[Differential diagnosis of pure ground glass nodules in lung with spectral CT imaging]

Objective: To evaluate the differential diagnostic performance of quantitative parameters derived from the spectral CT imagingin pure ground-glass nodules. Methods: A total of 44 patients with pure ground glass nodules underwent chest energy spectrum CT and with known subsequently pathological findings in the Imaging Department of the Second Affiliated Hospital of Soochow University from August 2017 to September 2019 were retrospectively analyzed. Among them, there are 18 males and 26 females, aged from 26 to 79 (51±12) years. They were divided into as the inflammatory group (n=12), pre-invasive adenocarcinoma group (n=17) and invasive adenocarcinoma group (n=15). The aforementioned three groups were further reclassified as non-invasive adenocarcinoma group (inflammatory lesion+pre-invasive lesion) and invasive adenocarcinoma group in order to evaluating the values of water concentration (WC) for the determination of adenocarcinoma infiltration status. The values of WC derived from the arterial and venous phase of the lesion, iodine concentration (IC), standardized iodine concentration (NIC) were measured respectively.The slope of the energy spectral curve (K_40-70KeV) derived from the arterial and venous phase of the lesion was also calculated. One-way ANOVA analysis was performed to compare the differences of the three groups and the multiple comparison method was used for further comparing. Intraclass correlation efficient (ICC) was used to assess the consistency of the three times of measurements. The area under curve(AUC) of Receiver Operating Characteristic (ROC) was conducted to evaluate the diagnostic performance of water based values. Results: The values of WC in the arterial and venous phases were significantly different. As in the inflammatory group, the pre-invasive lesion group and the invasive adenocarcinoma group, the values of WC was (291.95±58.66) mg/cm³, (297.61±63.96) mg/cm³and (374.52±60.62) mg/cm³ of the arterial phase, and (277.07±33.78) mg/cm³, (291.74±50.49) mg/cm³ and (373.33±75.12) mg/cm³ of the venous phase, respectively(all P<0.05). Further comparison demonstrated that no significant difference was observed for the values of WC derived from the arterial phases and venous phases between the inflammatory lesion group and the pre-invasive lesion group (all P>0.05).There were an significant differences between the invasive adenocarcinoma group, the inflammatory lesion group and the pre-invasive lesion group (all P<0.05). The values of WC derived from the venous phase achieved the largest AUC (0.770) for differentiating invasive adenocarcinoma from non-invasive adenocarcinoma (inflammatory lesions+pre-invasive lesions) in the pure ground glass nodules. The sensitivity and specificity were 66.67% and 93.10%, respectively, when using 349.31 mg/cm³ as the optimal threshold. The slope of the spectral curve and iodine-related parameters (IC, NIC) derived from arterial or venous phases among the three groups were not significantly different (all P>0.05). Conclusion: The values of WC derived from the spectral CT can better distinguish inflammatory, pre-invasive lesions and invasive adenocarcinoma, which is helpful for the qualitative analysis for pure ground glass nodules.