C.T.W. Moonen

Effects of large vessels in functional magnetic resonance imaging at 1.5T

To further investigate the effects of large vessels on the activation maps generated with functional magnetic resonance imaging at 1.5T, we studied activation of the human visual and motor cortex using a multitude of dedicated FLASH and echo‐planar imaging (EPI) scanning techniques. Both slice and volume scans were performed to assess relative contributions of T2* effects, in‐flow, and phase‐shift effects, specifically within and around the larger vessels (around 1 mm in diameter). The contrast mechanism in single‐slice FLASH studies appeared to be predominantly sensitive to in‐flow and phase effects of the blood water within these larger vessels, and their relative contributions were dependent on experimental parameters and vascular geometry. The contrast mechanism in gradient echo EPI studies was governed predominantly by T2* effects in tissue water (and to a lesser extent cerebrospinal fluid) surrounding the larger vessels.

PRESTO, a Rapid 3D Approach for Functional MRI of Human Brain

Ogawa et al. [1, 2] proposed in 1990 that physiological information related to neuronal activity can be incorporated in functional magnetic resonance imaging (fMRI) based on changes in the concentration of deoxyhemoglobin in blood (blood oxygenation level dependent, or BOLD effect). As compared to positron emission tomography (PET) and single photon emission computed tomography (SPECT), BOLD fMRI offers substantial advantages: minimal discomfort, no exposure to ionizing radiation and excellent spatial and temporal resolution. Several studies have now demonstrated that sensory and language functions can be mapped with fMRI.