obviously you are using the ART SRS module for ART MV iso calibration. I try to understand what this module is exactly doing… According to the manual there are 2 options to perform the iso calibration, either “image center option” or “field center option”. Which one are you using and for what rational? Lets assume you performed ART iso calibration (with one or the other method) and applied the couch shift such that all RTDs are “0.0” at couch angle 0°. Then you rotate your couch e.g. to 270° and you will find some non zero RTDs. How did you validate the correctness of these RTDs at non zero couch angle?
One last question. Do you consider the ART SRS module as an aboslute necessity when applying arcs at non-zero couch angles and you don’t have a room based kV-imaging system to cross check patient positioning after couch rotation?