APPLIED RADIOLOGY, Nov 2007
George Gentchos, MD, and Jeffrey S. Klein, MD
Pulmonary embolism (PE) remains a leading cause of morbidity and mortality in the United States, with an incidence of approximately 500,000 to 650,000 cases annually. As many as one-third of victims of PE die from a future embolic event. Pulmonary embolism and its precursor, deep venous thrombosis (DVT), are manifestations of numerous conditions that lead to hypercoagulability, stasis, or endothelial damage, particularly in elderly, hospitalized, and oncology patients. Despite improvements in clinical algorithms and the introduction of sensitive serologic tests for excluding PE (such as the enzyme-linked immunosorbent assay [ELISA] d-dimer), the clinical evaluation of PE remains problematic, with the minority of patients presenting with "typical" signs or symptoms. Advances in multidetector computed tomography (MDCT) scanners (a technology that is now widely available) and an increased awareness of the importance of timely and accurate diagnosis of PE have resulted in increased use of MDCT for emergency department and hospitalized patients. The increased utilization of MDCT for possible PE has been associated with a decrease in the incidence of PE as detected by CT in the period 1998 to 2003. This result supports the concept that CT pulmonary angiography, by providing a global evaluation of the patient with acute chest disease, has become a widely utilized tool in these patients. This trend in MDCT utilization, which parallels its use in the evaluation of acute abdominal pain, is largely a result of its overall accuracy, cost-effectiveness, high negative predictive value, and safety and utility in the evaluation of PE (Figure 1). With its high accuracy and its ability to identify those conditions that account for acute chest symptomatology in the 75% to 90% of patients whose CT pulmonary angio-grams are negative for PE, MDCT has largely replaced ventilation-perfusion scanning and pulmonary angiography in the evaluation of PE.1-4 In as many as 4% of hospitalized patients and 1% of outpatients, unsuspected PE has been identified on routine contrast-enhanced MDCT scans of the chest not necessarily optimized for PE detection. This has reinforced the relatively high incidence of this often asymptomatic condition in the patient population and the diagnostic capabilities of the newest generation of MDCT scanners (Figure 2).