Inhomogeneity-informed Field-fitting for Quantitative Susceptibility Mapping (if-QSM)

Motivation: Inhomogeneity in measured multi-gradient echo (mGRE) field data corrupts reconstructions of quantitative susceptibility maps by obscuring the tissue field of interest with strong background field. Goal(s): To extend the voxel spread function (VSF) library implementation to a nonzero phase offset and demonstrate improvements on QSM. Approach: The measured field was estimated and inhomogeneity contributions computed using the extended library implementation. The inhomogeneity field was then estimated and subtracted from the total field to reduce the influence of strong background fields in the QSM reconstructionResults: Inhomogeneity-informed field-fitting for QSM is shown to improve total field reconstructions of the brain, carotid, and cervical spine. Impact: The voxel spread function (VSF) library implementation is extended to include initial phase offset contributions and reduce the effect of field inhomogeneity in quantitative susceptibility map (QSM) reconstruction.