Application of prospective respiratory gating based on 4D-CT in precise radiotherapy for lung cancer
Yin Li1, Gao Han1, Yuan Fangqin1, Wang Qi1, Liu Yatian1, Zhai Zhenyu1, Jiang Ming1, Sun Li1, Zhang Qian1, Zhu Jun1, He Xia1,2
1 Department of Radiation Oncology, The Affiliated Cancer Hospital of Nanjing Medical University & Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research, Nanjing 210009,China; 2 Collaborative Innovation Center for Cancer Personalized Medicine, Nanjing Medical University, Nanjing 210000, China
Abstract：Objective The respiratory waveform of lung cancer patients based on 4D-CT respiratory gating was analyzed to evaluate the accuracy of gating during radiotherapy, and to explore the off-target in the 4D-CT respiratory gating radiotherapy. Methods Clinical data of 18 patients with lung cancer admitted to Radiotherapy Department of Jiangsu Cancer Hospital were collected to obtain the respiratory waveform data during 4D-CT respiratory gating radiotherapy. The waveform in each treatment working cycle was compared with the waveform in 4D-CT scan to study whether there was a possibility of the off-target in the treatment of lung cancer patients. Results There were 154 treatment sessions and 20,790 treatment breathing cycles in 18 patients, among which the threshold of gated opening beam miss amplitude (Δm-en) was greater than 0 in 95 treatment breathing cycles in 7 patients, accounting for 0.46% of all breathing cycles, and the threshold of gated closing beam miss amplitude (Δm-dis) was greater than 0 in 1419 treatment breathing cycles in 13 patients, accounting for 6.83% of all cycles. Among the 13 patients withΔm-dis greater than 0, actual tumor range of motion (RG) was greater than the sum of the value of target margin (M) and the value of plan tumor range of motion (RT) in 7 patients, RG was more than 1.5 times of M+RT in 7 patients, and there were also 7 patients in the phase of rapid rise and fall of respiratory curve. The correlation efficients between RG-M-RT and the percentage of beam on miss phase (Ten%) and the percentage of beam closing off phase (Tdis%) were 0.41 and 0.57, respectively. Conclusions When RG is more than 1.5 times of M+RT value and the gating beam on phase contains the phases in the rapid rise and fall of the respiratory curve, the possibility of the off-target during radiotherapy is significantly increased.
Yin Li,Gao Han,Yuan Fangqin et al. Application of prospective respiratory gating based on 4D-CT in precise radiotherapy for lung cancer[J]. Chinese Journal of Radiation Oncology, 2022, 31(7): 605-610.
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