Image Domain Segmented Echo Planar Magnetic Resonance Imaging Using a 2D Excitation Radiofrequency Pulse

Patent metadata

Field	Value
Publication number	US-2016307301-A1
Application number	US-201615097530-A
Country	US
Kind code	A1
Filing date	Apr 13, 2016
Priority date	Apr 14, 2015
Publication date	Oct 20, 2016
Grant date	—

Abstract

Representative methods and systems are disclosed for reducing image distortion or increasing spatial resolution in echo planar magnetic resonance imaging. In representative embodiments, a targeted field of view (FOV) image is divided into segments, with each segment having a predetermined overlap region with an adjacent segment, such as in a phase-encoding direction. Image data is acquired for each segment, sequentially or simultaneously, using a reduced phase-encoding FOV with a 2D radiofrequency (RF) excitation pulse, and rotated and scaled magnetic field gradients. The 2D RF excitation pulse may also be modulated, such as onto a plurality of different carrier frequencies, for simultaneous acquisition of multiple segments in the same imaging plane. Using the spatial response of the 2D RF excitation pulse, the acquired image data for each segment of the plurality of segments is combined to generate a combined magnetic resonance image having the targeted field of view.

First claim

It is claimed:

1 . A method for reducing image distortion or increasing spatial resolution in magnetic resonance imaging (MRI), comprising:
using an MRI system, dividing a targeted field of view image into a plurality of segments, each segment of the plurality of segments having a predetermined overlap region with an adjacent segment; using the MRI system, acquiring image data for each segment of the plurality of segments using a reduced field of view with a 2D radiofrequency (RF) excitation pulse; using the MRI system, determining a spatial response of the 2D radiofrequency (RF) excitation pulse; and using the spatial response of the 2D radiofrequency (RF) excitation pulse in the phase-encoding direction, and using the MRI system, combining the acquired image data for each segment of the plurality of segments to generate a combined magnetic resonance image having the targeted field of view.

2 . The method of claim 1 , further comprising:
using the MRI system, selecting at least one segment of the plurality of segments for imaging by applying a pulse sequence of at least two magnetic field gradients corresponding to a rotated and scaled excitation k-space coverage.

3 . The method of claim 2 , wherein a first magnetic field gradient (G″y) is substantially in the phase-encoding direction and a second magnetic field gradient (G″z) is substantially in a slice-selection direction.

4 . The method of claim 3 , wherein the first magnetic field gradient (G″y) and the second magnetic field gradient (G″z) have been rotated and scaled to correspond to the rotated and scaled excitation k-space coverage, and have been determined as G″y=a·G′y and G″z=b·G′z, where

[

G
′


y

G
′


z

]

=

[

cos



θ

sin



θ

-
sin




θ

cos



θ

]



[

Gy

Gz

]

,

where θ is a predetermined angle of rotation, a and b are predetermined scaling factors, and Gy and Gz are orthogonal magnetic field gradients defining an on-axis square excitation k-space.

5 . The method of claim 1 , wherein using the spatial response of the 2D radiofrequency (RF) excitation pulse further comprises:
using the MRI system, weighting corresponding image intensities within the predetermined overlap region of a segment with an adjacent segment to provide a normalized image intensity.

6 . The method of claim 1 , wherein the step of combining the acquired image data for each segment of the plurality of segments to generate a combined magnetic resonance image having the targeted field of view further comprises:
using the MRI system, combining individual segments using:

S


(
y
)

=

∑

i
=
1

n





w
i



(
y
)



S
i



(
y
)

/

∑

i
=
1

n





w
i
2



(
y
)

where S i (y) is segmented image data, n is the total number of segments, w i (y) is the 2D RF pulse spatial response along the phase-encoding direction, and i represents the ith segment.

7 . The method of claim 1 , where

Assignees

• Univ Illinois

Inventors

• Zhou Xiaohong Joe
• Sui Yi

Classifications

• G01R33/5616

  using gradient refocusing, e.g. EPI · CPC title

• G01R33/5608

  Data processing and visualization specially adapted for MR, e.g. for feature analysis and pattern recognition on the basis of measured MR data, segmentation of measured MR data, edge contour detection on the basis of measured MR data, for enhancing measured MR data in terms of signal-to-noise ratio by means of noise filtering or apodization, for enhancing measured MR data in terms of resolution by means for deblurring, windowing, zero filling, or generation of gray-scaled images, colour-coded images or images displaying vectors instead of pixels (image data processing or generation, in general G06T) · CPC title

• G01R33/5602

  by filtering or weighting based on different relaxation times within the sample, e.g. T1 weighting using an inversion pulse · CPC title

• G01R33/4836 Primary

  using an RF pulse being spatially selective in more than one spatial dimension, e.g. a 2D pencil-beam excitation pulse · CPC title

• G06T5/001 Primary

  Physics · mapped topic