MAGNETIC RESONANCE METHOD AND APPARATUS USING DUAL ECHOES FOR DATA ACQUISITION

• US 20100268061A1
• Filed: 04/17/2009
• Published: 10/21/2010
• Est. Priority Date: 04/17/2009
• Status: Active Grant

• Current Assignee: Siemens AG, UK Research and Innovation
• Original Assignee: Siemens AG
• Inventors: Schwarzbauer, Christian, Porter, David Andrew
• Granted Patent: US 9,316,712 B2
• Time in Patent Office: Days
• US Class Current: 600/410
• CPC Class Codes: A61B 2018/00446 Brain
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: G01R 33/4806 Functional imaging of brain activation
• CPC Class Codes: G01R 33/5618 using both RF and gradient refocusing, e.g. GRASE
• CPC Class Codes: G01R 33/56563 caused by a distortion of the main magnetic field B0, e.g. temporal variation of the magnitude or spatial inhomogeneity of B0 G01R33/56509, G01R33/56518, G01R33/56536 take precedence

Abstract

In a method and system for acquiring magnetic resonance image data from a subject, using a data acquisition unit in which a basic magnetic field is generated, a division is designated in a planar section through the subject that divides the planar section into a first section and a second section, with the homogeneity of the basic magnetic field being better in said first section than in said second section. An echo planar imaging sequence is implemented to acquire the magnetic resonance imaging data, with magnetic resonance data being acquired from the first section only from gradient echo signals in the echo planar imaging sequence, and magnetic resonance data from said the second section being acquired from both gradient echo signals and spin echo signals in the echo planar imaging sequence. The method and apparatus are particularly suited for acquiring functional magnetic resonance imaging (fMRI) data from the brain of a subject, in which the first section is an upper portion of the brain and the second section is a lower portion of the brain.

Claims

1. A method for acquiring magnetic resonance image data, comprising the steps of:

providing a magnetic resonance data acquisition unit operated by a control unit and having a magnet system that generates a basic magnetic field;

designating a division in a planar section through a human or animal subject that divides said planar section into a first section in which said basic magnetic field has a first homogeneity and a second section in which said basic magnetic field has a second homogeneity that is less homogenous than said first homogeneity;

generating a control protocol incorporating the designation of said division, that operates said magnetic resonance data acquisition unit to acquire magnetic resonance image data using an echo planar imaging sequence in which, according to said designation of said division, magnetic resonance image data are acquired from said first section only from gradient echo signals in said echo planar imaging sequence and magnetic resonance image data are acquired from said second section from both gradient echo signals and spin echo signals in said echo planar imaging sequence;

operating said magnetic resonance data acquisition unit from said control unit according to said control protocol to acquire said magnetic resonance image data from the subject; and

making the magnetic resonance image data from the subject available as an output from the magnetic resonance data acquisition unit in a form allowing reconstruction of a visible image of the subject therefrom.

2. A method as claimed in claim 1 comprising generating said visible image of the subject from said magnetic resonance image data that are output from the magnetic resonance data acquisition unit.

3. A method as claimed in claim 1 comprising designating said division in said planar section as a homogeneity threshold in said planar section.

4. A method as claimed in claim 1 comprising acquiring said magnetic resonance data from the brain of the subject, and designating said division in a sagittal section, as said planar section, through the brain of the subject.

5. A method as claimed in claim 4 comprising designating said division to divide the brain of the subject in said sagittal section into an upper region, as said first region, and a lower region, as said second region.

6. A method as claimed in claim 5 comprising designating said division with said upper region encompassing approximately two-thirds of the brain of the subject in said sagittal section and with said lower section encompassing approximately one-third of the brain of the subject in said sagittal section.

7. A method as claimed in claim 1 comprising operating said magnetic resonance data acquisition unit according to said control protocol to acquire said magnetic resonance data from successive slices of the subject.

8. A method as claimed in claim 7 comprising generating an echo planar imaging sequence in said control protocol that comprises a 90°

focusing pulse, followed by a gradient echo readout gradient in which said gradient echo signal is read out, followed by a 180°

refocusing pulse, followed by a spin echo readout gradient in which said spin echo signal is read out, and comprising operating said magnetic resonance data acquisition unit according to said control protocol to execute a gradient echo loop comprising said 90°

focusing pulse and said gradient echo readout gradient to acquire said magnetic resonance data from successive slices in said first section and to execute a dual echo loop, comprising said 90°

focusing pulse, said gradient echo readout gradient, said 180°

refocusing pulse, and said spin echo readout gradient, to acquire said magnetic resonance data from successive slices in said second section.

9. A method as claimed in claim 1 comprising designating said division manually via an input unit connected to said control unit.

