The interaction of the patient with the RF coil, which causes shifts of the resonance frequency and damping of the coil's resonance and hence reduction of the quality factor because of magnetic induction and dielectric losses in the patient.
The design and construction of a MRI coil is determined by the load on the coil. The load is either a phantom or the actual sample being imaged.

See also Radio Frequency Coil.

Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterized by the complete absence of electrical resistance and the damping of the interior magnetic field. A ideal superconductor can carry an electrical current without experiencing energy losses (resistance, heat). The resistance of superconducting wire is nearly equal to zero at temperature near to absolute zero (-273.15° C or 0 K). This temperature is usually established by using liquid helium.

See also Superconducting Magnet, and Cryogen.