Comparison between subtraction images. Subtraction images before [left] and after [right] registration. In the right note the portal and hepatic veins, their course and the better identification of several anatomic details. Recognition of the enhancing lesion in 8th segment is improved (open arrow in the right image). It is clear on the subtracted image after registration that the round zone of enhancement in 4th segment is not a focal lesion but a branching portal ramus (white arrow in the right image). Finally, the high signal intensity artifact on the lateral and anterior margins of the liver disappears after registration (arrows in the left image).