Dosimetric characteristics of the InterSource103 palladium brachytherapy source

Pd-103 brachytherapy sources are being used for interstitial implants in tumor sites such as the prostate. Recently, the InterSource(103) palladium source has been introduced, which has a design different from that of other sources presently on the market. Dosimetric characteristics (i.e., dose rate constant, radial dose function, and anisotropy function) of this source were experimentally and theoretically determined following the AAPM Task Group 43 (TG-43) recommendations and were related to the 1999 NIST calibration assigned to this source [S-k, 99std]. Measurements were performed in a solid water phantom using LiF thermoluminescent dosimeters. The measured data was compared with Monte Carlo simulations performed in solid water using the PTRAN code. The calculations were then performed in liquid water to obtain the dosimetric information for clinical applications as per TG-43 recommendation. The results indicated that the dose rate constant, Lambda, of the InterSource(103) palladium source was 0.664 +/- 5% cGy/h/U using TLD measurements and 0.660 +/- 3% cGy/h/U using Monte Carte simulations in solid water. The calculated value in liquid water was found to he 0.696 +/- 3% cGy/h/U. The radial dose function, g(r), of the new Pd-103 source was measured at distances ranging from 0.5 to 10 cm using LiF TLD in solid water phantom material. The Monte Carlo simulations were performed at distances ranging from 0.1 to 10 cm from the source center in solid water and liquid water. The anisotropy function, F(r, theta), was measured at distances of 2, 3, 5, and 7 cm from the source center and calculated at distances of 0.5, 1, 2, 3, 5, and 7 cm from the source center. Complete dosimetric data are described in this paper. Per TG-43, the values reported in water should be used for clinical treatment planning systems. (C) 2000 American Association of Physicists in Medicine. [S0094-2405(00)03205-3].