title: Metallic artifacts from internal scaphoid fracture fixation screws: comparison between C-arm flat-panel, cone-beam, and multidetector computed tomography.
abstract: OBJECTIVE
  The aim of this study was to compare image quality and extent of artifacts from scaphoid fracture fixation screws using different computed tomography (CT) modalities and radiation dose protocols.
  
  
  METHODS
  Imaging of 6 cadaveric wrists with artificial scaphoid fractures and different fixation screws was performed in 2 screw positions (45° and 90° orientation in relation to the x/y-axis) using multidetector CT (MDCT) and 2 flat-panel CT modalities, C-arm flat-panel CT (FPCT) and cone-beam CT (CBCT), the latter 2 with low and standard radiation dose protocols. Mean cartilage attenuation and metal artifact-induced absolute Hounsfield unit changes (= artifact extent) were measured. Two independent radiologists evaluated different image quality criteria using a 5-point Likert-scale. Interreader agreements (Cohen κ) were calculated. Mean absolute Hounsfield unit changes and quality ratings were compared using Friedman and Wilcoxon signed-rank tests.
  
  
  RESULTS
  Artifact extent was significantly smaller for MDCT and standard-dose FPCT compared with CBCT low- and standard-dose acquisitions (all P < 0.05). No significant differences in artifact extent among different screw types and scanning positions were noted (P > 0.05). Both MDCT and FPCT standard-dose protocols showed equal ratings for screw bone interface, fracture line, and trabecular bone evaluation (P = 0.06, 0.2, and 0.2, respectively) and performed significantly better than FPCT low- and CBCT low- and standard-dose acquisitions (all P < 0.05). Good interreader agreement was found for image quality comparisons (Cohen κ = 0.76-0.78).
  
  
  CONCLUSIONS
  Both MDCT and FPCT standard-dose acquisition showed comparatively less metal-induced artifacts and better overall image quality compared with FPCT low-dose and both CBCT acquisitions. Flat-panel CT may provide sufficient image quality to serve as a versatile CT alternative for postoperative imaging of internally fixated wrist fractures.
authors.affiliation: From the *Institute of Diagnostic and Interventional Radiology and †Division of Plastic and Reconstructive Surgery, University Hospital Zurich; ‡Institute of Anatomy, University Zurich; and §Department of Radiology, Orthopaedic University Hospital of Balgrist, Zurich, Switzerland.
authors.forename: Tim
authors.initials: T
authors.lastname: Finkenstaedt
authors.forename: Fabian
authors.initials: F
authors.lastname: Morsbach
authors.forename: Maurizio
authors.initials: M
authors.lastname: Calcagni
authors.forename: Magdalena
authors.initials: M
authors.lastname: Vich
authors.forename: Christian W A
authors.initials: CW
authors.lastname: Pfirrmann
authors.forename: Hatem
authors.initials: H
authors.lastname: Alkadhi
authors.forename: Val M
authors.initials: VM
authors.lastname: Runge
authors.forename: Gustav
authors.initials: G
authors.lastname: Andreisek
authors.forename: Roman
authors.initials: R
authors.lastname: Guggenberger
mesh_terms: D016477:Artifacts; D001863:Bone Screws; D002102:Cadaver; D054893:Cone-Beam Computed Tomography / Q000379:methods; D050723:Fractures, Bone / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D016268:Internal Fixators; D008670:Metals; D061330:Multidetector Computed Tomography / Q000379:methods; D015588:Observer Variation; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods; D015203:Reproducibility of Results; D021361:Scaphoid Bone / Q000000981:diagnostic imaging* / Q000293:injuries* / Q000601:surgery; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D008670:Metals