US4737718A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic resonance imaging apparatus including a bird-cage r.f. coil
Assignee: US Philips Corp
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Filing: 1986-08-01
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Granted: 1988-04-12
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Expires: 2006-08-01
Abstract
Abstract Disclosed is a magnetic resonance imaging apparatus, with an r.f. coil which is designed on the basis of the sinusoidal current distribution across a circular-cylindrical surface about a central coil axis and which is, subject to a generally applicable looping-through condition z 1 =-K z 2 , when K is a positive constant which depends on the number of bars and geometrical deviations, z 1 is the impedance of the bar conductors, and z 2 is the impedance of ring conductor elements between each two pair of bar conductors. The coil based on the above condition is particularly adapted to parasitic capacitances of the bar conductors and to the general shape of objects to be examined.
Inventors
- 👤 Rudolf Kemner
- 👤 Wilhelmus R. M. Mens
- 👤 Hilco T. Kalmijn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 21:33
CPC Classifications
G; G01; G01N; G01N24/00; G01N24/08; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/32; G01R33/34; G01R33/34046; G01R33/34076; G01R33/36; G01R33/3628
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
146 words
A magnetic resonance imaging apparatus comprising an r.f coil having a plurality of bar conductors which extend axially about a generally cylindrical surface of a measurement space having a central axis and means for activating said coil so as to generate a substantially cosinusoidal current distribution, said activating means comprising a plurality of ring conductors arranged around said central axis and coupled to said bar conductors, said bar conductors having an impedance which is substantially inductive at a resonant frequency of said coil and said ring conductors having an impedance which is substantially capacitive at said resonant frequency, said ring conductors being positioned and coupled so that the following looping-through condition is satisfied: ##EQU2## where z 1 is the impedance of a ring conductor portion between two bar conductors, z 2 is the impedance of a bar conductor, and n is the number of bar conductors.
Claim 2
Dependent Claim
146 words
A magnetic resonance imaging apparatus comprising an r.f coil having a plurality of bar conductors which extend axially about a generally cylindrical surface of a measurement space having a central axis and means for activating said coil so as to generate a substantially cosinusoidal current distribution, said activating means comprising a plurality of ring conductors arranged around said central axis and coupled to said bar conductors, said bar conductors having an impedance which is substantially inductive at a resonant frequency of said coil and said ring conductors having an impedance which is substantially capacitive at said resonant frequency, said ring conductors being positioned and coupled so that the following looping-through condition is satisfied: ##EQU2## where z 1 is the impedance of a ring conductor portion between two bar conductors, z 2 is the impedance of a bar conductor, and n is the number of bar conductors.
Claim 3
Dependent Claim
26 words
A magnetic resonance imaging apparatus as claimed in claim 1 wherein said bar conductors are not all spaced by an equal distance from said central axis.
Claim 4
Dependent Claim
21 words
A magnetic resonance imaging apparatus as claimed in claim 1 or 2 wherein said r.f. coil has a substantially elliptical cross-section.
Claim 5
Dependent Claim
22 words
A magnetic resonance imaging apparatus as claimed in claim 1 wherein said bar conductors are not uniformly distributed about said cylindrical surface.
Claim 6
Dependent Claim
50 words
A magnetic resonance imaging apparatus as claimed in claim 1 wherein the number of said bar conductors is a multiple of 4 and including a single tuning circuit which is coupled to said r.f. coil via a bar conductor which is situated halfway between two mutually orthogonally oriented bar conductors.
Claim 7
Dependent Claim
142 words
A magnetic resonance imaging apparatus comprising an r.f. coil having a plurality of bar conductors which extend axially about a generally cylindrical surface of a measurement space having a central axis and means for activating said coil so as to generate a substantially cosinusoidal current distribution, said activating means comprising a plurality of ring conductors arranged around said central axis and coupled to said bar conductors, said bar conductors having an impedance which is substantially inductive and said ring conductors having an impedance which includes a series connection of a capacitance and a self-inductance, said ring conductors being positioned and coupled so that the following looping-through condition is satisfied: ##EQU3## where z 1 is the impedance of a ring conductor portion between two bar conductors, z 2 is the impedance of a bar conductor, and n is the number of bar conductors.
Claim 8
Dependent Claim
142 words
A magnetic resonance imaging apparatus comprising an r.f. coil having a plurality of bar conductors which extend axially about a generally cylindrical surface of a measurement space having a central axis and means for activating said coil so as to generate a substantially cosinusoidal current distribution, said activating means comprising a plurality of ring conductors arranged around said central axis and coupled to said bar conductors, said bar conductors having an impedance which is substantially inductive and said ring conductors having an impedance which includes a series connection of a capacitance and a self-inductance, said ring conductors being positioned and coupled so that the following looping-through condition is satisfied: ##EQU3## where z 1 is the impedance of a ring conductor portion between two bar conductors, z 2 is the impedance of a bar conductor, and n is the number of bar conductors.
Claim 9
Dependent Claim
26 words
A magnetic resonance imaging apparatus as claimed in claim 6 wherein said bar conductors are not all spaced by an equal distance from said central axis.
Claim 10
Dependent Claim
21 words
A magnetic resonance imaging apparatus as claimed in claim 6 or 7 wherein said r.f. coil has a substantially elliptical cross-section.
Claim 11
Dependent Claim
22 words
A magnetic resonance imaging apparatus as claimed in claim 6 wherein said bar conductors are not uniformly distributed about said cylindrical surface.
