Abstract: A series topology is provided for the magnetic-field-generating coil and storage capacitor in the circuitry driving the coil of an MRI system. The coil and capacitor thus form a series resonant circuit that can deliver a sinusoidal current through the coil at a resonant frequency. A power source and switch are connected in series with the coil and capacitor, and current flow to the coil is initiated and interrupted by closing and opening the switch.

Abstract: A unitary, generally cylindrical member supports both the primary and shielding coils. By supporting both coils on a unitary member it is possible to take advantage of the antiphase relationship between the primary and shielding coils and thereby reduce the acoustic noise generated by the gradient coil assembly. The unitary member can be formed by starting with a mandrel to which the primary coil is applied, and then successively adding layers each having a cylindrical outer surface aligned with the same longitudinal axis. Each new cylindrical surface is formed by adding material and then removing some of the material while rotating the member about the longitudinal axis (e.g., turning on a lathe, or passing a blade past a still liquid skim coat). Additional primary and shielding coils are applied after each new aligned, cylindrical surface is formed.

Abstract: A unitary, generally cylindrical member supports both the primary and shielding coils. By supporting both coils on a unitary member it is possible to take advantage of the antiphase relationship between the primary and shielding coils and thereby reduce the acoustic noise generated by the gradient coil assembly. The unitary member can be formed by starting with a mandrel to which the primary coil is applied, and then successively adding layers each having a cylindrical outer surface aligned with the same longitudinal axis. Each new cylindrical surface is formed by adding material and then removing some of the material while rotating the member about the longitudinal axis (e.g., turning on a lathe, or passing a blade past a still liquid skim coat). Additional primary and shielding coils are applied after each new aligned, cylindrical surface is formed.

Abstract: A series topology is provided for the magnetic-field-generating coil and storage capacitor in the circuitry driving the coil of an MRI system. The coil and capacitor thus form a series resonant circuit that can deliver a sinusoidal current through the coil at a resonant frequency. A power source and switch are connected in series with the coil and capacitor, and current flow to the coil is initiated and interrupted by closing and opening the switch.

Abstract: Narrower conductive strips are provided in a segmented RF shield to reduce the gradient coil power loss attributable to the shield. Narrower conductive strips reduce the eddy current losses experienced by the gradient coil, thereby reducing the power required to operate the gradient coil, especially in high speed imaging where high frequencies up to 10 KHz are used. The conductive strips can be made sufficiently narrow to substantially reduce the gradient coil power loss attributable to the shield. When these strips are made in this manner, a third conductive layer may be placed over a transition region where there is a substantial change in the direction of the conductive strips. In such a transition region, RF current tends to travel in curved paths across the pattern of conductive strips instead of along the lengths of the strips, with resulting decrease in coil quality factor, Q. The third conductive layer provides a lower impedance path for RF currents in the transition region, to reduce RF power loss.