Magnetic resonance imaging apparatus

• US 5,389,880 A
• Filed: 06/30/1993
• Issued: 02/14/1995
• Est. Priority Date: 06/30/1992
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Mori, Issei
• Primary Examiner(s): Tokar, Michael J.
• Application Number:
  US08/085,742
• Time in Patent Office: 594 Days
• Field of Search: 324/300, 324/307, 324/309, 324/310, 324/311, 324/312, 324/306, 324/313, 324/314, 324/318, 324/322
• US Class Current: 324/318
• CPC Class Codes: G01R 33/34061 Helmholtz coils
• CPC Class Codes: G01R 33/34084 implantable coils or coils being geometrically adaptable to the sample, e.g. flexible coils or coils comprising mutually movable parts
• CPC Class Codes: G01R 33/3415 comprising arrays of sub-coils , i.e. phased-array coils with flexible receiver channels
• CPC Class Codes: G01R 33/3628 Tuning/matching of the transmit/receive coil
• CPC Class Codes: G01R 33/3678 involving quadrature drive or detection, e.g. a circularly polarized RF magnetic field
• CPC Class Codes: G01R 33/56 Image enhancement or correction, e.g. subtraction or averaging techniques , e.g. improvement of signal-to-noise ratio and resolution

Abstract

Four QD surface coil assemblies each constituted by an 8-shaped coil and a rectangular coil are one-dimensionally arranged under the spine array of a patient in the direction of the body axis of the patient. Each 8-shaped coil senses an RF magnetic field in an x direction near the spine array of the patient, and each rectangular coil senses an RF magnetic field in a y direction. Outputs from the 8-shaped coils and the rectangular coils are input to 90° hybrid combiner circuits through pre-amplifiers, the phase of any one of the outputs is shifted by 90°, and then the outputs are added to each other. Outputs from the 90° hybrid combiner circuits are supplied as raw data, through receiver/data acquisition systems, to a data processing unit (computer). In the data processing unit, raw data are two-dimensionally Fourier-transformed to form image signals p_i (x,y,z) (i=1 to 4). The signals p₁ (x,y,z) are squared, the sum of p_i (x,y,z) is calculated with respect to i, and finally, the square root of the sum is calculated to obtain an image.

Claims

1. A magnetic resonance imaging apparatus for receiving radio frequency signals generated by an object to be imaged;

said apparatus comprising;

a radio-frequency coil array formed of a plurality of radio-frequency coil assemblies arranged in at least one dimension, each radio-frequency coil assembly for receiving radio-frequency signals from two directions perpendicular to each other generated at a predetermined portion of the object and for generating two output signals in response thereto;

each radio-frequency coil assembly having an associated means for shifting a phase of one of the two output signals by about 90° and

for synthesizing the two output signals to obtain one synthesized signal;

means for substantially simultaneously operating at least two of said plurality of radio-frequency coil assemblies to generate substantially simultaneously at least two synthesized signals; and

means for reconstructing an image of the object on the basis of said at least two synthesized signals.

2. An apparatus according to claim 1, wherein

said plurality of radio-frequency coil assemblies are arranged in a body axis direction of the object;

and

each of said plurality of radio-frequency coil assemblies is formed of a substantially circular or rectangular surface coil having a sensitivity for receiving radio-frequency signals in a horizontal direction perpendicular to the body axis and a substantially 8- shaped conductor having a sensitivity for receiving radio-frequency signals in a vertical direction perpendicular to the body axis.

3. An apparatus according to claim 2, wherein said surface coil is a differential type surface coil.

4. An apparatus according to claim 1, wherein each of said plurality of radio-frequency coil assemblies is formed of a substantially 8-shaped single coil, having two resonance modes, for generating the two output signals each corresponding to a resonance mode.

