Hlustik, P., Noll, D. C., & Small, S. L. (1998). Suppression of Vascular Artifacts in Functional Magnetic Resonance Images Using MR Angiograms. NeuroImage, 7, 224-231.
This paper describes a method for processing functional magnetic resonance images that suppresses signal changes originating from macroscopic veins visible in acquired magnetic resonance angiograms. Finger tapping experiments were performed on a 1.5-T scanner and the response was evaluated with voxel-by-voxel cross-correlation of the time course with a sinusoid at the paradigm frequency. After applying a vascular mask to suppress signal changes under macroscopic vessels, the vascular and nonvascular subpopulations of the data were compared. By visual inspection, the method was found to remove extracortical activation while preserving activation in the parenchyma. The observed higher signal amplitudes and temporal phase lags of the vascular population agree with theoretical models and previous studies. A significant portion of negatively correlated voxels occurs adjacent to through-plane vessels. Finally, comparing the centers of mass of the activated area before and after vascular suppression showed significant shifts in some subjects.