Dosimetric characteristics of the bests double-wall 103Pd brachytherapy source.

103Pd and 125I brachytherapy sources are being used for interstitial implants in tumor sites such as the prostate. Recently, a double-wall 103Pd source has been introduced, which has a design different from that of sources presently on the market. Dosimetric characteristics (dose rate constant, radial dose function, and anisotropy function) of this source were experimentally and theoretically determined following the AAPM Task Group 43 recommendations and were related to the October 10, 2000 revision of the NIST 1999 SK Standard for 103Pd. Measurements were performed in a Solid Water phantom using LiF thermoluminescent dosimeters. For these measurements, slabs of Solid Water phantom material were machined to accommodate the source and LiF TLD chips of dimensions (3.1 x 3.1 x 0.8 mm3) and (1.0 x 1.0 x 1.0 mm3). The TLD chips were surrounded by at least 10 cm of Solid Water phantom material to provide full scattering conditions. The Monte Carlo simulations were performed in Solid Water and liquid water using the PTRAN code. The results of this investigation show an excellent agreement (within 5%) between the measured (0.67+/-8% cGy h(-1) U(-1)) and calculated (to be 0.65+/-3% cGy h(-1) U(-1)) dose rate constant in Solid Water. The Monte Carlo calculated dose rate constant of the Best 103Pd in water was found to be 0.67+/-0.02 cGy h(-1) U(-1). The radial dose function, g(r), of the new 103Pd source was measured at distances ranging from 0.5 and 7 cm using LiF TLD in Solid Water phantom material. Moreover, the radial dose function of the new source was calculated in liquid water and Solid Water at distances ranging from 0.1 to 7 cm using the PTRAN Monte Carlo Code. The anisotropy function, F(r, theta), of the new 103Pd source was also measured in Solid Water and calculated in both Solid Water and water phantom material. From the anisotropy functions, the anisotropy factors, and anisotropy constant were calculated for each medium. The results indicated that the measured anisotropy constant of the Best 103Pd source in Solid Water was 0.89+/-5%. Complete dosimetric data are described in this manuscript.