  Estimating magnetic susceptibility using MRI depends on inverting a forward
relationship between the susceptibility and measured Larmor frequency. However,
an often-overlooked constraint in susceptibility fitting is that the Larmor
frequency is only measured inside the sample, and after background field
removal, susceptibility sources should only reside inside the same sample. Here
we test the impact of accounting for such effects in susceptibility fitting and
demonstrate that such effects should not be ignored.
