title: The NMR multi-transmit phased array: a Cartesian feedback approach.
abstract: The use of Cartesian feedback is proposed to solve the problem of using an array of coils for the purposes of transmission in magnetic resonance imaging. The difficulties caused by direct and sample-mediated coil interactions are briefly examined, and the known solutions of using power-mismatched pre-amplifiers and transmitters noted. It is then shown that, without loss of transmitter efficiency, a high effective impedance may be created in series with each coil in the array by the use of Cartesian negative feedback. A bench experiment is described that confirms the theory. The solution is also viable for signal reception and is more efficacious than pre-amplifier damping, albeit over a smaller bandwidth.
authors.affiliation: Institute for Biodiagnostics, National Research Council, 435 Ellice Avenue, Winnipeg, Man., Canada R3B 1Y6. david.hoult@nrc-cnrc.gc.ca
authors.forename: D I
authors.initials: DI
authors.lastname: Hoult
authors.forename: G
authors.initials: G
authors.lastname: Kolansky
authors.forename: D
authors.initials: D
authors.lastname: Kripiakevich
authors.forename: S B
authors.initials: SB
authors.lastname: King
mesh_terms: D004867:Equipment Design; D005246:Feedback; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D019047:Phantoms, Imaging