Medical device manufacturer, Varian Medical Systems, has issued a medical device safety alert concerning its On-Board Imager.
The manufacturer has received three reports that the shaft of the Type 01 elbow motor for Exact arms used in the On-Board Imager [OBI] device have failed due to belt over-tensioning. This over-tensioning would have taken place during servicing. This failure would allow the Exact arm to swing freely with gravity. No injuries have been reported to-date. Only Type 01 elbow motors are subject to these potential failures.
According to the manufacturer, potential injury from the kV source striking a patient is dependent upon the anatomic site being treated and the height of the couch. The risk is greatest when the OBI x-ray source is extended or retracted while it is above the patient. A geometric analysis determined that when the couch is positioned for a pelvis treatment [e.g., prostate treatments], the head of the patient could be positioned within the arc travelled by the kV source. If the kV source were to strike the patient's head or chin, a fracture injury is possible. Pelvic treatments with couch vertical positions less than 10 centimeters below isocenter have the highest potential for injury.
The manufacturer instructs all affected users not to extend or retract the kV Source arm when it is above a patient until the manufacturer inspects the OBI Exact arms. Users should ensure that the gantry is positioned so that the kV Source is lateral to, or underneath, the patient-couch prior to extending or retracting the arm.
According to the manufacturer, the affected products were distributed in Hong Kong.
If you are in possession of the affected products, please contact your supplier for necessary actions.
Posted on 26 March 2014