The impact of resolution to Gamma pass rate in the verification of dose distribution / 中华放射肿瘤学杂志

ABSTRACT

Objective To study the impact of the resolution of reference dose distribution and evaluated dose distribution to Gamma rate in the verification of IMRT. Methods Designed four fields, the resolution of dose distribution calculated in water phantom and exported from TPS are 1 ,2,3 ,4,5,6 mm. To calculate Gamma index by IBA's OmniPro-I'mRT software in different sampling resolution. Results When the resolution of evaluated dose distribution was fixed, the change of reference dose distribution's resolution has little effect on Gamma rate (5％ to IMRT field) ;When the resolution of reference dose distribution was fixed , the Gamma rate increased as the evaluated dose distribution's resolution ( ＞ 1 mm) raise ( the Gamma rate increase ( 15. 2 ±6. 2) ％ ( t = 11. 99 ,P < 0. 01 ) and ( 14. 9 ± 5. 5) ％ ( t = 13. 24 , P ＜ 0. 01 ) while the resolution of evaluated dose distribution changed from 6 mm t0 3 mm and from 3 mm to 1 mm　respectively) .Conclusions To use Camma method for verification of IMRT, the measured data can be as a reference dose distribution without　interpolation;the computed data by TPS can be as a evaluated dose distribution and it is more appropriate for the resolution of 1 mm.