초록 ▼

A generator (13A, . . . 13C) of a time-variable magnetic field (B1) of a magnetic resonance device (1) which has an examination space (9,9A) for accommodating at least one area to be examined of an examination subject (7), in which examination area the time-variable magnetic field (B1) is generated

A generator (13A, . . . 13C) of a time-variable magnetic field (B1) of a magnetic resonance device (1) which has an examination space (9,9A) for accommodating at least one area to be examined of an examination subject (7), in which examination area the time-variable magnetic field (B1) is generated by means of a current through a conductor (15, 19, 31). The magnetic field lines (23) of the magnetic field (B1) close with the aid of a field flux return space (17), in which there is arranged at least one sub-assembly (27) which has magnetizable material. A reduction of a magnetic energy density in the field flux return space (17) is produced by this means. This increases e.g. the efficiency in the generation of high-frequency magnetic fields (B1) or of gradient fields with the aid of the conductor (15,19,31).

대표청구항 ▼

The invention claimed is: 1. A generator for generating a time-variable magnetic field of a magnetic resonance device having an examination area for accommodating at least one area to be examined of an examination subject, the examination area adapted to be exposed to the generated time-variable ma

The invention claimed is: 1. A generator for generating a time-variable magnetic field of a magnetic resonance device having an examination area for accommodating at least one area to be examined of an examination subject, the examination area adapted to be exposed to the generated time-variable magnetic field, the generator comprising: at least one electrical conductor assigned to the generator for generating the magnetic field using a current flow through the conductor, the at least one electrical conductor comprising a first portion spaced from a second portion whereby a space is defined there between; a return flow area adapted to allow a field backflow for closing magnetic-field lines the magnetic field, the return flow area formed adjacent to the first portion and the second portion; and at least one sub-assembly having magnetizable material, the sub-assembly arranged within the return flow area for reducing a magnetic energy density within the flow area. 2. The generator according to claim 1, wherein the at least one electrical conductor extends within an area shaped as a disc spaced from an area shaped as a ring. 3. The generator according to claim 1, wherein the at least one electrical conductor is an antenna conductor of a high-frequency antenna unit and the time-variable magnetic field is a high-frequency field for exciting magnetic resonance signals. 4. The generator according to claim 3, wherein the high-frequency antenna unit comprises at least one ferrite pole for bridging a gap between the return flow area and the examination area enabling a closing of the magnetic field lines of the magnetic field not affected by the return flow area. 5. The generator according to claim 3, wherein the antenna conductor is embodied as a high-frequency shield. 6. The generator according to claim 1, wherein the at least one electrical conductor is a gradient conductor of a primary gradient-coil unit and the time-variable magnetic field is a spatially and temporally varying primary gradient field. 7. The generator according to claim 6, wherein the primary gradient-coil unit is enclosed by an antenna conductor of a high-frequency antenna, a portion of the antenna conductor extending into the return flow area. 8. The generator according to claim 6, wherein the at least one electrical conductor further comprising a secondary gradient conductor of a secondary gradient-coil unit, the time-variable magnetic field is a spatially and temporally varying secondary gradient field counteracting the primary gradient field outside the examination area, and the return flow area is arranged on a second side of the secondary gradient conductor, the second side facing toward the examination space. 9. The generator according to claim 8, wherein the sub-assembly is shaped as a flat disk and arranged between the primary and secondary gradient-coil units. 10. The generator according to claim 9, wherein the primary gradient-coil units are shaped as disks sheathed by a high-frequency shield, the high-frequency shield acting as an antenna conductor of a high-frequency antenna within an area adjacent to a primary coil of the primary coil unit. 11. The generator according to claim 1, wherein the return flow area is arranged on a first side of the at least one electrical conductor, the first side facing away from the examination area. 12. The generator according to claim 11, wherein an edge surface of the return flow area is limited by a high-frequency shield. 13. The generator according to claim 1, wherein the return flow area is separated from other parts of the generator by a high-frequency shield. 14. The generator according to claim 1, wherein a first magnetic energy density within the return flow area measured without the sub-assembly installed is greater than a second magnetic energy density measured within the examination space when the generator is in operation. 15. The generator according claim 1, wherein the sub-assembly is shaped as a flat disk arranged within a high frequency antenna resonator, the high frequency antenna resonator comprising at least two planar antenna conductors arranged in parallel. 16. The generator according to claim 15, wherein the antenna conductors are shaped as disks. 17. The generator according to claim 1, the sub-assembly comprising a plurality of segments arranged to form a flat disk. 18. The generator according to claim 1, wherein the magnetizable material is ferrimagnetic and/or ferromagnetic. 19. The generator according to claim 18, wherein the magnetizable material is ferrite or iron powder. 20. The generator according to claim 1, wherein the magnetizable material is encapsulated by an insulating substrate. 21. A magnetic resonance device having a first generator for generating a time-variable magnetic field of a magnetic resonance device having an examination area for accommodating at least one area to be examined of an examination subject, the examination area adapted to be exposed to the generated time-variable magnetic field, the first generator comprising: at least one electrical conductor assigned to the first generator for generating the magnetic field using a current flow through the conductor; a space formed within the at least one electrical conductor; a return flow area adapted to allow a field backflow for closing magnetic-field lines of the magnetic field, the return flow area accessible through the space formed within the at least one electrical conductor; and at least one sub-assembly having magnetizable material, the sub-assembly arranged within the return flow area for reducing a magnetic energy density within the return flow area. 22. The magnetic resonance device according to claim 21, further comprising: a second generator having the same features as the first generator, and a C-shaped permanent magnet having a first and a second pole plate for generating a main magnetic field, each pole plate arranged on an end of the C-shaped permanent magnet and facing the other pole plate, wherein the examination area is arranged between the pole plates and the first and second generators are arranged on the first and second pole plates respectively.