Helical CT scanning in the diagnosis of pulmonary embolism

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