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Three-dimensional source position verification in image-guided high-dose-rate brachytherapy using an XCT-based gel
Miki Yonemura1, Hidenobu Tachibana1, Toru Kojima2
1Radiation Safety and Quality Assurance Division, National Cancer Center Hospital East, Chiba, Japan.
Medical Physics
|October 26, 2024
Summary
This study introduces an X-ray computed tomography (XCT)-based gel dosimeter for efficient quality assurance in image-guided brachytherapy (IGBT). The novel dosimeter accurately verifies 3D source dwell positions, enhancing treatment workflow precision.
Area of Science:
- Medical Physics
- Radiation Oncology
- Dosimetry
Background:
- Comprehensive quality assurance (QA) for high-dose-rate brachytherapy (HDR-BT) workflows, including imaging, planning, and irradiation, is often lacking.
- Current QA for source dwell position verification is typically limited to one or two dimensions.
- Magnetic resonance imaging (MRI)-based gel dosimetry is effective for 3D dose verification in image-guided brachytherapy (IGBT), but MRI scanners are not universally accessible and scanning is time-consuming.
Purpose of the Study:
- To design and develop an efficient X-ray computed tomography (XCT)-based polymer gel dosimeter for QA.
- To enable a seamless workflow for image-guided brachytherapy (IGBT) using a novel gel dosimeter compatible with XCT.
Main Methods:
- A modified polymer gel dosimeter was developed for direct insertion of brachytherapy applicators.
- The gel dosimeter was evaluated for reproducibility of source dwell positions, detectability of positional errors, effect of transfer tube looping, inter-observer variation, and gel robustness.
- Source dwell positions were determined using XCT by analyzing irradiated volumes in pre- and post-irradiation images, and compared with planned positions.
Main Results:
- The developed gel dosimeter exhibited 1250% greater hardness than previous formulations.
- QA testing, including CT acquisition, planning, irradiation, and analysis, was completed in approximately one hour.
- Source dwell position verification demonstrated high precision, with average displacements within 0.5 mm for reproducibility and < 1 mm for detecting introduced errors (except along the source path), and minimal inter-observer variation (< 0.57 mm).
Conclusions:
- The XCT-based gel dosimeter provides a precise and efficient method for verifying 3D source dwell positions in IGBT.
- This technology facilitates a seamless QA workflow for image-guided brachytherapy, improving treatment accuracy and efficiency.
