NMR probe with enhanced power handling ability
First Claim
Patent Images
1. A planar MR/RF coil exhibiting desired RF resonant properties, comprising:
- a plurality of substantially concentrically nested elemental spiral conductors, each said elemental spiral conductor having an inner end being confined within an inner side of the MR/RF coil and an outer end disposed within an outer side of the MR/RF coil, the inner ends of adjacent said elemental spiral conductors geometrically displaced towards each other by an angular amount Δ
θ
to obtain a desired RF offset phase difference(Δ
Φ
).
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Abstract
A phase-shifted coil comprises nested concentric spiral portions, the terminals of which are progressively offset. Separately tuned concentric such coils of different dimensions exhibit relatively close intercoil clearance in one dimension and relatively large clearances in the orthogonal dimension provide different flux return characteristics for selective RF coupling.
73 Citations
21 Claims
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1. A planar MR/RF coil exhibiting desired RF resonant properties, comprising:
a plurality of substantially concentrically nested elemental spiral conductors, each said elemental spiral conductor having an inner end being confined within an inner side of the MR/RF coil and an outer end disposed within an outer side of the MR/RF coil, the inner ends of adjacent said elemental spiral conductors geometrically displaced towards each other by an angular amount Δ
θ
to obtain a desired RF offset phase difference(Δ
Φ
).- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A planar RF resonant coil component comprising:
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at least two closely spaced, concentric spiral conductors, each said spiral conductor having an inductance each pair of said spiral conductors having a distributed capacitance and a mutual inductance therebetween, whereby at least one resonant frequency characterizes said planar RF resonant coil component, each said spiral conductor supporting a standing wave corresponding to at least one said resonance. each said spiral conductor geometrically displaced in relation to at least one of the adjacent spiral conductors by an angular amount Δ
θ
whereby a phase shift is introduced therebetween that allows for the accumulation of a substantial capacitance due to an RF offset phase difference Δ
Φ
.
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13. A multi-resonant planar MR/RF coil structure comprising:
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nested inner and outer adjacent spiral conductors coaxially disposed on a common substrate forming outer and inner MR/RF coils respectively, each said spiral conductor of said outer and inner MR/RF coils having an inner end being confined within an inner side of the respective MR/RF coil and an outer end disposed on an outer side of the respective MR/RF coil, the inner ends of said adjacent elemental spiral conductors geometrically displaced towards each other by an angular amount Δ
θ
to obtain a desired RF offset phase difference Δ
Φ
,said outer MR/RF coil having first and second symmetry axes on said surface, said inner MR/RF coil closely approaching the outer coil along said first axis and said inner MR/RF coil spaced apart from said outer MR/RF coil by a selected separation along said second axis for optimizing isolation between said inner and outer MR/RF coils. - View Dependent Claims (14, 15, 16, 17)
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18. A method of uniformly distributing RF current density over a planar RF resonant structure comprising the steps of:
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providing at least one MR/RF coil having concentrically nested elemental spiral conductors, each said conductor enclosing an angle substantially different from a multiple of 2π
,coupling RF power to each said elemental spiral conductor, and geometrically offsetting each said adjacent elemental spiral conductor to obtain an RF phase shift between each of the adjacent elemental spiral conductors, that cause capacitive coupling between each said elemental spiral conductor and each of the adjacent conductors, resulting in an RF current density that is uniformly distributing over the RF resonant structure.
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19. An NMR probe for use in an NMR apparatus, comprising:
a pair of planer RF coils, each said planer RF coil comprising a plurality of substantially concentrically nested elemental spiral conductors, each said elemental spiral conductor having an inner end and an outer end, the inner ends of adjacent said elemental spiral conductors being confined by said pair of RF coils and geometrically displaced therebetween so that the RF phase of each of said spiral conductors is shifted with respect to each said adjacent elemental spiral conductor to obtain a desired RF phase difference Δ
Φ
, said pair of RF coils disposed spaced apart on a common axis and communicating mutually with one another to produce a desired RF magnetic field in the space therebetween, whereby RF coupling between said coil pair and an RF terminal occurs.
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20. An NMR apparatus for examination of a composition of matter, comprising:
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a magnetic field of controllable properties, a RF source and a RF receiver selectively coupled to an RF probe assembly, said probe assembly comprising;
at least a pair of planar RF coils, each said planar RF coil comprising spaced, concentric spiral conductors that each have an inner and outer ends disposed respectively within an inner and an outer side of each respective RF coil;
each said spiral conductor having an inductance, each pair of said spiral conductors having distributed capacitance and a mutual inductance therebetween, whereby at least one resonant frequency characterizes the resonance component, each said spiral conductor of each said RF coil substantially supporting a standing wave corresponding to at least one said resonance, each said spiral conductor geometrically displaced in relation to at least one of the adjacent spiral conductors whereby a phase shift Δ
θ
is introduced therebetween that allows for accumulation a substantial capacitance due to an RF offset phase difference Δ
Φ
.
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21. A system for coupling a multi-resonant MR/RF coil with an RE source comprising:
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said multi-resonant MR/RF coil comprising nested inner and outer adjacent spiral conductors coaxially disposed on a common substrate forming outer and inner MR/RF coils respectively, each said spiral conductor of said outer and inner MR/RF coils having an inner end being confined within an inner side of the respective MR/RF coil and outer end disposed within an other side of the respective MR/RF coil, the inner ends of said adjacent elemental spiral conductors geometrically displaced towards each other by an angular amount Δ
θ
to obtain a desired RF offset phase difference Δ
Φ
,said outer MR/RF coil having first and second symmetry axes on said surface, said inner MR/RF coil closely approaching the outer coil along said first axis and said inner MR/RF coil spaced from said outer MR/RF coil by a selected separation along said second axis, said outer and inner MR/RF coils exhibiting a first and second resonant frequency respectively, a first coupling loop for selectively coupling RF power at the second resonant frequency to said inner MR/RF coil said first coupling loop is disposed to concurrently superimpose a projection therefrom on both am interior region of said inner MR/RF coil and another region, said another region external to said Inner MR/RF coil and internal to said outer MR/RF coil, said first coupling loop having a butterfly shape, and a second coupling loop for selectively coupling RF power at the first resonant frequency to aid outer MR/RF coil, said second coupling loop is disposed to concurrently superimpose a projection therefrom on both an interior region of said inner MR/RF coil and another region, said another region external to said inner MR/RF coil and internal to said outer MR/RF coil, said second coupling loop having a simple shape.
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Specification