Figure 1b. Posterior (a) and superoinferior (b) views of the modal anatomy of the PVs, from a three-dimensional volume-rendered image data set obtained with contrast-enhanced multisection computed tomography (CT) (four sections, 2.5-mm collimation, 1.25-mm reconstruction interval) in a 45-year-old man prior to ablation therapy. Four independent ostia are visible in the dorsal aspect of the left atrium. Note that the right middle PV has a normal drainage into the central part of the right superior PV and that the lingular PV drains into the left superior PV. LI = left inferior, LS = left superior, RI = right inferior, RM = right middle, RS = right superior.