Sorry for my slightly delayed response. Before we introduced SGRT we were using a spirometer based system at our centres too, although not the ABC system. There’s a couple of things to consider here. With spirometer based systems the aim of them is to reproduce the exact lung volume on a daily basis, whether this is a ‘forced’ BH or a voluntary BH that the patient is in control of. If the patient is breathing deeper than when they were planned I would think they would need re-planning, as their lung volume and breast position will be different to what has been planned in the first instance. This will be picked up using AlignRT and also on imaging.
The ideal situation is to use the AlignRT software to deliver DIBH treatment without ABC. We completed a study on this and the clinical results are the same as with a spirometer system but the patient experience is MUCH improved! Also it takes about half the time in the treatment room as there is not kit to set up, or for the patient to use.
I wouldn’t increase the threshold in the SGRT system, as its showing you a potential clinical positioning error. However it may be worth looking at your pre-set thresholds. For DIBH I would expect them to be set at 3mm approx., are yours less?
Very happy to discuss the workflow with you using just the SGRT system if that would help. Shout up if any of that didn’t make sense?