Validation of the Effectiveness of Visual Feedback Systems in Respiratory Gating Carbon Ion Radiation Therapy

This study aimed to evaluate the efficacy of respiratory-gated irradiation using visual feedback (VF) in carbon-ion radiotherapy (CIRT). Furthermore, in patients with liver cancer undergoing CIRT, the treatment times of treatments with and without VF (non-VF) were compared.

Thirty-three patients with liver cancer were analyzed. VF system was applied in 10 patients with liver tumors. To evaluate the efficacy of VF, patients treated non-VF were selected as a control group. All treatments were performed under free-breathing conditions in both the VF and non-VF groups. For each VF patient, 1-3 candidate non-VF patients were identified by matching the CTV size and irradiation gate width (amplitude). From these candidates, 1 non-VF patient was selected as a matched control for each VF patient. The average treatment time for each VF patient was compared with that of the corresponding non-VF patient. The effect of the reduced treatment time for VF was calculated by comparing each VF patient with the corresponding non-VF patient. To quantify respiratory variability, the root mean square error and standard deviation were calculated.

The treatment time was reduced in 8 of 10 pairs. Further, in 6 of 8 pairs, the treatment time was reduced by more than 5 minutes when using VF compared with non-VF. The RMSE value was significantly reduced at 50% and 100% (P < .05). The RMSE value decreased by 28.2% in the VF compared with non-VF. VF was effective in improving respiratory waveform reproducibility in most pairs.

The results suggest that VF contributes to a reduction in treatment time, indicating improved time efficiency during irradiation sessions. In addition, VF improves respiratory waveform reproducibility, which may contribute to enhanced treatment accuracy. Furthermore, shortening the treatment time may reduce the treatment burden on patients and improve overall treatment workflow.