White matter integrity measured by fractional anisotropy correlates poorly with actual individual fiber anisotropy
Leow, A. D., Zhan, L., Zhu, S., Hageman, N., Chiang, M. C., Barysheva, M., Toga, A. W., McMahon, K. L., de Zubicaray, G. I., Wright, M. J., & Thompson, P. M. (2009) White matter integrity measured by fractional anisotropy correlates poorly with actual individual fiber anisotropy. In 2009 6th IEEE International Symposium on Biomedical Imaging: From Nano to Macro Proceedings, IEEE, Boston, USA, pp. 622-625.
Fractional anisotropy (FA), a very widely used measure of fiber integrity based on diffusion tensor imaging (DTI), is a problematic concept as it is influenced by several quantities including the number of dominant fiber directions within each voxel, each fiber's anisotropy, and partial volume effects from neighboring gray matter. High-angular resolution diffusion imaging (HARDI) can resolve more complex diffusion geometries than standard DTI, including fibers crossing or mixing. The tensor distribution function (TDF) can be used to reconstruct multiple underlying fibers per voxel, representing the diffusion profile as a probabilistic mixture of tensors. Here we found that DTIderived mean diffusivity (MD) correlates well with actual individual fiber MD, but DTI-derived FA correlates poorly with actual individual fiber anisotropy, and may be suboptimal when used to detect disease processes that affect myelination. Analysis of the TDFs revealed that almost 40% of voxels in the white matter had more than one dominant fiber present. To more accurately assess fiber integrity in these cases, we here propose the differential diffusivity (DD), which measures the average anisotropy based on all dominant directions in each voxel.
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|Item Type:||Conference Paper|
|Keywords:||Diffusion tensor imaging, Fractional anisotropy, High-angular resolution diffusion imaging|
|Divisions:||Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
|Copyright Owner:||Copyright 2009 IEEE|
|Deposited On:||09 Oct 2015 05:27|
|Last Modified:||21 Oct 2015 03:39|
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