MR imaging with pre-sequence including plural saturation pulses

• US 6,320,377 B1
• Filed: 03/26/1998
• Issued: 11/20/2001
• Est. Priority Date: 03/28/1997
• Status: Expired due to Term

• Current Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Miyazaki, Mitsue, Sugiura, Satoshi
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): FETZNER, TIFFANY A
• Application Number:
  US09/048,290
• Time in Patent Office: 1,335 Days
• Field of Search: 324/128.6, 324/53.2, 324/300-322, 600/408, 600/410, 600/411, 600/413
• US Class Current: 324/306
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 6/541 involving acquisition triggered by a physiological signal
• CPC Class Codes: G01R 33/4838 using spatially selective suppression or saturation of MR signals
• CPC Class Codes: G01R 33/563 of moving material, e.g. flow contrast angiography

Abstract

An artery vein visually separated MRA image and/or a higher blood/parenchyma contrast MRA image are provided by a magnetic resonance imaging system. The system comprises, in addition to a magnet generating a static magnetic field, a gradient generation unit generating magnetic gradients superimposed on the static magnetic field, a transmission/reception unit transmitting to a subject spin-exciting RF signal and receiving an MR signal emanated from the subject, a reconstruction unit reconstructing the image based on the MR, and a sequencer for performing a scan sequence of pulses through control of the gradient generation unit and the transmission/reception unit. The scan sequence of pulses is formed for producing the functions of: applying not only a plurality of saturation pulses in time series to a pre-saturated slice positionally different from the imaging slice but also a slice gradient pulse for selecting the pre-saturated slice concurrently with the plurality of saturation pulses, and performing a data acquisition sequence applying to the imaging slice a pulse train for acquiring an MR signal from the imaging slice after application of the plurality of saturation pulses and the slice gradient pulse.

Claims

1. A magnetic resonance system obtaining an MR (magnetic resonance) angiography image of an imaging slice of a subject, comprising:

first means for performing a pre-sequence including a plurality of saturation pulses applied sequentially in time to the same pre-saturated slice of the subject which is positionally different from the imaging slice, said plurality of saturation pulses providing an MT effect,

second means for thereafter performing a data acquisition sequence for acquiring MR signals from the imaging slice after the performance of the pre-sequence; and

means for repeatedly operating said first and second means in succession and for producing an angiography image based on acquired MR signals.

2. The system of claim 1, wherein the pre-sequence include at least one slice gradient pulse applied in parallel with the plurality of saturation pulses, the gradient pulse being used for determining a spatial position of the pre-saturated slice differently from a spatial position of the imaging slice.

3. The system of claim 2, wherein the slice gradient pulse includes a plurality of slice gradient pulses, each applied in parallel with a corresponding one of the plurality of saturation pulses.

4. The system of claim 3, wherein the plurality of saturation pulses are juxtaposed in a time axis direction without a temporal gap between adjacent ones of the saturation pulses.

5. The system of claim 2, wherein the at least one slice gradient pulse consists of a single slice gradient pulse applied in parallel with all the plurality of saturation pulses.

6. The system of claim 2, wherein the pre-sequence includes a plurality of gradient spoiler pulses, a spoiler pulse being applied to the subject after each of the saturation pulses.

7. The system of claim 2, wherein the pre-sequence includes at least one gradient spoiler pulse applied to the subject for a first time after the plurality of saturation pulses have been applied.

8. The system of claim 7, wherein the at least one gradient spoiler pulse includes at least a gradient spoiler pulse applied in a slice direction common with the imaging slice.

9. The system of claim 7, wherein the at least one gradient spoiler pulse includes three gradient spoiler pulses applied in three directions, respectively:

a slice direction common with the imaging slice, and phase-encoding and read-out directions perpendicular to the slice direction.

10. The system of claim 2, wherein each of the plurality of saturation pulses causes a magnetic spin in the pre-saturated slice to turn at a flip angle of less than 100 degrees.

11. The system of claim 2, wherein at least one of the plurality of saturation pulses causes a magnetic spin in the pre-saturated slice to turn at a flip angle that is different from that caused by another of the saturation pulses.

12. The system of claim 11, wherein each of the plurality of saturation pulses causes a magnetic spin in the pre-saturation slice to turn at a flip angle that is different from all others of the saturation pulses.

