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Verification Results Analysis of IMRT Plan Based On Disease Differences and Establishment of Gamma Threshold of Each Disease

X Lin*, Z Li , Q Qiu , Y Yin , Shandong Cancer Hospital Affiliated to Shandong University, Jinan, Shandong


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: To study the difference of IMRT planning gamma pass rate among different diseases and the establishment of standard gamma pass threshold for different diseases.

Methods: 100 cases of proven nasopharyngeal cancer, breast cancer, esophageal cancer, lung cancer and pelvic tumor IMRT plans that the dose verification have passed were selected respectively, the gamma analysis index was 3mm/3%/,10%, The gamma pass-rate greater than 90% was used as the dose verification standard. The difference of gamma-ray pass-rate between the five types of diseases was determined by the quartile deviation analysis. The IMRT plan of different disease types was tested by using a single pass rate threshold, and the pass rate threshold of IMRT plan of different disease types was calculated according to the normal distribution law.

Results: The quartile deviation of the five types of diseases had statistical significance, the statistical results of breast cancer, both nasopharyngeal cancer and the other three groups were P = 0.001. The statistical results between the pelvic cancer group, the esophageal cancer group and the lung cancer group were P= 0.011 and P= 0.025, respectively. The threshold values of nasopharyngeal cancer, breast cancer, esophageal cancer, lung cancer and pelvic cancer were 92.48%, 92.54%, 96.68%, 95.25% and 95.77%, respectively.

Conclusion: The use of a conventional single threshold (usually gamma pass rate≥90%) as an IMRT QA standard for different disease types is clearly inappropriate. The normal distribution law can be used to calculate the gamma threshold of different diseases. It is necessary to set the gamma threshold for specific diseases.


Validation, Treatment Verification


TH- External beam- photons: Quality Assurance - IMRT

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