PURPOSE: To evaluate a model-independent, multi-directional anisotropy (MDA) metric that is analytically and experimentally equivalent to fractional anisotropy (FA) in single-direction diffusivity, but potentially superior to FA in its sensitivity to the underlying anisotropy of multi-directional diffusivity. MATERIALS AND METHODS: An expression for MDA was defined from the orientation distribution function (ODF) and its analytical relation to FA was derived. Simulations of single and crossed double-fibers were performed using a compressed-sensing-accelerated diffusion-spectrum-imaging (CS-DSI) scheme. In vivo brain imaging using CS-DSI was performed on eight healthy subjects. MDA was compared with FA and with another ODF-based metric known as generalized FA (GFA). RESULTS: In simulated single-direction fibers, MDA was shown to be equivalent to FA (from FA = 0.2 to 0.8). In crossed fibers, MDA provided superior differentiation of the underlying anisotropy as compared to FA and GFA. In vivo analysis shows that the MDA was superior to both FA (P = 0.015) and GFA (P = 0.021) in terms of its relative accuracy in crossed fiber regions. CONCLUSION: MDA provides a potentially superior measure of fiber anisotropy relative to conventional FA or GFA, and may be used to improve the assessment of disease in regions with multi-directional brain fibers.
PURPOSE: To evaluate a model-independent, multi-directional anisotropy (MDA) metric that is analytically and experimentally equivalent to fractional anisotropy (FA) in single-direction diffusivity, but potentially superior to FA in its sensitivity to the underlying anisotropy of multi-directional diffusivity. MATERIALS AND METHODS: An expression for MDA was defined from the orientation distribution function (ODF) and its analytical relation to FA was derived. Simulations of single and crossed double-fibers were performed using a compressed-sensing-accelerated diffusion-spectrum-imaging (CS-DSI) scheme. In vivo brain imaging using CS-DSI was performed on eight healthy subjects. MDA was compared with FA and with another ODF-based metric known as generalized FA (GFA). RESULTS: In simulated single-direction fibers, MDA was shown to be equivalent to FA (from FA = 0.2 to 0.8). In crossed fibers, MDA provided superior differentiation of the underlying anisotropy as compared to FA and GFA. In vivo analysis shows that the MDA was superior to both FA (P = 0.015) and GFA (P = 0.021) in terms of its relative accuracy in crossed fiber regions. CONCLUSION: MDA provides a potentially superior measure of fiber anisotropy relative to conventional FA or GFA, and may be used to improve the assessment of disease in regions with multi-directional brain fibers.
Authors: Robert J Young; Ek T Tan; Kyung K Peck; Mehrnaz Jenabi; Sasan Karimi; Nicole Brennan; Jennifer Rubel; John Lyo; Weiji Shi; Zhigang Zhang; Marcel Prastawa; Xiaofeng Liu; Jonathan I Sperl; Robin Fatovic; Luca Marinelli; Andrei I Holodny Journal: Magn Reson Imaging Date: 2016-10-11 Impact factor: 2.546
Authors: Philip R Szeszko; Ek Tsoon Tan; Aziz M Uluğ; Peter B Kingsley; Juan A Gallego; Kathryn Rhindress; Anil K Malhotra; Delbert G Robinson; Luca Marinelli Journal: Prog Neuropsychopharmacol Biol Psychiatry Date: 2017-10-28 Impact factor: 5.067
Authors: Thomas Welton; Jerome J Maller; R Marc Lebel; Ek T Tan; Dominic B Rowe; Stuart M Grieve Journal: Neuroimage Clin Date: 2019-07-22 Impact factor: 4.881