Sandra,
Our unit has never been down for an extended period of time (days). Usually restarting computer and cameras fix most glitches we encounter. If it were to be down for a day then we would cancel our DIBH patients. If the system were down for multiple days, we have the option to send our patients to another center within our system. Depending on MD, patient preference and how long the system were down our other options to consider would be the patient taking a break until system came back up or re-planning off free breathing scan. Since we take FB and DIBH scans during initial CT, no extra scan would be required helping to speed up the planning process. We would not treat a DIBH patient in DIBH position without a way to monitor and confirm correct position.
Hope this helps!