Fig. 4
Receiver operating characteristic curve to demonstrate the optimal cutoff value of DECT parameters to detect presence of extensive disease of CTD-ILD. The optimal cut-off value was 2.510, 2.775, − 762.30 HU and − 746.50 HU for average Zeff value, Zeff_RL, average MCTN and MCTN_RL, respectively. AUC area under the curve, CI confidence interval, Z_RL Zeff value of right lower lung lobe, MCTN_RL monochromatic CT number of right lower lung lobe. Average Zeff value Zeff value averaged over the whole lung, Average MCTN monochromatic CT number at 70 keV averaged over the whole lung