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Neuroimage. 2016 Jan 1;124(Pt A):824-833. doi: 10.1016/j.neuroimage.2015.09.049. Epub 2015 Oct 1.

Fiber ball imaging.

Author information

1
Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, USA; Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA. Electronic address: jense@musc.edu.
2
Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, USA; Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA; Department of Neurosciences Sciences, Medical University of South Carolina, Charleston, SC, USA.

Abstract

By modeling axons as thin cylinders, it is shown that the inverse Funk transform of the diffusion MRI (dMRI) signal intensity obtained on a spherical shell in q-space gives an estimate for a fiber orientation density function (fODF), where the accuracy improves with increasing b-value provided the signal-to-noise ratio is sufficient. The method is similar to q-ball imaging, except that the Funk transform of q-ball imaging is replaced by its inverse. We call this new approach fiber ball imaging. The fiber ball method is demonstrated for healthy human brain, and fODF estimates are compared to diffusion orientation distribution function (dODF) approximations obtained with q-ball imaging. The fODFs are seen to have sharper features than the dODFs, reflecting an enhancement of the higher degree angular frequencies. The inverse Funk transform of the dMRI signal intensity data provides a simple and direct method of estimating a fODF. In addition, fiber ball imaging leads to an estimate for the ratio of the fraction of MRI visible water confined to the intra-axonal space divided by the square root of the intra-axonal diffusivity. This technique may be useful for white matter fiber tractography, as well as other types of microstructural modeling of brain tissue.

KEYWORDS:

Brain; Diffusion MRI; Fiber orientation density function; Funk transform; High-angular-resolution diffusion imaging; Q-ball imaging

PMID:
26432187
PMCID:
PMC4651772
DOI:
10.1016/j.neuroimage.2015.09.049
[Indexed for MEDLINE]
Free PMC Article

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