Simultaneous multislice spiral imaging using z-gradient modulation and parallel receive coils

INTRODUCTION: Simultaneous multislice imaging decreases the required scan time for a given volume, which is particularly beneficial in fMRI, as well as in a variety of other applications. We propose a new method for spiral simultaneous multislice imaging that uses a z-gradient modulation during readout, along with a multiple-coil receive array. Previous methods have used a z-gradient encoding only for Cartesian readouts [1], which do not share the benefits of spirals in fMRI such as improved signal recovery (spiral-in trajectories) and shorter readout times [2]. We use a model-based, iterative reconstruction method similar to [3] and [4] to separate the slices. THEORY: In simultaneous multislice imaging, the complex signal acquired in coil is ∑ , , where is the Fourier transform operator, each , is a diagonal matrix consisting of the sensitivity of coil to slice , each is a vectorized slice , and is the number of slices simultaneously acquired. Combining the equations for all coils into one, we have ⋮ , , ⋯ , , , ⋯ , ⋮ ⋮ ⋱ ⋮ , , ⋯ , ⋮ , (1)