Off-resonance correction for pseudo-continuous arterial spin labeling

Patent metadata

Field	Value
Publication number	US-2016296126-A1
Application number	US-201614999198-A
Country	US
Kind code	A1
Filing date	Apr 8, 2016
Priority date	Apr 9, 2015
Publication date	Oct 13, 2016
Grant date	—

Abstract

Systems and methods are provided to incorporate an off-resonance correction into the pulse labeling train of PCASL/VEPCASL. In one or more aspects, the systems and methods are based on a method for generating an encoding scheme for any number and arrangement of blood vessels. The off-resonance correction can be incorporated into the generation of optimized encodings to acquire arterial spin labeling (ASL) data, such as PCASL and VEPCASL data.

First claim

What is claimed:

1 . A method for off-resonance correction prior to the acquisition of arterial spin labeling (ASL) data, comprising:
A. Providing a medical imaging device; B. Positioning a subject in association with the medical imaging device; C. Acquiring information about the location of blood vessels of interest in the subject and phase offsets at the location of the blood vessels; D. Determining the encodings to apply to a labeling plane to encode the blood vessels of interest whilst accounting for the phase offset at each blood vessel location for, which information is acquired; and E. Acquiring arterial spin labeling (ASL) data, which includes the blood vessels of interest in the subject, using the determined encodings and using the medical imaging device.

2 . The method of claim 1 , further including the steps of:
determining the encodings by taking a Fourier transform of an idealized “image” of the blood vessels, including phase offsets at the location of the blood vessels; up-weighting the resulting Fourier transform of the image to up-weight lower spatial frequencies in a Fourier space (or transform domain); and finding a maximum intensity point in the up-weighted Fourier space.

3 . The method of claim 1 , wherein the arterial spin labeling (ASL) data acquired includes PCASL or VEPCASL data or both.

4 . The method of claim 1 , wherein the step of acquiring information about the location of blood vessels of interest and phase offsets at the location of the blood vessels involves a field map of the desired labeling plane, includes input of the blood vessel locations, includes creating an encoding matrix, or two or more thereof.

5 . The method of claim 1 , wherein the step of acquiring information about the location of blood vessels of interest and phase offsets at the location of the blood vessels includes creating an encoding matrix and the blood vessels are placed in the encoding matrix at positions corresponding to their physical Cartesian coordinates within a labeling plane.

6 . The method of claim 2 , further including the step of zero-padding the “image”.

7 . The method of claim 2 , wherein the step of up-weighting the resulting Fourier transform includes masking spatial frequencies within the Fourier space, or wherein before the maximum intensity point is found, the absolute value of the Fourier transform is taken and normalized to its maximum value and then the up-weighting is done, or both.

8 . The method of claim 1 , wherein off-resonance corrected encodings are calculated for more than three vessels.

9 . The method of claim 1 , wherein the step of acquiring information about the location of blood vessels of interest and phase offsets at the location of the blood vessels includes creating an encoding matrix and the step is repeated for each cycle of the encoding scheme.

10 . The method of claim 1 , wherein the data includes perfusion data or static/dynamic angiography data.

11 . A system for off-resonance for off-resonance correction prior to the acquisition of arterial spin labeling data comprising: at least one medical imaging device configured for positioning a subject in association with the medical imaging device; at least one computing device in data communication with the medical imaging device; and an application executable in the at least one computing device, the application comprising logic that:
A. Acquires information about the location of blood vessels of interest in the subject and phase offsets at the location of the blood vessels; B. Determines the encodings to apply to a labeling plane to encode the blood vessels of interest whilst accounting for the phase offset at each blood vessel location for which information is acquired; and C. Acquires arterial spin labeling data, which includes the blood vessels of interest in the subject, using the determined encodings and using the medical imaging device.

12 . The system of claim 11 , wherein the application further comprises logic that:
determines the encodings by taking a Fourier transform of an idealized “image” of the blood vessels, including phase offsets at the location of the blood vessels; up-weights the resulting Fourier transform of the image to up-weight lower spatial frequencies in a Fourier space (or transform domain); and finds a maximum intensity point in the up-weighted Fourier space.

13 . The system of claim 11 , wherein the logic that acquires information about the location of blood vessels of interest and phase offsets at the location of the blood vessels involves a field map of the desired labeling plane, includes input of the blood vessel locations, includes creating an encoding matrix, or two or more thereof.

14 . The system of claim 11 , wherein the logic that acquires information about the location of blood vessels of interest and phase offsets at the location of the blood vessels creates an encoding matrix and places the blood vessels in the encoding matrix at positions corresponding to their physical Cartesian coordinates within a labeling plane.

15 . The system of claim 12 , wherein the logic that up-weights the resulting Fourier transform masks spatial frequencies within the Fourier space, or wherein before the maximum intensity point is found, takes the absolute value of the Fourier transform and normalizes it to its maximum value, or both.

16 . A non-transitory computer-readable medium employing a program executable in at least one computing device, comprising code that.
A. Acquires information about the location of blood vessels of interest in a subject and phase offsets at the location of the blood vessels of interest from a medical imaging device configured for positioning the subject in association with the medical imaging device; B. Determines the encodings to apply to a labeling plane to encode the blood vessels of interest whilst accounting for the phase offset at each vessel location for which information is acquired; and C. Acquires arterial spin labeling data, which includes the blood vessels of interest in the subject, using the determined encodings and using the medical imaging device.

17 . The non-transitory computer-readable medium of claim 16 , wherein the code:
determines the encodings by taking a Fourier transform of an idealized “image” of the blood vessels, including phase offsets at the location of the blood vessels; up-weights the resulting Fourier transform of the image to up-weight lower spatial frequencies in a Fourier space (or transform domain); and finds a maximum intensity point in the up-weighted Fourier space.

18 . The non-transitory computer-readable medium of claim 16 , wherein the code that acquires information about the location of blood vessels of interest and phase offsets at the location of the blood vessels involves a field map of the desired labeling plane, includes input of the blood vessel locations, includes creating an encoding matrix, or two or more thereof.

19 . The non-transitory computer-readable medium of claim 16 , wherein the code creates an encoding matrix and places the blood vessels in the encoding matrix at positions corresponding to their physical Cartesian coordinates within a labeling plane.

20 . The non-transitory computer-readable medium of claim 17 , wherein the code masks spatial frequencies within the Fourier space, or wherein before the maximum intensity point is found, takes the absolute value of the Fourier transform and normalizes it to its maximum value, or both.

Assignees

• Isis Innovation

Inventors

• Berry Eleanor
• Okell Thomas
• Jezzard Peter

Classifications

• A61B5/489

  Blood vessels · CPC title

• A61B5/0263 Primary

  using NMR · CPC title

• G01R33/56366

  Perfusion imaging · CPC title

• G16H30/40

  for processing medical images, e.g. editing · CPC title

• G01R33/5635

  Angiography, e.g. contrast-enhanced angiography [CE-MRA] or time-of-flight angiography [TOF-MRA] · CPC title