title: Evaluation of motion and its effect on brain magnetic resonance image quality in children.
abstract: BACKGROUND
  Motion artifacts pose significant problems for the acquisition of MR images in pediatric populations.
  
  
  OBJECTIVE
  To evaluate temporal motion metrics in MRI scanners and their effect on image quality in pediatric populations in neuroimaging studies.
  
  
  METHODS
  We report results from a large pediatric brain imaging study that shows the effect of motion on MRI quality. We measured motion metrics in 82 pediatric patients, mean age 13.4 years, in a T1-weighted brain MRI scan. As a result of technical difficulties, 5 scans were not included in the subsequent analyses. A radiologist graded the images using a 4-point scale ranging from clinically non-diagnostic because of motion artifacts to no motion artifacts. We used these grades to correlate motion parameters such as maximum motion, mean displacement from a reference point, and motion-free time with image quality.
  
  
  RESULTS
  Our results show that both motion-free time (as a ratio of total scan time) and average displacement from a position at a fixed time (when the center of k-space was acquired) were highly correlated with image quality, whereas maximum displacement was not as good a predictor. Among the 77 patients whose motion was measured successfully, 17 had average displacements of greater than 0.5 mm, and 11 of those (14.3%) resulted in non-diagnostic images. Similarly, 14 patients (18.2%) had less than 90% motion-free time, which also resulted in non-diagnostic images.
  
  
  CONCLUSIONS
  We report results from a large pediatric study to show how children and young adults move in the MRI scanner and the effect that this motion has on image quality. The results will help the motion-correction community in better understanding motion patterns in pediatric populations and how these patterns affect MR image quality.
authors.affiliation: Department of Radiology, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave., WB215, Boston, MA, 02115, USA. onur.afacan@childrens.harvard.edu.
authors.forename: Onur
authors.identifier: http://orcid.org/0000-0003-2112-3205
authors.initials: O
authors.lastname: Afacan
authors.affiliation: Department of Radiology, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave., WB215, Boston, MA, 02115, USA.
authors.forename: Burak
authors.initials: B
authors.lastname: Erem
authors.affiliation: Department of Radiology, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave., WB215, Boston, MA, 02115, USA.
authors.forename: Diona P
authors.initials: DP
authors.lastname: Roby
authors.affiliation: Robin Medical Inc., Baltimore, MD, USA.
authors.forename: Noam
authors.initials: N
authors.lastname: Roth
authors.affiliation: Robin Medical Inc., Baltimore, MD, USA.
authors.forename: Amir
authors.initials: A
authors.lastname: Roth
authors.affiliation: Department of Radiology, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave., WB215, Boston, MA, 02115, USA.
authors.forename: Sanjay P
authors.initials: SP
authors.lastname: Prabhu
authors.affiliation: Department of Radiology, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave., WB215, Boston, MA, 02115, USA.
authors.forename: Simon K
authors.initials: SK
authors.lastname: Warfield
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009038:Motion; D012189:Retrospective Studies; D055815:Young Adult
keywords: Artifacts; Brain; Children; Magnetic resonance imaging; Motion; Motion measurements