Correlation Between Quantitative Spectral CT Parameters and Ki-67 Expression in Lung Adenocarcinomas Manifesting as Ground-glass Nodules

Objective: We assessed the feasibility of spectral CT imaging for diagnosing lung adenocarcinomas manifesting as ground-glass nodules (GGNs) with varying Ki-67 expression. Methods: Spectral CT parameters in 116 patients with lung adenocarcinomas manifesting as GGNs were analyzed. Cases were grouped into pre-invasive/minimally invasive adenocarcinoma (pre/MIA) and invasive adenocarcinoma (IA) groups. The Ki-67 labeling index (Ki-67 LI) was measured and compared between the two groups. Ki-67 LI was divided into three grades based on the number of positive-stained cells. Spectral CT parameters (diameter, water, and iodine concentrations of the lesion [WCL and ICL], the slope of the spectral Hounsfield unit curve [λHU], and CT values from 40 to 140 keV [at 10 keV intervals]) were compared among the three different grades. The correlation between quantitative spectral CT imaging parameters and Ki-67 LI was analyzed using Spearman correlation analysis. Results: Ki-67 LI in the IA group was significantly higher than in the pre/MIA group (p < 0.01). Grade 2 had higher diameter, WCL, and monochromatic CT values, and grade 1 had higher ICL and λHU. The WCL and monochromatic CT values were highly and positively correlated with Ki-67 LI. CT40keV had the highest correlation with Ki-67 LI, the diameter was moderately correlated with Ki- 67 LI, and ICL and λHU were weakly correlated with Ki-67 LI. Conclusion: Spectral CT, a noninvasive diagnostic method, is valuable for predicting Ki-67 expression higher in IA, thus allowing preoperative evaluation of lung adenocarcinomas manifesting as GGNs.