Premium
Unaliasing by Fourier‐encoding the overlaps using the temporal dimension (UNFOLD), applied to cardiac imaging and fMRI
Author(s) -
Madore Bruno,
Glover Gary H.,
Pelc Norbert J.
Publication year - 1999
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/(sici)1522-2594(199911)42:5<813::aid-mrm1>3.0.co;2-s
Subject(s) - temporal resolution , computer science , contrast (vision) , dynamic contrast enhanced mri , dimension (graph theory) , real time mri , signal (programming language) , k space , artificial intelligence , encoding (memory) , computer vision , frame rate , magnetic resonance imaging , nuclear magnetic resonance , fourier transform , physics , mathematics , optics , medicine , quantum mechanics , pure mathematics , radiology , programming language
In several applications, MRI is used to monitor the time behavior of the signal in an organ of interest; e.g., signal evolution because of physiological motion, activation, or contrast‐agent accumulation. Dynamic applications involve acquiring data in a k – t space, which contains both temporal and spatial information. It is shown here that in some dynamic applications, the t axis of k – t space is not densely filled with information. A method is introduced that can transfer information from the k axes to the t axis, allowing a denser, smaller k – t space to be acquired, and leading to significant reductions in the acquisition time of the temporal frames. Results are presented for cardiac‐triggered imaging and functional MRI (fMRI), and are compared with data obtained in a conventional way. The temporal resolution was increased by nearly a factor of two in the cardiac‐triggered study, and by as much as a factor of eight in the fMRI study. This increase allowed the acquisition of fMRI activation maps, even when the acquisition time for a single full time frame was actually longer than the paradigm cycle period itself. The new method can be used to significantly reduce the acquisition time of the individual temporal frames in certain dynamic studies. This can be used, for example, to increase the temporal or spatial resolution, increase the spatial coverage, decrease the total imaging time, or alter sequence parameters e.g., repetition time (TR) and echo time (TE) and thereby alter contrast. Magn Reson Med 42:813–828, 1999. © 1999 Wiley‐Liss, Inc.