A good quality CT pulmonary angiogram has a high accuracy rate for the evaluation of pulmonary embolism. Investigators have reported that the subsegmental emboli can be missed; however, visualization of smaller arterial branches, and therefore, detection of small emboli may improve with the availability of multidetector scanners. Some of the advantages of using CT for pulmonary embolism compared with lung scintigraphy include: (1) direct visualization of emboli on CT, (2) evaluation of lung parenchyma and mediastinum, which may provide an alternate diagnosis, and (3) capability to acquire CT venogram without additional contrast with "one-stop examination" for evaluation of thromboembolic disease.