Figure 2. A photograph showing respiratory-gated lung tumor stereotactic radiotherapy under abdominal compression using the vacuum-assisted fixation device and the compression block with a 20 cm wide strap to apply pressure to the block.

The laser sensor detects abdominal displacement caused by respiration and generates a respiratory curve. Then, gating thresholds were set on the respiratory curve by referring to the tumor displacement relative to the end-expiration, and the resulting gating signal was exported to a linac to control the beam delivery. Again, the portable display was placed over the patient’s face to visually guide stable breathing.