Spatial dose distribution analysis of Co-60 HDR brachytherapy of cervical cancer using an AQUAJOINT®-based VIPET polymer gel dosimeter

Abstract

High-dose rate brachytherapy treatment has become more complicated with the use of three-dimensional image-guided brachytherapy (3D-IGBT) to prepare treatment plans using 3D images, such as those obtained from computed tomography (CT). In planning a 3D-IGBT, spatial measurement of dose distribution verification is recommended. In this study, the spatial dose distribution of intrauterine cavity irradiation by a Co-60 sealed brachytherapy source was acquired using an AQUAJOINT® polymer gel dosimeter. A CT/magnetic resonance imaging (MRI) compatible applicator was inserted into the gel in a bottle. It was irradiated and visualized using MRI. The image was converted to an R2 image using a DD-System (R-TECH INC, Japan), and dose distribution was evaluated using the dose–R2 response curve. The obtained dose distribution, dose profile of the radiotherapy treatment planning system, isodose curve, and gradient passing were calculated. In the dose profile, the dose difference was large near the applicator (high-dose region) and was less than ±2% in the middle-dose region. The isodose curves showed good agreement in the region of 2–6 Gy near the prescription point. The gamma analysis was 87.594% on the sagittal cross-section and 93.711% on the coronal cross-section based on the dose difference (DD)/distance to agreement (DTA) of 3%/3 mm.