OBJECTIVE. The purpose of this study was to evaluate whether two-phase dual-ener - gy CT can differentiate between lung perfusion patterns of patients with chronic pulmonary thromboembolism (PTE) and those of patients with acute PTE.
SUBJECTS AND METHODS. A total of 114 patients clinically suspected to have PTE were prospectively enrolled. All patients underwent dual-energy CT at pulmonary artery (PA) and delayed phases. Of 68 patients diagnosed with PTE on CT, 42 were finally included. Iodine-related attenuation values (IRAs) were measured in PA and delayed phases for each lung segment, and IRA change ratios were calculated using the formula 100% × [(IRA of de - layed phase) – (IRA of PA phase)]/(IRA of PA phase).
RESULTS. Among the 42 patients (19 men and 23 women; mean age, 60.3 ± 13.2 years; range, 28–82 years), 24 had a diagnosis of acute PTE and 18 of chronic PTE. Those segments with both perfusion and filling defects ( n = 143) in patients with acute PTE showed no sig - nificant changes of mean IRA between PA and delayed phases, whereas the segments from patients with chronic PTE ( n = 94) showed significantly increased IRA on delayed phase as compared with PA phase. The mean IRA change ratios in acute and chronic PTE were –3.14% and 191.9%, respectively ( p < 0.0001).
CONCLUSION. Chronic PTE segments were significantly more enhanced on the de - layed phase of two-phase dual-energy CT images than were acute PTE segments, possibly resulting from more extensive systemic collateral formation in chronic PTE. Two-phase dual- energy CT can be used to differentiate distinct regional perfusion patterns between acute and chronic PTE.