Abstract
Surface rendering of MRI brain scans may lead to identification of the participant through facial characteristics. In this study, we evaluate three methods that overwrite voxels containing privacy‐sensitive information: Face Masking, FreeSurfer defacing, and FSL defacing. We included structural T1‐weighted MRI scans of children, young adults and older adults. For the young adults, test–retest data were included with a 1‐week interval. The effects of the de‐identification methods were quantified using different statistics to capture random variation and systematic noise in measures obtained through the FreeSurfer processing pipeline. Face Masking and FSL defacing impacted brain voxels in some scans especially in younger participants. FreeSurfer defacing left brain tissue intact in all cases. FSL defacing and FreeSurfer defacing preserved identifiable characteristics around the eyes or mouth in some scans. For all de‐identification methods regional brain measures of subcortical volume, cortical volume, cortical surface area, and cortical thickness were on average highly replicable when derived from original versus de‐identified scans with average regional correlations >.90 for children, young adults, and older adults. Small systematic biases were found that incidentally resulted in significantly different brain measures after de‐identification, depending on the studied subsample, de‐identification method, and brain metric. In young adults, test–retest intraclass correlation coefficients (ICCs) were comparable for original scans and de‐identified scans with average regional ICCs >.90 for (sub)cortical volume and cortical surface area and ICCs >.80 for cortical thickness. We conclude that apparent visual differences between de‐identification methods minimally impact reliability of brain measures, although small systematic biases can occur.
Highlights
Advances in magnetic resonance imaging (MRI) technology enable researchers to collect good quality structural MRI scans of the brain
We focus on agerelated effects by including children, young adults, and older adults
We evaluated three de-identification methods for structural MRI scans: Defacing in FreeSurfer, defacing in FSL, and the Face Masking toolbox
Summary
Advances in magnetic resonance imaging (MRI) technology enable researchers to collect good quality structural MRI scans of the brain. From an ethical viewpoint sharing identifiable data may compromise the confidentiality participants consented to For these reasons, more and more open-access datasets contain MRI scans that were subjected to some type of de-identification method. Face Masking (Milchenko & Marcus, 2013, nrg.wustl.edu/software/facemasking) masks the face and, optional, the ear region and preserves more anatomical landmarks than defacing methods An advantage of the latter toolbox is that it can be applied to raw DICOM images, which limits the number of intermediate processing steps. We assessed whether de-identification altered brain measures differently in children, young adults, and older adults To this end, we extracted regional subcortical and cortical volumes, cortical surface area, and cortical thickness of original scans and de-identified scans. We quantified how the effects of de-identification techniques on brain measures compared to test–retest reliability in young adults
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