A longitudinal study to characterize quantitative MRI changes due to progressive formalin-fixation in whole postmortem human brains
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Date
2017-11-29
Authors
Shatil, Anwar Shahadat
Journal Title
Journal ISSN
Volume Title
Publisher
Frontiers in Neurology
Abstract
Postmortem MRI can be used to reveal important pathologies and establish radiology-pathology correlations. However, quantitative MRI values are altered by tissue fixation. Therefore, the purpose of this thesis was to investigate time-dependent effects of formalin fixation on MR relaxometry (T1 and T2), diffusion tensor (fractional anisotropy, FA; and mean diffusivity, MD), and myelin water fraction (MWF) measurements throughout intact human brain specimens. Two whole, neurologically-healthy human brains were immersed in 10% formalin solution and then scanned at 13 time-points between 0 and 1032 hours. Whole brain maps of longitudinal (T1) and transverse (T2) relaxation times, FA, MD, and MWF were generated at each time-point to illustrate the changes over time, and region-of-interest analyses were performed in eight brain structures to quantify the changes with progressive fixation.Although neither of the diffusion measures (FA nor MD) showed significant changes as a function of formalin fixation, both T1 and T2-relaxation times were significantly decreased, and MWF estimates were significantly increased. These results suggest that T1-relaxation, T2-relaxation and myelin water fraction estimates must be performed very early, or at consistent time-points, in the fixation process to avoid formalin-induced changes compared to in vivo values or between samples, respectively.
Description
Keywords
Ex vivo, Formalin, Fixation, MRI, Neuroimaging, Postmortem, Diffusion, T1, T2, Myelin
Citation
Shatil, A. S., Matsuda, K. M., & Figley, C. R. (2016). A Method for Whole Brain Ex Vivo Magnetic Resonance Imaging with Minimal Susceptibility Artifacts. Frontiers in Neurology, 7, 208. http://doi.org/10.3389/fneur.2016.00208