Phase navigator correction in 3D fMRI improves detection of brain activation: quantitative assessment with a graded motor activation procedure.

Motion poses severe problems for BOLD fMRI, particularly in clinical studies, as patients exhibit more involuntary movements than controls. This study focuses on the merits of a motion correction technique incorporated in multishot fMRI scans, so-called phase navigator correction. The technique entails real-time assessment and off-line elimination of signal fluctuations caused by subject motion. The purpose of this study was to quantify and characterize the effect of this type of improvement on 3D fMRI brain activity maps. For imaging, the 3D PRESTO method was used, with a relatively simple finger opposition task. The followed strategy was guided by the notion that application of any fMRI imaging tool in clinical studies requires several qualities, such as high and spatially homogeneous sensitivity to brain activity, and low sensitivity to motion. A graded motor activation protocol in 10 healthy subjects revealed that image stability was improved by approximately 20%, by the use of phase navigator correction. As a result, sensitivity for task-related BOLD signal change was enhanced considerably in the brain activity maps. Implications for use of this fMRI technique in patient studies are discussed.