Abstract
The purpose of this study is to investigate the potential use of Ir-192 as the source for real time imaging during HDR (High Dose Rate) brachytherapy treatment. Phantom measurement was performed to determine outside of the body dose. Monte Carlo code, EGSnrcMP egs_inprz, was used for the simulation to calculate the outside of the body x-ray signal for CT reconstruction. Matlab code was developed to reconstruct the Ir-192 source and for 3D visualization in order to assess reconstructed CT resolution, signal-to-noise ratio, and imaging dose information. The measured dose was 0.67 ± 0.04 cGy, which was comparable to the Monte Carlo simulation result 0.71 ± 0.20 cGy. The reconstructed source diameter dimension was 1.3 mm compared with 1.1 mm for the real source dimension. The signal-to-noise ratio was 19.91 db following de-noising. Source position was within a 1 mm difference between programmed and simulated results. Although the Ir-192 signal is weak for CT imaging, it is possible to use it as a CT imaging x-ray source for HDR treatment localization, verification and dosimetry purposes. Further study is needed for the detailed design of an outside of the body CT-like device for use in brachytherapy imaging.
Highlights
The purpose of this study is to investigate the potential use of Ir-192 as the source for real time imaging during HDR (High Dose Rate) brachytherapy treatment
The Ir-192 signal is weak for CT imaging, it is possible to use it as a CT imaging x-ray source for HDR treatment localization, verification and dosimetry purposes
With the goal of sparing organs at risk (OARs), new radiation therapy techniques have been developed in the past two decades to treat the target while avoiding healthy tissues
Summary
With the goal of sparing organs at risk (OARs), new radiation therapy techniques have been developed in the past two decades to treat the target while avoiding healthy tissues. In 2010, Shi et al used dosimetry algorithm and inverse treatment planning to calculate threedimensional (3D) IMBT dose distributions [4]. All these studies focused on the IMBT concept and dosimetry. Image guidance is more important in brachytherapy than external treatment due to the large dose variation as a result of applicator position uncertainty. In a recent review of HDR (High Dose Rate) safety, authors reported about 8 events per 33,000 treatments each year [13]. The causes of these events were mostly due to wrong length, distance, or applicator. Imaging verification during treatment is important for preventing adverse events
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