ANATOMIC LOCALIZATION AND QUANTITATIVE-ANALYSIS OF GRADIENT REFOCUSEDECHO-PLANAR FMRI SUSCEPTIBILITY ARTIFACTS

Functional magnetic resonance imaging (fMRI) techniques, such as echo- planar imaging, can permit rapid, sensitive, whole-brain measurements of local blood how-induced MR signal changes seen during cognitive par adigms. Changes in blood oxygenation due to mismatch of how and oxygen metabolism cause dynamic variations in microscopic susceptibility eff ects, leading to the blood oxygenation level-dependent (BOLD) signal m easured by fMRI techniques. A related static macroscopic susceptibilit y effect is known to cause artifacts that attenuate the MR signal, lea ding to ''blind spots'' in some regions of brain adjacent to bone and air sinuses, The anatomical location, spatial extent, and magnitude of signal loss artifact are quantitated for a common whole-brain fMRI te chnique. Resting gradient-echo EPI studies were obtained in four healt hy volunteers. Signal loss was primarily localized to inferior frontal regions (medial orbital gyri and gyrus rectus) and to inferior latera l temporal lobe (including part of fusiform gyrus) bilaterally. Increa sed echo time (TE) uniformly produced larger artifacts. The orientatio n of acquired slices and choice of phase-encoding direction influenced the location, shape, and extent of the artifacts. Regions of the brai n with severe artifact may have attenuated activation signal, with pot ential implications for the design and interpretation of fMRI studies targeting activations in these areas. (C) 1997 Academic Press.