10. A method as claimed in claim 1 comprising designating said division non-manually, automatically in said control unit based on a magnetic field map in said planar section of said subject.

19. A system as claimed in claim 1 wherein said division designation unit is configured to designate said division with said upper region encompassing approximately two-thirds of the brain of the subject in said sagittal section and with said lower section encompassing approximately one-third of the brain of the subject in said sagittal section.

11. A method for acquiring functional magnetic resonance image (fMRI) data, comprising the steps of:

providing a magnetic resonance data acquisition unit operated by a control unit and having a magnet system that generates a basic magnetic field;

designating a division in a sagittal section through the brain of a human or animal subject that divides the brain into an upper section in which said basic magnetic field has a first homogeneity and a lower section in which said basic magnetic field has a second homogeneity that is less homogenous than said first homogeneity;

generating a control protocol incorporating the designation of said division, that operates said magnetic resonance data acquisition unit to acquire fMRI data using an echo planar imaging sequence in which, according to said designation of said division, fMRI data are acquired from said upper section only from gradient echo signals in said echo planar imaging sequence and fMRI data are acquired from said lower section from both gradient echo signals and spin echo signals in said echo planar imaging sequence;

operating said magnetic resonance data acquisition unit from said control unit according to said control protocol to acquire said fMRI data from the subject; and

making the fMRI data from the subject available as an output from the magnetic resonance data acquisition unit in a form allowing reconstruction of a visible image of the subject therefrom.

12. A method as claimed in claim 11 comprising generating said visible image of the subject from said fMRI data that are output from the magnetic resonance data acquisition unit.

13. A method as claimed in claim 11 comprising designating said division with said upper region encompassing approximately two-thirds of the brain of the subject in said sagittal section and with said lower section encompassing approximately one-third of the brain of the subject in said sagittal section.

14. A system for acquiring magnetic resonance image data, comprising:

a magnetic resonance data acquisition unit operated by a control unit and having a magnet system that generates a basic magnetic field;

a division designation unit configured to designate a division in a planar section through a human or animal subject into a first section in which said basic magnetic field has a first homogeneity and a second section in which said basic magnetic field has a second homogeneity that is less homogenous than said first homogeneity;

said control unit being configured to generate a control protocol that incorporates the designation of said division, and to operate said magnetic resonance data acquisition unit to acquire magnetic resonance image data using an echo planar imaging sequence by, according to said designation of said division, acquiring magnetic resonance image data from said first section only from gradient echo signals in said echo planar imaging sequence and acquiring magnetic resonance image data from said second section from both gradient echo signals and spin echo signals in said echo planar imaging sequence; and

said control unit being configured to make the magnetic resonance image data from the subject available as an output from the magnetic resonance data acquisition unit in a form allowing reconstruction of a visible image of the subject therefrom.

15. A system as claimed in claim 14 comprising an image reconstruction computer configured to generate said visible image of the subject from said magnetic resonance data that are output from the magnetic resonance data acquisition unit.

16. A system as claimed in claim 14 wherein said division designation unit is configured to designate said division in said section as a homogeneity threshold in said section.

17. A system as claimed in claim 14 wherein said magnetic resonance data acquisition unit is configured to acquire said magnetic resonance data from the brain of the subject, and wherein said division designation unit is configured to designate said division in a sagittal section, as said planar section, through the brain of the subject.

18. A system as claimed in claim 17 wherein said division designation unit is configured to designate said division to divide the brain of the subject in said sagittal section into an upper region, as said first region, and a lower region, as said second region.

20. A system as claimed in claim 14 wherein said control unit is configured to operate said magnetic resonance data acquisition unit according to said control protocol to acquire said magnetic resonance data from successive slices of the subject.

21. A system as claimed in claim 20 wherein said control unit is configured to generate an echo planar imaging sequence in said control protocol that comprises a 90°

focusing pulse, followed by a gradient echo readout gradient in which said gradient echo signal is read out, followed by a 180°

refocusing pulse, followed by a spin echo readout gradient in which said spin echo signal is read out, and to operate said magnetic resonance data acquisition unit according to said control protocol to execute a gradient echo loop comprising said 90°

focusing pulse and said gradient echo readout gradient to acquire said magnetic resonance data from said first section and to execute a dual echo loop, comprising said 900 focusing pulse, said gradient echo readout gradient, said 180°

refocusing pulse, and said spin echo readout gradient, to acquire said magnetic resonance data from said second section.

22. A system as claimed in claim 14 wherein said division designation unit is an input unit connected to said control unit that allows manual designation of said division.

23. A system as claimed in claim 14 wherein said division designation unit is a software module in said control unit configured to cause the control unit to execute an algorithm to automatically designate said division based on a magnetic field map in said planar section of said subject.