Dose specification for Ir-192 high dose rate brachytherapy in terms of dose-to-water-in-medium and dose-to-medium-in-medium

Gabriel Paiva Fonseca*, Asa Carlsson Tedgren, Brigitte Reniers, Josef Nilsson, Maria Persson, Helio Yoriyaz, Frank Verhaegen

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Dose calculation in high dose rate brachytherapy with Ir-192 is usually based on the TG-43U1 protocol where all media are considered to be water. Several dose calculation algorithms have been developed that are capable of handling heterogeneities with two possibilities to report dose: dose-to-medium-inmedium (D-m,D-m) and dose-to-water-in-medium (D-w,D-m). The relation between D-m,D-m and D-w,D-m for Ir-192 is the main goal of this study, in particular the dependence of D-w,D-m on the dose calculation approach using either large cavity theory (LCT) or small cavity theory (SCT). A head and neck case was selected due to the presence of media with a large range of atomic numbers relevant to tissues and mass densities such as air, soft tissues and bone interfaces. This case was simulated using a Monte Carlo (MC) code to score: D-m,D-m, D-w,D-m (LCT), mean photon energy and photon fluence. D-w,D-m (SCT) was derived from MC simulations using the ratio between the unrestricted collisional stopping power of the actual medium and water. Differences between D-m,D-m and D-w,D-m (SCT or LCT) can be negligible (
Original languageEnglish
Pages (from-to)4565-4579
JournalPhysics in Medicine and Biology
Volume60
Issue number11
DOIs
Publication statusPublished - 7 Jun 2015

Keywords

  • brachytherapy
  • Ir-192
  • dose-to-water-in-medium
  • dose-to-medium-in-medium

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