Simultaneous multislice (SMS) imaging can significantly increase image acquisition rates and improve temporal resolution and contrast in gradient-echo blood oxygen level–dependent (BOLD) functional MRI (fMRI) experiments. Through-plane signal loss due to B0 inhomogeneities at air–tissue interfaces limits fMRI of structures near the nasal cavity and ear canals. This study implemented spectral–spatial (SPSP) radiofrequency pulses for reduced through-plane signal loss across multiple simultaneously excited slices.
Theory and Methods
Multiband (MB) and power independent of number of slices (PINS) methods are combined with SPSP excitation for signal loss compensation in slice-accelerated human brain imaging. Nine simultaneous slices of 5-mm thickness and 20 mm apart were excited using standard MB radiofrequency pulses and the proposed SPSP-SMS pulses, yielding coverage of 36 slices in four shots with 350-ms volume pulse repetition time. The pulses were compared in breath-hold fMRI at 3T.
The SPSP-SMS pulses recovered ∼45% of voxels with signal loss in standard SMS images. Activation in areas of signal recovery increased by 26.4% using a 12.6-ms SPSP-MB pulse and 20.3% using a 12.1-ms SPSP-PINS pulse.
It is demonstrated that SPSP-SMS pulses can improve BOLD sensitivity in areas of signal loss across simultaneous multiple slices. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.
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