Small field output factor measurement and correction method based on IAEA report No.483 / 中华放射肿瘤学杂志

ABSTRACT

Objective The IAEA report No.483 describes the latest method of small field dosimetry.The field output factor measurement and correction methods are used to improve the accuracy and consistency of the measurement results for different type detectors.Methods The field output factors from 0.6 cm×0.6 cm to 10 cm× 10 cm were measured using IBA's CC13 ionization chamber,CC01 ionization chamber,PFD semiconductor detector,EFD semiconductor detector and Razor semiconductor detector,respectively.The field output correction factors were used to correct the measurement result.Results Compared with the corrected data,the results of ionization chamber are mainly affected by the volume averaging and the fluence perturbation effect,lead to the measurement result which is 4.70％ lower at 0.6 cm × 0.6 cm;The results of Shielded semiconductors are mainly affected by fluence perturbation effect,lead to the measurement result which is 4.80％ higher at 0.6 cm × 0.6 cm.The results of unshielded semiconductors are mainly affected by energy response and fluence perturbation effect,resulting in lower measurement results at the field size＞0.8 cm×0.8 cm,2.10％ lower at field size of 1.5 cm× 1.5 cm,higher measurement results at field size＜0.8 cm×0.8 cm and 1.1％ higher at field size of 0.6 cm×0.6 cm.Before the correction,the measurement results from different types of detectors are quite different,average standard deviation is 0.016 6.After the correction,the difference among the detectors is significantly reduced,average standard deviation is 0.006 6.Conclusions For detectors such as ionization chambers and semiconductors,the field output correction factors can be used to correct the output factors of the small field to improve the accuracy and consistency of the measurement results.