Development of a hybrid line dosimeter using lead (II) iodide and Gd₂O₂S:Tb for dose monitoring in brachytherapy

Abstract

In brachytherapy, a radiation source is injected into the human body, and accurate evaluation of the source location is critical for patient safety. However, identification of the source location each time is difficult. Therefore, in this study, a PbI2-based hybrid line dosimeter that can reduce drift current while measuring dose in real time was fabricated by adding Gd2O2S:Tb (0–20 wt%), and the sensitivity of the hybrid line sensor was characterized using an 192Ir source. Before creating the line dosimeter, a unit-cell sensor was fabricated to define the optimal addition of Gd2O2S:Tb. The results showed that a dosimeter with 20 wt% Gd2O2S:Tb yielded the lowest drift current, which was 92% lower than that with PbI2alone (relative standard deviation [RSD], 0.73%) to allow the most stable signal output. Evaluation of the line dosimeter showed that the signal output was stable with RSD ≤ 1.5% and R 2 ≥ 0.9990 for all 25 pixels except one. The sensitivity was high at the pixel closest to the source location, and the accuracy of the source location was as high as ±2 mm. The PbI2-based hybrid line dosimeter with Gd2O2S:Tb fabricated in this study was shown to be applicable as a dosimeter to determine the source location accurately in brachytherapy.