Evaluation of an efficient calibration protocol for use in radiochromic film dosimetry for photon beams

Purpose: Films and TLDs have been the common choices for passive in-vivo dose measurement in radiotherapy. This study was carried out to introduce a new and accurate calibration method for GafChromic EBT3 films irradiated using Ir-192 photon energy from a miniature High Dose Rate (HDR) Brachytherapy source. Materials and methods: A film holder made of Styrofoam was used to hold the EBT3 film at its center. It was placed inside the mini water phantom and the films were irradiated by Ir-192 source of microSelectron HDR afterloading brachytherapy system. Two different setups: Single catheter-based film exposure and dual catheter-based film exposure were compared. The films were analyzed in three different color channels: red, green, and blue using Image J software. The dose calibration graphs were generated using the third-order polynomial equations fitted on the data points from two different methods of the calibration procedure. mean dose difference between TPS calculated and measured was analyzed. Results: The measured dose difference from the TPS calculated doses were evaluated for the three groups of dose ranges (low, medium, and high). In the high dose range, the standard uncertainty of dose difference is ±2.3%, ±2.9%, and ±2.4% respectively for the red, green, and blue color channel when the TPS calculated dose was compared with single catheter-based film calibration equation. Whereas it is observed as 1.3%, 1.4%, and 3.1% for the red, green, and blue color channels respectively when compared with the dual catheter-based film calibration equation. Conclusion: Source miniature size, reproducible positioning of the film, and catheter system inside the water medium are the major challenges in the film calibration with Ir-192 beam. To overcome these situations dual catheter-based film calibration was found more accurate and reproducible as compared to single catheter-based film calibration. Keywords- Film calibration, Brachytherapy, ImageJ software, GafChromic EBT3 films, TG235.

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“…Two measurement quantities are commonly used for film calibration such as transmittance (T) and optical density (OD) [16].…”

Section: Film Scanning and Readout Methodsmentioning

confidence: 99%

Comparison of single catheter versus dual catheter-based EBT3 film calibration for the Ir-192 beam energy

Trivedi

Singh

Oinam

2023

Biomed. Phys. Eng. Express

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“…Once the calibration is performed, RCFs can be used as dosimeters for measuring unknown doses by means of evaluation of the PV or OD. The problem of the definition of the calibration function is widely discussed in the literature [9][10][11][12][13]. Most works mainly propose the use of polynomial or exponential functions that best fit the experimental data.…”

Section: Introductionmentioning

confidence: 99%

The physics of radiochromic process: one calibration equation for all film types

2019

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A: A unique calibration equation for all radiochromic film types is proposed. The determination of this equation comes from an analogy that the authors made between the radiochromic and photographic processes. Photography dynamics is ruled by a differential equation, the logistic equation, describing phenomena of growth versus competition. A solution of the logistic equation is the Green-Saunders equation which was used for the first time by the same authors in a previous referred work for the calibration of a set of EBT3 Gafchromic films. Since this equation has a fundamental physical interpretation, the fitting parameters also represent important physical quantities and two of them in particular fix the film dynamics; one being the contrast and the other the abscissa of the inflection point of the sensitometric curve. In order to show the validity of this approach for more than one radiochromic film type, two sets of radiochromic films, the B3 and HD-V2 Gafchromic films were exposed to several known doses and the Green-Saunders equation was found to perfectly fit the experimental data. A comparison with the same procedure used for EBT3 Gafchromic films is proposed. The findings of this work are an important step forward in the understanding of an interesting and widely used dosimetry technique.

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A Monte Carlo approach for predictive tools in gamma irradiator: a review

Saputro,

Nuraeni

2024

J Radioanal Nucl Chem

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Evaluation of an efficient calibration protocol for use in radiochromic film dosimetry for photon beams

Cited by 9 publications

References 28 publications

Comparison of single catheter versus dual catheter-based EBT3 film calibration for the Ir-192 beam energy

Comparison of single catheter versus dual catheter-based EBT3 film calibration for the Ir-192 beam energy

The physics of radiochromic process: one calibration equation for all film types

A Monte Carlo approach for predictive tools in gamma irradiator: a review

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