Figure 5a. Sagittal oblique 2D cine MR images of the right superior vena cava. (a) Image obtained with the left atrium (straight white arrow) at maximal volume shows that the right disk of the ASO (black arrow) does not protrude into the vein (curved white arrow). (b) Image obtained with the left atrium (straight white arrow) at minimal volume shows protrusion of the disk (black arrow) into the vein (curved white arrow).