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| Small Field Output Factor Measurement and Verification Based on TRS-483 |
| ZHANG Xi,WANG Zhi-peng,WANG Kun,HUANG Ji,QI Ya-ping,LIU Fu-bin,JIN Sun-jun |
| National Institute of Metrology, Beijing 100029, China |
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Abstract To measure small field output factor, the tissue-phantom ratio (TPR20,10(10)) of the Elekta Synergy linear accelerator nominal radiation energy of 6MV and 10MV were measured using TRS-483 report method published by IAEA, which were 0.683 and 0.735.By calculating the minimum FWHM applicable to the ionization chamber, various measurable radiation field ranges of the ionization chamber were verified. The FWHM of the selected ionization chambers are between 3～4cm.By comparing the sensitive volume, linearity of measured dose and dose rate, leakage current, repeatability and stability, a total of 21 detectors from 18 different models were selected.Under the condition of TPR20,10(10)=0.683, 0.735, source skin distance (SSD) of 90cm and 100cm, 1cm×1cm,2cm×2cm, 3cm×3cm, 4cm×4cm, 5cm×5cm and 8cm×8cm square field to 10cm×10cm square field output factors were measured and multiplied by the correction factor reported by TRS-483.The maximum difference between the corrected radiation field output factor and the mean value is less than 0.025.The results show that using the correction factor reported by TRS-483 can improve the consistency of measurement of small field dose by different detectors.
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Received: 04 July 2021
Published: 18 May 2023
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2023, Vol. 44 
