Neuroscience 2001 Abstract
| Presentation Number: | 83.10 |
|---|---|
| Abstract Title: | A practical z-shim method in functional imaging with a three-Tesla magnetic resonance scanner. |
| Authors: |
Takahashi, T.*1,2,3
; Xiao, R.1,2
; Kansaku, K.1,2
; Kawano, K.1,2
; Iijima, T.1,2
; Kitazawa, S.1,3
1National Institute of AIST, Tsukuba, Japan 2CREST of JST, Kawaguchi, Japan 3TOREST of JST, Kawaguchi, Japan |
| Primary Theme and Topics |
Cognition and Behavior - Human Cognition and Behavior -- Other higher functions |
| Secondary Theme and Topics | Cognition and Behavior<br />- Human Cognition and Behavior<br />-- Language |
| Session: |
83. Human cognition and behavior: other higher functions I Poster |
| Presentation Time: | Sunday, November 11, 2001 9:00 AM-10:00 AM |
| Location: | Exhibit Hall TT-32 |
| Keywords: | FMRI, AUDITORY LANGUAGE TASK, SUSCEPTIBILITY ARTIFACTS, INFEROTEMPORAL CORTEX |
The gradient echo-echo planar imaging (GRE-EPI) sequence is widely used in functional magnetic resonance imaging (fMRI) studies. However, it causes severe signal loss at the boundaries of organs of different magnetic susceptibility, especially with a high Tesla scanner. Frahm et al. (1988) proposed a z-shim method that reduces signal loss by reconstructing one image from multiple images, each acquired with a refocusing gradient pulse (RGP) of different strength. However, this technique has been applied to fMRI studies infrequently, owing to the difficulty in taking a large number of images with different RGPs while maintaining a practical sampling frequency, and the number of slices required. Here, we propose an effective and practical z-shim method. In the pre-scanning process, a number of image volumes (16-32) is taken with RGP strengths covering the range from 30% to 170% of the default value in steps of 4 - 9%. Then a limited number (around 5) of optimal RGP strengths is chosen, by observing the signal intensities within a pre-defined volume of interest in the pre-scanned images, and used for scanning during task sequences. We adapted this method to a conventional GRE-EPI sequence on an ultra-high Tesla scanner (3.0 Tesla GE Signa LX), and tested its applicability with an auditory language task. Brain activation was clearly observed in the inferotemporal cortex, where signal loss is most severe with conventional techniques. This result shows that the z-shim technique proposed here is very useful for fMRI studies.
Supported by CREST and TOREST of JST
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2001 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2001. Online.
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