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| Paper IPM / Cognitive / 13959 |
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Due to the mechanism of contrast origin in BOLD fMRI, generally only the magnitude data is used for activation detection. Through the use of SSFP sequences, we are able to detect fMRI activation directly based on phase variation induced by frequency shift. BOSS fMRI utilizes
this phase information in addition to magnitude changes for activation detection1, 2. The contribution of phase, however, is highly dependent on the position of the center frequency on the SSFP profile2 and therefore may not be quantified accurately. Averaged- BOSS (A-BOSS)3, which has recently been introduced for fMRI by compressing the SSFP profile into a single voxel, also indicates that activation patterns should exist in both phase and magnitude images. Figure 1 graphically shows this concept. Because of its averaging nature, this method provides a novel approach for quantitative analysis of fMRI induced phase changes while removing its sensitivity to the off-resonance frequency. Method: A-BOSS signal is essentially similar to BOSS, but the SSFP profile
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