Dosimetry audits research for 31 medical accelerators by using radiophoto luminescent glass dosimeter in Jiangsu province / 中华放射医学与防护杂志

ABSTRACT

Objective:To perform dosimetric audits on medical accelerators in radiotherapy institutions in Jiangsu province by using a radiophoto luminescent glass dosimeter (RPLGD) and to evaluate both the accuracy of radiotherapy doses and the effectiveness of RPLGD as an auditing tool.Methods:Firstly, the purposive sampling method was used to select three prefecture-level cities in Jiangsu province with good cooperation between radiotherapy institutions and a large number of patients treated by medical accelerators. Secondly, a simple random sampling method was used to select 31 radiotherapy institutions from all radiotherapy institutions in the selected three cities. Finally, one medical accelerator was selected from each institution for dose audit. A dose audit was performed by using RPLGD combined with a 30 cm × 30 cm × 30 cm standard phantom. The dosimeter was placed 10 cm underwater in the center of a 10 cm × 10 cm field with a 100 cm source skin distance. The dosimeter was irradiated with absorbed dose of 2 Gy. After the completion of irradiation, the dosimeter was read by the reader and the deviation was calculated. The acceptance level of the present research was ±5%. A non-parametric test was used to test the significance of differences between different manufacturers, installation years, and geographic distribution.Results:The dose deviation of 31 accelerators was from -16.9% to 2.0%. Of these, 28 accelerators pass the audit with pass rate of 90.3%. A follow-up audit was conducted on the only accelerator whose dose deviation exceeds±10%, also with discrepancy within ±5%. Two accelerators with a dose deviation larger than ±5% were re-measured using ionization chambers, both with dose deviation within ±3%. The non-parametric test result showed that there were no significant statistical differences in dose deviation for accelerators with different manufacturers, installation years, and geographic distribution( P>0.05). Conclusions:The levels of dose deviation for accelerators in Jiangsu province are consistent with those in the previous studies. However, there is still a difference with developed countries. RPLGD is feasible as a dose audit tool. The coverage of the RPLGD audit should be expanded to promote the quality of the radiotherapy through dose aduit.