Dual-energy CT Can Evaluate Both Hilar and Mediastinal Lymph Nodes and Lesion Vascularity with a Single Scan at 60 Seconds after Contrast Medium Injection

Rationale and Objectives: The aim of this study was to investigate whether 80-kVp and weighted-average 120-kVp computed tomographic (CT) images scanned at 60 seconds after contrast material injection using a dual-source CT scanner could substitute for conventional 120-kVp images obtained at 30 and 100 seconds. Materials and Methods: Eighty-three consecutive patients with suspected lung cancer were enrolled. Images were obtained in dual-energy mode (80 and 140 kVp) at 60 seconds and conventional 120-kVp mode at 30 and 100 seconds after contrast injection. The CT numbers of the pulmonary artery, pulmonary vein, hilar zone lymph nodes, and pulmonary lesions were measured. Contrasts between the pulmonary artery/pulmonary vein and lymph nodes and beam-hardening artifacts were visually evaluated using five-point and four-point scales, respectively. The degree of enhancement was evaluated on 30-second 120-kVp, 100-second 120-kVp, and 60-second weighted-average 120-kVp images. Results: The mean differences in attenuation between the pulmonary artery/pulmonary vein and lymph nodes on the 30-second 120-kVp, 60-second 80-kVp, and 60-second weighted-average 120-kVp images were 184/155, 130/140, and 84/92 Hounsfield units, respectively (all . P values <.001). The mean contrast scores for the hilar/mediastinal lymph nodes were 4.5/4.7, 3.7/4.2, 3.3/3.6, and 2.4/2.5 for these three and for 100-second 120-kVp images, respectively (all . P values <.01). The mean artifact scores of the four images were 1.2, 3.4, 3.6, and 4.0, respectively. On 60-second weighted-average 120-kVp images, 55 of 60 lesions (92%) showed higher enhancement than on 100-second conventional 120-kVp images. Conclusions: Dual-energy CT images scanned 60 seconds after contrast injection show excellent vessel-lymph node contrast and enhancement of lesions and can replace dual-phase scan protocols.