MRI APPARATUS, IMAGE PROCESSING APPARATUS, AND IMAGE PROCESSING METHOD

• US 20170097399A1
• Filed: 09/29/2016
• Published: 04/06/2017
• Est. Priority Date: 10/06/2015
• Status: Active Grant

• Current Assignee: Canon Medical Systems Corporation (Canon Inc.)
• Original Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Inventors: SHIODERA, Taichiro, TAKEGUCHI, Tomoyuki
• Granted Patent: US 10,429,466 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2576/00 Medical imaging apparatus involving image processing or analysis A61B1/00009, A61B6/52 and A61B8/52 take precedence; image processing per se G06T; details of algorithms for analysing medical images G06T7/0012
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: G01R 33/34 Constructional details, e.g. resonators , specially adapted to MR
• CPC Class Codes: G01R 33/3415 comprising arrays of sub-coils , i.e. phased-array coils with flexible receiver channels
• CPC Class Codes: G01R 33/385 using gradient magnetic field coils
• CPC Class Codes: G01R 33/443 Assessment of an electric or a magnetic field, e.g. spatial mapping, determination of a B0 drift or dosimetry
• CPC Class Codes: G01R 33/543 Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription G01R33/546 takes precedence
• CPC Class Codes: G01R 33/546 Interface between the MR system and the user, e.g. for controlling the operation of the MR system or for the design of pulse sequences
• 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
• CPC Class Codes: G01R 33/5611 Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE structural details of arrays of sub-coils G01R33/3415
• CPC Class Codes: G01R 33/56545 caused by finite or discrete sampling, e.g. Gibbs ringing, truncation artefacts, phase aliasing artefacts
• 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
• CPC Class Codes: G06T 2207/10088 Magnetic resonance imaging [MRI]
• CPC Class Codes: G06T 7/0012 Biomedical image inspection

Abstract

According to one of embodiments, an MRI apparatus includes at least one receiving coil configured to receive magnetic resonance signals from an object; and processing circuitry configured to generate an image based on the magnetic resonance signals, calculate a weighting map of the image based on at least one of a sensitivity characteristic of the receiving coil and a distance from a magnetic field center, and generate a quantitative susceptibility image, which quantitatively indicates magnetic susceptibility inside a body, from the image by using the weighting map.

Claims

1. An MRI apparatus comprising:

at least one receiving coil configured to receive magnetic resonance signals from an object; and

processing circuitry configured to

generate an image based on the magnetic resonance signals,

calculate a weighting map of the image based on at least one of a sensitivity characteristic of the receiving coil and a distance from a magnetic field center, and

generate a quantitative susceptibility image, which quantitatively indicates magnetic susceptibility inside a body, from the image by using the weighting map.

2. The MRI apparatus according to claim 1,

wherein the processing circuitry is configured to calculate the weighting map in such a manner that the weighting map has a larger value at a position where sensitivity of the receiving coil is higher.

3. The MRI apparatus according to claim 1,

wherein the processing circuitry is configured to calculate the weighting map in such a manner that the weighting map has a larger value at a position with a higher signal to noise ratio.

4. The MRI apparatus according to claim 1,

wherein the at least one receiving coil comprises a plurality of receiving coils;

and

the processing circuitry is configured to calculate the weighting map by using a sensitivity characteristic of each of the plurality of receiving coils.

5. The MRI apparatus according to claim 1,

wherein the at least one receiving coil comprises a plurality of receiving coils;

and

the processing circuitry is configured to calculate the weighting map based on a geometry factor calculated from a sensitivity characteristic of each of the plurality of receiving coils.

6. The MRI apparatus according to claim 5,

wherein the processing circuitry is configured to calculate the weighting map by using inverse of the geometry factor.

7. The MRI apparatus according to claim 1,

wherein the processing circuitry is configured to calculate the weighting map by combining a sensitivity map and a distance map, the sensitivity map being calculated from a sensitivity characteristic of the receiving coil, and the distance map being calculated from the distance from a magnetic field center.

8. The MRI apparatus according to claim 1,

wherein the at least one receiving coil comprises a plurality of receiving coils;

and

the processing circuitry is configured to

calculate a geometry factor based on a sensitivity characteristic of each of the plurality of receiving coils, and

calculate the weighting map by combining any two or all of a map of inverse of the geometry factor, a sensitivity map, and a distance map, the sensitivity map being calculated from a sensitivity characteristic of the receiving coil, and the distance map being calculated from the distance from a magnetic field center.

9. The MRI apparatus according to claim 1,

wherein the processing circuitry is configured to correct the weighting map based on an imaging condition excluding a sensitivity characteristic of the receiving coil and the distance from a magnetic field center.

10. The MRI apparatus according to claim 1,

wherein the processing circuitry is configured to correct the weighting map based on changing signal intensity of the image, when signal intensity of the image changes depending on at least one of space and time.

11. The MRI apparatus according to claim 1,

wherein the processing circuitry is configured to generate the quantitative susceptibility image from a phase image indicative of phase information of the image, by performing weighted optimization processing based on the weighting map.

12. The MRI apparatus according to claim 11,

wherein the weighted optimization processing is processing of minimizing an objective function which includes a data term and a regularization term, by applying the weighting map to the data term.

13. The MRI apparatus according to claim 11,

wherein the weighted optimization processing is processing of minimizing an objective function which includes a data term and a regularization term, by applying the weighting map to at least one of the data term and the regularization term.

14. The MRI apparatus according to claim 1,

wherein the processing circuitry is configured to

calculate a phase component attributable to a body tissue from a phase image indicative of phase information of the image, by removing influence of a background magnetic field, and

generate the quantitative susceptibility image from the phase component attributable to the body tissue.

15. An image processing apparatus configured to generate a quantitative susceptibility image from an image generated by an MRI apparatus, the image processing apparatus comprising:

an acquisition circuit configured to acquire the image; and

processing circuitry configured to

generate a quantitative susceptibility image, which quantitatively indicates magnetic susceptibility inside a body from the image, by using a weighting map calculated based on at least one of a sensitivity characteristic of a receiving coil used for imaging the image by the MRI apparatus and a distance from a magnetic field center of the MRI apparatus.

16. The image processing apparatus according to claim 15,

wherein the weighting map is added to data of the image as accompanying information thereof.

17. The image processing apparatus according to claim 15,

wherein the sensitivity characteristic of the receiving coil is added to data of the image as accompanying information thereof;

and

the processing circuitry is configured to calculate the weighting map by using the sensitivity characteristic of the receiving coil.

18. The image processing device according to claim 15,

wherein information on the distance from a magnetic field center is added to data of the image as accompanying information thereof;

and

the processing circuitry is configured to calculate the weighting map by using the information on the distance from a magnetic field center.

19. An image processing method comprising:

acquiring an image generated by an MRI apparatus; and

generating a quantitative susceptibility image, which quantitatively indicates magnetic susceptibility inside a body from the image, by using a weighting map calculated based on at least one of a sensitivity characteristic of a receiving coil used for imaging the image by the MRI apparatus and a distance from a magnetic field center of the MRI apparatus.

20. The image processing method according to claim 19,

wherein the weighting map is calculated based on a geometry factor calculated from sensitivity characteristics of a plurality of receiving coils of the MRI apparatus.