title: Head motion during MRI acquisition reduces gray matter volume and thickness estimates.
abstract: Imaging biomarkers derived from magnetic resonance imaging (MRI) data are used to quantify normal development, disease, and the effects of disease-modifying therapies. However, motion during image acquisition introduces image artifacts that, in turn, affect derived markers. A systematic effect can be problematic since factors of interest like age, disease, and treatment are often correlated with both a structural change and the amount of head motion in the scanner, confounding the ability to distinguish biology from artifact. Here we evaluate the effect of head motion during image acquisition on morphometric estimates of structures in the human brain using several popular image analysis software packages (FreeSurfer 5.3, VBM8 SPM, and FSL Siena 5.0.7). Within-session repeated T1-weighted MRIs were collected on 12 healthy volunteers while performing different motion tasks, including two still scans. We show that volume and thickness estimates of the cortical gray matter are biased by head motion with an average apparent volume loss of roughly 0.7%/mm/min of subject motion. Effects vary across regions and remain significant after excluding scans that fail a rigorous quality check. In view of these results, the interpretation of reported morphometric effects of movement disorders or other conditions with increased motion tendency may need to be revisited: effects may be overestimated when not controlling for head motion. Furthermore, drug studies with hypnotic, sedative, tranquilizing, or neuromuscular-blocking substances may contain spurious "effects" of reduced atrophy or brain growth simply because they affect motion distinct from true effects of the disease or therapeutic process.
authors.affiliation: Massachusetts General Hospital, Department of Neurology, 55 Fruit Street, Boston, MA 02114, USA; Massachusetts General Hospital, Department of Radiology, A.A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Suite 2301, Charlestown, MA 02129, USA; Massachusetts Institute of Technology, Computer Science and Artificial Intelligence Laboratory, Cambridge, MA 02139, USA; Harvard Medical School, 25 Shattuck St., Boston, MA 02115, USA. Electronic address: mreuter@nmr.mgh.harvard.edu.
authors.forename: Martin
authors.initials: M
authors.lastname: Reuter
authors.affiliation: Massachusetts General Hospital, Department of Radiology, A.A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Suite 2301, Charlestown, MA 02129, USA; Harvard Medical School, 25 Shattuck St., Boston, MA 02115, USA.
authors.forename: M Dylan
authors.initials: MD
authors.lastname: Tisdall
authors.affiliation: Massachusetts General Hospital, Department of Neurology, 55 Fruit Street, Boston, MA 02114, USA; Harvard Medical School, 25 Shattuck St., Boston, MA 02115, USA.
authors.forename: Abid
authors.initials: A
authors.lastname: Qureshi
authors.affiliation: Massachusetts General Hospital, Department of Radiology, A.A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Suite 2301, Charlestown, MA 02129, USA; Harvard Medical School, 25 Shattuck St., Boston, MA 02115, USA.
authors.forename: Randy L
authors.initials: RL
authors.lastname: Buckner
authors.affiliation: Massachusetts General Hospital, Department of Radiology, A.A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Suite 2301, Charlestown, MA 02129, USA; Harvard Medical School, 25 Shattuck St., Boston, MA 02115, USA.
authors.forename: André J W
authors.initials: AJW
authors.lastname: van der Kouwe
authors.affiliation: Massachusetts General Hospital, Department of Radiology, A.A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Suite 2301, Charlestown, MA 02129, USA; Massachusetts Institute of Technology, Computer Science and Artificial Intelligence Laboratory, Cambridge, MA 02139, USA; Harvard Medical School, 25 Shattuck St., Boston, MA 02115, USA.
authors.forename: Bruce
authors.initials: B
authors.lastname: Fischl
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D015415:Biomarkers; D066128:Gray Matter / Q000033:anatomy & histology*; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011786:Quality Control
chemical_list: D015415:Biomarkers
keywords: Bias; Cortical gray matter estimates; Head motion; MRI; Quality control; Spurious effect; Thickness; Volume