Increased sensitivity and signal-to-noise ratio in diffusion-weighted MRI using multi-echo acquisitions

Area of Science:

• Neuroimaging
• Diffusion MRI
• Post-mortem studies

Background:

• Post-mortem diffusion MRI (dMRI) offers high resolution but suffers from long scan times and reduced image quality due to incomplete signal decay.
• Temporal inefficiencies in standard dMRI acquisition strategies, especially with low signal intensities, limit image quality and increase scan duration.

Purpose of the Study:

• To introduce and validate Multi Echo (ME) acquisitions for post-mortem dMRI on a human MRI system.
• To enhance Signal-to-Noise Ratio (SNR) and reduce noise bias in dMRI images through a time-efficient approach.

Main Methods:

• Implementation of Multi Echo (ME) acquisitions within dMRI protocols.
• Validation using numerical Monte Carlo simulations.
• Application to a post-mortem chimpanzee brain, employing Maximum Likelihood Estimation for echo combination.

Main Results:

• ME-dMRI demonstrated a substantial SNR increase (white matter: ~1.6x, grey matter: ~1.9x) with optimal SNR from Maximum Likelihood Estimation echo combination.
• The method achieved this improvement with only a 30% increase in scanning time.
• A general reduction in noise bias was observed across the dMRI images.

Conclusions:

• Multi Echo (ME) acquisitions represent a time-efficient advancement for post-mortem dMRI.
• The proposed method significantly improves SNR and reduces noise bias, leading to higher quality structural imaging data.
• ME-dMRI is a valuable technique for detailed post-mortem brain analysis, offering enhanced image quality and efficiency.