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The Quantitative Analysis of Dose Verification Results for IMRT Plans

S Wu1*, J Chen1 , Z Li1 , Q Qiu1 , X Wang1 , C Li1 , Y Yin1 , (1) Shandong Cancer Hospital & Institute, Shandong Cancer Hospital affiliate to Shandong University, Jinan


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: Intensity-modulated radiation therapy (IMRT) plays an increasingly important role in clinical applications, and dose verification is particularly crucial for each patient. In this study, we retrospectively analyzed the results of dose verification in 924 actual IMRT plans, including the relationship between gamma pass rates and the location of lesions, and the total number of Monitor Units (MU) and the maximum area of the collected dose.

Methods: All the 924 IMRT plans implemented in a Varian Trilogy accelerator between January 1, 2014 and March 31, 2016 at Shandong Cancer Hospital were acquired. The Varian Eclipse planning system was used for all treatment planning and verification. The, actual implemented plans were transplanted into a water phantom. Subsequently, the derived fluence was compared with the actual measured fluence by gamma analysis with the gamma criteria (3%/3mm).

Results: Nine hundred and twenty-four IMRT plans were categorized into six groups, including the brain, head and neck, chest, abdomen, pelvis, and breast. The gamma pass rate average was above 98% for 902 IMRT plans while 22 plans did not pass the first time. A correlation was observed between the treatment site and gamma pass rate (P=0.017). Meanwhile, a negative correlation was observed between gamma pass rate and total number of MU (P <0.001), largest area of the acquisition dose (P <0.001), respectively. Varian Trilogy accelerator IMRT QA data has a stable pass rate with a 100-CL (confidence limit) value of 95.19.

Conclusion: There was a correlation between the pass rate and the treatment site, the total number of MUs, and the maximum area of collected dose. When using Mapcheck for patient plan dose verification, the gamma pass rate is very high, and only a few of them need to be analyzed.


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