期刊
NEUROIMAGE
卷 52, 期 4, 页码 1374-1389出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.neuroimage.2010.05.043
关键词
Diffusion MRI; Active imaging; Axon diameter; Fibre density; White matter; Microstructure
资金
- EPSRC [EP/E056938/1, EP/E007748]
- National Science and Engineering Research Council of Canada (NSERC)
- Lundbeck Foundation
- EU
- BBSRC [BB/E002226/1] Funding Source: UKRI
- EPSRC [EP/E064280/1, EP/G007748/1, EP/H046410/1] Funding Source: UKRI
- Biotechnology and Biological Sciences Research Council [BB/E002226/1] Funding Source: researchfish
- Engineering and Physical Sciences Research Council [EP/H046410/1, EP/E064280/1, EP/G007748/1, GR/T02669/01] Funding Source: researchfish
- Lundbeck Foundation [R17-2007-1690] Funding Source: researchfish
This paper proposes and tests a technique for imaging orientationally invariant indices of axon diameter and density in white matter using diffusion magnetic resonance imaging. Such indices potentially provide more specific markers of white matter microstructure than standard indices from diffusion tensor imaging. Orientational invariance allows for combination with tractography and presents new opportunities for mapping brain connectivity and quantifying disease processes. The technique uses a four-compartment tissue model combined with an optimized multishell high-angular-resolution pulsed-gradient-spin-echo acquisition. We test the method in simulation, on fixed monkey brains using a preclinical scanner and on live human brains using a clinical 3 T scanner. The human data take about one hour to acquire. The simulation experiments show that both monkey and human protocols distinguish distributions of axon diameters that occur naturally in white matter. We compare the axon diameter index with the mean axon diameter weighted by axon volume. The index differs from this mean and is protocol dependent, but correlation is good for the monkey protocol and weaker, but discernible, for the human protocol where greater diffusivity and lower gradient strength limit sensitivity to only the largest axons. Maps of axon diameter and density indices from the monkey and human data in the corpus callosum and corticospinal tract reflect known trends from histology. The results show orientationally invariant sensitivity to natural axon diameter distributions for the first time with both specialist and clinical hardware. This demonstration motivates further refinement, validation, and evaluation of the precise nature of the indices and the influence of potential confounds. (c) 2010 Elsevier Inc. All rights reserved.
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