DIPPI is a novel sequence that allows the measurement of the off-resonance field experienced by intra-axonal water, which in myelinated axons is modulated by the surrounding myealin sheath allowing for estimation of the g-ratio. Unlike other g-ratio imaging methods, DIPPI does not rely on combining multiple modalities and can provide g-ratio estimates for individual crossing fibre populations rather than averaged over voxels. We present the first in-vivo DIPPI measurements and correct it for confounds such as subject movement and eddy currents. We then estimate the g-ratio in multiple white matter tracts from the processed off-resonance field maps.
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