Diffusion MRI of the neonate brain: acquisition, processing and analysis techniques

Abstract

Diffusion MRI (dMRI) is a popular noninvasive imaging modality for the investigation of the neonate brain. It enables the assessment of white matter integrity, and is particularly suited for studying white matter maturation in the preterm and term neonate brain. Diffusion tractography allows the delineation of white matter pathways and assessment of connectivity in vivo. In this review, we address the challenges of performing and analysing neonate dMRI. Of particular importance in dMRI analysis is adequate data preprocessing to reduce image distortions inherent to the acquisition technique, as well as artefacts caused by head movement. We present a summary of techniques that should be used in the preprocessing of neonate dMRI data, and demonstrate the effect of these important correction steps. Furthermore, we give an overview of available analysis techniques, ranging from voxel-based analysis of anisotropy metrics including tract-based spatial statistics (TBSS) to recently developed methods of statistical analysis addressing issues of resolving complex white matter architecture. We highlight the importance of resolving crossing fibres for tractography and outline several tractography-based techniques, including connectivity-based segmentation, the connectome and tractography mapping. These techniques provide powerful tools for the investigation of brain development and maturation.

Measuring the progression of upper motor neuron disease using diffusion MRI and its correlation with Clinical phenotype

“…Quantitative FA measures are believed to reflect changes in the myelination, fiber density and packing (Mädler, Drabycz et al 2008). Generally speaking, decreased diffusivity and increased diffusion anisotropy reflects more structural organization and better WM structural integrity (Pannek, Guzzetta et al 2012). What we know about DTI metrics is largely based upon empirical studies that investigate how these measures correlate with the underlying pathology.…”

“…Figure 3.1 summarizes the workflow for diffusion data pre-processing suggested by Pannek et al (Pannek, Guzzetta et al 2012), which was followed in this study. While this pre-processing workflow was initially developed for use with neonates, the same approach was followed here because motion artefacts are frequently observed in ALS patients who are often restless, due to their disease symptoms.…”

“…DTI is increasingly being used to show changes in fiber tracts in neurodegenerative diseases. Generally speaking, decreased diffusivity and increased diffusion anisotropy reflect greater structural organization and white matter (WM) structural integrity (Pannek, Guzzetta et al 2012). …”

Investigating neural connectivity of corticomotor networks in ataxia telangiectasia: improving our understanding of the clinical phenotype

“…These technical issues have in part been addressed through a series of data pre-processing and correction steps to reduce image distortions inherent to the acquisition technique, as well as those caused by involuntary head movement, 20 allowing dMRI studies to be performed in A-T. Such studies are urgently needed to fully elucidate the relationship between mutation of the ATM gene and loss in the integrity of motor circuitry.…”

“…An extensive pre-processing procedure was followed to detect and correct for image artefacts caused by head motion and image distortions, 20 thereby enabling the use of all patient subjects for analysis.…”