US 7,064,549 B1Granted

NMR RF coils with split movable capacitance bands

AssigneeVarian, Inc.

InventorAlexander M J Hudson

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Abstract

A split capacitance-tuning band of a nuclear magnetic resonance (NMR) distributed-capacitance radio-frequency (RF) coil includes a fixed band and a longitudinally-movable (sliding) band, both disposed to overlap a central coil structure. The fixed band is situated along the boundary of the RF coil window. The movable band can move between a proximal position abutting the fixed band and various distal positions. The fixed band provides an RF current path close to the RF coil window, while the movable band allows tuning the coil capacitance and resonance frequency by varying the area of overlap between the movable band and the central coil structure. A longitudinal coupling member is attached to the movable band and to an actuator piston disposed under a probe lower insulator. A chip capacitor is connected between the coupling member and the actuator piston, to provide RF insulation for the movable capacitance band.

Claims18

Dependent claims

A nuclear magnetic resonance apparatus comprising a nuclear magnetic resonance radio-frequency coil, the coil comprising:

a distributed-capacitance central coil structure comprising
a pair of longitudinally-spaced conductive rings including a first band-shaped ring and a second band-shaped ring, wherein a coil window is defined in a space between the first ring and the second ring, and
a plurality of longitudinal conductive segments each electrically interconnecting the first ring to the second ring;
a first ring-shaped capacitance band overlapping the first ring and having a first diameter;
and
a second ring-shaped capacitance band, wherein the second capacitance band has a second diameter substantially equal to the first diameter, is situated adjacent to the first ring-shaped capacitance band on the same side of the coil window as the first capacitance band and distant from the coil window, and is longitudinally-movable between a proximal position and a distal position, the distal position being situated further away from the coil window than the proximal position, wherein the second capacitance band in the proximal position overlaps the first ring, and wherein longitudinally moving the second capacitance band tunes a resonance frequency of the coil.

3 more elements

Dependencies are inferred from the claim text.