3.1 Features Extraction and Selection
Based on single-phase and two-phase CT images, 1409 features were extracted from CMP and NP respectively, and 2818 features from CMP+NP. Firstly, a number of 347, 349 and 699 features were screened from CMP, NP and CMP+NP using variance threshold method, respectively. Then with the SelectKBest method, we selected 28, 20 and 30 features from CMP, NP and CMP+NP, respectively. Finally, 6, 5 and 6 optimal features were identified with LASSO algorithm from CMP, NP and CMP+NP, respectively (Fig. 1 ).