Method for retrospective estimation of natural head movement during structural MRI

Area of Science:

• Neuroimaging
• Quantitative MRI
• Brain Morphometry

Background:

• Head motion during structural MRI scans introduces bias in brain morphometry measurements.
• Quantitative retrospective methods for estimating head motion from MRI are not well-evaluated.

Purpose of the Study:

• To test if average edge strength (AES) and entropy (ENT), computed retrospectively from MRI, are sensitive to in-scanner head motion.
• To assess the utility of these metrics in differentiating healthy controls (HC) and Parkinson's disease (PD) patients.

Main Methods:

• Retrospective analysis of 3D MPRAGE MRI scans from 83 HC and 120 PD patients acquired at 3T.
• Comparison of AES and ENT distributions between HC and PD groups.
• Correlation analysis between tremor score (TS) and AES/ENT in PD patients.
• Investigation of associations between AES/ENT and cortical thickness, gray-white matter contrast, and gray matter density.

Main Results:

• AES, unlike ENT, significantly differentiated HC and PD patients (P=0.02).
• In PD patients, AES showed a negative correlation with tremor score (ρ=-0.21, P=0.02).
• AES demonstrated significant relationships with structural covariance of cortical thickness and gray-white matter contrast in numerous cortical regions.

Conclusions:

• Average edge strength (AES) serves as a reliable retrospective index of head motion during structural MRI acquisition.
• AES can identify brain regions where morphometric measures are influenced by motion, particularly in populations susceptible to head motion.
• This metric aids in understanding motion-related biases in neuroimaging studies.