Local coil arrangement having integrated shim conductor
View Patent ↗When a portion of a structure enclosing a local coil is inserted in a homogeneity region of a basic magnetic field of a magnetic resonance system, the local coil is operable to receive magnetic resonance signals originating from a specific detection zone for the local coil arrangement. At least one conductor is arranged in the structure. Field lines of a compensation magnetic field generated by current encircling the conductor form a compensation magnetic field angle with the basic magnetic field in an edge area of the detection zone. Return conductors complete an electric circuit containing the conductor and extend in the direction of the basic magnetic field and/or are arranged such that field lines of an interfering magnetic field counteracting the compensation magnetic field encircle the respective return conductor and form an interfering magnetic field angle with the basic magnetic field in the edge area.
1. A local coil arrangement for magnetic resonance purposes, the local coil arrangement comprising:
at least one local coil;
at least one conductor and associated return conductors; and
a mechanical holding structure, in which the at least one local coil and the at least one conductor with the associated return conductors are arranged, wherein when the entirety or a portion of the mechanical holding structure surrounds the at least one local coil and is inserted in a homogeneity region of a basic magnetic field of a magnetic resonance system, wherein the local coil or another receive coil is operable to receive magnetic resonance signals originating from a specific detection zone for the local coil arrangement;
wherein the at least one conductor is exposable to direct current or low-frequency alternating current, the at least one conductor being arranged such that the at least one conductor extends orthogonally to a direction of the basic magnetic field, and wherein the at least one conductor generates a compensation magnetic field when exposed to the direct current or the low-frequency alternating current, the compensation magnetic field comprising field lines that encircle the at least one conductor and form a compensation magnetic field angle with the direction of the basic magnetic field in an edge area of the specific detection zone; and
wherein the return conductors complete an electric circuit containing the at least one conductor, wherein at least one return conductor, running parallel with the at least one conductor, generates an interfering magnetic field counteracting the compensation magnetic field when exposed to the direct current or the low-frequency alternating current, the interfering magnetic field comprising field lines that encircle the respective return conductor and form an interfering magnetic field angle with the direction of the basic magnetic field in the edge area, the interfering magnetic field angle being larger than the compensation magnetic field angle, and the respective return conductor being further away from the edge area than the at least one conductor,
wherein the at least one conductor is arranged outside the specific detection zone at an edge of the edge area.
2. The local coil arrangement as claimed in claim 1 , wherein the at least one conductor and the return conductors lie in a plane, and
wherein with a parallel projection of the edge area directed into the plane at a right angle to the plane, the at least one conductor is arranged between at least a part of the edge area and the return conductors with an interfering magnetic field that counteracts the compensation magnetic field.
3. The local coil arrangement as claimed in claim 1 , wherein viewed in the direction of the basic magnetic field, the specific detection zone has a maximum extension, and
wherein viewed in the direction of the basic magnetic field, a distance of the return conductors with an interfering magnetic field that counteracts the compensation magnetic field from the edge area is at least as large as the maximum extension of the specific detection zone.
4. The local coil arrangement as claimed in claim 1 , further comprising at least one band-stop filter matched to a Larmor frequency of the magnetic resonance system, at least one choke, or the at least one band-stop filter and the at least one choke, the at least one band-stop filter, the at least one choke, or the at least one band-stop filter and the at least one choke being arranged in the electric circuit containing the at least one conductor and the return conductors.
5. The local coil arrangement as claimed in claim 1 , wherein the local coil arrangement is a breast coil arrangement comprising two cup-shaped receptacles for breasts of an object under examination, and
wherein the specific detection zone includes at least one of the two cup-shaped receptacles.
6. The local coil arrangement as claimed in claim 5 , wherein the at least one conductor is arranged in a region of a lower edge of the two cup-shaped receptacles.
7. The local coil arrangement as claimed in claim 1 , wherein the local coil arrangement is a spine coil arrangement.
8. The local coil arrangement as claimed in claim 7 , wherein the at least one conductor is arranged in a region of the mechanical holding structure on which a neck of an object under examination lies.
9. The local coil arrangement as claimed in claim 2 , wherein viewed in the direction of the basic magnetic field, the specific detection zone has a maximum extension, and
wherein viewed in the direction of the basic magnetic field, a distance of the return conductors with an interfering magnetic field that counteracts the compensation magnetic field from the edge area is at least as large as the maximum extension of the specific detection zone.
10. The local coil arrangement as claimed in claim 2 , further comprising at least one band-stop filter matched to a Larmor frequency of the magnetic resonance system, at least one choke, or the at least one band-stop filter and the at least one choke, the at least one band-stop filter, the at least one choke, or the at least one band-stop filter and the at least one choke being arranged in the electric circuit containing the at least one conductor and the return conductors.
11. The local coil arrangement as claimed in claim 3 , further comprising at least one band-stop filter matched to a Larmor frequency of the magnetic resonance system, at least one choke, or the at least one band-stop filter and the at least one choke, the at least one band-stop filter, the at least one choke, or the at least one band-stop filter and the at least one choke being arranged in the electric circuit containing the at least one conductor and the return conductors.
12. The local coil arrangement as claimed in claim 2 , wherein the local coil arrangement is a breast coil arrangement comprising two cup-shaped receptacles for breasts of an object under examination, and
wherein the specific detection zone includes at least one of the two cup-shaped receptacles.
13. The local coil arrangement as claimed in claim 3 , wherein the local coil arrangement is a breast coil arrangement comprising two cup-shaped receptacles for breasts of an object under examination, and
wherein the specific detection zone includes at least one of the two cup-shaped receptacles.
14. The local coil arrangement as claimed in claim 4 , wherein the local coil arrangement is a breast coil arrangement comprising two cup-shaped receptacles for breasts of an object under examination, and
wherein the specific detection zone includes at least one of the two cup-shaped receptacles.
15. The local coil arrangement as claimed in claim 2 , wherein the local coil arrangement is a spine coil arrangement.
16. The local coil arrangement as claimed in claim 3 , wherein the local coil arrangement is a spine coil arrangement.