Abstract
Commercially available radiochromic films are primarily designed for clinical X-ray dosimetry. These films change color upon exposures to radiation as a result of solid-state polymerization (SSP). Built on a previous model developed for SSP upon exposures to ultraviolet (UV) radiation, a new model was developed in the present work for X-ray-induced coloration in Gafchromic EBT3 films. Monte Carlo simulations using the Monte Carlo N-Particle (MCNP) code were employed to model the transport and interaction of photons and the generated secondary electrons within the film active layer. The films were exposed to continuous-energy photon beams. The dose DE in the external radiation detector (i.e., ionization chamber) was determined and the realistic dose DA in the film active layer was then obtained using the calibration coefficient R (=DA/DE). The finite element method (FEM) was used to solve the classical steady-state Helmholtz equation using the multifrontal massively parallel sparse direct solver (MUMPS). An extensive grid independence test was carried out and the numerical stability of the present model was ensured. The reflected light intensity from the film surface was used to theoretically obtain the net reflective optical density of the film exposed to X-ray. Good agreement was obtained between the experimental and theoretical results of the net reflective optical density of the film. For X-ray doses >~600 cGy, due to the already formed densely cross-linked structure in the active layer of the EBT3 film so further bond formation was less likely, the reflected light intensity from the film surface increased at a relatively lower rate when compared to those for dose values <~600 cGy.
Highlights
Available radiochromic films were designed for X-ray dosimetry [1], where coloration of the films was used to obtain the dose–response relationship
We built on a previous model developed for solid-state polymerization (SSP) to develop a new model
We built on a previous model developed for SSP to develop a new model for X-ray-induced coloration in EBT3 films
Summary
Available radiochromic films were designed for X-ray dosimetry [1], where coloration of the films was used to obtain the dose–response relationship. Monte Carlo simulation was employed to model the interactions of X-ray photons and the generated secondary electrons in the EBT3 film active layer using the Monte Carlo N-Particle (MCNP) code package [4]. The realistic amount of energy transferred to the EBT3 film active layer was obtained through Monte. Materials and Methods monomers in the EBT3 film active layer [9], was used to obtain the density changes of the EBT3 film. The density of the unexposed film active layer was used to further refine the results examined by carefully relaxing the system at the desired exposed energy and temperature The experimental employed in which the present work with the modeled data temperature here) atdata a specific pressure, correlated withfor thecomparison energy irradiating the films. PTW, Freiburg, Germany) and ranged from ~11 to 1500 cGy [10]
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