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Purpose: study the effect of respiratory movement on IMRT dose verification of lung cancer based on the real respiratory movement parameters of patients.
Methods: patients with lung cancer who had underwent 4DCT scan and received IMRT were analyzed to obtain the three-dimensional tumor motion amplitude and respiratory period. Based on the above movement parameters, the dose distribution of tumor on the respiratory movement platform in the superior-inferior (SI) and left-right (LR) directions were measured respectively. The difference of dose distribution between the respiratory movement state and the rest state was compared by using two-dimensional gamma analysis method, and the effect of respiratory movement on the dose verification was analyzed.
Results: average respiratory period of the patients was 3.3 seconds. The average tumor motion amplitude (5.6 mm) in the SI direction was larger than that in the LR directions (2.1 mm) and the anterior-posterior directions (2.3 mm), and the maximum was 18 mm. The average value of the ? pass rate of the SI and the LR direction in respiratory movement state was lower than that in the rest state (P < 0.001), and with the increase of the tumor motion amplitude, the ? pass rate decreased gradually. When the tumor motion amplitude was greater than 3mm, the ? pass rate began to be less than 90%. When the tumor motion amplitude is greater than 7 mm in the SI direction, the ? pass rate of all fields is less than 90%. There was no significant difference in ? pass rate between different respiratory period.
Conclusion: tumor motion amplitude has an effect on the IMRT dose verification of lung cancer, it is suggested that the tumor motion amplitude should be controlled within 3 mm during radiotherapy. The tumor motion period has no effect on the ? passing rate.
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