4 research outputs found
High spatio-temporal resolution in functional MRI with 3D echo planar imaging using cylindrical excitation and a CAIPIRINHA undersampling pattern
Purpose
The combination of 3D echo planar imaging (3DâEPI) with a 2DâCAIPIRINHA undersampling scheme provides high flexibility in the optimization for spatial or temporal resolution. This flexibility can be increased further with the addition of a cylindrical excitation pulse, which exclusively excites the brain regions of interest. Here, 3DâEPI was combined with a 2D radiofrequency pulse to reduce the brain area from which signal is generated, and hence, allowing either reduction of the field of view or reduction of parallel imaging noise amplification.
Methods
3DâEPI with cylindrical excitation and 4âĂâ3âfold undersampling in a 2DâCAIPIRINHA sampling scheme was used to generate functional MRI (fMRI) data with either 2âmm or 0.9âmm inâplane resolution and 1.1âs temporal resolution over a 5âcm diameter cylinder placed over both temporal lobes for an auditory fMRI experiment.
Results
Significant increases in image signalâtoânoise ratio (SNR) and temporal SNR (tSNR) were found for both 2âmm isotropic data and the highâresolution protocol when using the cylindrical excitation pulse. Both protocols yielded highly significant blood oxygenation levelâdependent responses for the presentation of natural sounds.
Conclusion
The higher tSNR of the cylindrical excitation 3DâEPI data makes this sequence an ideal choice for high spatiotemporal resolution fMRI acquisitions. Magn Reson Med 79:2589â2596, 2018. © 2017 International Society for Magnetic Resonance in Medicine
Simultaneous Multislice (SMS) Imaging Techniques
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