Figure 4.

Average registration errors (average over voxels) plotted as a function of the number of angles retained in test state nine for the first configuration (config I) of the NCAT phantom with default angulation of the heart and clinically relevant noise levels in the projections. Errors are plotted for when all angles are retained in reference state 5 (dashed lines), which is the standard methodology and when, as per our algorithm, only the angles in common between the two states are retained (solid lines). The two estimation methodologies are plotted for the NAR going from 30 to 2 in steps of 2 at the start, middle, or the end of acquisition for each head.