Diagnostic approach in acute pulmonary embolism: perfusion scintigraphy versus spiral computed tomography

For diagnosing acute pulmonary embolism, perfusion scintigraphy in combination with ventilation studies is a well-established and sensitive method. Recently, computed tomography (CT) incorporating an angiographic technique was introduced for evaluating the pulmonary arterial system without breathing artefacts. The present study compared lung scans with spiral CT data to establish the diagnostic value of the latter approach. Twenty-five patients with a clinical suspicion of acute pulmonary embolism were examined using both methods. Perfusion and ventilation lung scans were done and spiral volumetric CT studies were performed. In 18 patients, pulmonary embolism was diagnosed using both methods. However, the results were interpreted differently. Particularly when centrally localized emboli were present in both pulmonary arteries, assessment of the more affected side was difficult on CT and depended on the experience of the physicians interpreting the scans. Small, (sub-)segmental emboli could not be demonstrated on CT. This may explain the false-positive and false-negative results, respectively. Spiral CT enables an exact demonstration of thrombosis in severe, centrally localized emboli. In incompletely occluded vessels, estimation of the degree and the location of perfusion defects is better with scintigraphy. Based on the present results and the technical equipment necessary for spiral CT, it is concluded that perfusion scintigraphy remains the method of choice for diagnosing acute pulmonary emboli.