Patent EP0213665A1 successfully refreshed from Google Patents.
EP0213665A1
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EP
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Magnetic resonance imaging apparatus including a bird-cage r.f. coil
Assignee: Koninklijke Philips NV
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Filing: 1986-08-01
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Granted: —
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Expires: 2006-08-01
Abstract
Abstract In a magnetic resonance imaging apparatus the r.f. coil is designed on the basis of the sinusoidal current distribution across a circular-cylindrical surface about a central coil axis, subject to a generally applicable looping-through condition z₁ = - K z₂, K is a positive constant value which depends on the number of bars and geometrical deviations, z₁ is the impedance of the bar conductors, and z₂ is the impedance of ring conductor elements between each time two bar conductors. The coil based on the above condition is adapted notably to parasitic capacitances of notably the bar conductors in the apparatus and to a general shape of objects to be examined.
Inventors
- 👤 Rudolf Kemner
- 👤 Wilhelmus Reinerius Maria Mens
- 👤 Hilco Theodorus Kalmijn
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 17:43
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: 13
Claim 1
Independent Claim
97 words
A magnetic resonance imaging apparatus which includes a substantially cylindrical r.f. coil in which a number of bar conductors which extend axially across a cylinder surface of the cylinder generate a substantially cosinusoidal current distribution across a circular-cylinder circumference, characterized in that the bar conductors are activated via ring conductors around the cylinder axis and are positioned and coupled so that the following looping-through condition is satisfied: where z₁ is the impedance of a ring conductor portion between two bar conductors, z₂ is the impedance of the bar conductor, and n is the number of bar conductors.
Claim 2
Dependent Claim
97 words
A magnetic resonance imaging apparatus which includes a substantially cylindrical r.f. coil in which a number of bar conductors which extend axially across a cylinder surface of the cylinder generate a substantially cosinusoidal current distribution across a circular-cylinder circumference, characterized in that the bar conductors are activated via ring conductors around the cylinder axis and are positioned and coupled so that the following looping-through condition is satisfied: where z₁ is the impedance of a ring conductor portion between two bar conductors, z₂ is the impedance of the bar conductor, and n is the number of bar conductors.
Claim 3
Dependent Claim
40 words
A magnetic resonance imaging apparatus as claimed in Claim 1, characterized in that the impedance of the bar conductors is substantially inductive and that the impedance of the ring conductors is substantially capacitive for a resonant frequency of the coil.
Claim 4
Dependent Claim
40 words
A magnetic resonance imaging apparatus as claimed in Claim 1, characterized in that the impedance of the bar conductors is substantially inductive and that the impedance of the ring conductors includes a series connection of a capacitance and a self-inductance.
Claim 5
Dependent Claim
38 words
A magnetic resonance imaging apparatus as claimed in Claim 1, characterized in that the impedance of the bar conductors is substantially inductive, the impedance of the ring conductors including a parallel connection of a self-inductance and a capacitance.
Claim 6
Dependent Claim
26 words
A magnetic resonance imaging apparatus as claimed in Claim 4, characterized in that the switching circuit of the ring conductor elements is formed by coaxial cables.
Claim 7
Dependent Claim
39 words
A magnetic resonance imaging apparatus as claimed in Claim 1, characterized in that the impedance of the bar conductors includes a capacitively operating circuit formed by a self-inductance and a capacitance, the impedance of the ring conductor being inductive.
Claim 8
Dependent Claim
40 words
A magnetic resonance imaging apparatus as claimed in any one of the Claims 1 to 5, characterized in that a capacitance value of the bar conductors is formed by the parasitic capacitance of the conductor with respect to the environment.
Claim 9
Dependent Claim
26 words
A magnetic resonance imaging apparatus as claimed in any one of the preceding Claims, characterized in that the arrangement of the bar conductors is not equiradial.
Claim 10
Dependent Claim
31 words
A magnetic resonance imaging apparatus as claimed in any one of the preceding Claims, characterized in that the bar conductors are not uniformly distributed accross a cylinder surface of a cylinder.
Claim 11
Dependent Claim
25 words
A magnetic resonance imaging apparatus as claimed in any one of the preceding Claims, characterized in that the r.f. coil has a substantially elliptical cross-section.
Claim 12
Dependent Claim
45 words
A magnetic resonance imaging apparatus as claimed in any one of the preceding Claims, characterized in that the r.f. coil includes 4n bar conductors and a single tuning circuit which is coupled via a bar which is situated halfway between two mutually orthogonally oriented bars.
Claim 13
Dependent Claim
30 words
A magnetic resonance imaging apparatus as claimed in Claim 5, characterized in that the magnet system includes a superconducting magnet of generating a steady field of at least 2 tesla.
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