A universal dose–response curve for radiochromic films

Purpose: This paper presents a model for dose–response curves of radiochromic films. It is based on a modified version of single‐hit model to take into account the growth experienced by lithium salt of pentacosa‐10,12‐diynoic acid polymers after irradiation. Methods: Polymer growth in radiochromic f...

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Bibliographic Details
Published in:Medical physics (Lancaster) 2015-01, Vol.42 (1), p.221-231
Main Authors: Martín‐Viera Cueto, J. A., Parra Osorio, V., Moreno Sáiz, C., Navarro Guirado, F., Casado Villalón, F. J., Galán Montenegro, P.
Format: Article
Language:English
Subjects:
07 ISOTOPES AND RADIATION SOURCES
60 APPLIED LIFE SCIENCES
Active layer
Algorithms
calibration
critical phenomena
dosimetry
Dosimetry/exposure assessment
FILM DOSIMETRY
Fractals
Image scanners
Models, Theoretical
percolation
Polymer films
POLYMERS
radiation therapy
radiochromic films
RADIOTHERAPY
Scintigraphy
sensitometry
Therapeutic applications, including brachytherapy
Thin film growth
Uncertainty
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Summary:Purpose: This paper presents a model for dose–response curves of radiochromic films. It is based on a modified version of single‐hit model to take into account the growth experienced by lithium salt of pentacosa‐10,12‐diynoic acid polymers after irradiation. Methods: Polymer growth in radiochromic films is a critical phenomenon that can be properly described by means of percolation theory to provide an appropriate distribution function for polymer sizes. Resulting functional form is a power function featuring a critical exponent and two adjustable parameters. Moreover, these parameters act as scaling factors setting a natural scale for sensitometric curves where the dependence on channel sensitivity is removed. A unique reduced response curve is then obtained from all the color channels describing film behavior independently of film dosimetry system. Results: Resulting functional form has been successfully tested in several sensitometric curves from different Gafchromic EBT models, providing excellent agreement with experimental data in a wide dose range up to about 40 Gy and low dose uncertainty. Conclusions: The model presented in this paper describes accurately the sensitometric curves of radiochromic films in wide dose ranges covering all typical ranges used in external radiotherapy. Resulting dose uncertainty is low enough to render a reasonably good performance in clinical applications. Due to cross‐correlation, only one of the adjustable parameters is totally independent and characterizes film batches.
ISSN:0094-2405
2473-4209
DOI:10.1118/1.4903301