Usefulness of dual-energy CT scanning at 80 kVp for identifying hilar and mediastinal structures: Evaluation of contrast enhancement of the pulmonary vessels and lymph nodes

Purpose We examined whether the 80-kVp CT images scanned at 100 s after contrast material injection using a dual-source scanner could be substituted for the conventional 120-kVp images obtained at an earlier timing of 30 s. Materials and methods Seventy-eight patients with suspected lung cancer were examined with a 120-kVp mode at 30 s after contrast material injection (early phase) and a dual-energy (80 and 140 kVp) mode at 100 s (late phase). CT numbers of the pulmonary artery (PA), pulmonary vein (PV) and hilar zone lymph nodes (LN) were measured. Contrast between the PA/PV and LN was visually evaluated using a 5-point scale. Beam-hardening artifacts were also visually assessed. Results The mean difference in attenuation between the PA/PV and LN on the early phase 120-kVp, late phase 80-kVp and late phase weighted-average 120-kVp images was 171.3/160.8, 100.5/106.8 and 67.5/67.5, respectively (p<0.001). The mean contrast score of these three images for the hilar/mediastinal LN was 4.5/4.7, 3.4/3.8 and 2.9/ 3.3, respectively (all p<0.05). The mean artifact score of the three images was 2.6, 4.0 and 4.0, respectively; on most early phase images, the beam-hardening artifacts influenced the diagnosis (p<0.001). Conclusion The late phase 80-kVp images showing few artifacts may be an alternative to early phase 120-kVp images.