Abstract
PURPOSE: Relaxation time constants are useful as markers of tissue properties. Imaging ex vivo tissue is done for research purposes; however, T(1) relaxation time constants are altered by tissue fixation in a time-dependent manner. This study investigates regional changes in T(1) relaxation time constants in ex vivo brain tissue over 6 months of fixation. METHODS: Five ex vivo human brain hemispheres in 10% formalin were scanned over 6 months. Mean T(1) relaxation time constants were measured in regions of interest (ROIs) representing gray matter (GM) and white matter (WM) regions and analyzed as a function of fixation time. RESULTS: Cortical GM ROIs had longer T(1) relaxation time constants than WM ROIs; the thalamus had T(1) relaxation time constants similar to those of WM ROIs. T(1) relaxation time constants showed rapid shortening within the first 6 weeks after fixation followed by a slower rate of decline. CONCLUSION: Both GM and WM T(1) relaxation time constants of fixed brain tissue show rapid decline within the first 6 weeks after autopsy and slow by 6 months. This information is useful for optimizing MR imaging acquisition parameters according to fixation time for ex vivo brain imaging studies. Magn Reson Med 77:774-778, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.