Magnetic measurement of human iron stores

This paper provides a review of the principles and practice of biomagnetic susceptometry, with particular reference to magnetic susceptibility measurements of the human liver. A novel SQUID biomagnetic susceptometer is described consisting of a second-order gradiometer combined with a superconducting field coil assembly. We report the first clinical non-invasive diagnosis of liver iron overload achieved with this susceptometer at the Metropolitan General Hospital in Cleveland. Estimates are provided for the limiting resolution of the method. Ongoing efforts to apply the same principles to the determination of iron overload in the heart are briefly described. Our work represents the first clinical diagnostic procedure to utilize the recently developed superconducting technology of weak field measurement.