Dose distribution verification for GYN brachytherapy using EBT Gafchromic film and TG-43 calculation

Abstract

Aim

Verification of dose distributions for gynecological (GYN) brachytherapy implants using EBT Gafchromic film.

Background

One major challenge in brachytherapy is to verify the accuracy of dose distributions calculated by a treatment planning system.

Materials and methods

A new phantom was designed and fabricated using 90 slabs of 18[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]16[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]0.2[[ce:hsp sp="0.25"/]]cm Perspex to accommodate a tandem and Ovoid assembly, which is normally used for GYN brachytherapy treatment. This phantom design allows the use of EBT Gafchromic films for dosimetric verification of GYN implants with a cobalt-60 HDR system or a LDR Cs-137 system. Gafchromic films were exposed using a plan that was designed to deliver 1.5[[ce:hsp sp="0.25"/]]Gy of dose to 0.5[[ce:hsp sp="0.25"/]]cm distance from the lateral surface of ovoids from a pair of ovoid assembly that was used for treatment vaginal cuff. For a quantitative analysis of the results for both LDR and HDR systems, the measured dose values at several points of interests were compared with the calculated data from a commercially available treatment planning system. This planning system was utilizing the TG-43 formalism and parameters for calculation of dose distributions around a brachytherapy implant.

Results

The results of these investigations indicated that the differences between the calculated and measured data at different points were ranging from 2.4% to 3.8% for the LDR Cs-137 and HDR Co-60 systems, respectively.

Conclusion

The EBT Gafchromic films combined with the newly designed phantom could be utilized for verification of the dose distributions around different GYN implants treated with either LDR or HDR brachytherapy procedures.