Characterization of white matter degeneration in elderly subjects by magnetic resonance diffusion and FLAIR imaging correlation

Abstract

Fluid attenuated inversion recovery (FLAIR) and diffusion tensor imaging (DTI) techniques have been widely used to evaluate white matter (WM) alterations associated with aging, dementia and cerebral vascular disease. The relationship between FLAIR detected WM lesions (WML) and DTI detected WM integrity changes, however, remains unclear. To investigate this association, voxelwise correlations between 4 Tesla DTI and FLAIR images from elderly subjects were performed by relating WML volume and intensity in FLAIR to fractional anisotropy (FA) and mean diffusivity (MD) in DTI. Significant DTI-FLAIR correlations were found in regions overlapping with the WML of moderate intensities in FLAIR. No significant correlations were detected in periventricular regions where the FLAIR intensities are particularly high. The findings are consistent with a transitional model for WM degeneration from normal WM to cerebrospinal fluid (CSF). The results show that the correlation between DTI and FLAIR disappears when the FLAIR intensity of WML reaches its maximum at a certain lesion severity, and that the correlations may remerge with reversed signs when the lesion severity is further increased. These results suggest that the different stages of WM degeneration in elderly subjects can be better characterized by regional DTI-FLAIR correlations than single modality alone.

Age-related decline in white matter tract integrity and cognitive performance: A DTI tractography and structural equation modeling study

“…Two had extensive confluent deep white matter hyperintensities (WMH), and 5 had either small- or medium-sized focal WMH in deep white matter. WMH may affect white matter microstructural integrity (FA), though a relationship between these measures is only just beginning to be understood (Zhan et al, 2009). It is also possible that relationships between white matter tract integrity and specific cognitive tests were present, but not detected.…”

Quantifying the effects of normal ageing on white matter structure using unsupervised tract shape modelling

“…For those subjects with significant white matter lesion load, lesion areas, defined as regions with abnormal signal intensity typically 25 % greater than the average intensity of surrounding normal-appearing white matter (Zhan et al, 2009), were extracted from bias field corrected FLAIR images (FAST; FMRIB, Oxford, UK).…”

The Role of Diffusion Tensor Imaging in the Study of Cognitive Aging

“…First, the number of studies that have measured both FLAIR and DTI in the same individuals, and directly evaluated what information about prevalent aging-related white matter pathology is shared between the two or unique to one or the other, is still very small. One study has suggested that by investigating relationships between FLAIR signal intensity and DTI measures within WMHs, we can effectively categorize WMHs according to the severity of WMH dysfunction, but the clinical value of such deeper characterization of WMH severity is currently unclear (Zhan et al 2009). Second, while several serial FLAIR studies have used multiple scans per individual to directly chart the longitudinal course of WMH changes in relation to risk factors and cognition, only three analogous serial DTI studies have appeared that report associations between DTI-based measures and ancillary variables of interest (Charlton et al 2010;Teipel et al 2010;Sullivan et al 2010).…”