Effect of Noise-Optimized Monoenergetic Postprocessing on Diagnostic Accuracy for Detecting Incidental Pulmonary Embolism in Portal-Venous Phase Dual-Energy Computed Tomography

Objectives: The aim of this study was to evaluate the diagnostic accuracy of virtual monoenergetic images (MEI+) at low kiloelectronvolt levels for the detection of incidental pulmonary embolism (PE) in oncological follow-up portal-venous phase dual-energy (DE-CTpv) staging. Materials and Methods: Twenty-six patients with incidental PE in DE-CTpv staging, which was confirmed by computed tomography pulmonary angiography (CTPA), were included in this study. In addition, 26 matched control patientswho were negative for PE in both DE-CTpv and CTPA were included. All examinations were performed on a third-generation DE-CT system in single-energy (CTPA) and dual-energymode (DE-CTpv). Subsequently, 2 series of MEI+ data sets were reconstructed at 40 and 55 keV from the DE-CTpv data and compared with CTPA and the linearly blended CTpv images. Diagnostic accuracy and diagnostic confidence were calculated and compared for MEI+ reconstructions and for CTpv images regarding the detection of PE with CTPA as standard of reference. Results: In 3 patients, PE was only detectable in CTPA and in the 40-kV and 55-kVMEI+ reconstructions but not in CTpv images. Diagnostic accuracy increased significantly for both MEI+ series (40 keV; area under the curve [AUC], 0.928; 95% confidence interval [CI], 0.879-0.978; 55 keV; AUC, 0.960; 95% CI, 0.922-0.998) as compared with CTpv (AUC, 0.814; 95% CI, 0.741-0.887; P = 0.004). Diagnostic confidence was rated highest in CTPA (median, 5; range, 3-5) followed by 55-keV MEI+ and 40-keV MEI+ (median, 5; range, 2-5 and median, 5; range, 2-5, respectively) and was lowest for CTpv (median, 4; range, 1-5), with significant differences to CTPA and MEI+ reconstructions (P = 0.001). Conclusions: Monoenergetic image reconstructions fromDE-CT data sets at low kiloelectronvolt levels improve diagnostic accuracy for the detection of incidental PE in oncological follow-up DE-CTpv staging, with the highest subjective diagnostic confidence in MEI+ at 55 keV.