Pulmonary thrombi clearly visualized on non-contrast electron density images using dual-source, dual-energy computed tomography: a case report

A 77-year-old man was diagnosed with pulmonary embolism in the central-right and lower-left pulmonary arteries on chest contrast computed tomography (CT) scan at a local hospital, and was referred to our institution. We performed a 1-week follow-up study using dual-source CT (SOMATOM Pro.Pulse; Siemens Healthineers, Germany). Non-contrast-enhanced images were taken using the dual-energy mode, generating images equivalent to 120 kVp (Figure 1A–C); however, we were unable to conclusively identify any thrombi in them. Electron density images were therefore generated and processed using a denoising filter, which facilitated the clear identification of residual thrombi in the right pulmonary artery (Figure 1D–F). Finally, contrast-enhanced CT-angiography images were also acquired in the dual-energy mode, which confirmed the presence of residual thrombi (Figure 1G–I). Lung perfusion maps showed extensive perfusion defects in the right lung (Figure 1J). We therefore decided to continue anticoagulant therapy. To our knowledge, this is the first study to demonstrate that electron density images generated by dual-source CT systems can enhance the visualisation of pulmonary artery thrombi without the need for intravenous iodinated contrast agents, suggesting that the electron density images may be safe alternatives for patients in whom contrast-enhanced CT angiography is contraindicated.