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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 (R G) was greater than the sum of the value of target margin (M) and the value of plan tumor range of motion (R T) in 7 patients, R G was more than 1.5 times of M+R T in 7 patients, and there were also 7 patients in the phase of rapid rise and fall of respiratory curve. The correlation efficients between R G-M-R T and the percentage of beam on miss phase (T en%) and the percentage of beam closing off phase (T dis%) were 0.41 and 0.57, respectively. Conclusion:When R G is more than 1.5 times of M+R T 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.
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Objective To evaluate the application of the placement of titanium clips in the upper and lower tumor margins in precision radiotherapy for early esophageal cancer. Methods:Seventeen patients with early esophageal cancer underwent endoscopy-guided implantation of titanium clips to mark the upper and lower tumor margins. CT-based simulation was performed to delineate the gross tumor volume ( GTV) . The application value of this technology in precision radiotherapy was evaluated. Results:For all patients (including 13 cases with initial treatment and 4 patients requiring radiotherapy after endoscopic resection), the esophageal tumors were not explicitly displayed on CT and barium meal images and the GTV range could not be accurately determined. The esophageal tumors were marked by successful placement of at least one titanium clip in the upper and lower tumor margins. Subsequently, the esophageal tumors were successfully displayed on CT simulation and the target area was accurately delineated. No grade 3-4 adverse events, such as bleeding and perforation occurred. Conclusion Endoscopy-guided titanium clip placement is convenient and feasible for early esophageal cancer, which is of clinical significance for determining the target area of radiotherapy.