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Front. Neurol. | doi: 10.3389/fneur.2018.00092

Understanding the Physiopathology Behind Axial and Radial Diffusivity Changes – What Do We Know?

 Pawel J. Winklewski1*, Agnieszka Sabisz1, Patrycja Naumczyk2, Krzysztof Jodzio2,  Edyta Szurowska1 and  Arkadiusz Szarmach1
  • 1Gdańsk Medical University, Poland
  • 2University of Gdańsk, Poland

The use of the diffusion tensor imaging (DTI) is rapidly growing in the neuroimaging field. Nevertheless, rigorously performed quantitative validation of DTI pathologic metrics remains very limited owing to the difficulty in co-registering quantitative histology findings with magnetic resonance imaging. The aim of this review is to summarise the existing state of the art knowledge with respect to axial (λ║) and radial (λ┴) diffusivity as DTI markers of axonal and myelin damage, respectively.
Firstly, we provide technical background for DTI and briefly discuss the specific organization of white matter in bundles of axonal fibres running in parallel; this is the natural target for imaging based on diffusion anisotropy. Secondly, we discuss the four seminal studies that paved the way for considering axial (λ║) and radial (λ┴) diffusivity as potential in vivo surrogate markers of axonal and myelin damage, respectively. Then, we present difficulties in interpreting axial (λ║) and radial (λ┴) diffusivity in clinical conditions associated with inflammation, oedema, and white matter fibre crossing. Finally, future directions are highlighted.
In summary, DTI can reveal strategic information with respect to white matter tracts, disconnection mechanisms, and related symptoms. Axial (λ║) and radial (λ┴) diffusivity seem to provide quite consistent information in healthy subjects, and in pathological conditions with limited oedema and inflammatory changes. DTI remains one of the most promising non-invasive diagnostic tools in medicine.

Keywords: Diffusion Tensor Imaging, axial diffusivity, radial diffusivity, Myelin Dysfunction, axonal injury

Received: 01 Dec 2017; Accepted: 09 Feb 2018.

Edited by:

Lars Ersland, Haukeland University Hospital, Norway

Reviewed by:

Gerardo Morfini, University of Illinois at Chicago, United States
Rodolfo G. Gatto, University of Illinois at Chicago, United States  

Copyright: © 2018 Winklewski, Sabisz, Naumczyk, Jodzio, Szurowska and Szarmach. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: MD, PhD. Pawel J. Winklewski, Gdańsk Medical University, Gdańsk, Poland, pawelwinklewski@wp.pl