RF reception coil and magnetic resonance imaging apparatus using same

• US 9,182,468 B2
• Filed: 01/26/2011
• Issued: 11/10/2015
• Est. Priority Date: 03/30/2010
• Status: Active Grant

• Current Assignee: FUJIFILM Healthcare Corp. (Fujifilm Holdings Corporation)
• Original Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Inventors: Kaneko, Yukio, Habara, Hideta, Soutome, Yoshihisa, Otake, Yosuke, Ochi, Hisaaki, Bito, Yoshitaka
• Primary Examiner(s): Vargas, Dixomara
• Application Number:
  US13/577,241
• Publication Number:
  US 20120306497A1
• Time in Patent Office: 1,749 Days
• US Class Current: 1/1
• CPC Class Codes: G01R 33/34076 Birdcage coils
• CPC Class Codes: G01R 33/3415 comprising arrays of sub-coils , i.e. phased-array coils with flexible receiver channels
• CPC Class Codes: G01R 33/3657 Decoupling of multiple RF coils wherein the multiple RF coils do not have the same function in MR, e.g. decoupling of a transmission coil from a receive coil
• CPC Class Codes: G01R 33/3664 Switching for purposes other than coil coupling or decoupling, e.g. switching between a phased array mode and a quadrature mode, switching between surface coil modes of different geometrical shapes, switching from a whole body reception coil to a local reception coil or switching for automatic coil selection in moving table MR or for changing the field-of-view G01R33/3671 takes precedence
• CPC Class Codes: G01R 33/3678 involving quadrature drive or detection, e.g. a circularly polarized RF magnetic field
• 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

There is provided a technique for improving quality of images obtained with an MRI apparatus by using the geometric structures of the conventional RF transmission coil and RF reception coil and without increasing burden on patients or MRI technicians. A conductor loop of an RF reception coil disposed between a subject and an RF transmission coil is used also as a loop for magnetic field adjustment in order to shield or enhance a rotating magnetic field B₁ generated by the RF transmission coil. Further, the conductor loop operated as a conductor loop for magnetic field adjustment among the conductor loops constituting the RF reception coil is driven so that inhomogeneity of the rotating magnetic field B₁ is reduced.

Claims

1. An RF reception coil for receiving a magnetic resonance signal generated from a subject in response to receiving a radio frequency signal transmitted by an RF transmission coil in a magnetic resonance imaging apparatus, wherein:

the RF reception coil is disposed in a bore formed by the RF transmission coil,

the RF reception coil comprises a plurality of conductor loops,

at least one of the conductor loops comprises;

at least one capacitor and

a switch circuit that is connected to the capacitor in parallel, and controls electrical connection, and

when the switch circuit is driven, the switch circuit makes the conductor loop having the switch circuit function as a magnetic field adjustment circuit that shields or enhances a magnetic field generated by the RF transmission coil.

2. The RF reception coil according to claim 1, wherein:

the conductor loop having the switch circuit is disposed so as to reduce inhomogeneity in distribution of the magnetic field generated by the RF transmission coil.

3. The RF reception coil according to claim 1, wherein:

each of the plurality of the conductor loops has a respective said switch circuit, and

the switch circuit of at least one conductor loop defined beforehand is driven at the time of irradiation of the radio frequency signal so that inhomogeneity in distribution of the magnetic field generated by the RF transmission coil is reduced.

4. The RF reception coil according to claim 3, wherein:

each conductor loop further comprises a magnetic decoupling circuit,

the magnetic decoupling circuit is connected to the one capacitor of the conductor loop in parallel, and

the magnetic decoupling circuit of a conductor loop of which the switch circuit is not driven at the time of transmission of the radio frequency signal is driven.

5. The RF reception coil according to claim 1, wherein:

a respective said switch circuit is connected in parallel to each of the capacitors provided in the conductor loop.

6. The RF reception coil according to claim 1, wherein:

the switch circuit comprises a diode.

7. The RF reception coil according to claim 1, wherein:

the switch circuit comprises a micro-electro-mechanical system.

8. The RF reception coil according to claim 1, wherein:

the switch circuit comprises a variable resistor.

9. The RF reception coil according to claim 4, wherein:

the magnetic decoupling circuit is a circuit comprising a diode and an inductor connected in series.

10. A magnetic resonance imaging apparatus comprising a static magnetic field formation portion to form a static magnetic field, a gradient magnetic field application portion to apply a gradient magnetic field, a radio frequency signal transmission portion to transmit a radio frequency signal to a subject, a magnetic resonance signal reception portion to receive a magnetic resonance signal generated from the subject, and a control portion to control the gradient magnetic field application portion, the radio frequency signal transmission portion, and the magnetic resonance signal reception portion, wherein:

the magnetic resonance signal reception portion includes the RF reception coil according to claim 1.

11. A magnetic resonance imaging apparatus comprising a static magnetic field formation portion to form a static magnetic field, a gradient magnetic field application portion to apply a gradient magnetic field, a radio frequency signal transmission portion to transmit a radio frequency signal to a subject, a magnetic resonance signal reception portion receive a magnetic resonance signal generated from the subject, and a control portion to control the gradient magnetic field application portion, the radio frequency signal transmission portion, and the magnetic resonance signal reception portion, wherein:

the magnetic resonance signal reception portion includes the RF reception coil according to claim 4, and

the control portion includes an electrical connection control portion that drives the switch circuit and the magnetic decoupling circuit at the time of transmission of the radio frequency signal.

12. The magnetic resonance imaging apparatus according to claim 11, wherein:

the control portion further comprises a function determination portion that determines in which conductor loop the switch circuit is driven at the time of transmission of the radio frequency signal.

13. The magnetic resonance imaging apparatus according to claim 10, wherein:

the radio frequency signal transmission portion transmit a plurality of radio frequency signals of which amplitude and phase are independently controlled to the subject, so that inhomogeneity in distribution of a magnetic field is reduced.

14. The magnetic resonance imaging apparatus according to claim 13, wherein:

the control portion determines values of amplitude and phase of the plurality of the radio frequency signals at the time of transmission of the radio frequency signals.