Assessing potential correlation between T₂ relaxation and diffusion of lactate in the mouse brain

Area of Science:

• Neuroimaging
• Biophysics
• Metabolomics

Background:

• Diffusion and T2 relaxation are fundamental properties in Magnetic Resonance Spectroscopy (MRS).
• While intracellular metabolites show little correlation between diffusion and T2 relaxation, lactate's dual localization (intra- and extracellular) suggests potential T2 dependence on its diffusion.
• Understanding this relationship is crucial for accurate lactate diffusion modeling in MRS.

Purpose of the Study:

• To investigate the potential T2 dependence on lactate diffusion in the mouse brain using diffusion-weighted MRS.
• To assess if echo time (TE) affects apparent diffusivity and kurtosis of lactate.
• To determine if T2 relaxation influences lactate diffusion measurements.

Main Methods:

• Utilized a frequency-selective diffusion-weighted spin-echo sequence to cancel J-modulation of lactate at 1.3 ppm.
• Acquired data at varying echo times (TE) from 50.9 to 110.9 ms, maintaining a constant diffusion time.
• Measured apparent diffusivity and kurtosis of lactate in the mouse brain.

Main Results:

• No significant difference was observed in diffusion-weighted signal attenuation for any metabolite with increasing TE.
• Apparent diffusivity and kurtosis of lactate remained constant across the tested echo times.
• The J-modulation of lactate was successfully suppressed even at longer echo times.

Conclusions:

• No significant TE dependence of diffusivity and kurtosis was measured for lactate in the 50-110 ms range.
• Potential T2 effects on lactate diffusion can be ignored when interpreting or modeling diffusion-weighted MRS data.
• This study validates a novel diffusion sequence for robust lactate diffusion assessment.