Sensitivity of fiber orientation dependent to temperature and post mortem interval.

Area of Science:

• Neuroimaging
• Biophysics
• Magnetic Resonance Imaging

Background:

• Diffusion MRI is sensitive to white matter fiber orientation relative to the scanner's B0 field.
• Understanding post mortem changes is crucial for interpreting imaging data.

Purpose of the Study:

• Compare in vivo and post mortem brain white matter fiber orientation dependent diffusion MRI.
• Investigate the impact of temperature and post mortem interval (PMI) on these measurements.

Main Methods:

• Acquired diffusion MRI data at 3T using a multi-echo gradient-echo sequence.
• Computed white matter fiber orientation with diffusion tensor imaging (DTI).
• Fitted orientation-dependent diffusion MRI signals using a previously proposed model.

Main Results:

• Diffusion MRI signal orientation dependency decreased post mortem.
• Higher order orientation dependent signal components correlated negatively with temperature.
• Orientation independent signal components showed no significant correlation with temperature or PMI.

Conclusions:

• Lower brain temperature in post mortem samples likely explains the reduced diffusion MRI fiber orientation dependency.
• Diffusion tensor imaging successfully estimated fiber angles despite reduced post mortem diffusivity.