5. A magnetic resonance imaging apparatus for receiving radio-frequency signals generated by an object to be imaged, said apparatus comprising:

a radio-frequency coil array formed of at least two pairs of radio-frequency coil assemblies arranged in at least one dimension, each pair of said radio-frequency coil assemblies is positioned with the object therebetween, and having a sensitivity for receiving two radio-frequency signals in two directions perpendicular to each other at a predetermined portion of the object, and for generating two output signals corresponding to the two radio-frequency signals received;

each pair of radio-frequency coil assembly having an associated means for shifting a phase of one of the two output signals by about 90° and

for synthesizing the two output signals to obtain one synthesized signal;

means for substantially simultaneously operating said at least two pairs of said radio-frequency coil assemblies to substantially simultaneously acquire a plurality of synthesized signals; and

means for reconstructing an image of the object on the basis of the plurality of synthesized signals.

6. An apparatus according to claim 5, wherein said at least two pairs of said radio-frequency coil assemblies are arranged in a body axis direction of the object;

and

each of the pair of said radio-frequency coil assemblies is formed of a substantially circular or rectangular surface coil having a sensitivity for receiving radio-frequency signals in a horizontal direction perpendicular to the body axis and a substantially 8-shaped conductor having a sensitivity for receiving radio-frequency signals in a vertical direction perpendicular to the body axis.

7. An apparatus according to claim 6, wherein said surface coil is a differential type surface coil.

8. A magnetic resonance imaging apparatus for receiving radio-frequency signals generated by an object to be imaged;

said apparatus comprising;

plural volume coil assemblies arranged in an axis of the object said assemblies positioned to surround the object and for receiving radio-frequency signals generated by the object and for producing plural output signals in response thereto;

means for substantially simultaneously operating said plural volume coil assemblies to substantially simultaneously acquire said plural output signals from said plural volume coil assemblies; and

means for reconstructing an image of the object on the basis of the plural output signals from said plural volume coil assemblies which are simultaneously acquired.

9. An apparatus according to claim 8, wherein each of said volume coil assemblies has a sensitivity for receiving radio-frequency signals from two directions perpendicular to each other at a predetermined portion of the object and for producing two output signals corresponding to the two radio-frequency signals.

10. An apparatus according to claim 9, further comprising:

means for shifting a phase of one of two output signals from each of said volume coil assemblies by about 90°

an synthesizing the two output signals to obtain one synthesized signal.

11. A magnetic resonance imaging apparatus for receiving radio-frequency signals generated by an object to be imaged;

said apparatus comprising;

a radio-frequency volume coil array formed of at least two radio-frequency volume coil assemblies arranged in a direction of a body axis of the object, each of the radio-frequency volume coil assemblies being formed of two radio-frequency coil assemblies sandwiching the object, and each of the volume radio-frequency coil assemblies having a sensitivity for receiving radio-frequency signals in two directions perpendicular to each other at a predetermined portion of the object and for producing two output signals corresponding to the two radio-frequency signals in response thereto;

each volume coil assembly having an associated means for shifting a phase of one of two output signals by about 90° and

synthesizing the two output signals to obtain one synthesized signal;

means for substantially simultaneously operating said at least two radio-frequency volume coil assemblies to substantially simultaneously acquire a plurality of synthesized signals; and

means for reconstructing an image of the object on the basis of the plurality of synthesized signals which are simultaneously acquired.

12. A magnetic resonance imaging apparatus for receiving radio-frequency signals generated by an object to be imaged;

said apparatus comprising;

a radio-frequency surface coil assembly formed of two radio-frequency surface coil assemblies, having a sensitivity for receiving radio-frequency signals in two directions perpendicular to each other at a predetermined portion of the object and for producing two surface output signals corresponding to the two radio-frequency signals received;

a radio-frequency volume coil assembly formed of two radio-frequency coil assemblies surrounding the object, having a sensitivity for receiving radio-frequency signals in two directions perpendicular to each other at a predetermined portion of the object and for producing two volume output signals corresponding to the two radio-frequency signals received;

first synthesizing means for shifting a phase of one of two surface output signals by about 90° and

for synthesizing the two surface output signal to obtain a first synthesized signal;

second synthesizing means for shifting a phase of one of two volume output signals by about 90° and

for synthesizing the two volume output signals to obtain a second synthesized signal;

means for substantially simultaneously operating said radio-frequency surface coil assembly and said radio-frequency volume coil assembly to substantially simultaneously acquire the first and second synthesized signals; and

means for reconstructing an image of the object on the basis of the first and second synthesized signals which are simultaneously acquired.