Figure 5. Respiratory-gated CBCT images acquired during stereotactic gated IMRT for a lung tumor case in Video 2 using a noncoplanar seven-port sliding-window technique with couch angles of 0°, 10°, and 350°.

Specifically, the intrafraction half-scan CBCT images were acquired immediately after the first ports were completed with a 0° couch angle, with the linac gantry manually rotated 200° for CBCT imaging each time the measured respiratory signal amplitude met the preconfigured gate-on condition. During the CBCT data acquisition, the patient was instructed to maintain the same breathing pattern as before. In this figure, the gating window ITV is shown in sky blue and the planning target volume (PTV) is shown in red. The tumor appeared to remain within the gating window ITV during the stereotactic gated sliding-window IMRT.

CBCT: cone-beam computed tomography; IMRT: intensity-modulated radiotherapy; ITV: internal target volume; PTV: planning target volume