Claim 12
Dependent Claim
50 words
A magnetic resonance imaging apparatus as claimed in claim 6 wherein the number of said bar conductors is a multiple of 4 and including a single tuning circuit which is coupled to said r.f. coil via a bar conductor which is situated halfway between two mutually orthogonally oriented bar conductors.
Claim 13
Dependent Claim
142 words
A magnetic resonance imaging apparatus comprising an r.f. coil having a plurality of bar conductors which extend axially about a generally cylindrical surface of a measurement space having a central axis and means for activating said coil so as to generate a substantially cosinusoidal current distribution, said activating means comprising a plurality of ring conductors arranged around said central axis and coupled to said bar conductors, said bar conductors having an impedance which is substantially inductive and said ring conductors having an impedance which includes a series connection of a self-inductance and a capacitance, said ring conductors being positioned and coupled so that the following looping-through condition is satisfied: ##EQU4## where z 1 is the impedance of a ring conductor portion between two bar conductors, z 2 is the impedance of a bar conductor, and n is the number of bar conductors.
Claim 14
Dependent Claim
142 words
A magnetic resonance imaging apparatus comprising an r.f. coil having a plurality of bar conductors which extend axially about a generally cylindrical surface of a measurement space having a central axis and means for activating said coil so as to generate a substantially cosinusoidal current distribution, said activating means comprising a plurality of ring conductors arranged around said central axis and coupled to said bar conductors, said bar conductors having an impedance which is substantially inductive and said ring conductors having an impedance which includes a series connection of a self-inductance and a capacitance, said ring conductors being positioned and coupled so that the following looping-through condition is satisfied: ##EQU4## where z 1 is the impedance of a ring conductor portion between two bar conductors, z 2 is the impedance of a bar conductor, and n is the number of bar conductors.
Claim 15
Dependent Claim
26 words
A magnetic resonance imaging apparatus as claimed in claim 11 wherein said bar conductors are not all spaced by an equal distance from said central axis.
Claim 16
Dependent Claim
21 words
A magnetic resonance imaging apparatus as claimed in claim 11 or 12 wherein said r.f. coil has a substantially elliptical cross-section.
Claim 17
Dependent Claim
22 words
A magnetic resonance imaging apparatus as claimed in claim 13 wherein said bar conductors are not uniformly distributed about said cylindrical surface.
Claim 18
Dependent Claim
50 words
A magnetic resonance imaging apparatus as claimed in claim 11 wherein the number of said bar conductors is a multiple of 4 and including a single tuning circuit which is coupled to said r.f. coil via a bar conductor which is situated halfway between two mutually orthogonally oriented bar conductors.
Claim 19
Dependent Claim
22 words
A magnetic resonance apparatus as claimed in claim 11 wherein said ring conductors are sections of coaxial cables connected between bar conductors.
Claim 20
Dependent Claim
24 words
A magnetic resonance imaging apparatus as claimed in claim 16, including a superconducting magnet for generating a steady field of at least 2 tesla.
Claim 21
Dependent Claim
144 words
A magnetic resonance imaging apparatus comprising an r.f. coil having a plurality of bar conductors which extend axially about a generally cylindrical surface of a measurement space having a central axis and means for activating said coil so as to generate a substantially cosinusoidal current distribution, said activating means comprising a plurality of ring conductors arranged around said central axis and coupled to said bar conductors, said bar conductors having an impedance which includes a capacitively operating circuit formed by a self-inductance and a capacitance, and said ring conductors having an impedance which is substantially inductive, said ring conductors being positioned and coupled so that the following looping-through condition is satisfied: ##EQU5## where z 1 is the impedance of a ring conductor portion between two bar conductors, z 2 is the impedance of a bar conductor, and n is the number of bar conductors.
Claim 22
Dependent Claim
144 words
A magnetic resonance imaging apparatus comprising an r.f. coil having a plurality of bar conductors which extend axially about a generally cylindrical surface of a measurement space having a central axis and means for activating said coil so as to generate a substantially cosinusoidal current distribution, said activating means comprising a plurality of ring conductors arranged around said central axis and coupled to said bar conductors, said bar conductors having an impedance which includes a capacitively operating circuit formed by a self-inductance and a capacitance, and said ring conductors having an impedance which is substantially inductive, said ring conductors being positioned and coupled so that the following looping-through condition is satisfied: ##EQU5## where z 1 is the impedance of a ring conductor portion between two bar conductors, z 2 is the impedance of a bar conductor, and n is the number of bar conductors.
Claim 23
Dependent Claim
26 words
A magnetic resonance imaging apparatus as claimed in claim 18 wherein said bar conductors are not all spaced by an equal distance from said central axis.
Claim 24
Dependent Claim
21 words
A magnetic resonance imaging apparatus as claimed in claim 18 or 19 wherein said r.f. coil has a substantially elliptical cross-section.
Claim 25
Dependent Claim
22 words
A magnetic resonance imaging apparatus as claimed in claim 18 wherein said bar conductors are not uniformly distributed about said cylindrical surface.
Claim 26
Dependent Claim
50 words
A magnetic resonance imaging apparatus as claimed in claim 18 wherein the number of said bar conductors is a multiple of 4 and including a single tuning circuit which is coupled to said r.f. coil via a bar conductor which is situated halfway between two mutually orthogonally oriented bar conductors.
References Cited (Backward Citations)
US4591818A
Cited
US4638253A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-04-12 | 1991-10-12 | 1992-04-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-04-12 | 1995-10-12 | 1996-04-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-04-12 | 1999-10-12 | 2000-04-12 | $7700.00 | Window Closed / Lapsed |