Figure 3a. Coronal oblique 2D cine MR images of the right superior pulmonary vein. (a) Image obtained with the left atrium (straight black arrow) at maximal volume shows that the left disk of the ASO (curved black arrow) does not protrude into the vein (white arrow). (b) Image obtained with the left atrium (straight black arrow) at minimal volume shows protrusion of the disk (curved black arrow) into the vein (white arrow).