The Value Of Spectral CT In Low-Dose Scanning And Diagnosing Lauren Classification Of Gastric Cancer

Part One The Value of Virtual Unenhanced Imaging in Displaying Gastric Cancer LesionObjective: To explore the value of virtual unenhanced imaging(VUE)derived from spectral CT in displaying gastric cancer lesions.Materials and Methods: Forty-four patients who underwent conventional plain scan and dual-phase enhanced spectral imaging were enrolled and to reconstruct arterial and venous phase virtual plain scan image AP-VUE,PP-VUE,AP-MSI and PP-MSI.Subjective evaluation:Two radiologists independently scored the image quality and lesion displaying clarity of the TUE and virtual plain scan images.The images and lesions scoring reached 3 or higher points could meet the diagnostic requirements.Compare the subjective scores of the five groups.Objective evaluation: Measure the CT values of gastric cancer lesions,gastric cavity water,metastatic lymph nodes,normal liver parenchyma,psoas major muscle,abdominal aorta and SD values of subcutaneous fat of anterior abdominal wall of each group.Calculate the CNR of gastric cancer lesionsagainst the background of gastric cavity water.CTDIvol and DLP of conventional three-phase scanning and dual-phase enhanced spectral scanning were recorded,respectively,and the effective radiation dose ED were calculated.Compare the CT,CNR and SD values among the groups,and compare the radiation dose of dual-phase enhanced spectral imaging and conventional three-phase scanning.Two independent samples t test or rank sum test were used to compare the quantitative data between two groups.One-way ANOVA or K-W test were used to compare the quantitative data among multiple groups,and further comparation were carried out by LSD-t test.Kappa test was used to analyze the consistency between the two observers.Results: The DLP and ED of conventional upper abdominal plain and dual-phase enhanced sanning were(947.36±193.62)m Gy·cm and(14.21±2.90)m Sv,respectively,of which were(633.80±129.69)m Gy·cm and(9.51±1.95)m Sv from dual-phase enhanced spectral imaging.There was significant difference in effective radiation dose between the two scanning schemes(Z=-6.817,P<0.001).The effective radiation dose was reduced by 33.5% in the dual-phase enhanced spectral imaging.There were significant differences in the scores of images and lesions(H=68.846~105.179,all P<0.001),and further comparison showed that in the image score of physician 1,TUE vs PP-VUE(t=0.6076,P=0.544),TUE vs AP-VUE?AP-MSI?PP-MSI(t=4.709~7.748,all P<0.001);in the lesion score,TUE vs AP-VUE?PP-VUE(t=2.420~0.569,P=0.016~0.570),TUE vs AP-MSI?PP-MSI(t=7.258~6.547,all P<0.001).In the image score of physician 2,TUE vs PP-VUE(t=1.396,P=0.164),TUE vs AP-VUE?AP-MSI?PP-MSI(t=4.344~8.067,all P<0.001);in the lesion score,TUE vs AP-VUE?PP-VUE(t=2.850~1.425,P=0.005~0.156),TUE vs AP-MSI?PP-MSI(t=6.697~6.839,all P<0.001).The Kappa values of the two physicians were 0.57~0.86 among these groups,and the consistency was moderate to good.Comparison of objective evaluation showed that there were significant difference between CT values of aorta,liver and SD values of fat(H=33.418,P<0.001;H=10.745,P=0.03;H=14.529,P=0.006,respectively),andfurther comparison showed that in CT values of aorta: TUE vs AP-VUE?PP-VUE?PP-MSI(t=-2.481~-0.521,P=0.014~0.603),TUE vs AP-MSI(t=-3.862,P<0.001);in SD values of fat: TUE vs PP-VUE(t=-3.291,P=0.001),TUE vs AP-VUE?AP-MSI?PP-MSI(t=-1.325~-1.045,P=0.187~0.297).In CT values of liver,there were no significant difference between virtual plain scan images and TUE(t=2.046~-0.829,P=0.042~0.408).Conclusion: Venous phase virtual plain image derived from Revolution CT could provide reliable information for clinical diagnosis as it is very closely to conventional plain scan image both in image quality and CT values of each organ.Part Two The Value of Spectral CT in Diagnosing Lauren Classification of gastric cancerObjective: To explore the differential value of quantitative parameters derived from spectral CT between intestinal and diffuse gastric cancer and the correlation between different Lauren classification of gastric cancer and clinical or pathological factors.Materials and Methods: Fifty patients who underwent conventional plain scan and dual-phase enhanced spectral imaging were enrolled in this study.Iodine concentrations(ICs)of lesions and aortas were measured,and ICs of arterial and venous phase were recorded as AP-IC and PP-IC,respectively.Normalised iodine concentrations(NICs)were calculated by dividing the iodine concentration of lesions by the iodine concentration of abdominal aorta in the same period.The NICs of both phases were expressed as AP-NIC and PP-NIC,respectively.The monochromatic imaging level of 40—140 keV were adjusted and to record the CT values of lesions at different levels.Theslopes of 40-70 keV,70-100 keV and 100-140 keV curves in the both phases were calculated,which were expressed as AP40-70,AP70-100,AP100-140,PP40-70,PP70-100 and PP100-140 respectively,for example AP40-70=(CT value of 40 keV –CT value of 70 keV)/(70-40).Compare the difference of clinicopathological feature between intestinal and diffuse lesions,and to compare the slopes,ICs and NICs between the two classifications.Two independent samples t test or rank sum test were used to compare the quantitative datas,and chi-square test was used to compare the qualitative datas.Then ROC curves of different diagnostic indicators were drawn,and the area under each curve were calculated.Combine the maximum principle of Yoden index with the actual clinical situation,the appropriate differential diagnostic thresholds of each parameter were selected,and the corresponding sensitivity and specificity were obtained.Results: The comparison of each parameter showed that there were significant differences in AP-NIC,PP40-70,PP-IC and PP-NIC(Z=-4.005~-2.266,all P<0.05),there were no significant difference in the others(Z=-1.942~-0.809,P=0.052~0.089);ROC curve was drawn by combining PP-IC and PP-NIC,and AUC value reached 0.858,the sensitivity and specificity were 77.8% and 87.5%,respectively.There were significant differences in differentiation degree,CEA,CA724,smoking and drinking history between the two classifications(?2=4.584~19.100,all P<0.05).Conclusion: AP-IC,PP40-70,PP-IC,PP-NIC were different between intestinal and diffuse gastric cancer,and the combination of PP-IC and PP-NIC reached the greatest diagnostic value;the proportion of smoking and drinking is higher in intestinal gastric cancer patients,the positive rate of CEA and CA724 are higher in diffuse gastric cancer patients,and the degree of differentiation of diffuse gastric cancer is lower.