Shielded gradients. And the general solution to the near field problem of electromagnet design.

The development of actively shielded gradients introduced the concept of surface distributed conductors for the production of electromagnetic fields. This represented the most significant step in electromagnetic coil design since the discovery of the electromagnetic field equations a century earlier. Further, the associated recognition of the Biot-Savart equation as the convolution of the current distribution function with the inverse square spatial dispersion, permits a solution of the general near field problem with implications for other scientific fields that have yet to be explored.