Figure 2c. Normal ECG-gated multi–detector row CT anatomy of the RCA and its branches. (a) Oblique volume-rendered (VR) image of the top of the heart shows the RCA (arrow) arising from the right sinus of Valsalva and coursing in the right atrioventricular groove toward the posterior interventricular septum. A = aorta, PA = pulmonary artery. The conus artery and the sinoatrial node artery were too small to be seen in this case. (b) Lateral oblique VR image shows the caudal course of the proximal RCA (arrow), which gives off an acute marginal branch (arrowheads) to the right ventricle. (c) Posterior oblique VR image shows that the distal RCA divides into the PDA (straight arrow) and posterior left ventricular branches (arrowheads). The PDA courses in the posterior interventricular groove, parallel to the middle cardiac vein (curved arrow).