title: How does arm positioning of polytraumatized patients in the initial computed tomography (CT) affect image quality and diagnostic accuracy?
abstract: OBJECTIVE
  To evaluate the influence of different arm positions on abdominal image quality during initial whole-body CT (WBCT) in polytraumatized patients and to assess the risk of missing potentially life-threatening injuries due to arm artifacts.
  
  
  METHODS
  Between July 2011 and February 2013, WBCT scans of 203 patients with arms in the abdominal area during initial WBCT were analyzed. Six different arms-down positions were defined: patients with both (group A)/one arm(s) (group B) down alongside the torso, patients with both (group C)/one arm(s) (group D) crossed in front of the upper abdomen, patients with both (group E)/one arm(s) (group F) crossed in front of the pelvic area. A group of 203 patients with elevated arms beside the head served as a control group. Two observers jointly evaluated image quality of different organ regions using a 4-point scale system. Follow-up examinations (CT scans and/or ultrasound) were analyzed to identify findings missed during initial WBCT due to reduced image quality.
  
  
  RESULTS
  Image quality for most of the organ regions analyzed was found to be significantly different among all groups (p<0.05). Image quality was most severely degraded in group A, followed by groups E and C. Positioning with one arm up resulted in significantly better image quality than both arms down (p<0.05). Overall, arms-up positioning showed significantly better image quality than arms-down positions (p<0.05). In one case, liver hemorrhage missed in the initial WBCT because of arm artifacts, was revealed by follow-up CT.
  
  
  CONCLUSIONS
  In WBCT arms-down positioning significantly degrades abdominal image quality and artifacts might even conceal potentially life-threatening injuries. If the patient's status does not allow elevation of both arms, image quality can benefit from raising at least one arm. Otherwise, arms should be placed in front of the upper abdomen instead of alongside the torso.
authors.affiliation: Department of Radiology, Charité, Charitéplatz 1, 10117 Berlin, Germany. Electronic address: johannes.kahn@charite.de.
authors.forename: Johannes
authors.initials: J
authors.lastname: Kahn
authors.affiliation: Department of Radiology, Charité, Charitéplatz 1, 10117 Berlin, Germany. Electronic address: ulrich.grupp@charite.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Grupp
authors.affiliation: Department of Radiology, Charité, Charitéplatz 1, 10117 Berlin, Germany. Electronic address: martin.maurer@charite.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Maurer
mesh_terms: D000007:Abdominal Injuries / Q000000981:diagnostic imaging*; D001132:Arm / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009104:Multiple Trauma / Q000000981:diagnostic imaging*; D015588:Observer Variation; D056888:Patient Positioning / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Arm position; Artifact; CT; Image quality; Polytrauma