FIGURE 2. Generation of a pulmonary time–activity curve from the multiple-image dataset during washout in 1 pig. Regions of interest (ROIs) are drawn on multiple transverse slices of the first PET image obtained during washout (0–5 s) of 13N-N2. These ROIs are then superimposed on subsequent frames. For clarity, only one ROI and one of the multiple thoracic slices are displayed on 5 of 37 time points.