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High Accuracy Measurement of Absorbed Dose to Water Using Optically Stimulated Luminescence Dosimeter in High-Energy Photon Beam Field

S Goto1,2*, H Hayashi1, H Yamaguchi2, M Shimizu2, R Akino3, H Sekiguchi3, (1) College Of Medical, Pharmaceutical And Health Sciences, Kanazawa University, Kanazawa, Japan, (2) National Institute Of Advanced Industrial Science And Technology, Japan, (3) Nagase-Landauer, Ltd.

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: In order to establish a postal dose audit service using the Optically Stimulated Luminescence dosimeter (OSLD) for dose management of clinical linear accelerators, we would like to estimate the characteristics of the dosimeter for high-energy photon beam. The purpose of this study is to optimize a procedure for reading and analyzing the OSLD, and to propose the analytic way for precise dose evaluation.

Methods: We investigated the uncertainties related to reading and analyzing the OSLD using the Japanese primary standard field. OSLDs were placed in the water-phantom and irradiated with 6 MV photon beam. After irradiation, OSLDs were read out independently using commercially available reader; dosimeter position was reset for each read out. Then, we evaluated the uncertainty related to reading the OSLD by calculating the standard deviation of read values. We also estimated the individual sensitivity of each OSLD and its uncertainty. Finally, we calculated a combined standard uncertainty when the OSLD will be applied to absorbed dose evaluation.

Results: for 1-time reading was estimated to be 0.8%. It was found that the reading uncertainty can be reduced by 0.4% when using 5-times readings. Uncertainty concerning differences of individual sensitivity for each OSLD was 2.0%, but we can reduce this uncertainty to be 0.8% by considering the correction factor of individual sensitivity. It was found that the OSLD can evaluate the absorbed dose with 1.0% combined uncertainty.

Conclusion: evaluated the uncertainties of the OSLD for absorbed dose measurement. OSLD can perform high precision measurement by reducing the largest uncertainties; we found that reading uncertainty and uncertainty related to differences of individual sensitivities are mainly affected on the total uncertainty. We expect that OSLDs will be used in postal dose audit.

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Funding Support, Disclosures, and Conflict of Interest: This is a collaborative research with Kanazawa University, National Institute of Advanced Industrial Science and Technology and Nagase Landauer Ltd. Others of Ryuji Akino and Hiroshi Sekiguchi are employees of Nagase-Landauer, Ltd.

Keywords

Optical Dosimetry, Linear Accelerator, Quality Assurance

Taxonomy

TH- External Beam- Photons: Quality Assurance - Linear accelerator

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