This may improve the statistical overlay maps. Motion artifacts are determined on the basis of the difference in the number of pixels that increase above the noise floor and decrease below it. The control parameter is the percentage of pixels that must change to flag a motion artifact Spikes are detected on the basis of the number of pixels that increase above the noise floor on successive images. As calculation progresses, you may note that the black line under the image, which represents the paradigm reference vector, is sometimes sprinkled with colored spots. These represent images in which one or more of the artifact categories exceeds the threshold.
Red marks indicate spike artifacts.
Grey bars extending over the whole height of the display area indicate images which were ignored in the statistical calculation. For some real-world examples, have a look at Section 6B . When this center of mass shifts, the shift can be detected and quantified, resulting in a method of tracking the direction and degree of subject motion. In addition to using this statistic as a category of artifact detection, scan STAT can represent it in a graphical form which can be useful for observing subject motion. This display can be accessed by selecting Show Motion Bullseye from the Display menu.