We propose a novel sequence that adds a second asymmetric spin echo after a standard Stejskal-Tanner sequence. This allows the estimation of the off-resonance frequency of the diffusion-weighted signal due to the myelin magnetic susceptibility. Varying the orientation of the diffusion-weighting gradient dephases different fibre populations. In simulations we show that for a sufficiently high b-value (>~3 ms/μm2), the intra-axonal water will dominate leading to a simple relation between the myelin-induced frequency shift and the log g-ratio. This allows the difference in log g-ratio between crossing fibres to be measured and hence estimate the myelination of individual crossing tracts.