The Application Of Spectral CT Imaging In The Diagnosis Of Gastric Cancer And The Evaluation Of Lymphovascular Invasion

Objective:To explore the application value of spectral computed tomography(CT)imaging in the diagnosis of gastric cancer and the evaluation of lymphovascular invasion(LVI)in gastric cancer,and investigate the correlation between clinicopathological features and LVI in patients in this study.Material and Methods:Sixty patients who were clinically diagnosed as primary gastric cancer and confirmed by surgery and pathology from August 2018 to November 2019 in our hospital were enrolled in this single-institution study.Among them,35 were male patients and 25 were female patients,the age was 21-78 years old,median age was 57 years.They were undergone plain scan,arterial phase,portal venous phase and venous phase enhanced scan by GE Revolution CT in gemstone spectral imaging(GSI)mode within one week before surgery.All the images of patients were measured and analyzed by GSI analysis software on the workstation of GE ADW4.7.The lesion outline on the largest cross-section was measured as region of interest(ROI)by hand,the normal gastric wall tissue and the same layer abdominal aorta were measured by circular ROI in the axial CT images.The iodine concentrations in the arterial phase,portal venous phase and venous phase(ICAP,ICPVP,ICVP)of all the ROIs were obtained automatically in the iodine images.The normalized iodine concentration(nIC)was calculated as the ratio of the target IC to the abdominal aorta IC.The slope values of the 40-70keV spectral curve of the lesion and the normal gastric wall was calculated by the spectral curve.According to the postoperative pathological results,the patients were divided into two groups:LVI positive group and LVI negative group.At the same time,the clinicopathological characteristics of patients were recorded:gender,age,location,Lauren classification,differentiation,T staging,lymph node metastasis(LNM).T-test and Mann-Whitney U test were used to evaluate whether there were statistical differences in spectral CT parameters between the gastric cancer lesions and the normal gastric wall tissues,LVI group and non-LVI group,and ROC curve and AUC were used to compare the diagnostic efficacy of parameters with statistical differences,then selected the cut-off value to calculate its sensitivity and specificity.The correlation between clinicopathological features and LVI was performed by spearman correlation.Results:1.60 patients with gastric cancer were confirmed by the surgical pathology examination,and 19patients with LVI while 41 patients without LVI.There were 13 cases located in cardia and fundus,151ocated in body area,32 located in antral pyloric area.The number of patients with diffuse type,intestinal type and mixed type was 43,14 and 13 cases,respectively.There were 13 cancers of well and moderately differentiated,47 cancers of poorly differentiated;4 cancers with T1 staging,5 cancers with T2 staging,32 cancers with T3 staging,and 19 cancers with T4a staging;44 cases with LNM and 16cases without LNM.2.The IC,nIC and the slope values of arterial phase,portal venous phase and venous phase were all higher in the gastric cancer lesion compared with normal gastric wall tissue,and the differences were statistically significant(all P=0.001);the AUC value for ICVP was the highest(AUC=0.868,P=0.000),it diagnose the sensitivity and specificity of 75.0%and 88.3%,respectively.3.ICPVP,slope-PVP,ICVP,nICVP and slope-VP in the LVI positive group were all higher compared with the negative LVI group,and the differences were statistically significant(P=0.001-0.021);the AUC value for slope-PVP was highest(AUC=0.723,P=0.006),it predicted the LVI with a sensitivity and specificity of 73.7%and 63.4%,respectively.4.Among the clinical parameters,only tumor differentiation was associated with LVI in gastric cancer.Conclusion:1.Spectral CT imaging parameters(IC,nIC and slope of spectral curve)in AP、PVP and VP are helpful for the diagnosis of gastric cancer,especially the IC in venous phase.2.The parameters(ICPVP,slope-PVP,ICVP,nICVP and slope-VP)derived from spectral CT imaging provides a noninvasive method to assess LVI,especially the slope of 40 keV-70keV spectral curve in portal venous phase.3.Tumor differentiation was associated with LVI in gastric cancer.