The XA SOP Class does not encode some information to fully characterize the geometry of the conic projection acquisition, such as the position of the Positioner Isocenter on the FOV area. Indeed, the XA SOP Class assumes that the isocenter is projected in the middle of the FOV.
The Enhanced XA SOP Class encodes the position of the Isocenter on the detector, as well as specific FOV attributes (origin, rotation, flip) per-frame or shared. It encodes some existing attributes from DX to specify information of the Digital Detector and FOV. It also allows differentiating the image intensifier vs. the digital detector and then defines conditions on attributes depending on image intensifier or digital detector.