Dual-energy CT for differentiating acute and chronic pulmonary thromboembolism: an initial experience

The purpose of this study was to prospectively evaluate the diagnostic capability of single-phase dual-energy CT (DECT) angiography to differentiate acute and chronic pulmonary thromboembolism (APTE, CPTE). We prospectively enrolled 26 patients (M:F = 9:17; mean age, 61 years old) with a filling defect in the pulmonary artery on DECT angiography. They were divided into two groups-APTE and CPTE-based on the clinical criteria. Two investigators quantitatively measured the following parameters at the embolism and main pulmonary artery: CT attenuation density [Hounsfield unit (HU) values], iodine-related HU value (IHU), and iodine concentration (IC, mg/ml). These parameters of the embolism and their ratio divided by those of the main pulmonary artery were compared between APTE and CPTE groups. Among 26 patients, 15 were categorized into the APTE group and 11 into the CPTE group. The mean HU, IHU, and IC values of emboli were significantly different between the APTE and CPTE groups (32.2 ± 17.0 vs. 52.1 ± 13.6 HU; P = 0.016, 7.2 ± 2.8 vs. 27.3 ± 12.7 HU; P < 0.001, and 0.57 ± 0.23 vs. 1.56 ± 0.67; P < 0.001). The mean HU, IHU, and IC ratios between emboli and main pulmonary arteries were also significantly different between the two groups (0.085 ± 0.046 vs. 0.156 ± 0.064 HU; P = 0.003, 0.023 ± 0.013 vs. 0.099 ± 0.053; P < 0.001, and 0.048 ± 0.035 vs. 0.130 ± 0.064; P = 0.001). DECT angiography using a quantitative analytic methodology can be used to differentiate between APTE and CPTE.