J. zu Münster
we are currently using the exact same setup – Elekta Linac/Versa HD, Align RT + automated beamhold and VMAT/SBRT treatments in the chest/upper body – though not yet on Lung/Liver. In our experience an automated beamhold caused by the gantry position can be almost completely avoided by planning the Treatment ROI accordingly. If the System has enough body surface to register the patient, the gantry will not cause too much of a difference in the translations/rotations to cause a beamhold. This of course has effects on the framerate and the automated beamhold if it drops below around 5 fps. So don’t make the ROIs too large and keep an eye on the fps. The ROI should cover both sides and the front of the patient and have enough size and meaningful structures to register properly. Working with breath hold allows to work better within narrower tolerances (here 3 mm/3° in Align RT, though we try to get as close as possible to zero before starting CBCT/treatment). But with a good ROI this also worked easily with free breathing and a gated reference capture. Try to avoid including structures like arms/axillae/chin that are too ”moveable” for the ROI. If in doubt use the treatment capture/postural video function to confirm the position of the arms. Hope this helps a bit.