Technicare Corporation

David C Flugan

Radio frequency apparatus for a magnetic resonance system is provided which includes an r.f. coil and DC controlled circuitry for selectively altering the characteristics of the coil. A loading coil is provided which is selectively activated to de-Q the coil during r.f. transmission so as to minimize the loading effects of the subject and their effect on coil impedance. A switched network is provided which selectively destroys the normal resonant condition of the coil when a second r.f. coil is operative to minimize interaction between the two coils.

Radio frequency coils for nuclear magnetic resonance imaging systems

A family of high Q radio frequency coils for an NMR imaging system is provided. The coil family includes a transmitting coil for transmitting an r.f. field aligned with a given plane. The transmitting coil is used with one of the described receiving coils, each of which is responsive to NMR signals in a plane oriented orthogonally to said given plane. The receiving coils employ an open, arcuate configuration, which alleviates sensations of confinement characteristic of fully enclosing coil forms. Arcuate sections of the receiving coils are curved away from the patient, to decrease signal reception at areas from which meaningful signals cannot be gathered. To prevent interaction between the transmitting and receiving coils, means are provided for rendering each coil nonresponsive to NMR and radio signal frequencies when the coils are not being operated.

Compensation is provided for a gradient field of an NMR imaging system which compensates for the effects of eddy fields developed in the static magnetic field from metallic components during gradient field switching. The compensation comprises providing current overshoot to the gradient coil during gradient switching. The overshoot current decays with a time constant chosen to substantially offset the decay of eddy fields following gradient switching. In a preferred embodiment, a time constant network representative of eddy field decay is coupled in combination with a feedback signal from a current sampling resistor of the gradient coil.

Growing community of inventors

Hudson, OH, United States of America

David C Flugan