Supplement to the 2004 update of the AAPM Task Group No. 43 Report

Abstract

Since publication of the 2004 update to the American Association of Physicists in Medicine (AAPM) Task Group No. 43 Report (TG-43U1), several new low-energy photon-emitting brachytherapy sources have become available. Many of these sources have satisfied the AAPM prerequisites for routine clinical use as of January 10, 2005, and are posted on the Joint AAPM/RPC Brachytherapy Seed Registry. Consequently, the AAPM has prepared this supplement to the 2004 AAPM TG-43 update. This paper presents the AAPM-approved consensus datasets for these sources, and includes the following 125I sources: Amersham model 6733, Draximage model LS-1, Implant Sciences model 3500, IBt model 1251L, IsoAid model IAI-125A, Mentor model SL-125/ SH-125, and SourceTech Medical model STM1251. The Best Medical model 2335 103Pd source is also included. While the methodology used to determine these data sets is identical to that published in the AAPM TG-43U1 report, additional information and discussion are presented here on some questions that arose since the publication of the TG-43U1 report. Specifically, details of interpolation and extrapolation methods are described further, new methodologies are recommended, and example calculations are provided. Despite these changes, additions, and clarifications, the overall methodology, the procedures for developing consensus data sets, and the dose calculation formalism largely remain the same as in the TG-43U1 report. Thus, the AAPM recommends that the consensus data sets and resultant source-specific dose-rate distributions included in this supplement be adopted by all end users for clinical treatment planning of low-energy photon-emitting brachytherapy sources. Adoption of these recommendations may result in changes to patient dose calculations, and these changes should be carefully evaluated and reviewed with the radiation oncologist prior to implementation of the current protocol.

Monte Carlo calculations and experimental measurements of the TG‐43U1‐recommended dosimetric parameters of 125I (Model IR‐Seed2) brachytherapy source

“…The discrepancy between the measured and calculated anisotropy functions at different distances of 2 cm, 3 cm, and 5 cm is within experimental uncertainty ($\pm 7\%$). Figure 8 displays a discrepancy of $\pm 7\%$ between the MC calculated anisotropy function of the IR‐Seed2 source to water in water with the published data of the 6702 ${}^{125}\mathrm{I}$, IBt Model 1251L, and Mills Biopharmaceuticals (Mills Biopharmaceuticals Inc., Oklahoma City, OK) model SL‐125/SH‐125 ${}^{125}\mathrm{I}$ sources at a distance of 5 cm 3 , 15 . This figure indicates larger anisotropy functions at small angles for the International Brachytherapy InterSource125, which can be attributed to the absence of end caps on that source model.…”

“…A good agreement (within experimental uncertainties) between the measured and calculated values can be seen in this figure. Figure 5(b) shows a comparison between the calculated ${\mathrm{g}}_{\mathrm{L}}false(rfalse)$ of the Model IR‐Seed2 seed with three other available brachytherapy sources 3 , 15 . The values of ${\mathrm{g}}_{\mathrm{L}}false(rfalse)$ and ${\mathrm{normalg}}_{\mathrm{normalP}}(\mathrm{r})$ in Plexiglas and water phantoms are listed in Table 3.…”

“…These determinations were performed in accordance with the TG‐43U1 recommendations (3) . The results of these investigations were compared with the published data by the Task Group 43 report 3 , 15 . The value of the dose rate constant, Λ, in water was calculated for clinical applications and was found to be $0.992\pm 0.025\hspace{0.17em}\text{cGy}\hspace{0.17em}{\mathrm{normalU}}^{-1}{\mathrm{normalh}}^{-1}$, which is close to the dose‐rate constant of ${}^{125}\mathrm{I}$ source, for 6702, (3) MBI, (15) and IBt (15) models.…”

Brachytherapy dose‐volume histogram commissioning with multiple planning systems

“…The AAPM Task Group 43 (TG‐43) report from 1995 and updates TG‐43U1 and TG‐43U1S1 are currently recognized as the worldwide standard for low‐energy, photon‐emitting brachytherapy dose calculations 11 , 12 , 13 . The high‐energy, photon‐emitting brachytherapy dosimetry protocol is described by the joint AAPM/ESTRO High Energy Brachytherapy Dosimetry Working Group Report (14) .…”

“…Brachytherapy dosimetry parameters used in the point‐source approximation are those detailed in the updated AAPM TG‐43U1 report 12 , 13 . Specific parameters employed include a dose‐rate constant (Λ) of $0.965\hspace{0.17em}\text{cGy}\hspace{0.17em}{\mathrm{normalh}}^{-1}{\mathrm{normalU}}^{-1}$, radial dose function $false(g_{P}false(rfalse)false)$ taken in 1 cm increments, and mean lifetime (τ) of 2053 h (12) .…”