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Characterization, prediction, and correction of geometric distortion in 3 T MR images
Author(s) -
Baldwin Lesley N.,
Wachowicz Keith,
Thomas Steven D.,
Rivest Ryan,
Fallone B. Gino
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2402331
Subject(s) - imaging phantom , distortion (music) , scanner , artificial intelligence , medical imaging , computer vision , computer science , physics , optics , amplifier , computer network , bandwidth (computing)
The work presented herein describes our methods and results for predicting, measuring and correcting geometric distortions in a 3 T clinical magnetic resonance (MR) scanner for the purpose of image guidance in radiation treatment planning. Geometric inaccuracies due to both inhomogeneities in the background field and nonlinearities in the applied gradients were easily visualized on the MR images of a regularly structured three‐dimensional (3D) grid phantom. From a computed tomography scan, the locations of just under 10 000 control points within the phantom were accurately determined in three dimensions using a MATLAB ‐based computer program. MR distortion was then determined by measuring the corresponding locations of the control points when the phantom was imaged using the MR scanner. Using a reversed gradient method, distortions due to gradient nonlinearities were separated from distortions due to inhomogeneities in the backgroundB 0field. Because the various sources of machine‐related distortions can be individually characterized, distortions present in other imaging sequences (for which 3D distortion cannot accurately be measured using phantom methods) can be predicted negating the need for individual distortion calculation for a variety of other imaging sequences. Distortions were found to be primarily caused by gradient nonlinearities and maximum image distortions were reported to be less than those previously found by other researchers at 1.5 T . Finally, the image slices were corrected for distortion in order to provide geometrically accurate phantom images.