The Open-Access European Prevention of Alzheimer’s Dementia (EPAD) MRI dataset and processing workflow

The European Prevention of Alzheimer Dementia (EPAD) is a multi-center study that aims to characterize the
preclinical and prodromal stages of Alzheimer’s Disease. The EPAD imaging dataset includes core (3D T1w, 3D
FLAIR) and advanced (ASL, diffusion MRI, and resting-state fMRI) MRI sequences.
Here, we give an overview of the semi-automatic multimodal and multisite pipeline that we developed to
curate, preprocess, quality control (QC), and compute image-derived phenotypes (IDPs) from the EPAD MRI
dataset. This pipeline harmonizes DICOM data structure across sites and performs standardized MRI pre-
processing steps. A semi-automated MRI QC procedure was implemented to visualize and flag MRI images next to
site-specific distributions of QC features — i.e. metrics that represent image quality. The value of each of these
QC features was evaluated through comparison with visual assessment and step-wise parameter selection based
on logistic regression. IDPs were computed from 5 different MRI modalities and their sanity and potential clinical
relevance were ascertained by assessing their relationship with biological markers of aging and dementia.
The EPAD v1500.0 data release encompassed core structural scans from 1356 participants 842 fMRI, 831
dMRI, and 858 ASL scans. From 1356 3D T1w images, we identified 17 images with poor quality and 61 with
moderate quality. Five QC features — Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR), Coefficient of
Joint Variation (CJV), Foreground-Background energy Ratio (FBER), and Image Quality Rate (IQR) — were
selected as the most informative on image quality by comparison with visual assessment. The multimodal IDPs
showed greater impairment in associations with age and dementia biomarkers, demonstrating the potential of
the dataset for future clinical analyses.