Journal ArticleDOI
Centric ordering is superior to gradient moment nulling for motion artifact reduction in EPI
TLDR
Two methods of artifact reduction for motion in the phase‐encode direction are evaluated and computer simulations and experiments in flow phantoms and rabbits in vivo show that uncompensated centric ordering produces the highest image quality.Abstract:
Echo-planar imaging (EPI) is sensitive to motion despite its rapid data acquisition rate. Compared with traditional imaging techniques, it is more sensitive to motion or flow in the phase-encode direction, which can cause image artifacts such as ghosting, misregistration, and loss of spatial resolution. Consequently, EPI of dynamic structures (eg, the cardiovascular system) could benefit from methods that eliminate these artifacts. In this paper, two methods of artifact reduction for motion in the phase-encode direction are evaluated. First, the k-space trajectory is evaluated by comparing centric with top-down ordered sequences. Next, velocity gradient moment nulling (GMN) of the phase-encode direction is evaluated for each trajectory. Computer simulations and experiments in flow phantoms and rabbits in vivo show that uncompensated centric ordering produces the highest image quality. This is probably due to a shorter readout duration, which reduces T2* relaxation losses and off-resonance effects, and to the linear geometry of phantoms and vessels, which can obscure centric blurring artifacts.read more
Citations
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Regulation of the Neural Circuitry of Emotion by Compassion Meditation: Effects of Meditative Expertise
TL;DR: Data indicate that the mental expertise to cultivate positive emotion alters the activation of circuitries previously linked to empathy and theory of mind in response to emotional stimuli.
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Magnetic Field Shift due to Mechanical Vibration in Functional Magnetic Resonance Imaging
TL;DR: The frequency drift correction method efficiently corrects spurious motion due to magnetic field drifts during fMRI and is compared to the standard image realignment method.
Journal ArticleDOI
Free-breathing 3D coronary MRA: the impact of "isotropic" image resolution.
René M. Botnar,René M. Botnar,Matthias Stuber,Matthias Stuber,Kraig V. Kissinger,Warren J. Manning +5 more
TL;DR: The good delineation of the coronary arteries in all views suggests that isotropic 3D coronary MRA might be a preferred technique for the assessment of coronary disease, although at the expense of prolonged scan times.
Journal ArticleDOI
Center-out EPI (COEPI): A fast single-shot imaging technique with a short TE.
TL;DR: To develop a center‐out echo planar imaging (COEPI) acquisition technique to increase SNR through minimizing the TE.
Journal ArticleDOI
The importance of k-space trajectory on off-resonance artifact in segmented echo-planar imaging
TL;DR: Segmented interleaved echo planar imaging is a highly efficient data acquisition technique; however, EPI is sensitive to artifacts from off-resonance spins, and inferior image quality was observed for the center-out trajectory in a single volunteer.
References
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Peter Jezzard,Robert S. Balaban +1 more
TL;DR: A method is described for the correction of geometric distortions occurring in echo planar images, caused in large part by static magnetic field inho‐mogeneities, leading to pixel shifts, particularly in the phase encode direction.
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Motion artifact suppression technique (MAST) for MR imaging
Pradip M. Pattany,Jeffrey J. Phillips,Lee C. Chiu,James D. Lipcamon,Jeffrey L. Duerk,James M. McNally,Surya N. Mohapatra +6 more
TL;DR: A technique has been developed that significantly improves the image resolution and reduces motion artifacts in conventional two- and three-dimensional Fourier transform magnetic resonance imaging sequences and has allowed diagnostic quality T1- and T2-weighted images to be obtained with one acquisition per view, thus reducing the total scan time.
Journal ArticleDOI
A Velocity k-Space Analysis of Flow Effects in Echo-Planar and Spiral Imaging
TL;DR: To compare the effects of trajectory differences, simulated images were generated by computing the k‐space values for an in‐plane vessel with parabolic flow, and whereas the resulting echo‐planar images demonstrate distortions and ghosting that depend on the vessel orientation, the spiral images exhibit minimal artifacts.
Journal ArticleDOI
On the nature and reduction of the displacement artifact in flow images
TL;DR: Of the four methods studied, the projection‐reconstruction sequence proved to be the most effective, completely eliminating the displacement artifact.
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