Quasi-3D Dosimetry System with Solid Polyurethane-Based Dosimeter
J Cho1,2,3*, S Jung1, J Son1, H Jin1,2, C Choi1, J Park1, J Kim1, (1) Seoul National University Hospital, Seoul, KR, (2) Biomedical Research Institute, Seoul National University Hospital, Seoul, KR, (3) Yonsei University College of Medicine, Seoul, KR
Presentations
PO-GePV-T-190 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: To evaluate a quasi-3D dosimetry system using a solid polyurethane-based dosimeter when conducting patient-specific quality assurances (QAs) in radiation therapy.
Methods: The patient-specific QA is the procedure to verify the coincidence between measurement and calculated dose distribution for intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VAMT) plans by using gamma analysis. A VAMT plan for a pancreas patient was analyzed with a criterion of both 2%/2 mm and 3%/3 mm, a threshold value of 10%, and a tolerance level of 90%. For the plan, the 2D gamma analysis was fulfilled with a MapCHECK2, and the 3D gamma analysis was performed using in-house solid polyurethane-based dosimeters and a quasi-3D phantom. The phantom was produced by drilling 25 holes of 9.4 mm in diameter and 56 mm in depth at even intervals, and it was made to be used by inserting a solid polyurethane-based dosimeter of the same size as the hole. A total of 9 solid polyurethane-based dosimeters were positioned according to the dose distribution of the plan. The 3D gamma analysis was performed on a region of interest of 5.5 mm in diameter and 35 mm in depth using a free platform for biomedical research, (3D) Slicer.
Results: For the 3D gamma analysis, the average passing rates with 2%/2 mm and 3%/3 mm criteria for relative dose distribution were 91.6% ± 1.4% and 99.4% ± 0.7%, respectively. For the 2D gamma analysis showed passing rates of 97.5%, 99.3% with 2%/2 mm and 3%/3 mm criteria, respectively.
Conclusion: The quasi-3D dosimetry system was evaluated by performing patient-specific QAs with the solid polyurethane-based dosimeters and quasi-3D phantom. As the 3D gamma index for all solid polyurethane-based dosimeters showed more than 90% for 2%/2 mm criteria, this result means there was a possibility that the quasi-3D dosimetry system was clinically acceptable.
ePosters
Keywords
Gel Dosimeter, Quality Assurance, Dosimetry
Taxonomy
TH- Radiation Dose Measurement Devices: 3D solid gel/plastic
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