Relative indices of water diffusion anisotropy are equivalent in live and formalin-fixed mouse brains.
Formalin fixation of tissue is a common laboratory practice. A direct comparison of diffusion tensor imaging (DTI) parameters from mouse brains before (in vivo) and after (ex vivo) formalin fixation is reported herein. Five diffusion indices were examined in a cohort of seven mice: relative anisotropy (RA), directional correlation (DC), trace (Tr(D)), trace-normalized axial diffusivity (D(axially)), and radial diffusivity (D(radially)). Seven regions of interest (ROIs), including five in white matter and two in gray matter, were selected for examination. Consistent with previous findings, a significant decrease of Tr(D) was observed for all ROIs after fixation. However, water diffusion anisotropy, as defined by the indices RA, DC, D(axially), and D(radially), remained unchanged after fixation. Thus, fixation does not appear to alter diffusion anisotropy in the mouse brain. This finding supports the utility of diffusion anisotropy analysis of fixed tissue. The combination of DTI measurements and standard histology may shed light on the microstructural determinants of diffusion anisotropy in normal and disease states.
Sun
Shu-Wei
SW
Department of Radiology, Washington University School of Medicine, St. Louis, Missouri.
Neil
Jeffrey J
JJ
Song
Sheng-Kwei
SK
D000818:Animals; D016880:Anisotropy; D001921:Brain / Q000033:anatomy & histology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005404:Fixatives; D005557:Formaldehyde; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016707:Tissue Fixation; D014867:Water
D005404:Fixatives; D014867:Water; D005557:Formaldehyde