With the evolution of multi-detector CT scanners, CT is rapidly becoming the initial study of choice for detecting pulmonary embolism (PE). Sensitivities and specificities above 95% have been achieved with multi-slice CT using 2mm slices. Sub-millimeter slices can be easily obtained in less than 5 seconds with our new 64-slice scanner.

In addition, subsegmental arteries can be imaged allowing for identification of even smaller PE's with reduced intravenous contrast loads. Furthermore, CT offers other information concerning associated pathology that is not available with conventional angiography or nuclear ventilation perfusion scans.

In more than 50% of patients, other causes for symptoms ascribed to PE, including pleural effusion, consolidation, emphysema, bronchogenic neoplasm, segmental or lobar atelectasis, and pulmonary fibrosis, are identified leading to improvement in diagnostic ability and accuracy. A recent prospective clinical trial showed that the risk of pulmonary embolism at 9 months after a negative multi-detector CT scan for PE was only 1%.

Another significant advantage of multi-detector CT in patients with suspected PE is its ability to obtain a simultaneous CT venogram of the deep vein system. Multi-detector CT venography for the diagnosis of deep venous thrombosis has achieved sensitivities and specificities well above 95%. Combined multi-detector CT angiography-venography can provide the combination needed to become the single exam of choice for suspected pulmonary embolism.