Siemens—COHERENCE Oncologist: Incorrect Offset Values May Lead to Incorrect Patient Repositioning and Incorrect Dose Location

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In a Field Safety Notice letter posted by the German Federal Institute for Drugs and Medical Devices (BfArM), Siemens states that when the portal image is displayed alongside the reference image on the above software, the user normally activates the interactive shift or landmark registration functions to align the reference and the portal images. The user then activates the offset calculation once the alignment is accepted; this action shows the relative offset and/or absolute table positions in the Beam Visualization (lower right) segment. The portal image display and offset calculations are correct at this point; however, when a filtering action is performed, the portal image display will shift into two segments: the upper right and lower left (blended). Only the visual display of the image is changed; the offset values remain correct. Users must not further correct the image alignment at this time. Correcting the image alignment after the shift of the display would result in incorrect offset values, potentially causing the patient to be repositioned incorrectly and the dose to be delivered to the wrong location. The problem occurs only when an offset calculation is followed by a filter operation. FDA's Center for Devices and Radiological Health (CDRH) states that the manufacturer...