Spiral readout improves in vivo MR axon radius estimation in human white matter

We compared spiral and EPI diffusion imaging at ultra-high b-values for axon radius estimation in the white matter. For data acquisition, a custom multiband spiral sequence was combined with trajectory monitoring and higher order image reconstruction. The lower echo time of the spiral sequence led to increased relative SNR compared to EPI and improved estimation of axon radii. The resulting axon radius maps from spiral scans were more homogeneous especially in low-SNR regions. We also found, that denoising performed on complex data instead of magnitude data significantly improved axon radius estimation.