Usefulness of electron density imaging from dual-energy CT for detecting pulmonary thromboembolism in unenhanced CT

This study aimed to evaluate the diagnostic value of electron density (ED) imaging in detecting pulmonary thromboembolism (PTE) on unenhanced dual-energy CT (UCT) and to analyze stage-dependent changes in ED values.

In the in vitro study, venous blood samples were incubated to form thrombi and scanned to assess attenuation and ED changes across different thrombus stages. The in vivo study retrospectively analyzed patients who underwent UCT within 1 day of CT pulmonary angiography, measuring HU and ED values of PTE. Statistical analyses were conducted to compare these parameters and determine cut-off values for PTE detection.

In vitro, HU and ED values significantly decreased over time across PTE stages (p < 0.001). The in vivo study included 384 PTEs from 118 patients (M:F = 63:55; mean age, 64.47 ± 13.68 years), comprising 220 acute (57.3%), 85 subacute (22.1%), and 79 chronic PTEs (20.6%). On ED images, 66.8% of acute PTEs were visible, compared to 36.4% on UCT. For subacute and chronic PTEs, ED images identified 10.6% and 8.9% of cases, respectively, while none were detected on UCT. The diagnostic cut-off values were 63.3 HU and 104.4% of the ED of water.

ED imaging enhanced PTE visualization on UCT. ED values progressively decreased with advancing PTE stage in both in vitro and in vivo analyses. A higher number of detectable PTEs were identified in the acute stage compared with subacute or chronic stages on ED images, and overall, more PTEs were detected with ED imaging than with conventional UCT.

Question The detectability of pulmonary thromboembolism (PTE) on electron density (ED) images from unenhanced dual-energy CT (UCT) and its variations across different PTE stages remain unexplored. Findings In vitro and in vivo studies demonstrated that ED values on UCT decreased as PTE progressed, with acute stages exhibiting statistically higher detection rates. Clinical relevance ED imaging may substantially enhance the detection of PTE on UCT compared with conventional UCT, thereby improving diagnostic accuracy and patient management.