Unbiasing orientationally-averaged diffusion MRI signal
Tomasz Pieciak1, Maryam Afzali2,3, Antonio Tristán-Vega1, and Santiago Aja-Fernández1
1Laboratorio de Procesado de Imagen (LPI), Universidad de Valladolid, Valladolid, Spain, 2Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom, 3Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, United Kingdom
The orientationally-averaging or the so-called power-averaging is a common approach to reduce the impact of macroscopic anisotropy in diffusion MRI (dMRI). This paper analytically derives two new closed-form unbiased orientationally-averaging diffusion MRI signal estimators and shows that the noise-related bias could be significantly suppressed with these new findings. The new formulas might be applied to retrospectively orientationally-averaged dMRI signals with minimal computational effort.
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