Pseudo-continuous asymmetric signal targeting alternating radio frequency (pASTAR) for magnetic resonance angiography

1. A magnetic resonance imaging (MRI) system for effecting MR imaging based upon arterial spin labeling (ASL), said MRI system comprising:

an MRI gantry including a static magnetic field coil, gradient magnetic field coils, at least one radio frequency (RF) coil configured to couple with an object located in an imaging volume;

an MRI sequence controller configured to perform an RF pulse sequence comprising (1) applying a tagging pulse train including a plurality of saturation pulses to a tagging area followed by applying a first imaging pulse train to an imaging area, and (2) applying a control pulse train to a control area followed by applying a second imaging pulse train to the imaging area, wherein the tagging area, the control area, and the imaging area are located at respectively different positions in relation to the object;

and

at least one digital data processor configured to:

receive first digital data and second digital data corresponding respectively to NMR signals responsive to the first imaging pulse train and to NMR signals responsive to the second imaging pulse train;

generate at least one tag image from the received first digital data and at least one control image from the received second digital data;

form a diagnostic MR image of the object based upon the at least one tag image and the at least one control image; and

output the diagnostic MR image to a display, or data storage in a non-transient digital data storage medium, or an outbound data transmission port.

2. The MRI system of claim 1 , wherein the MRI sequence controller is further configured to include the same number of saturation pulses in the tagging pulse train and the control pulse train.

3. The MRI system of claim 1 , wherein the MRI sequence controller is further configured to set a flip angle between 90 to 180 degrees for the saturation pulses.

4. The MRI system of claim 3 , wherein the flip angle of saturation pulses of the tagging pulse train and the flip angle of saturation pulses of the control pulse train are identical.

5. The MRI system of claim 1 , wherein the MRI sequence controller is further configured to set respective tagging pulses of the tagging pulse train to include one or more amplitude-changing gradient spoiler pulses.

6. The MRI system of claim 1 , wherein a width of the tagging area is set so that the arterial transit time (ATT) from the tagging area to the imaging area is substantially uniform.

7. The MRI system of claim 6 , wherein the tagging area is a thin slice configured to be between 1-5 centimeters in thickness.

8. The MRI system of claim 1 , wherein the MRI sequence controller is further configured to apply the tagging pulse train over a duration of 1 to 3 seconds.

9. The MRI system of claim 8 , wherein the MRI sequence controller is further configured to set intervals between consecutive tagging pulses based upon blood flow speed to be imaged in a specific part of the object being imaged.

10. The MRI system of claim 1 , wherein the MRI sequence controller is further configured to apply the tagging pulse train over a length of time exceeding a cardiac cycle.

11. The MRI system of claim 1 , wherein the MRI sequence controller is further configured to set the tagging and control areas at an oblique angle in relation to the object.

12. The MRI system of claim 1 , wherein said applying the tagging pulse train followed by the first imaging pulse train, and said applying the control pulse train followed by the second imaging pulse train is performed alternately.

13. The MRI system of claim 1 , wherein the MRI sequence controller is further configured to apply two-dimensional (20) sequences corresponding to three-dimensional (30) sequences as independent preparation scans with varying tagging pulse delays to determine a desired tagging pulse delay, and to set an interval between consecutive tagging pulses in the tagging pulse train in accordance with the determined desired pulse delay.

14. The MRI system of claim 1 , wherein the MRI sequence controller is further configured to apply 20 sequences corresponding to 30 sequences as independent preparation scans with varying tagging slice thicknesses to determine a desired tagging slice thickness, and to set the tagging area to have a width corresponding to the determined desired tagging slice thickness.

15. A magnetic resonance imaging (MRI) method for effecting MR imaging based upon arterial spin labeling (ASL), said MRI method comprising:

placing an object into an MRI gantry including a static magnetic field coil, gradient magnetic field coils, at least one radio frequency (RF) coil configured to couple with an imaging volume;

using an MRI sequence controller to perform an RF pulse sequence comprising (1) applying a tagging pulse train including a plurality of saturation pulses to a tagging area followed by applying a first imaging pulse train to an imaging area, and (2) applying a control pulse train to a control area followed by applying a second imaging pulse train to the imaging area,

wherein the tagging area, the control area, and the imaging area are located at respectively different positions in relation to the object;

receiving first digital data and second digital data corresponding respectively to echo data responsive to the first imaging pulse train and to echo data responsive to the second imaging pulse train;

generating at least one tag image from the received first digital data and at least one control image from the received second digital data;

forming a diagnostic MR image of the object based upon the at least one tag image and the at least one control image; and

outputting the diagnostic MR image to a display, or data storage in a non-transient digital data storage medium, or an outbound data transmission port.

16. A non-transitory computer readable storage medium, having executable computer program instructions recorded thereon, which when executed by at least one processor of a magnetic resonance imaging (MRI) system having an MRI gantry including a static magnetic field coil, gradient magnetic field coils, at least one radio frequency (RF) coil, causes the at least one processor to generate a final MRI image an object, by performing operations comprising:

configuring a sequence controller to perform an RF pulse sequence comprising (1) applying a tagging pulse train including a plurality of saturation pulses to a tagging area followed by applying a first imaging pulse train to an imaging area, and (2) applying a control pulse train to a control area followed by applying a second imaging pulse train to the imaging area,

wherein the tagging area, the control area, and the imaging area are located at respectively different positions in relation to the object;

receiving first digital data and second digital data corresponding respectively to echo data responsive to the first imaging pulse train and to echo data responsive to the second imaging pulse train;

generating at least one tag image from the received first digital data and at least one control image from the received second digital data;

forming a diagnostic MR image of the object based upon the at least one tag image and the at least one control image; and

outputting the diagnostic MR image to a display, or data storage in a non-transient digital data storage medium, or an outbound data transmission port.