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Self‐navigated spiral fMRI: Interleaved versus single‐shot
Author(s) -
Glover Gary H.,
Lai Song
Publication year - 1998
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.1910390305
Subject(s) - shim (computing) , functional magnetic resonance imaging , blood oxygen level dependent , spiral (railway) , magnetic resonance imaging , single shot , temporal resolution , nuclear magnetic resonance , computer science , physics , optics , medicine , radiology , mathematics , mathematical analysis , erectile dysfunction
This study compares the measured activation volumes in motor cortex as well as the fluctuation noise and off‐resonance characteristics for 1‐, 2‐, and 4‐shot spiral gradient‐recalled echo blood oxygen level dependent contrast functional magnetic resonance imaging (fMRI) acquisitions, under conditions of constant resolution and scan time and with two readout durations. Reconstructions were made with and without self‐navigator correction. It was found that the navigator correction provided a 50% reduction in image fluctuation noise with 4‐shot acquisitions, and that multishot acquisitions perform as well as single‐shot techniques when self‐navigation is employed. An analysis of blurring showed that off‐resonance Af causes blurring when Δ f > 1/(2* T ad ), where T ad is the readout duration. Off‐resonance effects were readily corrected during reconstruction with retrospective linear shim, even with the longer readout duration needed for single‐shot methods. With navigator and shim correction, single‐shot and multishot spiral methods are highly effective for fMRI acquisitions.