Increased Sensitivity and Signal-to-Noise Ratio in Diffusion-Weighted MRI using Multi-Echo Acquisitions

Post-mortem diffusion MRI (dMRI) enables high SNR (signal-to-noise ratio) images with high spatial resolution - at the expense of longer scanning times. The typically used segmented image acquisition leads to an incomplete signal decay before continuing the MR coding. Especially in diffusion-weighted MRI, with low signal intensities and lengthy contrast encoding, such inefficiency translates into reduced image quality and longer scanning times. This study introduces Multi Echo (ME) acquisitions to dMRI - a time-efficient approach, which increases SNR and reduces noise bias for dMRI images. The benefit of the introduced ME dMRI method were validated using Monte Carlo simulations and applied on a post mortem wild chimpanzee brain. The proposed strategy comes at a small price in scanning time (here 30% additional) and leads to increased SNR (here 1.9x) and a general reduction of the noise bias.