental and theoretical methods in water and Perspex phantom. Also, the calculated value of anisotropy constant in water was equal to 0.88. Discussion and Conclusion: A discrepancy of less than 10% between the calculated and the measured values indicates a reasonable agreement between the simulation and the measurement method. Also, the dosimetric parameters of this seed have been compared to the dosimetric parameters of the first Pd-103 seed manufactured at AMIRS and some other seeds. The obtained results indicate that the seeds manufactured at AMIRS have acceptable dosimetric parameters suitable for brachytherapy applications