Abstract

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Author(s):: CHEN Li1; 2; LI Guangjun1; BAI Long1; QUAN Hong2; BAI Sen1; 1. Radiation Physics Center, West China Hospital of Sichuan University, Chengdu 610041, China 2. School of Physics and Technology, Wuhan University, Wuhan 430072, China

Abstract:: Abstract: Objective To measure the time delay in respiratory gating by fitting the dose profiles of films, thereby providing a guidance for clinical treatment. Methods During respiratory gating treatment, the phantom was used to drive the films to perform periodic motion, and the corresponding dose profiles were extracted. Then Matlab software was used to simulate pulsed beam delivery. Based on the location distribution of the dose profiles formed by each pulsed beam delivery on film, the cumulative dose of each pixel was calculated for obtaining the dose profiles of a respiratory cycle. The dose profiles with different respiratory gating delay time was compared with the actual dose profiles, and the least square method was used to find the optimal solution, thereby obtaining the corresponding respiratory gating delay time. Results The fitted film dose profiles were in good agreement with the actual dose profiles. The average time delay for beam-on was greater than that of beam-off ［(252±20) ms vs (10±7) ms］. Conclusion The method based on film dose fitting can measure the time delay in respiratory gating accurately. For any gating devices, the time delay should be measured before clinical use.