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

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.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 delayed phase) - (IRA of PA phase)]/(IRA of PA phase).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 (p0.0001).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.