The Effect of Single-Detector CT Versus MDCT on Clinical Outcomes in Patients with Suspected Acute Pulmonary Embolism and Negative Results on CT Pulmonary Angiography

We sought to compare the clinical outcomes of patients in whom pulmonary embolism (PE) has been ruled out with single-detector CT versus MDCT, given the improved visualization of subsegmental clots with the latter and the recent increase in use of CT for evaluation of PE. Two cohorts of patients undergoing CT for suspected PE with either single-detector CT (3-mm collimation and pitch of 1.7) or MDCT (2-mm collimation and pitch of 1) scanners were prospectively observed and compared using predefined criteria for evidence of subsequent thromboembolic disease during the 6 months after the acquisition of their initial scan. Ninety-eight patients were scanned using a single-detector CT scanner. Of these, none had evidence of subsequent PE or deep venous thrombosis (DVT), and six (6.1%) died of unrelated causes. Of the 100 patients scanned using an MDCT scanner, one (1.0%) had a subsequent nonfatal PE 2 months after the initial scanning, one (1.0%) had DVT 1 month after the initial scanning, and eight (8.0%) died of unrelated causes. No significant difference was found in either the probability of subsequent thromboembolic events (chi(2) = 0.3183, degrees of freedom [df] = 1, p = 1) or frequency of unrelated deaths (chi(2) = 0.2655, df = 1, p = 0.7829) between patients scanned using single-detector CT or MDCT protocols. Our results show that patients with suspected acute PE and negative CT results have acceptable clinical outcomes in the absence of anticoagulation treatment up to 6 months after acquisition of their initial scan. Furthermore, we found that the increased visualization of smaller, more peripheral arteries afforded by multislice technology did not affect clinical outcome.