Fast and accurate Slicewise OutLIer Detection (SOLID) with informed model estimation for diffusion MRI data

• Published in: NeuroImage (Orlando, Fla.) Vol. 181; pp. 331 - 346
• Main Authors: Sairanen, Viljami, Leemans, A., Tax, C.M.W.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2018; Elsevier Limited
• Subjects: Algorithms; Artefacts; Brain - diagnostic imaging; Brain research; Data Interpretation, Statistical; Diffusion Magnetic Resonance Imaging - methods; Diffusion Magnetic Resonance Imaging - standards; Humans; Image processing; Infant, Newborn; Magnetic resonance imaging; Models, Theoretical; Neonates; Neuroimaging - methods; Neuroimaging - standards; Population studies; Sensitivity and Specificity; Simulation; Spatial distribution; Netherlands
• ISSN: 1053-8119; 1095-9572; 1095-9572
• DOI: 10.1016/j.neuroimage.2018.07.003

The accurate characterization of the diffusion process in tissue using diffusion MRI is greatly challenged by the presence of artefacts. Subject motion causes not only spatial misalignments between diffusion weighted images, but often also slicewise signal intensity errors. Voxelwise robust model estimation is commonly used to exclude intensity errors as outliers. Slicewise outliers, however, become distributed over multiple adjacent slices after image registration and transformation. This challenges outlier detection with voxelwise procedures due to partial volume effects. Detecting the outlier slices before any transformations are applied to diffusion weighted images is therefore required. In this work, we present i) an automated tool coined SOLID for slicewise outlier detection prior to geometrical image transformation, and ii) a framework to naturally interpret data uncertainty information from SOLID and include it as such in model estimators. SOLID uses a straightforward intensity metric, is independent of the choice of the diffusion MRI model, and can handle datasets with a few or irregularly distributed gradient directions. The SOLID-informed estimation framework prevents the need to completely reject diffusion weighted images or individual voxel measurements by downweighting measurements with their degree of uncertainty, thereby supporting convergence and well-conditioning of iterative estimation algorithms. In comprehensive simulation experiments, SOLID detects outliers with a high sensitivity and specificity, and can achieve higher or at least similar sensitivity and specificity compared to other tools that are based on more complex and time-consuming procedures for the scenarios investigated. SOLID was further validated on data from 54 neonatal subjects which were visually inspected for outlier slices with the interactive tool developed as part of this study, showing its potential to quickly highlight problematic volumes and slices in large population studies. The informed model estimation framework was evaluated both in simulations and in vivo human data. •Slicewise artefacts due to subject motion or hardware issues are a common issue in diffusion MRI.•We propose a model-free slicewise outlier detection for diffusion MRI, coined SOLID.•We propose a model-free slicewise outlier detection algorithm for diffusion data, coined SOLID.•SOLID is validated with manually labelled outliers from 54 newborn subjects and extensive simulations.•SOLID-information is used as measurement uncertainty to provide robust diffusion and kurtosis tensor estimates.