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Dosimetric characterization of a novel intracavitary mold applicator for Ir 192 high dose rate endorectal brachytherapy treatment
Author(s) -
Poon Emily,
Reniers Brigitte,
Devic Slobodan,
Vuong Té,
Verhaegen Frank
Publication year - 2006
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2364054
Subject(s) - brachytherapy , imaging phantom , shielded cable , materials science , electromagnetic shielding , dosimetry , ionization chamber , balloon , dose profile , monte carlo method , nuclear medicine , biomedical engineering , calibration , radiation therapy , physics , medicine , ionization , radiology , surgery , composite material , computer science , ion , telecommunications , statistics , mathematics , quantum mechanics
The dosimetric properties of a novel intracavitary mold applicator forIr192high dose rate (HDR) endorectal cancer treatment have been investigated using Monte Carlo (MC) simulations and experimental methods. The 28 cm long applicator has a flexible structure made of silicone rubber for easy passage into cavities with deep‐seated tumors. It consists of eight source catheters arranged around a central cavity for shielding insertion, and is compatible for use with an endocavitary balloon. A phase space model of the HDR source has been validated for dose calculations using the GEANT4 MC code. GAFCHROMIC ™ EBT model film was used to measure dose distributions in water around shielded and unshielded applicators with two loading configurations, and to quantify the shielding effect of a balloon injected with an iodine solution ( 300 mg I ∕ mL ) . The film calibration procedure was performed in water using anIr192HDR source. Ionization chamber measurements in a Lucite phantom show that placing a tungsten rod in the applicator attenuates the dose in the shielded region by up to 85%. Inserting the shielded applicator into a water‐filled balloon pushes the neighboring tissues away from the radiation source, and the resulting geometric displacement reduces the dose by up to 53%; another 8% dose reduction can be achieved when the balloon is injected with an iodine solution. All experimental results agree with the GEANT4 calculations within measurement uncertainties.