MV detector Distance

Is it possible to know the distance of the MV Detector from the isocenter with a fantom in pylinac?? I would like to measure each month this distance but I don t know how to proceed ???


Do you mean checking the EPID distance along the beam axis or perpendicular? DICOM has a tag in it for the distance. If you don’t trust that the next step would be to simply shoot a square field of known size and compare the result of the EPID size (for magnification errors) or CAX vs digital center of the EPID (lateral shifts). If you don’t trust your jaws/MLCs then you could use a phantom I suppose. It would depend highly on your method of setup though. Any human positioning error would likely be greater than your EPID shift.

There is no explicit tool in pylinac for this, however, several of the core modules can be helpful if making a tool for this, such as the profile module if looking at lateral shifts.