Susceptibility-Induced Off-Resonance Field Calculation Methods in MRI

Different theoretical methods to calculate susceptibility-induced B0 inhomogeneity in magnetic resonance imaging (MRI) are available in the literature.These include numerical solution of the magnetic scalar potential equation, surface monopole field integration, and summation of dipolar magnetic fields.They can all be used to calculate susceptibility-induced static magnetic field, which is particularly important for high-field MRI.This paper reviews the classical theory of magnetic field in a medium that forms the basis of these methods, to facilitate their understanding and critical comparison.Emphasis is given to the concept of demagnetization and the role of the contact dipolar magnetic field.