Increased SNR by Simultaneous Encoded Complex-Valued Slices with Through-Plane Acceleration in FMRI

In functional Magnetic Resonance Imaging (fMRI), a topic of study is to accelerate the number of images per unit time to create each volume. Techniques have been developed such as Sensitivity Encoding (SENSE) and Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) that measure less data in a slice (in-plane), but still are able to reconstruct an image. The simultaneous multi-slice (SMS) techniques provide an alternative reconstruction method in which multiple slices are acquired and aliased together concurrently (through-plane). Controlled Aliasing in Parallel Imaging (CAIPI) technique achieves slice-wise image shift to decrease the influence of the geometry factor (g-factor) of coil sensitivities. The Hadamard phase-encoding technique allows different combinations of the aliased slices and prevents the singular problem of the design matrix. In this paper, a CAIPI approach for multi-coil separation of parallel encoded complex-valued slices (mSPECS-CAIPI), a novel SMS approach is presented, combined with two slice-wise imaging shift techniques and Hadamard encoding method. The bootstrap sampling method and the least squares estimation function are also incorporated to calculate the reconstructed images. The signal-to-noise ratio (SNR) map and contrast-to-noise ratio (CNR) map are generated and compared with techniques without CAIPI shifts. An improvement of SNR, CNR, and activation values is achieved by the new approach.