Recommendations of the American Association of Physicists in Medicine

In March 2004, the recommendations of the American Association of Physicists in Medicine sAAPMd on the interstitial brachytherapy dosimetry using I and Pd were reported in Medical Physics fTG-43 Update: Rivard et al., 31, 633–674 s2004dg. These recommendations include some minor changes in the dose-calculation formalism and a major update of the dosimetry parameters for eight widely used interstitial brachytherapy sources. A full implementation of these recommendations could result in unintended changes in delivered dose without corresponding revisions in the prescribed dose. Because most published clinical experience with permanent brachytherapy is based upon two widely used source models, the I Model 6711 and Pd Model 200 sources, in this report we present an analysis of the dosimetric impact of the 2004 TG-43 dosimetry parameters on the history of dose delivery for these two source models. Our analysis indicates that the currently recommended prescribed dose of 125 Gy for Model 200 Pd implants planned using previously recommended dosimetry parameters fAAPM Pd dose prescription: Williamson et al., Med. Phys. 27, 634–642 s2000dg results in a delivered dose of 120 Gy according to dose calculations based on the 2004 TG-43 update. Further, delivered doses prior to October 1997 varied from 113 to 119 Gy for a prescribed dose of 115 Gy compared to 124 Gy estimated by the AAPM 2000 report. For I implants using Model 6711 seeds, there are no significant changes sless than 2%d. Practicing physicians should take these results into account when selecting the clinically appropriate prescribed dose for Pd interstitial implant patients following implementation of the 2004 TG-43 update dose-calculation recommendations. The AAPM recommends that the radiation oncology community review this report and consider whether the currently recommended dose level s125 Gyd needs to be revised. © 2005 American Association of Physicists in Medicine. fDOI: 10.1118/1.1884925g