Bias and Variability of Mean Diffusivity from DTI Across Two Head Coils: a Traceable Phantom Study

Motivation: Variability and bias of diffusion parameters need to be assessed to separate the measurement-induced variability from biological effects. Goal(s): Our goal was to assess the bias and variability of mean diffusivity (MD) from the Diffusion Tensor Model using a traceable phantom. Approach: The NIST/QIBA phantom was scanned multiple times using two different head coils on the same system. The differences between MD measured using different head coils and bias to NIST-reported values were investigated. Results: A significant difference in measured MD with two coils can be found across multiple vials. Both coils introduce non-negligible bias to NIST-reported values for lower MD values. Impact: Using traceable phantoms is essential in the development of Diffusion MRI-based Quantitative Imaging Biomarkers (QIBs). Different head coils can introduce significant differences across MD values and should be treated as confounding factors in QIBs studies.