This is a contiguous series of chest CT slices in a 31y old male. No intravascular contrast has been administered to the patient. You can look at the video frame by frame and try to identify the lettered structures to which lines are drawn. Sometimes a structure has a line drawn to it in only one of the sections in which it can be seen; in other cases the same structure may have lines drawn to it in a few sections, not necessarily contiguous. The answers will be revealed when you click on the appropriately labelled drop-down arrows below the image.