| Cao Ying,Yang Zhen,Qiu Xiaoping,Yang Xiaoyu,Tang Huimin,Lyu Zhiping,Zhang Zijian,Lei Mingjun,Liu Gui,Hu Yongmei.The IMRT accumulative dosimetric verification of NPC using MLC log files[J].Chinese Journal of Radiological Medicine and Protection,2015,35(9):665-669 |
| The IMRT accumulative dosimetric verification of NPC using MLC log files |
| Received:April 13, 2015 |
| DOI：10.3760/cma.j.issn.0254-5098.2015.09.006 |
| KeyWords:Nasopharyngeal carcinoma IMRT dynalog file Position error Dosimetry |
| FundProject:湖南省科技计划项目(2011SK3220) |
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| Abstract:: |
| Objective To verify the accumulative dose of intensity-modulated radiotherapy (IMRT) of nasopharyngeal carcinoma (NPC) using linac logfiles, and analyze the relationship between the leaf position errors of multileaf collimator (MLC) and dose distribution changes. Methods In total, 1 400 dynalog files of 28 fractions of 5 NPC patients were tracked and recorded. MLC leaf position information was compared with the planned MLC leaf position information to calculate the MLC leaf position errors of each leaf and the overall mean leaf position error of all patients, which were analyzed and extracted through Argus program. The MLC files were imported into treatment planning system (TPS) to recalculate the dose. Twenty-eight accumulative dose differences between original plans and reconstruction plans, and single relative dose differences were analyzed. Results About 90% of the leaf position errors were less than 0.50 mm, 4%-11% of the leaf position errors were between 0.50-1.00 mm, while there were about 8‰ leaf position errors within 1.00-1.50 mm and the average leaf position error was 0.16 mm. Compared with accumulated dose of original plans and that of reconstruction plans, the average relative dose discrepancies in targets and organs at risk (OARs) induced by leaf position errors were less than±0.1% and±0.6%, and the differences were not statistically significant (P>0.05). Compared with single dose of original plans, single dose differences in targets, brainstem, spinal cord and right lens of reconstruction plans were statistically significant (z=-2.02-4.61, 4.46, -4.51, 2.07, P<0.05). Conclusions The accumulative dose verification based on multi-fraction dynamic intensity-modulated MLC log files, to some extent, lessen the dose influence of the single-fraction leaf position errors and the verification results could manifest the practical irradiation dose more accurately. |
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