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Velocity encoding using ghost artifacts
Author(s) -
Madore Bruno,
Henkelman R. Mark
Publication year - 1996
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910350616
Subject(s) - ghosting , encoding (memory) , encode , pixel , computer science , signal (programming language) , computer vision , phase (matter) , magnitude (astronomy) , noise (video) , artificial intelligence , motion (physics) , algorithm , image (mathematics) , physics , biochemistry , chemistry , quantum mechanics , astronomy , gene , programming language
Motion artifacts represent a significant limitation of MRI, and an ideal solution to that problem has proved elusive. However, in this paper, motion artifacts are not considered as the usual enemy and are not suppressed; on the contrary, they are deliberately created to encode flow information. In MRI, velocity is encoded readily into the phase of a pixel. However, if the pixel contains overlapping signals, the phase of one of these signals now has consequences on both the magnitude and phase of the resulting pixel. It is shown here that an overlap of information may be used to encode velocity both in the phase and in the magnitude of an image, making the velocity‐encoding process faster. The overlap of information is obtained by superposing ghosting artifacts of different orders and information is retrieved about complex intensity and velocity in two dimensions using the equivalent of two images instead of the usual three images. The price to pay to do so is some loss of simplicity in the equations involved, an increase in reconstruction computing time requirements, and a factor of 4 decrease in signal‐to‐noise ratio in the velocity measurements.