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

• Published in: NeuroImage (Orlando, Fla.) Fla.), 2020-11, Vol.221, p.117172-117172, Article 117172
• Main Authors: Eichner, Cornelius, Paquette, Michael, Mildner, Toralf, Schlumm, Torsten, Pléh, Kamilla, Samuni, Liran, Crockford, Catherine, Wittig, Roman M., Jäger, Carsten, Möller, Harald E., Friederici, Angela D., Anwander, Alfred
• Format: Article
• Language: English
• Subjects: Animals; Autopsy; Bias; Bioengineering; Chimpanzee; Computer Simulation; Diffusion; Diffusion Magnetic Resonance Imaging - methods; Diffusion Magnetic Resonance Imaging - standards; dMRI; Echo-Planar Imaging - methods; Echo-Planar Imaging - standards; Female; Gray Matter - diagnostic imaging; Humans; Image Processing, Computer-Assisted - methods; Image Processing, Computer-Assisted - standards; Imaging; Life Sciences; Magnetic resonance imaging; Monte Carlo Method; MRI; Multi-echo; Neuroimaging; Neuroimaging - methods; Neuroimaging - standards; Neurons and Cognition; Neurosciences; Noise; Noise reduction; Normal distribution; Pan troglodytes; Post-mortem; Relaxometry; Reproducibility of Results; Scanning; Segmented EPI; Signal to noise ratio; SNR; Standard deviation; Substantia alba; Substantia grisea; White Matter - diagnostic imaging
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2020.117172

•Novel acquisition and reconstruction strategy to increase the signal to noise ratio (SNR) and contrast of diffusion MRI.•Statistical data modelling for image reconstruction with reduced noise bias.•Substantial SNR gain for only moderate increase in acquisition time. Post-mortem diffusion MRI (dMRI) enables acquisitions of structural imaging data with otherwise unreachable resolutions - at the expense of longer scanning times. These data are typically acquired using highly segmented image acquisition strategies, thereby resulting in an incomplete signal decay before the MRI encoding continues. Especially in dMRI, with low signal intensities and lengthy contrast encoding, such temporal inefficiency translates into reduced image quality and longer scanning times. This study introduces Multi Echo (ME) acquisitions to dMRI on a human MRI system - a time-efficient approach, which increases SNR (Signal-to-Noise Ratio) and reduces noise bias for dMRI images. The benefit of the introduced ME-dMRI method was validated using numerical Monte Carlo simulations and showcased on a post-mortem brain of a wild chimpanzee. The proposed Maximum Likelihood Estimation echo combination results in an optimal SNR without detectable signal bias. The combined strategy comes at a small price in scanning time (here 30% additional) and leads to a substantial SNR increase (here white matter: ~ 1.6x, equivalent to 2.6 averages, grey matter: ~ 1.9x, equivalent to 3.6 averages) and a general reduction of the noise bias.