Impact of tube current-time and tube voltage reduction in 64-detector-row computed tomography pulmonary angiography for pulmonary embolism in a porcine model.

Purpose: To evaluate the impact of dose reduction in multidetector computed tomography pulmonary angiography (CTPA) for detection of pulmonary embolism (PE). Materials and Methods: After induction of PE in 6 anesthetized pigs, a 64-detector-row CTPA was performed at 3 di! erent dose protocols: A (120kV/120mAse! .), B (120kV/80mAse! .), and C (80kV/80mAse! .). Images were evaluated by 2 radiologists independently. A high-dose CTPA (120kV/250mAse! .) served as a reference standard. Sensitivity, specificity, and positive and negative predictive values were calculated and compared using the Wilcoxon test. Interobserver agreement was determined by calculation of k values. Radiation exposure and objective image parameters were assessed and compared with a 2-sided t test. Results: In the reference scan, a total of 94 emboli were detected: 17 in the main and lobar pulmonary level (category A), 47 in the segmental level (category B), and 30 in the subsegmental level (category C). All protocols reached high diagnostic accuracy in the