Intervention description {11a}
failure of the Breathe Well device, this will
Training and simulation: The patients will be trained to perform DIBH with the assigned system and assessed for ability to perform a 20-s breath hold (at 80–90% of the maximal lung capacity). Based on this screening the patient will be deemed suitable for DIBH. For patients suitable for DIBH the breath hold AV guidance while acquiring the planning CT scan will be provided by the assigned system. The unallocated system will be set up to passively record motion. The RPM/RGSC marker block is not within the field of view of the Breathe Well camera, and the Breathe Well device does not interfere with RPM/RGSC tracking the marker block. The reference breath hold depth will be recorded for both systems.Treatment delivery: For treatment, similarly to simulation, both systems will be set up to monitor breathing motion. The patient will be guided with AV biofeedback from the assigned system depending which arm of the trial they have been randomised to. The unallocated system will passively acquire data but not interfere with treatment in any way. Prior tests showed that no interferences and difficulties are anticipated when operating the ‘Breathe Well’ system and the RPM/RGSC system at the same time. If any treatment fraction cannot be delivered due to a failure of the Breathe Well device, this will be recorded. The treatment will continue at the physician’s discretion either (1) using the RPM system, (2) the fraction will be rescheduled or (3) delivered using free breathing.