Magnetic resonance imaging using steering-propeller

Patent metadata

Field	Value
Publication number	US-9645211-B2
Application number	US-201113695159-A
Country	US
Kind code	B2
Filing date	Apr 29, 2011
Priority date	Apr 29, 2010
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

A GRASE-type PROPELLER sequence called Steer-PROP is disclosed. This sequence exploits a serious of steer blips together with rewinding gradient pulse to traverse k-space. Steer-PROP improves the scan time by a factor of 3 or higher compared to FSE-PROPELLER, provides improved robustness to off-resonance effects compared to EPI-PROPELLER, and addresses a long-standing phase correction problem inherent to GRASE based sequences. Steer-PROP also enables intra-blade, inter-blade, and inter-shot phase errors to be separately determined and independently corrected.

First claim

What is claimed:

1. In a magnetic resonance imaging (MRI) system, a computer-implemented method comprising:
applying to an object in the MRI system a first radio frequency (RF) pulse and, after a first fast spin echo (FSE) inter-echo time interval, applying to the object a second RF pulse;
applying to the object during the first FSE inter-echo time interval between the first and second RF pulses a first magnetic field gradient (G x ) pulse train along a first direction, the first G x pulse train comprising an integer number M adjacent G x pulses, each consecutive pair of G x pulses of the first G x pulse train being separated by a G x steering pulse, and the last G x pulse of the first G x pulse train being followed by a first G x rewinding pulse;
applying to the object simultaneously with the first G x pulse train a first magnetic field gradient (G y ) pulse train along a second direction, the first G y pulse train comprising M adjacent G y pulses, each G y pulse of the first G y pulse train forming a respective first-train G x -G y pulse pair with a simultaneous corresponding G x pulse of the first G x pulse train, each consecutive pair of G y pulses of the first G y pulse train being separated by a G y steering pulse that forms a respective first-train G x -G y steering-pulse pair with a simultaneous corresponding G x steering pulse of the first G x pulse train, and the last G y pulse of the first G y pulse train being followed by a first G y rewinding pulse that forms a first simultaneous G x -G y rewinding-pulse pair with the first G x rewinding pulse of the first G x pulse train;
acquiring k-space data along a first set of M mutually oblique lines intersecting in a central region of k-space, each of the M mutually oblique lines of the first set corresponding to a different respective first-train G x -G y pulse pair,
wherein applying each first-train G x -G y steering-pulse pair repositions a starting point for k-space traversal from one of the M mutually oblique lines of the first set to another,
and wherein applying the first simultaneous G x -G y rewinding-pulse pair repositions a starting point for k-space traversal to a reference location of k-space.

2. The method of claim 1 , further comprising:
applying to the object a third RF pulse at a second FSE inter-echo time interval following the second RF pulse;
applying to the object during the second FSE inter-echo time interval between the second and third RF pulses a second G x pulse train comprising M adjacent G x pulses, each consecutive pair of G x pulses of the second G x pulse train being separated by a G x steering pulse, and the last G x pulse of the second G x pulse train being followed by a second G x rewinding pulse;
applying to the object simultaneously with the second G x pulse train a second G y pulse train comprising M adjacent G y pulses, each G y pulse of the second G y pulse train forming a respective second-train G x -G y pulse pair with a simultaneous corresponding G x pulse of the second G x pulse train, each consecutive pair of G y pulses of the second G y pulse train being separated by a G y steering pulse that forms a respective second-train G x -G y steering-pulse pair with a simultaneous corresponding G x steering pulse of the second G x pulse train, and the last G y pulse of the second G y pulse train being followed by a second G y rewinding pulse that forms a second simultaneous G x -G y rewinding-pulse pair with second G x rewinding pulse of the second G x pulse train;
acquiring k-space data along a second set of M mutually oblique lines intersecting in a central region of k-space, each of the M mutually oblique lines of the second set corresponding to a different respective second-train G x -G y pulse pair,
wherein each of the M mutually oblique lines of the second set is parallel to a corresponding one of the M mutually oblique lines of the first set,
wherein applying each second-train G x -G y steering-pulse pair repositions a starting point for k-space traversal from one of the M mutually oblique lines of the second set to another,
and wherein applying the second simultaneous G x -G y rewinding-pulse pair repositions a starting point for k-space traversal to the reference location of k-space.

3. The method of claim 1 , wherein M is in the range 3-7.

4. The method of claim 1 , wherein applying the first simultaneous G x -G y rewinding-pulse pair causes a Carr-Purcell-Meiboom-Gill (CPMG) condition to be satisfied.

5. The method of claim 1 , further comprising applying to the object an initial pair of G x and G y pulses prior to the first G x pulse train in order to set the reference location of k-space.

6. The method of claim 1 , wherein the reference location of k-space is at an origin of k-space, the origin of k-space being the center of k-space.

7. The method of claim 1 , wherein the reference location of k-space is substantially close to an origin of k-space, the origin of k-space being the center of k-space.

8. The method of claim 1 , further comprising applying to the object an initial excitation RF pulse prior to the first RF pulse,
wherein the first and second RF pulses are refocusing RF pulses.

9. In a magnetic resonance imaging (MM) system, a computer-implemented method comprising:
applying to an object in the MRI system a first gradient and spin echo propeller (GRASP) pulse sequence comprising a first radio frequency (RF) sequence of periodic RF pulses, an accompanying first magnetic field gradient (G x ) sequence of periodic G x pulse trains along a first direction, and an accompanying corresponding first magnetic field gradient (G y ) sequence of periodic G y pulse trains along a second direction, the first RF, G x and G y sequences being configured to cause traversal in k-space along a first plurality of parallel line groupings, each parallel line grouping of the first plurality forming a respective first GRASP blade, and each respective first GRASP blade being oblique to the other respective first GRASP blades and intersecting the other respective first GRASP blades in a central region of k-space;
acquiring first GRASP k-space data from along the parallel line groupings of the first plurality during a first repetition time interval corresponding to a duration of the first GRASP pulse sequence;
applying to the object a second GRASP pulse sequence comprising a second radio RF sequence of periodic RF pulses, an accompanying second G x sequence of periodic G x pulse trains, and an accompanying corresponding second G y sequence of periodic G y pulse trains, the second RF, G x and G y sequences being configured to cause traversal in k-space along a second plurality of parallel line groupings, each parallel line grouping of the second plurality forming a respective second GRASP blade, and each respective second GRASP blade being oblique to the other respective second GRASP blades and intersecting the other respective second GRASP blades in a central region of k-space;
acquiring second GRASP k-space data from along the parallel line groupings of the second plurality during a second repetition time interval corresponding to a duration of the second GRASP pulse sequence; and
separately determining and independently correcting:
(i) phase errors in the acquired first GRASP k-space data between parallel lines of each respective first GRASP blade,
(ii) phase errors in the acquired first GRASP k-space data between the respective first GRASP blades,
(iii) phase errors in the acquired second GRASP k-space data between parallel lines of each respective second GRASP blade,
(iv) phase errors in the acquired second GRASP k-space data between the respective second GRASP

Assignees

• Zhou Xiaohong Joe
• Univ Illinois

Inventors

• Zhou Xiaohong Joe

Classifications

• G01R33/4824 Primary

  using a non-Cartesian trajectory · CPC title

• G01R33/5617

  using RF refocusing, e.g. RARE · CPC title

• G01R33/44 Primary

  using nuclear magnetic resonance [NMR] (G01R33/24, G01R33/62 take precedence) · CPC title

• G01R33/28

  Details of apparatus provided for in groups G01R33/44 - G01R33/64 · CPC title