Clinical Study Of Dual-energy CT Parameters In Predicting Regional Lymph Node Metastasis Of Colorectal Cancer

Objective: To evaluate the value of dual energy CT multi-parameter in predicting regional lymph node metastasis of colorectal cancer before operation.Materials and methods:A total of 63 patients with colorectal adenocarcinoma diagnosed pathologically in the Affiliated Hospital of Inner Mongolia Medical University from October2019 to October 2021 were collected.Three-phase contrast-enhanced CT scan was performed one week before operation.According to the postoperative pathological results,the patients were divided into two groups: lymph node metastasis positive group(n = 35)and negative group(n = 28).We compare the clinicopathological features,routine CT information and dual-energy CT parameters between two groups.Clinicopathological features include gender,age,longest diameter of tumor,tumor location,gross type,T stage,degree of differentiation,vascular invasion and preoperative CEA.Conventional CT parameters include virtual plain CT value(VNC),arterial CT value(CT-A),venous CT value(CT-B),delayed CT value(CT-D),arterial enhanced CT value(ΔCT-A),venous enhanced CT value(ΔCT-B),delayed enhanced CT value(ΔCT-D).Dual-energy CT parameters include iodine concentration value(IC),standardized iodine concentration(NIC),effective atomic number(Z),standardized effective atomic number(N-Z),electron density(Rho),standardized electron density(N-Rho),double energy index(DEI),standardized double energy index(N-DEI)and energy spectrum curve slope(λ).SPSS statistical analysis software(version 22.0)was used to analyze the data,and the clinicopathological features,conventional CT parameters and dual-energy CT parameters were compared between the two groups.The continuous numerical variables that obey normal distribution are expressed by mean ±standard deviation and compared by independent sample t-test,while those that do not obey normal distribution are expressed by median(upper quartile,lower quartile).Independent sample nonparametric test was used for comparison.The counting data were expressed by natural number and percentage,and compared by chi-square test.The variables with statistical differences selected by univariate analysis were analyzed by multivariate analysis.The independent predictors of regional lymph node metastasis of colorectal cancer were screened by Logistic regression,and the joint predictors were constructed.The diagnostic efficiency of independent predictors and combined predictors was evaluated by ROC curve.Results: 1.The lymph node metastasis rate was 65.1% in T3-4 group and 35.0% in T1-2group,and there was significant difference between the two groups(P < 0.05).The gender,age,longest tumor diameter,tumor location,gross type,differentiation degree,vascular invasion and CEA of the patients had no statistical difference between the two groups(P≥0.05).2.Among the parameters of conventional CT,the CT-D in N0 group was 63.6 ±6.1Hu,and that in N+ group was 69.3 ±6.3HU,there was significant difference between the two groups(P < 0.05).There was no significant difference in VNC,CT-A,CT-B,Δ CT-A,Δ CT-B,Δ CT-D between the two groups(P≥0.05).3.Among the dual-energy CT parameters,in N0 group and N+ group,the venous NIC is 0.41 ±0.08,0.47 ±0.14,the delayed NIC is 0.52±0.08,0.60 ±0.11,the venous N-DEI is 0.42 ±0.07,0.49 ±0.16,and the delayed N-DEI is 0.52±0.08,0.61 ±0.12,there are significant differences between the two groups(P < 0.05).However,IC,DEI,Rho,N-Rho,Z,N-Z and λ in venous phase and delayed phase had no statistical difference between the two groups(P≥0.05).The arterial IC,NIC,Rho,N-Rho,Z value,N-Z,DEI,N-DEI and λ had no statistical difference between the two groups(P≥0.05).4.Multivariate analysis showed that delayed NIC and delayed CT values were independent influencing factors of CRC lymph node metastasis.The joint prediction factor L=50.57 delayed NIC+ CT-D.5.The ROC curve shows that the AUC of NIC in delayed period was0.735,with 0.570 as the cut-off value,the sensitivity and specificity is 65.7% and 78.6%,respectively.The AUC of CT-D is 0.751,with 63.0 HU as the cut-off value,the sensitivity is94.3% and the specificity is 50.0%.The AUC of joint predictor L is 0.819,with a cut-off value of 92.428,the sensitivity is 88.6% and the specificity is 60.7%.Conclusion: There were significant differences in tumor T stage,venous NIC,venous N-DEI,delayed NIC,delayed N-DEI and CT-D between positive and negative lymph node metastasis groups.Delayed NIC and CT-D were independent influencing factors of CRC regional lymph node metastasis.The delayed NIC,CT-D and the combined predictor L have certain predictive value in judging whether regional lymph nodes metastasize or not,it provides more valuable information for individualized therapy.