title: Formalin fixation alters water diffusion coefficient magnitude but not anisotropy in infarcted brain.
abstract: This study was designed to determine whether formalin fixation alters diffusion parameters in the infarcted brain. Diffusion tensor images were obtained from anesthetized mice 1 hr after middle cerebral artery occlusion and repeated after formalin fixation of brains. In live animals, there was a significant decrease in the trace of the diffusion tensor (Tr(D)) in infarcted cortex and external capsule compared with contralateral brain areas, with no change in relative anisotropy (RA). After formalin fixation, Tr(D) was reduced 30-80%. However, the Tr(D) differential present in vivo between injured and healthy tissues was lost, with Tr(D) reduced to similar values in all tissues except for the edge of the cortical infarction, where it was lower than in surrounding tissues. RA values were unchanged after fixation. This study supports the preservation of diffusion anisotropy for both healthy and injured white matter in fixed mouse brain. However, the sensitivity of water diffusion in detecting tissue injury in vivo is not preserved in fixed tissues.
authors.affiliation: Department of Radiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Shu-Wei
authors.initials: SW
authors.lastname: Sun
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Neil
authors.forename: Hsiao-Fang
authors.initials: HF
authors.lastname: Liang
authors.forename: Yong Y
authors.initials: YY
authors.lastname: He
authors.forename: Robert E
authors.initials: RE
authors.lastname: Schmidt
authors.forename: Chung Y
authors.initials: CY
authors.lastname: Hsu
authors.forename: Sheng-Kwei
authors.initials: SK
authors.lastname: Song
mesh_terms: D000818:Animals; D016880:Anisotropy; D001834:Body Water / Q000378:metabolism*; D020520:Brain Infarction / Q000473:pathology*; D001931:Brain Mapping / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005404:Fixatives; D005557:Formaldehyde; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016707:Tissue Fixation
chemical_list: D005404:Fixatives; D005557:Formaldehyde