Effects of concentration and vendor specific composition of formalin on postmortem MRI of the human brain

• Published in: Magnetic resonance in medicine 2018-02, Vol.79 (2), p.1111-1115
• Main Authors: Birkl, Christoph, Soellradl, Martin, Toeglhofer, Anna Maria, Krassnig, Stefanie, Leoni, Marlene, Pirpamer, Lukas, Vorauer, Thomas, Krenn, Heinz, Haybaeck, Johannes, Fazekas, Franz, Ropele, Stefan, Langkammer, Christian
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Autolysis; Autopsy; Brain; Brain - diagnostic imaging; Composition effects; Crosslinking; Divergence; Female; Fixation; Fixatives - chemistry; Formaldehyde; Formaldehyde - chemistry; formalin concentration; formalin fixation; formalin fixed brain tissue; Humans; Magnetic measurement; magnetic properties of formalin; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Magnetic susceptibility; Male; Middle Aged; Nanoparticles; postmortem MRI; Proteins; relaxation properties of formalin; Relaxation time; Superconducting quantum interference devices; Superconductivity; Tissue Fixation - methods
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.26699

Purpose 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. Methods 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. Results 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. Conclusion 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.