System Stability of a 3T-MRI During Continuous EPI Scan

Shimada, Yasuhiro; Kochiyama, Takanori; Fujimoto, Ichiro; Shimizu, Masaki; Murase, Kenya

doi:10.6009/jjrt.64.1504

Cited by 4 publications

(2 citation statements)

References 26 publications

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“…We purposely used the average-slice signal measuring method (ASM), 18 i.e., the mean value of all voxels (pixels) within a slice, instead of a measurement based on the region of interest (ROI) 1,21,22 to eliminate any spatial variations in the ‰uctuations caused by image shifting in a plane. The sum of the total pixel values through the plane were divided by the number of pixels: 64×64＝4096 pixels/slice, giving S mean,i in Eq.…”

Section: Experiments 2: In‰uence Of Fat-saturation Pulse On Epi Time Smentioning

confidence: 99%

“…A large linear trend resulting from the contamination of fat signals in a voxel (pixel) time series in fat tissue has been reported. 5 In contrast, we often encounter nonlinear ‰uctuation in fMRI time series, 17,18 and the source is not limited to fat tissue. This observation suggests a more complex underlying mechanism than one that simply results in the progressive contamination of fat signals due to the ineŠectiveness of fat-saturation pulses.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Fat-saturation Pulse on EPI Time Series in the Presence of B0 Drift

Shimada

Kochiyama²,

Fujimoto³

et al. 2010

magn reson med sci

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Purpose: We examined the hypothesis that the fat-saturation pulse in a global oŠ-resonance state caused by magneticˆeld (B 0 ) drift produced signal ‰uctuation in echo planar imaging (EPI) time series.Methods: We performed 3 experiments using 2 types of phantoms, one of which was homemade and contained water and a well emulsiˆed fat source.Results: We found that B 0 drift was approximately ＋30 Hz in theˆrst 30-min EPI time series and ＋15 Hz in the second series. We experimentally reproduced the signal ‰uctua-tions observed during actual measurement in an artiˆcial global oŠ-resonance state using a fat-saturation pulse, the frequency proˆle of which also aŠected the pattern of ‰uctuation.Conclusion: These results are direct evidence that the fat-saturation pulse is a source of signal ‰uctuation in the presence of B 0 drift.

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