title: A comparison of the dose distributions between the brachytherapy 125I source models, STM1251 and Oncoseed 6711, in a geometry lacking radiation equilibrium scatter conditions.
abstract: The purpose of this study was to estimate the uncertainty in the dose distribution for the (125)I source STM1251, as measured with a radiophotoluminescent glass rod dosimeter and calculated using the Monte Carlo code EGS5 in geometry that included the source structure reported by Kirov et al. This was performed at a range of positions in and on a water phantom 18 cm in diameter and 16 cm in length. Some dosimetry positions were so close to the surface that the backscatter margin was insufficient for photons. Consequently, the combined standard uncertainty (CSU) at the coverage factor k of 1 was 11.0-11.2% for the measurement and 1.8-3.6% for the calculation. The calculation successfully reproduced the measured dose distribution within 13%, with CSU at k ≤ 1.6 (P > 0.3). Dose distributions were then compared with those for the (125)I source Oncoseed 6711. Our results supported the American Association of Physicists in Medicine Task Group No. 43 Updated Protocol (TG43U1) formalism, in which STM1251 dose distributions were more penetrating than those of Oncoseed 6711. This trend was also observed in the region near the phantom surface lacking the equilibrium radiation scatter conditions. In this region, the difference between the TG43U1 formalism and the measurement and calculation performed in the present study was not significant (P > 0.3) for either of the source models. Selection of the source model based on the treatment plans according to the TG43U1 formalism will be practical.
authors.affiliation: Graduate School of Sapporo Medical University, South 1, West 17, Chuo-ward, Sapporo, Hokkaido 060-8556, Japan tanakaken@sapmed.ac.jp.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Graduate School of Sapporo Medical University, South 1, West 17, Chuo-ward, Sapporo, Hokkaido 060-8556, Japan.
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Kamo
authors.affiliation: Graduate School of Sapporo Medical University, South 1, West 17, Chuo-ward, Sapporo, Hokkaido 060-8556, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tateoka
authors.affiliation: Sapporo Medical University Hospital, South 1, West 15, Chuo-ward, Sapporo, Hokkaido 060-8556, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Asanuma
authors.affiliation: Sapporo Medical University Hospital, South 1, West 15, Chuo-ward, Sapporo, Hokkaido 060-8556, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Sato
authors.affiliation: Sapporo Medical University Hospital, South 1, West 15, Chuo-ward, Sapporo, Hokkaido 060-8556, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Takeda
authors.affiliation: Graduate School of Sapporo Medical University, South 1, West 17, Chuo-ward, Sapporo, Hokkaido 060-8556, Japan.
authors.forename: Koh-ichi
authors.initials: K
authors.lastname: Sakata
authors.affiliation: Graduate School of Sapporo Medical University, South 1, West 17, Chuo-ward, Sapporo, Hokkaido 060-8556, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Takada
mesh_terms: D000465:Algorithms; D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D003198:Computer Simulation; D006801:Humans; D008954:Models, Biological; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D012984:Software
keywords: 125I; TG43U1; EGS5; brachytherapy; glass rod dosimeter