Improved differentiation between primary lung cancer and pulmonary metastasis by combining dual-energy CT–derived biomarkers with conventional CT attenuation

OBJECTIVES: To assess the clinical utility of dual-energy CT (DE-CT)–derived iodine concentration (IC) and effective Z (Z(eff)) in addition to conventional CT attenuation (HU) for the discrimination between primary lung cancer (LC) and pulmonary metastases (PM) from different primary malignancies. METHODS: DE-CT scans of 79 patients with LC (3 histopathologic subgroups) and 89 patients with PM (5 histopathologic subgroups) were evaluated. Quantitative IC, Z(eff), and conventional HU values were extracted and normalized to the thoracic aorta. Differences between groups were assessed by pairwise Welch’s t test. Correlation and linear regression analyses were used to examine the relationship of imaging parameters in LC and PM. Diagnostic accuracy was measured by the area under receiver operator characteristic curve (AUC) and validated based on resampling methods. RESULTS: Significant differences between subgroups of LC and PMs were noted for all imaging parameters, with the highest number of significant pairs for IC. In univariate analysis, only IC was a significant diagnostic feature for discriminating LC from PM (p = 0.03). All quantitative imaging parameters correlated significantly (p < 0.0001, respectively), with the highest correlation between IC and Z(eff) (r = 0.91), followed by IC and HU (r = 0.76) and Z(eff) and HU (r = 0.73). Diagnostic models combining IC or Z(eff) with HU (IC+HU: AUC = 0.73; Z(eff)+HU: AUC = 0.69; IC+Z(eff)+HU: AUC = 0.73) were not significantly different and outperformed individual parameters (IC: AUC = 0.57; Z(eff): AUC = 0.57; HU: AUC = 0.55) in diagnostic accuracy (p < 0.05, respectively). CONCLUSION: DE-CT-derived IC or Z(eff) and conventional HU represent complementary imaging parameters, which, if used in combination, may improve the differentiation between LC and PM. KEY POINTS: • Individual quantitative imaging parameters derived from DE-CT (iodine concentration, effective Z) and conventional CT (HU) provide complementary diagnostic information for the differentiation of primary lung cancer and pulmonary metastases. • A combination of conventional HU and DE-CT parameters enhances the diagnostic utility of individual parameters. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00330-020-07195-9) contains supplementary material, which is available to authorized users.