Brachytherapy dosimetry parameters calculated for a 131Cs source

A comprehensive analysis of the IsoRay Medical model CS-I Rev2 Cs-131 brachytherapy source was performed. Dose distributions were simulated using Monte Carlo methods (MCNP5) in liquid water, Solid Water (TM), and Virtual Water (TM) spherical phantoms. From these results, the in-water brachytherapy dosimetry parameters have been determined, and were compared with those of Murphy et al. [Med. Phys. 31, 1529-1538 (2004)] using measurements and simulations. Our results suggest that calculations obtained using erroneous cross-section libraries should be discarded as recommended by the 2004 AAPM TG-43U1 report. Our (MC)Lambda value of 1.046 +/- 0.019 cGy h(-1) U-1 is within 1.3% of that measured by Chen et al. [Med. Phys. 32, 3279-3285 (2005)] using TLDs and the calculated results of Wittman and Fisher [Med. Phys. 34, 49-54 (2007)] using MCNP5. Using the discretized energy approach of Rivard [Appl. Radiat. Isot. 55, 775-782 (2001)] to ascertain the impact of individual Cs-131 photons on radial dose function and anisotropy functions, there was virtual equivalence of results for 29.461 <= E-gamma <= 34.419 keV and for a mono-energetic 30.384 keV photon source. Comparisons of radial dose function and 2D anisotropy function data are also included, and an analysis of material composition and cross-section libraries was performed. (c) 2007 American Association of Physicists in Medicine.