title: Motion artefacts in cone beam CT: an in vitro study about the effects on the images.
abstract: OBJECTIVE
  In cone beam CT (CBCT), imperfect patient immobility, caused by involuntary movements, is one of the most important causes of artefacts and image quality degradation. Various works in literature address this topic, but seldom is the nature of the movement correlated with the type of artefact and the image degradation in a systematic manner, and the correlation analyzed and explained.
  
  
  METHODS
  All three types of movements that can occur during a scan-nodding, tilting and rolling-were applied to a dry skull, in various manners from abrupt to gradual through the entire scan, at different times and angles, over a wide range of displacements. 84 scans were performed, with different skull movements, and the resulting images examined by two skilled radiologists, rated in a four-point scale and statistically analyzed. A commercial CBCT machine was used, featuring supine patient positioning.
  
  
  RESULTS
  Different types of movements induce different artefacts, in different parts of the anatomy. In general, movement of short duration may lead to double contours (bilateral or monolateral depending upon the angle of the scan at which they occur), whereas gradual movements result into blurring.
  
  
  CONCLUSIONS
  Not all movements cause motion artefacts that equally jeopardize the image. Rolling is the type of movement that most severely affects the image diagnostic value.
  
  
  CONCLUSIONS
  These findings may help practitioners to identify the causes of motion artefacts and the resulting image degradation, and remediate them, and manufacturers to improve the patient-positioning devices.
authors.affiliation: 1 Department of Experimental and Clinical Biomedical Sciences, Radiodiagnostic Unit n. 2, University of Florence-Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.
authors.forename: Cosimo
authors.initials: C
authors.lastname: Nardi
authors.affiliation: 2 Arlington Heights, IL, USA.
authors.forename: Roberto
authors.initials: R
authors.lastname: Molteni
authors.affiliation: 3 Department of Health Science, University of Florence, Florence, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Lorini
authors.affiliation: 1 Department of Experimental and Clinical Biomedical Sciences, Radiodiagnostic Unit n. 2, University of Florence-Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.
authors.forename: Gian G
authors.initials: GG
authors.lastname: Taliani
authors.affiliation: 1 Department of Experimental and Clinical Biomedical Sciences, Radiodiagnostic Unit n. 2, University of Florence-Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Matteuzzi
authors.affiliation: 1 Department of Experimental and Clinical Biomedical Sciences, Radiodiagnostic Unit n. 2, University of Florence-Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Mazzoni
authors.affiliation: 1 Department of Experimental and Clinical Biomedical Sciences, Radiodiagnostic Unit n. 2, University of Florence-Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Colagrande
mesh_terms: D016477:Artifacts; D054893:Cone-Beam Computed Tomography; D006801:Humans; D066298:In Vitro Techniques; D009068:Movement; D056888:Patient Positioning; D012886:Skull / Q000000981:diagnostic imaging*