Thermoluminescent dosimetry for 103Pd seeds (model 200) in solid water phantom.

Dose measurements using LiF thermoluminescent dosimeters (TLD) have been performed for single 103Pd seeds (model 200) at the center of a solid water phantom. TLD cubes 1 mm on an edge were used for measurements from 1 mm to 1 cm at 1-mm intervals. The cubes were centered along transverse and longitudinal axes and along radial lines from seed center at 10 degrees increments. TLD chips of dimension 3.1 X 3.1 X 0.89 mm were used at distances of 2, 2.5, 3, and 4 cm at 15 degrees angular intervals. Data are presented as the product of distance squared and dose rate per unit source strength, plotted versus distance and angle. At 1 cm from seed center along the transverse axis this product was found to be 0.88 cGy cm2 mCi-1h-1. A dose-rate table in polar coordinates has been formulated for use with multiseed dose distribution calculations. Comparison with data of Meigooni et al. [Endocuriether./Hyperthermia Oncol. 6, 107-117 (1990)] shows general agreement for distances of 2 cm or greater. A comparison of our transverse axis data with Russell's calculated values (Theragenics Internal Report, 4 November 1984) for an ideal point source of 103Pd shows very good agreement except at distances less than 0.5 cm, where differences are attributable to the extended source effect in the actual seed.