RF coil coupling for MRI with tuned RF rejection circuit using coax shield choke

Claim 1

A coaxial cable RFI choke assembly for reducing transmission, via the outside of the outer coaxial conductor, of RF signals having a predetermined frequency while passing RF signals of the same predetermined frequency on the inside of said coaxial conductor, said assembly comprising: a coiled section of coaxial cable having an outer conductive member and including plural coil turns between first and second coil ends which cable, insofar as the outer conductive member is concerned, provides inductance L; a lumped fixed capacitor of capacitance C physically disposed transversely across one of said coil ends and electrically connected in parallel across both of said coil ends, said inductance L and capacitance C presenting a parallel resonant circuit approximately at said predetermined frequency which substantially impedes the flow of said RF signals via the outside of the outer conductive member; a conductive tuning rod positioned within the center of said coiled section so as to achieve parallel resonance of the assembly substantially at said predetermined frequency; adhesive material fixing said tuning rod and coiled section of coaxial cable in place relative one another; a forming cylinder of insulationg material with said coiled section of coaxial cable being wound thereonto and having a cavity in its center section into which said tuning rod is located; and a cylindrical housing, closed on each end, encapsulating said assembly, having a coaxial cable input connection disposed at one end of the housing and a coaxial cable output connection disposed at the other end of the housing.