Freddy Ståhlberg
Expert
Quantification of microscopic diffusion anisotropy disentangles effects of orientation dispersion from microstructure: Applications in healthy volunteers and in brain tumors
Författare
Summary, in English
The anisotropy of water diffusion in brain tissue is affected by both disease and development. This change can be detected using diffusion MRI and is often quantified by the fractional anisotropy (FA) derived from diffusion tensor imaging (DTI). Although FA is sensitive to anisotropic cell structures, such as axons, it is also sensitive to their orientation dispersion. This is a major limitation to the use of FA as a biomarker for "tissue integrity", especially in regions of complex microarchitecture. In this work, we seek to circumvent this limitation by disentangling the effects of microscopic diffusion anisotropy from the orientation dispersion. The microscopic fractional anisotropy (mu FA) and the order parameter (OP) were calculated from the contrast between signal prepared with directional and isotropic diffusion encoding, where the latter was achieved by magic angle spinning of the q-vector (qMAS). These parameters were quantified in healthy volunteers and in two patients; one patient with meningioma and one with glioblastoma. Finally, we used simulations to elucidate the relation between FA and mu FA in various micro-architectures. Generally, mu FA was high in the white matter and low in the gray matter. In the white matter, the largest differences between mu FA and FA were found in crossing white matter and in interfaces between large white matter tracts, where mu FA was high while FA was low. Both tumor types exhibited a low FA, in contrast to the mu FA which was high in the meningioma and low in the glioblastoma, indicating that the meningioma contained disordered anisotropic structures, while the glioblastoma did not. This interpretation was confirmed by histological examination. We conclude that FA from DTI reflects both the amount of diffusion anisotropy and orientation dispersion. We suggest that the mu FA and OP may complement FA by independently quantifying the microscopic anisotropy and the level of orientation coherence. (C) 2014 The Authors. Published by Elsevier Inc.
Avdelning/ar
- eSSENCE: The e-Science Collaboration
- MR Physics
- Multidimensional microstructure imaging
- Medicinsk strålningsfysik, Lund
- Neuroradiologi
- MultiPark: Multidisciplinary research focused on Parkinson´s disease
- Diagnostisk radiologi, Lund
- BioCARE: Biomarkers in Cancer Medicine improving Health Care, Education and Innovation
- Tumörmikromiljö
- Fysikalisk kemi
- Lund University Bioimaging Center
Publiceringsår
2015
Språk
Engelska
Sidor
241-252
Publikation/Tidskrift/Serie
NeuroImage
Volym
104
Fulltext
Länkar
Dokumenttyp
Artikel i tidskrift
Förlag
Elsevier
Ämne
- Radiology, Nuclear Medicine and Medical Imaging
Nyckelord
- Diffusion weighted imaging
- Microscopic anisotropy
- Microscopic
- fractional anisotropy
- Order parameter
- Magic angle spinning of the
- q-vector
Status
Published
Forskningsgrupp
- MR Physics
- Multidimensional microstructure imaging
- Neuroradiology
ISBN/ISSN/Övrigt
- ISSN: 1095-9572