Susceptibility-limited resolution in nuclear magnetic resonance microscopy

Abstract

Sensitivity considerations suggest that a voxel resolution of (10 μm) 3 should be possible for NMR microscopy at 400 MHz. It is shown however that diamagnetic susceptibility inhomogeneity can degrade this resolution and examples of image reconstruction for simple geometries are given. This degradation increases with the size of the polarizing field and the optimal resolution cannot be restored by simply increasing the gradient strength unless appropriate echo summation methods are used. Alternatively, susceptibility effects can be avoided by employing pulse sequences which refocus magnetic inhomogeneity but retain the k-space evolution due to the linear gradient.