Figure 9: Average registration errors of depending on the position of the frame after start of the contrast agent injection calculated over all sequences. Frame 1 denotes the first frame which contained contrast agent. The average error at the second frame after the CA injection was 11.8 mm 9.5 mm; the average error at the fifth frame was 5.5 mm 3.0 mm. The frame rate of all sequences was 7.5 fps. Assuming a heart rate of 60 bpm, one heart cycle takes approximately 7 frames. So a first portion of CA is ejected into the ventricle not later than at the 7th frame. Note that the number of sequences used for calculation was not constant for each frame number as several sequences had fewer than nine contrasted frames.