13. The system of claim 12, wherein the flip angle of each of the plurality of saturation pulses successively lowers gradually as successive saturation pulses are applied.

14. The system of claim 2, wherein the slice gradient defines the pre-saturated slice substantially in parallel with the imaging slice.

15. The system of claim 2, wherein the data acquisition sequence includes a pulse train constituting part of a fast FLAIR (Fluid Attenuated Inversion Recovery) sequence in which an inversion pulse is first applied before a pulse train applied after an inversion time from the application of the inversion pulse.

16. The system of claim 15, wherein the first means is constructed to perform the pre-sequence during the inversion time interval.

17. The system of claim 16, wherein the first and second means repeat the pre-sequence and the data acquisition sequences based on a multislice technique.

18. The system of claim 17, wherein the first and second means repeat both the pre-sequence and the data acquisition sequence in an interleaved mode for obtaining image data for each of a plurality of image slices.

19. A magnetic resonance imaging system for obtaining an MR (magnetic resonance) angiography image of an imaging slice of a subject, said system comprising:

a magnet for generating a static magnetic field into a space in which the subject is placed;

a gradient generation unit for generating via gradient coils slice, phase-encoding, and read-out magnetic gradients superimposed on the static magnetic field;

a transmission/reception unit including an RF coil transmitting to the subject a spin-exciting RF signal and receiving MR signals emanated from the subject;

a reconstruction unit for reconstructing the image based on the MR signals received by the reception unit; and

a sequencer for performing a scan sequence of pulses through control of the gradient generation unit and the transmission/reception unit,

wherein the scan sequence of pulses is formed for sequentially producing;

a pre-sequence including a plurality of saturation pulses applied sequentially in time to the same pre-saturated slice which is positionally different from the imaging slice concurrently with at least a slice gradient pulse for slice-selecting the pre-saturated slice, said plurality of saturation pulses providing an MT effect; and

a data acquisition sequence applied to the imaging slice, after application of the pre-sequence for acquiring MR signals from the imaging slice.

21. The system of claim 19, wherein the at least one slice gradient pulse includes a plurality of slice gradient pulses, each slice gradient pulse being applied in parallel with a corresponding one of the plurality of saturation pulses.

22. The system of claim 19, wherein the at least one slice gradient pulse consists of only a single slice gradient pulse applied in parallel with all the plurality of saturation pulses.

23. The system of claim 19, wherein the pre-sequence includes a plurality of gradient spoiler pulses each of which is applied to the subject after a corresponding one of the plurality of saturation pulses.

24. The system of claim 19, wherein the pre-sequence includes a gradient spoiler pulse applied to the subject for the first time after all the plurality of saturation pulses are applied.

25. The system of claim 19, wherein each of the plurality of saturation pulses causes a magnetic spin in the pre-saturated slice to turn at a flip angle of less than 100 degrees.

26. The system of claim 19, wherein at least one of the plurality of saturation pulses causes a magnetic spin in the pre-saturated slice to turn at a flip angle that is substantially different from remaining saturation pulses.

27. The system of claim 19, wherein the slice gradient defines the pre-saturated slice to be substantially in parallel with the imaging slice.

20. A method of imaging obtaining an MR (magnetic resonance) angiography image of an imaging slice of a subject, said method comprising:

first, performing a pre-sequence including a plurality of saturation pulses applied sequentially in time to the same pre-saturated slice which is selected to be positionally different from the imaging slice said plurality of saturation pulses providing an MT effect;

second, thereafter performing a data acquisition sequence for acquiring MR signals from the imaging slice; and

producing the angiography image using the acquired MR signals.

28. The imaging method of claim 20, wherein the pre-sequence includes at least one slice gradient pulse applied in parallel with the plurality of saturation pulses for determining a spatial position of the pre-saturated slice differently from a spatial position of the imaging slice.

29. The imaging method of claim 28, wherein the pre-sequence includes at least one gradient spoiler pulse applied to the subject for the first time after all the plurality of saturation pulses have been applied.

30. A method for selective MR imaging of flowing nuclei, said method comprising:

(a) performing at least one MR image data acquisition sequence for a selected volume to be imaged; and

(b) just prior to each said at least one MR image data acquisition sequence applying a pre-sequence of plural MR saturation pulses to a selected spatially offset volume that is upstream or downstream from the volume to be imaged with respect to said flowing nuclei, said plurality of saturation pulses providing an MT effect.