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Photon energy dependence of the sensitivity of radiochromic film and comparison with silver halide film and LiF TLDs used for brachytherapy dosimetry
Author(s) -
Muench Philip James,
Meigooni Ali S.,
Nath Ravinder,
McLaughlin William L.
Publication year - 1991
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 - 10.1118/1.596630
Subject(s) - dosimeter , dosimetry , materials science , lithium fluoride , thermoluminescent dosimeter , photon , optics , brachytherapy , thermoluminescence , radiation , photon energy , ionizing radiation , dose profile , optoelectronics , irradiation , nuclear medicine , physics , radiation therapy , luminescence , nuclear physics , medicine
There is a new radiochromic film, a highly uniform, thin (100‐μm) detector whose sensitive layer (6 μm thick) changes from colorless to blue by dye polymerization without processing, upon exposure to ionizing radiation. Because the dose gradients around brachytherapy sources are steep, the high spatial resolution offered by film dosimetry is an advantage over other detectors such as thermoluminescent dosimeters (TLDs). This compares the photon energy dependence of the sensitivities of GafChromic film, silver halide verification film (Kodak X‐Omat V Film), and lithium fluoride TLDs (Harshaw), over the photon energy range 28 keV to 1.7 MeV, which is of interest in brachytherapy. Sensitivity of the radiochromic film is observed to decrease by about 30% as effective photon energy decreases from 1710 keV (4‐MV x rays) to 28 keV (60‐kV x rays, 2‐mm Al filter). In contrast, the sensitivity of verification film increases by 980% and that of LiF TLDs increases by 41%. The variation of the sensitivity of radiochromic film with photon energy is considerably less than that for silver halide film and similar to that for LiF TLDs, but in the opposite direction. Radiochromic film, like LIF TLDs, does not exhibit the drastic sensitivity changes below 127 keV that silver halide film exhibits. Dose distribution in the immediate vicinity of a high activity (370 GBq) brachytherapy 1 9 2 Ir source has been mapped using radiochromic film and is presented to illustrate the applicability of this new technology to brachytherapy dosimetry.