Method for retrospective estimation of natural head movement during structural MRI

Background: Head motion during brain structural MRI scans biases brain morphometry measurements but quantitative retrospective methods estimating head motion from structural MRI have not been evaluated. Purpose: To verify the hypothesis that two metrics retrospectively computed from MR images: 1) average edge strength (AES, reduced with image blurring) and 2) entropy (ENT, increased with blurring and ringing artifacts) could be sensitive to in-scanner head motion during acquisition of T1-weighted MR images. Study Type: Retrospective. Population/Subjects/Phantom/Specimen/Animal Model: In all, 83 healthy control (HC) and 120 Parkinson's disease (PD) patients. Field Strength/Sequence: 3D magnetization-prepared rapid gradient-echo (MPRAGE) images at 3T. Assessment: We 1) compared AES and ENT distribution between HC and PD; 2) evaluated the correlation between tremor score (TS) and AES (or ENT) in PD; and 3) investigated cortical regions showing an association between AES (or ENT) and local...