brachytherapy sources

Monte Carlo calculations and TLD measurements have been performed for the purpose of characterizing dosimetric properties of new commercially available brachytherapy sources. All sources tested consisted of a solid core, upon which a thin layer of 125I has been adsorbed, encased within a titanium housing. The Phar-maSeed BT-125 source manufactured by Syncor is available in silver or palladium core configurations while the ADVANTAGE source from IsoAid has silver only. Dosimetric properties, including the dose rate constant, radial dose function, and anisotropy characteristics were determined according to the TG-43 protocol. Addi-tionally, the geometry function was calculated exactly using Monte Carlo and com-pared with both the point and line source approximations. The 1999 NIST standard was followed in determining air kerma strength. Dose rate constants were calcu-lated to be 0.95560.005, 0.96760.005, and 0.96260.005 cGy h21 U21 for the PharmaSeed BT-125-1, BT-125-2, and ADVANTAGE sources, respectively. TLD measurements were in excellent agreement with Monte Carlo calculations. Radial dose function, g(r), calculated to a distance of 10 cm, and anisotropy function, F(r,u), calculated for radii from 0.5 to 7.0 cm, were similar among all source configurations. Anisotropy constants, f ¯ an, were calculated to be 0.941, 0.944, and 0.960 for the three sources, respectively. All dosimetric parameters were found to be in close agreement with previously published data for similar source configura-tions. The MCNP Monte Carlo code appears to be ideally suited to low energ