Maintaining immobilisation devices on trauma patients during CT: a feasibility study

Pål Johan Stokkeland, Erlend Andersen, Maria Myhre Bjørndal, Arne Morten Mikalsen, Sindre Aslaksen, Per Kristian Hyldmo

To reduce the possibility of secondary deterioration of spinal injuries, it is desirable to maintain the spinal immobilisation that is applied in the prehospital setting throughout computed tomography (CT) scanning. A previous study found that metallic components within the inflation valve of the vacuum mattresses caused CT artefacts. The aim of our study was to investigate the effect of vacuum mattresses with plastic valves on CT artefacts, the radiation dose, and noise compared to a trauma transfer board and the spine boards currently used in our trauma system. We scanned an anthropomorphic whole body phantom with different immobilisation devices on a 128-slice CT scanner using the standard polytrauma CT-protocol at our institution. The phantom was scanned without any immobilisation device and with three different vacuum mattresses, two spine boards, and one trauma transfer board. Two radiologists independently assessed the artefacts. Agreement between the two radiologists was measured using the kappa coefficient. The radiation dose and noise were assessed. One spine board produced major artefacts due to its metal components. One of the vacuum mattresses resulted in artefacts that impaired clinical judgement. Otherwise, the artefacts predominantly did not impede clinical judgement and were mainly subtle. One of the vacuum mattresses resulted in no artefacts that affected clinical judgement. The overall inter-rater agreement was substantial (0.86, kappa 0.77). We did not observe any artefacts due to plastic valves. The mean CT radiation dose was slightly higher for two of the devices in the head series than that for the trauma transfer board, used as the standard in our system. Only marginal differences were noted for the other devices and series. Small differences in image noise were found between the devices. Our results indicate that it is feasible to maintain some vacuum mattresses with plastic valves on trauma patients during CT scanning. The tested mattresses did not result in a considerably increased radiation dose or artefacts that hampered clinical judgement. One of the tested vacuum mattresses produced no artefacts that hampered clinical judgement whatsoever.