Magnetic resonance imaging apparatus and radio frequency coil unit

1. A radio frequency (RF) coil unit comprising:

a plurality of RF surface coils arranged in a body-axis direction of an object to be imaged in an MRI system; and

an RF signal distributing/combining unit configured to produce new RF reception signals, forming respectively corresponding plural RF sensitivity distributions respectively different from RF sensitivity distributions of the plurality of surface coils, by distributing and combining RF reception signals from the plurality of RF surface coils in the body-axis direction.

2. The radio frequency coil unit according to claim 1 wherein:

the distributing/combining unit is configured such that a distribution and combining characteristic is represented by a matrix having an inverse matrix of N×N when the number of the surface coils is N.

3. The radio frequency coil unit according to claim 1 wherein:

the distributing/combining unit has only passive 0°-180° hybrid circuits.

4. The radio frequency coil unit according to claim 1 wherein:

the number of surface coils are four or more.

5. The radio frequency coil unit according to claim 1 , further comprising:

a path changing switch that switches a path of the reception signals output from the plurality of surface coils between a path passing through the distributing/combining unit and a path not passing through the distributing/combining unit.

6. The radio frequency coil unit according to claim 1 , wherein:

the plurality of surface coils includes surface coils that are arranged in a direction vertical to the body-axis direction,

a distributing/combining unit of a non-body-axis direction that distributes and combines reception signals in the direction vertical to the body-axis direction to output new reception signals from the surface coils arranged in the direction vertical to the body-axis direction,

the distributing/combining units distributing and combining reception signals obtained on the basis of reception signals from the surface coils arranged in the body-axis direction, reception signals distributed and combined by the distributing/combining unit of the non-body-axis direction and reception signals before being distributed and combined by the distributing/combining units, to produce new reception signals.

7. The radio frequency coil unit according to claim 1 , wherein:

the plurality of surface coils includes a first surface coil, a second surface coil, a third surface coil, and a fourth surface coil,

the distributing/combining units include a first 0°-180° hybrid circuit that is provided at output sides of the first and second surface coils, a second 0°-180° hybrid circuit that is provided at output sides of the third and fourth surface coils, a third 0°-180° hybrid circuit that is provided at a 0° output side of the first 0°-180° hybrid circuit and at a 0° output side of the second 0°-180° hybrid circuit, and a fourth 0°-180° hybrid circuit that is provided at a 180° output side of the first 0°-180° hybrid circuit and at a 180° output side of the second 0°-180° hybrid circuit.

8. A method for processing radio frequency (RF) MRI signals from an MRI radio frequency coil unit, said method comprising:

arranging a plurality of RF surface coils in a body-axis direction of an object to be imaged in an MRI system, and

producing new RF reception signals, forming respectively corresponding plural RF sensitivity distributions respectively different from RF sensitivity distributions of the plurality of surface coils, by distributing and combining RF reception signals from the plurality of surface coils in the body-axis direction.

9. The method according to claim 8 wherein:

the distributing and combining process has a distribution and combining characteristic represented by a matrix having an inverse matrix of N×N when the number of the surface coils is N.

10. The method according to claim 8 wherein:

the distributing and combining steps use only passive 0°-180° hybrid circuits.

11. The method according to claim 8 wherein:

the number of surface coils are four or more.

12. The method according to claim 8 , further comprising:

switch-changing a path of the reception signals output from the plurality of surface coils between a path including the distributing and combining steps and a path not including the distributing and combining steps.

13. The method according to claim 8 wherein:

the plurality of surface coils includes surface coils that are arranged in a direction orthogonal to the body-axis direction,

distributing and combining reception signals in the direction orthogonal to the body-axis direction to output new reception signals from the surface coils arranged in the direction orthogonal to the body-axis direction,

the distributing and combining steps distributing and combining reception signals obtained on the basis of reception signals from the surface coils arranged in the body-axis direction, reception signals distributed and combined by the distributing/combining unit of the orthogonal direction and reception signals as they existed before being distributed and combined to produce new reception signals.

14. The method according to claim 8 wherein:

the plurality of surface coils includes a first surface coil, a second surface coil, a third surface coil, and a fourth surface coil,

the distributing and combining steps use a first 0°-180° hybrid circuit provided at output sides of the first and second surface coils, a second 0°-180° hybrid circuit provided at output sides of the third and fourth surface coils, a third 0°-180° hybrid circuit provided at a 0° output side of the first 0°-180° hybrid circuit and at a 0° output side of the second 0°-180° hybrid circuit, and a fourth 0°-180° hybrid circuit provided at a 180° output side of the first 0°-180° hybrid circuit and at a 180° output side of the second 0°-180° hybrid circuit.