Water diffusion measurements in perfused human hippocampal slices undergoing tonicity changes

Area of Science:

• Neuroimaging
• Biophysics
• Magnetic Resonance Imaging

Background:

• Diffusion MRI offers insights into nervous tissue but requires long diffusion times, potentially causing signal confounds from compartmental exchange.
• Investigating human nervous tissue at shorter diffusion times is crucial for accurate interpretation and comparison with existing rat brain slice studies.

Purpose of the Study:

• To measure water diffusion in human hippocampal slices at short diffusion times.
• To assess the impact of osmotic perturbations on water diffusion parameters in human brain tissue.
• To validate findings against previous studies in rat brain slices and human brain in vivo.

Main Methods:

• Diffusion MRI was performed on 20 ex vivo human hippocampal slices using a 17.6-T magnet and 1000-mT/m gradients.
• Tissue viability was confirmed electrophysiologically.
• Osmotic challenges involved 20% hypotonic and 20% hypertonic artificial cerebrospinal fluid, with water diffusion analyzed using biexponential functions.

Main Results:

• Water diffusion signal attenuation was accurately described by a biexponential function (R(2) > 0.99).
• Mean diffusion parameters included F(fast) of 0.686 ± 0.082, fast ADC of 1.22 ± 0.22 x 10(-3) mm(2)/s, and slow ADC of 0.06 ± 0.02 x 10(-3) mm(2)/s.
• Hypotonic and hypertonic solutions induced significant changes in F(fast) (-8.2% and +10.1%, respectively; ANOVA, P < 0.001).

Conclusions:

• The results align with prior diffusion studies in rat brain slices and human brain in vivo.
• These findings provide a foundation for developing more accurate models of water diffusion in nervous tissue.
• This research is expected to enhance the clinical applicability of diffusion MRI for neurological conditions.