Variable Density Spiral FMRI

Catie Chang¹, Gary Harold Glover¹

We propose a novel variable-density (VD) spiral k-space trajectory for brain fMRI. The trajectory consists of an Archimedean spiral from the origin out to an arbitrary radius k1, extending beyond k1 with a spiral in which the sampling density decreases as the k-space radius increases. Thus, it allows for a reduction in readout time at the expense of undersampling only high spatial frequencies. We implemented the VD spiral in a single-shot 2D spiral-in/out sequence for high (128x128) resolution, and demonstrate improved activation in a sensory-motor task compared to conventional (fully Archimedean) single-shot and interleaved sequences.