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Magn Reson Med. 2001 Sep;46(3):515-22.

Spiral-in/out BOLD fMRI for increased SNR and reduced susceptibility artifacts.

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Department of Radiology, Center for Advanced MR Technology, Stanford University School of Medicine, Stanford, California 94305-5488, USA.


BOLD fMRI is hampered by dropout of signal in the orbitofrontal and parietal brain regions due to magnetic field gradients near air-tissue interfaces. This work reports the use of spiral-in trajectories that begin at the edge of k-space and end at the origin, and spiral in/out trajectories in which a spiral-in readout is followed by a conventional spiral-out trajectory. The spiral-in trajectory reduces the dropout and increases the BOLD contrast. The spiral-in and spiral-out images can be combined in several ways to simultaneously achieve increased signal-to-noise ratio (SNR) and reduced dropout artifacts. Activation experiments employing an olfaction task demonstrate significantly increased activation volumes due to reduced dropout, and overall increased SNR in all regions.

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