Magnetic resonance imaging apparatus, signal selection method in magnetic resonance imaging apparatus, and magnetic resonance imaging method in magnetic resonance imaging apparatus

• US 20060214662A1
• Filed: 03/23/2006
• Published: 09/28/2006
• Est. Priority Date: 03/23/2005
• Status: Active Grant

• Current Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Original Assignee: Toshiba Medical Systems Corporation (Canon Inc.), Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Adachi, Kohei
• Granted Patent: US 7,400,148 B2
• Time in Patent Office: Days
• US Class Current: 324/322
• CPC Class Codes: G01R 33/3415 comprising arrays of sub-coils , i.e. phased-array coils with flexible receiver channels
• CPC Class Codes: G01R 33/3621 NMR receivers or demodulators, e.g. preamplifiers, means for frequency modulation of the MR signal using a digital down converter, means for analog to digital conversion [ADC] or for filtering or processing of the MR signal such as bandpass filtering, resampling, decimation or interpolation

Abstract

A magnetic resonance imaging includes: a first converter that converts some of the magnetic resonance signals, to be processed, corresponding to a plurality of channels into signals corresponding to a plurality of effective channels set within a first frequency band and converts magnetic resonance signals corresponding to other channels into signals corresponding to channels set within a second frequency band different from the first frequency band; a synthesizer that synthesizes the channel-converted signals; an extractor that extracts a signal included in the first frequency band from the synthesized signals; and a divider that divides the extracted signal into magnetic resonance signals corresponding to the plurality of effective channels.

Claims

1. A magnetic resonance imaging apparatus of processing and imaging some of magnetic resonance signals corresponding to a plurality of channels, comprising:

a first converter that converts some of the magnetic resonance signals, to be processed, corresponding to the plurality of channels into signals corresponding to a plurality of effective channels set within a first frequency band and converts magnetic resonance signals corresponding to other channels into signals corresponding to channels set within a second frequency band different from the first frequency band;

a synthesizer that synthesizes the channel-converted signals;

an extractor that extracts a signal included in the first frequency band from the synthesized signals; and

a divider that divides the extracted signal into magnetic resonance signals corresponding to the plurality of effective channels.

2. The magnetic resonance imaging apparatus according to claim 1,

wherein the first converter includes:

a first generator that generates a plurality of first local signals corresponding to a plurality of input channels and can individually convert frequencies of the plurality of first local signals;

a mixer that mixes each of the plurality of first local signals corresponding to the input channels with a signal of each of the plurality of input channels; and

a controller that controls the first generator such that a frequency of the first local signal corresponding to the input channel to be processed becomes a frequency corresponding to each of the plurality of effective channels and frequencies of the first local signals corresponding to the input channels not to be processed become frequencies corresponding to channels set within the second frequency band.

3. The magnetic resonance imaging apparatus according to claim 2,

wherein the extraction unit filters, out of the synthesized signals, signals of channels set within the second frequency band, unnecessary image signals generated due to the conversion performed by the first converter, and the first local signals.

4. The magnetic resonance imaging apparatus according to claim 1,

wherein the divider includes:

a dividing unit that divides the extracted signal into a plurality of signals; and

an extraction unit that extracts a frequency band of each of the plurality of effective channels from the plurality of divided signals.

5. The magnetic resonance imaging apparatus according to claim 1, further comprising:

a second converter that converts the plurality of magnetic resonance signals divided by the divider into signals included in a third frequency band, respectively.

6. The magnetic resonance imaging apparatus according to claim 5,

wherein the second converter includes:

a second generator that generates a plurality of second local signals corresponding to the plurality of effective channels and can individually convert frequencies of the plurality of second local signals; and

a mixer that mixes each of the plurality of second local signals corresponding to the effective channels with each of the signals, corresponding to the plurality of effective channels, divided by the divider.

7. The magnetic resonance imaging apparatus according to claim 6,

wherein the second converter further includes an extraction unit that extracts the third frequency band from the plurality of signals output from the mixer.

8. The magnetic resonance imaging apparatus according to claim 1, further comprising:

first and second coil units each having a plurality of coil elements, each of the plurality of coil elements outputting a magnetic resonance signal corresponding to one channel,

wherein the first and second coil units are disposed at the back and abdomen sides of a patient'"'"'s body, respectively, and

the number of coil elements included in the second coil unit is smaller than the number of coil elements included in the first coil unit.

