Imaging in acute pulmonary embolism with special clinical scenarios.

Major advances in computed tomography (CT) technology, specifically multidetector CT (MDCT) with vastly improved spatial and temporal resolution,1 have led to a surge in the diagnosis of acute pulmonary embolism (PE) using computed tomography pulmonary angiography (CTPA).2–5 For persons between 35 and 74 years old, hospital diagnosis rates in 1981 for PE were 127.7 per 100 000 for blacks and 98.2 per 100 000 in whites.6 The reported incidence ranges from 43.7 to 145.0 per 100 000.7 These data are based on epidemiological studies based on physical examination and history, which underestimate the actual frequency of disease.8 However, data from autopsies confirms that only a small number of cases of PE are recognized clinically.8 If untreated, the hospital mortality rate for major PE is 30%, whereas the mortality drops markedly in anticoagulated patients,9 emphasizing the need for rapid, accurate imaging for diagnosis and prognosis. Although CTPA has largely solved the diagnostic question, “Does the patient have PE?” new questions have arisen. These include: Do patients warrant concurrent CTPA plus imaging of the pelvis and lower extremities? What is the risk for subsequent PE after negative CTPA? Is there an ideal management algorithm in patients with isolated subsegmental PE? What is the optimal imaging tool for evaluation of women who are either pregnant or of child bearing age? How can the patient radiation doses be reduced without compromising diagnostic capabilities? This review is to address these questions and looks toward the future of PE imaging.