What’s the FWAF? A Finite Width Adjustment Factor for the effect of finite pulse duration on the diffusion signal in impermeable cylinders

A common approach to microstructure imaging in diffusion MRI is to fit the signal with a weighted sum of geometric compartments. This approach is widespread but the need for analytical closed-form solutions necessitates highly restrictive assumptions about the underlying physics which are rarely met in practice. In particular, violation of the narrow-pulse approximation is a significant potential source of bias. This abstract investigates the effect of violating the narrow pulse approximation numerically and proposes a simple effect correction factor to reduce apparent bias as a scale factor on q as a function of δ.