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we have been using the Align RT System with our Elekta Linacs (Versa/Synergy Models) since January 2020 and went markerless on all sites a couple of weeks ago. It is indeed difficult, if not impossible, to monitor the patient during the CBCT/XVI imaging with all panels/source extended. Due to that the Panel/Source have to be manually retract by the therapist. There seems to be no way around this, if Elekta does not decide to increase usability by retracting the panels/source remotely in their next linac installments.
Regarding the height – we are using The ORFIT Industries sagitillt board for prone breast treatments and that has been the only case where the Align RT FOV reached its limits, as the patients are liftet at least an additional 15-20 cm above the regular table. And only then the FOV showed not detected areas/clipping on the back of the larger patients. Every other indication or positioning device has not come close to the FOV edge. One other lightly similar case was isocentric table rotation of 90/270° and even there we had only minimal clipping. As Anandakri mentioned it is dependent on the height of the installed Align RT Pods.
If you make a Reference Capture for a Pelvis Patient – how far does the Capture reach into the Gantry/how much of the patient is shown? At our sites it is, even with maximum cranial positioning due to patient length, more than enough to use sucessfully monitor every patient. If you have enough of the patients body on the Reference Capture, maybe try to enlarge the Pelvis ROI to the cranial body parts above the Pelvis. This might seem controintuitive but has helped us a lot with almost completely preventing beam holds due to the ROI being blocked by parts of the Gantry. If needed I could forward you an example of our ROIs look like. Just let me know.