Premium
SU‐E‐T‐378: Radiochromic Film Based Reference Dosimetry System for 192Ir Brachytherapy Sources
Author(s) -
Aldelaijan S,
Mohammed H,
Tomic N,
Liang L,
Deblois F,
Sarfehnia A,
AbdelRahman W,
Seuntjens J,
Devic S
Publication year - 2011
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 - 10.1118/1.3612332
Subject(s) - dosimetry , brachytherapy , monte carlo method , materials science , calibration , homogeneity (statistics) , absorbed dose , radiation , nuclear medicine , dose profile , optics , physics , computer science , radiation therapy , medicine , mathematics , statistics , quantum mechanics , machine learning
Purpose: Comparison between radiochromic film reference dosimetry system calibration curves established in water and Solid Water(TM) for high dose rate (HDR) 192‐Iridium brachytherapy source is described and assessed. Accordingly, a new reference dosimetry system protocol for HDR 192‐Iridium using the latest EBT‐2 model GAFCHROMIC(TM) film is suggested. Methods: Calibration curves were established in water and Solid Water(TM) using pieces of EBT‐2 GAFCHROMIC(TM) film irradiated with HDR 192‐Iridium brachytherapy source for a dose range from 0 to 50 Gy. A parallel‐opposed beam setup was specially designed to allow the positioning of the HDR source into two channels (catheters) with the film piece positioned mid‐way between them. This setup increases the dose homogeneity region over the film piece and reduces the positional uncertainty with respect to the radiation source. Responses of dosimetry systems were compared for irradiations in water and Solid Water(TM) by scaling the dose between media through Monte Carlo‐calculated conversion factor simulated for the two setups.Results: Monte Carlo calculated conversion factor, which converts dose delivered to the sensitive layer of the film in water to a dose delivered to the sensitive layer of the film in Solid Water(TM), was found to be 0.9941±0.0007. The EBT‐2 GAFCHROMIC(TM) film based reference dosimetry system described in this work can provide an overall one‐sigma uncertainty in measured dose of 2% for doses above 1 Gy Conclusions: Experimental confirmation of the Monte Carlo‐calculated factor that shows dose difference between measurements in water and Solid Water(TM) was provided. The remaining 0.6% difference between measurements in both media shows that Solid Water(TM) is a viable alternative to water as a reference medium in establishing the calibration curve at 192‐Iridium energy. Response curves utilizing green color channel only has shown superior precision if used alone in dosimetry for dose range that extends up to 50 Gy. This work was supported by the Natural Sciences and Engineering Research Council of Canada contract No. 386009. Saad Aldelaijan would like to acknowledge Saudi Food & Drug Authority for financial support during his graduate studies.