9. The magnetic resonance imaging apparatus according to claim 8,

wherein, in each of the first and second coil units, the coil elements are disposed in a matrix and in a first direction corresponding to the body width direction of the patient'"'"'s body and a second direction corresponding to the body axis direction of the patient'"'"'s body, and

the number of coil elements which are included in the second coil unit and are disposed in the first direction is set to be smaller than the number of coil elements which are included in the first coil unit and are disposed in the first direction, and the number of coil elements which are included in the second coil unit and are disposed in the second direction is set to be equal to the number of coil elements which are included in the first coil unit and are disposed in the second direction.

10. The magnetic resonance imaging apparatus according to claim 1, further comprising:

a coil unit having a plurality of coil elements each outputting a magnetic resonance signal corresponding to one channel,

wherein at least some of the plurality of coil elements is disposed along the first direction corresponding to the body width direction of a patient'"'"'s body, and

the sizes of the coil elements located at a middle portion of the coil unit in the first direction are smaller than the sizes of the coil elements located near both edges of the coil unit in the first direction.

11. The magnetic resonance imaging apparatus according to claim 1, further comprising:

a coil unit having a plurality of coil elements each outputting a magnetic resonance signal corresponding to one channel; and

a user interface unit that receives a designation with respect to coil elements, which output some of the magnetic resonance signals to be processed, on an image showing an arrayed state of the coil elements in the coil unit and a positional relationship between a patient'"'"'s body and the coil unit.

12. A magnetic resonance imaging apparatus of processing and imaging some of magnetic resonance signals corresponding to a plurality of channels, comprising:

a first converter that converts some of the magnetic resonance signals, to be processed, corresponding to the plurality of channels into signals corresponding to a plurality of effective channels set within a first frequency band and converts magnetic resonance signals corresponding to other channels into signals corresponding to channels set within a second frequency band different from the first frequency band;

a synthesizer that synthesizes the channel-converted signals; and

a reconstruction unit that reconstructs an image on the basis of a signal, included in the first frequency band, of the synthesized signals.

13. A signal selection method in a magnetic resonance imaging apparatus of processing and imaging some of magnetic resonance signals corresponding to a plurality of channels, comprising:

converting some of the magnetic resonance signals, to be processed, corresponding to the plurality of channels into signals corresponding to a plurality of effective channels set within a first frequency band and converting magnetic resonance signals corresponding to other channels into signals corresponding to channels set within a second frequency band different from the first frequency band;

synthesizing the channel-converted signals;

extracting a signal included in the first frequency band from the synthesized signals; and

dividing the extracted signal into magnetic resonance signals corresponding to the plurality of effective channels.

14. The signal selection method according to claim 13,

wherein the channel conversion process includes:

generating a plurality of first local signals corresponding to a plurality of input channels;

mixing each of the plurality of first local signals corresponding to the input channels with a signal of each of the plurality of input channels; and

controlling such that a frequency of the first local signal corresponding to the effective channel to be processed becomes a frequency corresponding to each of the plurality of input channels and frequencies of the first local signals corresponding to the input channels not to be processed become frequencies corresponding to channels set within the second frequency band.

15. The signal selection method according to claim 14,

wherein, in the extraction process, signals of channels set within the second frequency band, unnecessary image signals generated due to the conversion performed by the first converter, and the first local signals are filtered out of the synthesized signals.

16. The signal selection method according to claim 13,

wherein the division process includes:

dividing the extracted signal into a plurality of signals; and

extracting a frequency band of each of the plurality of effective channels from the plurality of divided signals.

17. The signal selection method according to claim 13, further comprising:

converting the plurality of divided magnetic resonance signals into signals included in a third frequency band, respectively.

18. The signal selection method according to claim 17,

wherein the process of converting the plurality of divided magnetic resonance signals into the signals included in a third frequency band includes:

generating a plurality of second local signals corresponding to the plurality of effective channels; and

mixing each of the plurality of second local signals corresponding to the effective channels with each of the divided signals corresponding to the plurality of effective channels.

19. The signal selection method according to claim 18,

wherein the process of converting the plurality of divided magnetic resonance signals into the signals included in a third frequency band further includes extracting the third frequency band from the plurality of mixed signals.

20. A magnetic resonance imaging method of processing and imaging some of magnetic resonance signals corresponding to a plurality of channels, comprising:

converting some of the magnetic resonance signals, to be processed, corresponding to the plurality of channels into signals corresponding to a plurality of effective channels set within a first frequency band and converting magnetic resonance signals corresponding to other channels into signals corresponding to channels set within a second frequency band different from the first frequency band;

synthesizing the channel-converted signals; and

reconstructing an image on the basis of a signal, included in the first frequency band, of the synthesized signals.