Quantitative evaluation of iodine and fat using dual-energy CT for assessments of the tumor aggressiveness in lung cancer

Background: The three-material decomposition method (3MD) of dual-energy applications can quantify iodine and fat contents of the tumor. The purpose of this study was to assess the usefulness of quantifying iodine and fat contents in the tumor grade, lymphovascular invasion, and pleural invasion to predict tumor aggressiveness in lung cancer (LC) using dual-energy computed tomography (DECT). We prospectively analyzed the cases of 32 patients with lung tumors who underwent preoperative contrast-enhanced DECT. Image data were processed with a 3MD using imaging software. Iodine and fat within the mass were quantified. In the 24 patients with cancerous lung tumors, we performed correlation analysis of iodine and fat contents with histological grade (grades 1-4), lymphovascular invasion and pleural invasion. Results: The iodine concentration (mg/mL) and fat-volume-fraction (%) showed no significant differences among histological grades (p = 0.514 and p = 0.405, respectively) (Jonckheere-Terpstra test). Likewise, pleural invasion was not associated with either the iodine concentration or the fat-volume-fraction (p = 0.673 and p = 0.251, respectively) (Mann-Whitney test). Lymphovascular invasion, however, was significantly associated with the fat-volume-fraction (39.3 +/- 23.4% vs. 62.3 +/- 29.5%, p = 0.007), but not with the iodine concentration (p= 0.137). The receiver operating characteristics curve of the fat-volume-fraction between the presence and absence of lymphovascular invasion revealed an area under the curve of 0.861 at the cut-off value of 37.8%, with a sensitivity of 1.000 and specificity of 0.722. Conclusion: The quantitative evaluation of fat within a tumor using DECT may predict lymphovascular invasion in LC.