Evaluation of Gafchromic EBT2 film for the measurement of anisotropy function for high-dose-rate Ir brachytherapy source with respect to thermoluminescent dosimetry

Abstract

Aim

The aim of this work was to assess the suitability of the use of a Gafchromic EBT2 film for the measurement of anisotropy function for microSelectron HDR ¹⁹²Ir (classic) source with a comparative dosimetry method using a Gafchromic EBT2 film and thermoluminescence dosimeters (TLDs).

Background

Sealed linear radiation sources are commonly used for high dose rate (HDR) brachytherapy treatments. Due to self-absorption and oblique filtration of radiation in the source capsule material, an inherent anisotropy is present in the dose distribution around the source which can be described by a measurable two-dimensional anisotropy function, F(r, θ).

Materials and methods

Measurements were carried out in a specially designed and locally fabricated PMMA phantom with provisions to accommodate miniature LiF TLD rods and EBT2 film dosimeters at identical radial distances with respect to the ¹⁹²Ir source.

Results

The data of anisotropy function generated by the use of the Gafchromic EBT2 film method are in agreement with their TLD measured values within 4%. The produced data are also consistent with their experimental and Monte Carlo calculated results for this source available in the literature.

Conclusion

Gafchromic EBT2 film was found to be a feasible dosimeter in determining anisotropy in the dose distribution of ¹⁹²Ir source. It offers high resolution and is a viable alternative to TLD dosimetry at discrete points. The method described in this paper is useful for comparing the performances of detectors and can be applied for other brachytherapy sources as well.