The effects of brain tissue decomposition on diffusion tensor imaging and tractography

Area of Science:

• Neuroimaging
• Diffusion Tensor Imaging (DTI)
• Postmortem Interval (PMI)

Background:

• High-resolution DTI studies are common in fixed animal brains but rare in human brains.
• Human tissue fixation is delayed postmortem, unlike animal tissue, potentially affecting diffusion properties.
• The postmortem interval (PMI) is a critical factor influencing tissue integrity and DTI metrics.

Purpose of the Study:

• To investigate the effect of the postmortem interval (PMI) on diffusion properties in fixed rodent brains.
• To quantify changes in diffusion metrics (ADC, FA) and tractography with varying PMIs.
• To establish the significance of PMI in interpreting DTI data from fixed brain tissue.

Main Methods:

• Eight mice brains were fixed in formalin at PMIs of 0, 1, 4, and 14 days.
• Post-fixation, brains were scanned using a 3D EPI DTI sequence at 4.7T.
• DTI data were processed to generate ADC and FA maps; tractography was performed.

Main Results:

• Regional FA and ADC values in gray and white matter significantly decreased with increasing PMI (p<0.05).
• DTI tractography revealed a reduction in the number and coherence of reconstructed fiber pathways between 0 and 14 days PMI.
• Statistical analysis confirmed a significant temporal decline in diffusion properties.

Conclusions:

• The time between death and tissue fixation (PMI) substantially alters brain diffusion properties.
• These findings are crucial for accurately interpreting DTI data from fixed brain samples.
• Researchers must consider PMI when analyzing DTI metrics in fixed brain studies.