2Department of Radiological Physics & Bio-Engineering, Sher I Kashmir Institute of Medical Sciences, UT of Jammu & Kashmir, Srinagar-India
3Department of Radiation Oncology, Sher I Kashmir Institute of Medical Sciences, UT of Jammu & Kashmir, Srinagar, India DOI : 10.5505/tjo.2022.3765 OBJECTIVE
Intracavitary brachytherapy is one of the most important methods of gynecological cancer treatment. The effect of attenuation by the applicators is not considered in the dose calculation method released by the AAPM TG-43. In this study, the attenuation due to various segmented vaginal cylinders made up of polyetheretherketone was measured.
METHODS
A plan created by the treatment planning system (TPS) for the patient was executed using Gafchromic
films that were taped on the surface of the applicator, and the dose recorded on the films was measured.
The same plan was also executed using a well-type ionization chamber. First, a water equivalent material,
Elasto-Gel was used in a well-type ionization chamber for charge collection, and then a segmented
vaginal cylinder was used for charge collection measurement; thus, the attenuation due to the various
segmented vaginal cylinders was obtained.
RESULTS
The doses recorded on the Gafchromic films were measured and showed that the TPS overestimated
the dose for the segmented vaginal applicators and that the maximum overestimation of the dose was
4.75% for 35 mm diameter vaginal cylinders. This was further confirmed by calculating the percentage
attenuation due to vaginal cylinders using a well-type ionization chamber.
CONCLUSION
Due to the attenuation by the various applicators used in vaginal vault brachytherapy, it can be concluded
that due to overestimation of dose by the TPS, the dose actually received by the target and the organs
at risk in vaginal vault brachytherapy are less and needs to be considered for actual dose estimation.