Microscopic Diffusion Anisotropy in the Human Brain: Age-Related Changes

TY - JOUR

T1 - Microscopic Diffusion Anisotropy in the Human Brain: Age-Related Changes

AU - Lawrenz, Marco

AU - Brassen, Stefanie

AU - Finsterbusch, Jürgen

N1 - Copyright © 2016 Elsevier Inc. All rights reserved.

PY - 2016/7/17

Y1 - 2016/7/17

N2 - The fractional anisotropy (FA) that can be derived from diffusion tensor imaging (DTI), is ambiguous because it not only depends on the tissue microstructure but also on the axon or fiber orientation distribution within a voxel. Measures of the microscopic diffusion anisotropy, like the microscopic anisotropy index (MA) that can be determined with so-called double-wave-vector (DWV) or double diffusion encoding (DDE) imaging, are independent of this orientation distribution and, thus, offer a more direct and undisguised access to the tissue structure on a cellular or microscopic scale. In this study, FA and MA measurements were performed in a group of aged (>60y), healthy volunteers and compared to the data obtained recently for a group of young (<33y), healthy volunteers to reveal age-related differences. The coefficients-of-variation (CV) determined for the aged group were considerably lower for MA than for FA in average and in most of the 16 ROIs analyzed due to lower between-subject variations of MA. FA differences between the young and the aged group were in line with previous DTI studies. MA was also decreased in the aged group but in more of the 16 ROIs and with a higher significance. Furthermore, MA differences were also observed in frontal brain regions containing fiber crossings that did not reveal significant FA differences, i.e. MA seems to provide a better sensitivity to detect microstructural changes in such regions. In some non-cortical gray matter structures like the putamen, FA was increased but MA was decreased in the aged group which could indicate a coherent fiber orientation in the aged group related to the loss of crossing or fanning fibers. In conclusion, MA not only could improve the detectability of differences of the tissue microstructure but, in conjunction with FA, could also help to identify the underlying changes.

AB - The fractional anisotropy (FA) that can be derived from diffusion tensor imaging (DTI), is ambiguous because it not only depends on the tissue microstructure but also on the axon or fiber orientation distribution within a voxel. Measures of the microscopic diffusion anisotropy, like the microscopic anisotropy index (MA) that can be determined with so-called double-wave-vector (DWV) or double diffusion encoding (DDE) imaging, are independent of this orientation distribution and, thus, offer a more direct and undisguised access to the tissue structure on a cellular or microscopic scale. In this study, FA and MA measurements were performed in a group of aged (>60y), healthy volunteers and compared to the data obtained recently for a group of young (<33y), healthy volunteers to reveal age-related differences. The coefficients-of-variation (CV) determined for the aged group were considerably lower for MA than for FA in average and in most of the 16 ROIs analyzed due to lower between-subject variations of MA. FA differences between the young and the aged group were in line with previous DTI studies. MA was also decreased in the aged group but in more of the 16 ROIs and with a higher significance. Furthermore, MA differences were also observed in frontal brain regions containing fiber crossings that did not reveal significant FA differences, i.e. MA seems to provide a better sensitivity to detect microstructural changes in such regions. In some non-cortical gray matter structures like the putamen, FA was increased but MA was decreased in the aged group which could indicate a coherent fiber orientation in the aged group related to the loss of crossing or fanning fibers. In conclusion, MA not only could improve the detectability of differences of the tissue microstructure but, in conjunction with FA, could also help to identify the underlying changes.

KW - Aged

KW - Aging/pathology

KW - Anisotropy

KW - Brain/cytology

KW - Diffusion

KW - Diffusion Magnetic Resonance Imaging/methods

KW - Female

KW - Humans

KW - Image Interpretation, Computer-Assisted/methods

KW - Male

KW - Middle Aged

KW - Reproducibility of Results

KW - Sensitivity and Specificity

KW - White Matter/cytology

U2 - 10.1016/j.neuroimage.2016.07.031

DO - 10.1016/j.neuroimage.2016.07.031

M3 - SCORING: Journal article

C2 - 27436594

VL - 141

SP - 313

EP - 325

JO - NEUROIMAGE

JF - NEUROIMAGE

SN - 1053-8119

ER -