Purpose: Relaxation time constants are useful as markers of tissue properties. Imaging ex vivo tissue is done for research purposes; however, T1 relaxation time constants are altered by tissue fixation in a time-dependent manner. This study investigates regional changes in T1 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 T1 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 T1 relaxation time constants than WM ROIs; the thalamus had T1 relaxation time constants similar to those of WM ROIs. T1 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 T1 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.
- ex vivo
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging