Study of the effect of tungsten shields on the radiation dose delivery in a gynecological applicator using Gafchromic film dosimetry

Abstract

Fletcher Suit Delclos applicator is employed for high dose rate intracavitary brachytherapy treatment of cervical cancer. It includes tungsten shields in the direction of bladder and rectum to limit their radiation exposure. Extent of shielding provided by these shields was measured in this study using Gafchromic film dosimetry. Films were wrapped around caps of shielded and unshielded ovoids. Dose distributions in planes above, below and on sides of the ovoid were obtained. 3D analysis of the dose profiles was carried out and results were compared with the dose distribution computed by Treatment Planning System (TPS), which does not account for the presence of tungsten shields. The difference among two demonstrates the shielding effect. For unshielded ovoid 90% of the film and TPS measurements agreed within ±5%. In case of shielded ovoid, the dose reduction of upto 20% and 25% were recorded in the anterior (bladder) and posterior (rectal) regions, respectively.