Harmonization of multi-site DTI and NODDI data using the combined association test

Abstract

When analyzing multi-site diffusion MRI (dMRI) data, metrics should be harmonized to remove the site effect. In this study, we applied the combined association test (ComBat), which uses regression of covariates with an empirical Bayes framework, for diffusion metrics based on diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI). The results showed that ComBat can harmonize site-related effects in DTI and NODDI metrics based on multi-site dMRI while preserving subject biological information, such as sex differences and correlation with age. Thus, ComBat could be applied in large multi-site studies to identify subtle white matter changes.