Transmission and receiving coil for mr apparatus

• US 20040155656A1
• Filed: 11/19/2003
• Published: 08/12/2004
• Est. Priority Date: 05/19/2001
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Leussler, Christoph Guenther
• Granted Patent: US 6,900,636 B2
• Time in Patent Office: Days
• US Class Current: 324/318
• CPC Class Codes: G01R 33/34046 Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils
• CPC Class Codes: G01R 33/34076 Birdcage coils
• CPC Class Codes: G01R 33/3628 Tuning/matching of the transmit/receive coil
• CPC Class Codes: G01R 33/5659 caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field G01R33/56509, G01R33/56518, G01R33/56536 take precedence

Abstract

The invention relates to an arrangement for generating RF fields in the examination volume (100) of an MR apparatus. A plurality of resonator segments are arranged around the examination volume (100) within the gradient tube (103), said resonator segments being connected together so as to form a body coil. Each resonator segment is provided with a conductor element (104) which is constructed as a planar strip and extends parallel to the longitudinal axis of the main field magnet. The resonator segments are electromagnetically decoupled from one another by means of intermediate capacitances, so that a separate transmission channel (1 to 8) can be associated with each resonator segment, the RF feeding into the relevant resonator segment taking place via said channel. Because the phase and the amplitude of the RF feeding can be individually selected for each resonator segment, the arrangement in accordance with the invention enables substantially complete control of the RF field distribution in the examination volume (RF shimming).

Claims

1. An arrangement for generating RF fields in the examination volume (100) of an MR apparatus, which arrangement includes a body coil which consists of a plurality of resonator segments which are arranged around the examination volume (100) and each of which consists of at least one conductor element (104) which extends parallel to the longitudinal axis of a main field magnet and of at least one capacitor element, characterized in that the resonator segments are electromagnetically decoupled from one another and that a separate transmission channel (1 to 8) is associated with each resonator segment, via which transmission channel RF feeding takes place into the relevant resonator segment, the phase and/or the amplitude of the RF feeding being individually selectable for each resonator segment.

2. An arrangement as claimed in claim 1, characterized in that the electromagnetic decoupling of the resonator segments is realized by means of capacitances (CD) or inductances which are connected between the conductor elements (104).

3. An arrangement as claimed in claim 1, characterized in that the conductor elements (104) are constructed essentially as rectangular, planar strips.

4. An arrangement as claimed in claim 3, characterized in that the edges of the conductor strips are provided with a sawtooth-like structure.

5. An arrangement as claimed in claim 3, characterized in that the surfaces of the conductor strips are provided with slits which extend parallel to the longitudinal direction thereof.

6. An arrangement as claimed in claim 1, characterized in that there is provided an RF shield (105) which extends around the body coil, the conductor elements (104) of the individual resonator segments being arranged at a small distance of from 0.5 to 2 cm from the RF shield (105).

7. An arrangement as claimed in claim 1, characterized in that the body coil is subdivided into at least two independent, axially successively arranged segments.

8. An arrangement as claimed in claim 1, characterized in that with each resonator segment there is associated a separate receiving channel (a to h) via which the MR signals detected by means of the relevant resonator detector segment are applied to a receiving unit (112) for further processing.

9. An arrangement as claimed in claim 1, characterized in that the examination volume (100) has an asymmetrical cross-section in the plane extending perpendicularly to the main field direction, the conductor elements (104) of the individual resonator segments being arranged at the periphery of said cross-section.

10. An MR apparatus which includes an arrangement for generating RF fields as claimed in claim 1, at least one main field coil for generating a uniform, steady magnetic field in an examination volume (100), a number of gradient coils for generating gradient pulses in different spatial directions, a body coil which consists of a plurality of resonator segments which are arranged around the examination volume (100) and each of which consists of at least one conductor element (104) which extends parallel to the longitudinal axis of the main field coil and of at least one capacitor element, at least one control unit (111) for controlling the succession in time of the RF and gradient pulses, and a reconstruction unit (115) and a visualization unit (116), characterized in that the resonator segments of the body coil are electromagnetically decoupled from one another, that a separate transmission channel (1 to 8) is associated with each resonator segment, via which transmission channel the RF feeding takes place into the relevant resonator segment, the phase and/or the amplitude of the RF feeding being individually selectable for each resonator segment, and that a separate receiving channel (a to h) is associated with each resonator segment, via which receiving channel the MR signals detected by means of the relevant resonator segment are applied to a receiving unit (112) for further processing by means of the reconstruction unit (115) and the visualization unit (116).

11. An MR apparatus as claimed in claim 10, characterized in that each transmission channel (1 to 8) is connected to an output of a connection network (combiner hybrid 109) which is associated with the relevant resonator segment and via which the power of a transmission amplifier (10) is distributed between the individual resonator segments, the phase and the amplitude of the respective RF signal fed in for each resonator segment being defined by the connection network (109).

12. An MR apparatus as claimed in claim 10, characterized in that with at least one resonator segment there is associated a measuring element (pick-up coil) via which the RF field strength emitted by the relevant resonator segment is determined, the measuring signal being applied to the control unit (111) in order to monitor and/or control the phase and the amplitude of the RF signal fed in.