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Monitoring X- Energy Variation in Daily QA3 Considering Uncertainty of Detector Inserted in Daily QA 3 Device

S Han*, J Kim, M Han, K Chang, K Park, J Kim, D Kim, Department of Radiation Oncology, Yonsei Cancer Center, Seoul, 41KR,

Presentations

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

Room: AAPM ePoster Library

Purpose: study focused on evaluation for the x-energy monitoring in Daily QA3(Sun Nuclear Corporation, Melbourne, USA) considering uncertainty of ionization chamber inserted in Daily QA 3 device

Methods: were carried using x-energy (6 MV,10 MV) of Elekta Agility Linear accelerators. The variation of x-energy measured from daily QA 3 was monitored for about a month. After checking the output and beam quality of machine according to TRS-398, the base line of daily QA 3 was decided and stared monitoring the variation of x-energy. Daily QA 3 used flatness that means changes of the average ratio between the 4 corner detectors to the center detector to detect energy variation. The signal variation of each detector was evaluated for monitoring x-energy to calculate energy variation considering uncertainty of detector

Results: the case of 10 MV, the energy variation within 1.5% during the monitoring period in Daily QA3 was confirmed. The signal for the four corner detectors was, 104.647 ± 0.314, 104.287 ± 0.312, 104.246 ± 0.341,104.5.72 ± 0.307, and the central detector was 99.89 ± 0.301. On the other hand, in the case of 6 MV compared to 10 MV energy variation within the same period was found to be within 3%. The signals for the four corner detectors were 106.767 ± 0.303, 106.116 ± 0.289, 106.027 ± 0.295, 105.814 ± 0.324, and the center detector was 100.181 ± 0.375. It was found that the flatness changed by 0.27% according to the energy change. Except for the center detector of 6 MV(0.37%),the coefficient of variation for all detectors was found to be within 0.31%.

Conclusion: daily QA3 was monitored for change of x-energy and was found to be within 3%.When there was an energy change in the machine, it was confirmed that the center detector reacts sensitively among the five detectors.

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