Figure 5.

Sample residual motion analysis. r(k) represents the magnitude of residual motion over the course of 49 acquired frames, and RMSE the root mean squared error of r(k), which are both significant under free-breathing (FB) conditions. The application of a simple lnear tracking factor of 0.6 in the superior-inferior direction (FB-TF) reduces this motion, but is susceptible to errors under varied breathing patterns. PROCO reduces the motion to a similar degree as navigator gated techniques (Nav Gate and Nav Gate-TF); however, PROCO frames are acquired consecutively, and both navigator gated techniques accept frames only at end-expiration, greatly reducing efficiency.