Correction of artifacts caused by Maxwell terms in MR echo-planar images
AssigneeGeneral Electric Company
InventorsYiping Du, Xiaohong Zhou, Matthew A. Bernstein, Joseph K. Maier
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Abstract
A method for correcting Maxwell field induced distortion, ghosting, and blurring artifacts in non-axially oriented EPI images is disclosed. In one embodiment phase corrections are calculated and used to offset Maxwell term errors during the image reconstruction process, and in another embodiment corrections are made after the image is reconstructed.
Claims10
A method for correcting Maxwell term errors produced by an NMR system during the acquisition of an NMR image data array using an echo-planar pulse sequence, the steps comprising:
- a) acquiring a k-space data set using the echo-planar pulse sequence;
- b) calculating a Maxwell phase error for signals emanating from locations at a distance (.vertline.z.vertline.) from an NMR system isocenter;
- c) applying the Maxwell phase error as a phase correction to the k-space data set;
- d) reconstructing an image data set from the phase corrected k-space data set;
- e) saving the data in the image data set corresponding to locations at the distance (.vertline.z.vertline.) in the NMR image data array;
- and
- f) repeating steps b) through e) at different distances (.vertline.z.vertline.) until the entire image data array is saved.
A method for correcting Maxwell term errors produced by an NMR system during the acquisition of an NMR image data array using an echo-planar pulse sequence, the steps comprising:
- a) acquiring a k-space data set using the echo-planar pulse sequence;
- b) reconstructing a distorted image data set from the k-space data set;
- c) calculating corrections for distortion along a phase encoding axis due to Maxwell terms using parameters of the echo-planar pulse sequence;
- d) correcting the distorted image data set using the calculated corrections by shifting the location of pixels in the image data set along the phase encoding axis;
- and
- e) calculating the intensity of pixels in the NMR image data array using values in the distorted image data set from corresponding locations therein.
Dependencies are inferred from the claim text.