title: Effects of concentration and vendor specific composition of formalin on postmortem MRI of the human brain.
abstract: Formalin fixation prevents tissue autolysis by crosslinking proteins and changes tissue microstructure and MRI signal characteristics. Previous studies showed high variations in MR relaxation time constants of formalin fixed brain tissue, which has been attributed to the use of different formalin concentrations. Our investigations confirmed the influence of formalin concentration on relaxation times and unexpectedly revealed an influence of vendor specific formalin composition, which has not been investigated so far.
  
  
  
  We systematically analyzed relaxation times of human brain tissue fixed with 4% and 10% formalin compared with unfixed condition at 3 Tesla MRI. Furthermore, we assessed relaxation times of nine formalin solutions from different vendors and performed comparisons of their magnetic susceptibility by SQUID (superconducting quantum interference device) magnetometry.
  
  
  
  Tissue relaxation times decreased approximately twice as fast using 10% than in 4% formalin fixation. The vendor specific composition of the formalin solutions and concentration dependent paramagnetic effects showed a substantial contribution to differences in relaxation times of formalin.
  
  
  
  Our study demonstrates that differences of the formalin composition have substantial effects on MRI signal characteristics after fixation, which can explain the divergence of reported relaxation times beyond the effect of differences in formalin concentration. Magn Reson Med 79:1111-1115, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Department of Neurology, Medical University of Graz, Austria.
authors.forename: Christoph
authors.identifier: 0000-0003-3101-4002
authors.initials: C
authors.lastname: Birkl
authors.affiliation: Department of Neurology, Medical University of Graz, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Soellradl
authors.affiliation: Department of Neuropathology, Institute of Pathology, Medical University of Graz, Austria.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Toeglhofer
authors.affiliation: Department of Neuropathology, Institute of Pathology, Medical University of Graz, Austria.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Krassnig
authors.affiliation: Department of Neuropathology, Institute of Pathology, Medical University of Graz, Austria.
authors.forename: Marlene
authors.initials: M
authors.lastname: Leoni
authors.affiliation: Department of Neurology, Medical University of Graz, Austria.
authors.forename: Lukas
authors.initials: L
authors.lastname: Pirpamer
authors.affiliation: Institute of Physics, Experimental Physics, University of Graz, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Vorauer
authors.affiliation: Institute of Physics, Experimental Physics, University of Graz, Austria.
authors.forename: Heinz
authors.initials: H
authors.lastname: Krenn
authors.affiliation: Department of Neuropathology, Institute of Pathology, Medical University of Graz, Austria.|Department of Pathology, Medical Faculty, Otto-von-Guericke-University, Magdeburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Haybaeck
authors.affiliation: Department of Neurology, Medical University of Graz, Austria.
authors.forename: Franz
authors.initials: F
authors.lastname: Fazekas
authors.affiliation: Department of Neurology, Medical University of Graz, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Ropele
authors.affiliation: Department of Neurology, Medical University of Graz, Austria.
authors.forename: Christian
authors.identifier: 0000-0002-7097-9707
authors.initials: C
authors.lastname: Langkammer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001344:Autopsy; D001921:Brain / Q000000981:diagnostic imaging*; D005260:Female; D005404:Fixatives / Q000737:chemistry*; D005557:Formaldehyde / Q000737:chemistry*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016707:Tissue Fixation / Q000379:methods*
chemical_list: D005404:Fixatives; D005557:Formaldehyde
keywords: formalin concentration; formalin fixation; formalin fixed brain tissue; magnetic properties of formalin; postmortem MRI; relaxation properties of formalin