Different Perfusion Pattern Between Acute and Chronic Pulmonary Thromboembolism: Evaluation With Two-Phase Dual-Energy Perfusion CT

OBJECTIVE. The purpose of this study was to evaluate whether two-phase dual-energy 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% x [(IRA of delayed 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 significant 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 delayed 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.