Lars Kasper1,2, Maximilian Hberlin1, Christoph Barmet1, Bertram Jakob Wilm1, Christian C. Ruff2,3, Klaas Enno Stephan2,3, Klaas Paul Prssmann1
1University & ETH Zurich, Institute for Biomedical Engineering, Zurich, Switzerland; 2University of Zurich, Laboratory for Social & Neural Systems Research, Zurich, Switzerland; 3University College of London, Wellcome Trust Centre for Neuroimaging, London, United Kingdom
Filtering is a common post-processing step in MRI. Specifically, the analysis of fMRI data frequently includes a Gaussian smoothing of the raw images. This application of a matched filter improves sensitivity at the spatial scale of the BOLD response. We show that the argument already holds at the acquisition stage and propose a 2D gradient-velocity modulated EPI sequence providing a Gaussian k-space density weighting. In the case of phantom and resting state fMRI, temporal SNR is thus raised by 60-80% while preserving overall measurement duration. Furthermore, for visual stimulation, t-contrast images reveal both increases in cluster sizes and peak t-values.