FIG. 9.

Navigator images corresponding to 8 interleaves in a diffusion-weighted scan. Top row: before registration. Bottom row: after registration to a reference navigator image. The third interleaf shows significant signal loss due to motion during the application of diffusion-encoding gradients. Such k-space data can be detected and eliminated by determining a correlation coefficient value following the registration of the individual navigators with the reference navigator (third row). As a rejection threshold for a particular shot a correlation coefficient lower than the median correlation coefficient (over all navigators) –3 × standard deviations can be used.