Virtual frequency encoding: achieving symmetry in k-space.
Chemical shift artifacts and other off-resonance spatial shifts in 2DFT MRI arise from the linear time dependence in the k-space data in the readout direction. Introduction of a view-dependent time shift of the readout window adds a time dependence to the phase-encoding direction and results in a virtual frequency-encoding direction that is a linear combination of the phase-encode and readout axes. By this method, the readout and phase-encode directions can be made identical in their sensitivity to off-resonance effects and can be arbitrarily swapped with no change in chemical shift or inhomogeneity effects, improving previously reported methods that swap these axes for signal averaging or reduction of motion artifacts.
Hinks
R S
RS
Department of Medical Biophysics, University of Toronto, Sunnybrook Health Science Center, Ontario, Canada.
Derbyshire
J A
JA
LeRoux
P L
PL
D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology; D003196:Computer Graphics; D005583:Fourier Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D014584:User-Computer Interface