Statistical determinations of the gating windows in the respiratory gated radiotherapy using the visible guiding system

Purpose: Respiratory gated radiation therapy (RGRT) is used to minimize the radiation dose to normal tissue in lung cancer patients. Determinations of the gating window in the respiratory phase of patients are important in RGRT but it is not easy. The objective of this study was to determine the optimal gating window with a visible guiding system in RGRT. Materials and Methods: Between April and October in 2014 the breathing signals of 23 lung cancer patients were recorded with a Real-time Position Management (RPM) respiratory gating system (Varian, USA). We performed statistical analysis with breathing signals to find the optimal gating window for the guided breathing for RGRT. Results: 19 of the 23 patients showed statistically significant differences (p < 0.05) when the breathing signals obtained before and after breathing training were compared, The standard deviation of the respiration signals after breathing training was the lowest in the phase of 30 % - 70 % (p < 0.05). Conclusions: RGRT with RPM system was confirmed the usefulness of the visible guiding system. Respiratory regularity was significantly improved with the use of the RPM with our visible guidance system, therefore, it would help improve the accuracy and efficiency of RGRT.