An Experimental Study Of Spectral CT Quantitative Assessment Of C6 Glioma Radiotherapy Combined With Dexamethasone

Objective The quantitative parameters of Spectral CT to evaluate the C6 glioma radiotherapy combined with dexamethasone on tumor solid proliferation inhibition and tumor immune microenvironment.Methods and materials 100 male Wister rats were implanted with C6 glioma cells in the right basal ganglia region,and the Spectral CT enhanced scan on the 14(T0 time point),20(T6 time point),and 26(T12 time point)days after the inoculation.At T0 time point,98 rats were determined to have tumors.The 24tumor-bearing rats were randomly divided into four groups for survival observation.74 rats were randomly divided into four groups,namely the control group(group A),the dexamethasone treatment group(group B),the radiotherapy group(group C),and the radiotherapy combined with dexamethasone group(group D).Six tumor-bearing mice in each group were randomly sacrificed at T0,T6,and T12 time points for brain tissue water content determination(3 mice)and brain tissue pathological analysis(3mice).Group A received a single sham irradiation on the first day after tumor formation(ie: T1 time point)and intravenous injection of normal saline(5mg/kg/12days)every day.Groups C and D received a single 8Gy stereotactic radiotherapy at T1 time point.Groups B and D received an intravenous injection of dexamethasone(5mg/kg/12 days)every day at T1 time point.The Spectral CT image is processed to calculate the spectral quantitative parameters of the tumor solid area(L1),the tumor peritumoral area(L2)and the tumor solid mirror brain tissue area(L3)at different time points,including 40Kev~70Kev single energy CT value,iodine concentration value(IC),water concentration value(WC),energy spectrum curve slope(λ).Count brain tissue water content,VEGF,Ki-67,CD11 b Immunohistochemical staining positive cell counts,and then statistically analyze the correlation between spectral parameters in different regions and brain tissue water content,VEGF,Ki-67,CD11 b positive cell counts.Results 1.Four groups of tumor-bearing mice tumor solid area(L1)iodine concentration(IC)[IC value at T6 A: B: C: D group =(7.63 ± 1.05):(6.35 ± 1.53):(3.47 ± 0.34)):(3.06±0.47)100ug/cm3,IC value at T12 A: B: C: D group =(7.48±1.12):(6.15±1.91):(1.55±0.19):(2.19±0.90)100ug/cm3] is statistically different(p<0.05).The four groups of tumor-bearing mice L1 area IC value and VEGF,Ki-67 proliferation index have a strong positive correlation(r>0.69,p<0.05).Among them,the IC value of group D had the strongest correlation with VEGF and Ki-67 proliferation index(r>0.89,p≤0.001).2.Four groups of tumor-bearing mice tumor solid area(L1)spectral curve slope(（？）)[T6 time point（？） value group A: B: C: D =(-1.43 ± 0.24):(-1.21 ± 0.23):(-0.63±0.08):(-0.55±0.08),T12 time point （？） Value Group A: B: C: D =(-1.36±0.13):(-1.15±0.34):(-0.31±0.11):(-0.4±0.22)] is statistically significant(p<0.05).A,C,D tumor-bearing mice L1 （？） value has a strong negative correlation with VEGF and Ki-67 proliferation index(r>-0.67,p<0.05).3.The water concentration value(WC)of group B,group C,group D and group A in the peritumoral area(L2)[WC value at time T6 Group B: C: D: A =(1047.82±5.67):(1069.74±6.79):(1057.78±4.61):(1057.74±5.23)mg/cm3,WC value at T12 time point Group B: C: D: A =(1048.74±8.68):(1078.41±3.31):(1055.74±8.27):(1065.92± 3.22)mg/cm3] has statistical difference(p<0.05).The WC value in the peritumoral area of the tumor-bearing mice in groups A,B,and C has a good positive correlation with CD11b(r>0.71,p<0.05),and the WC value in the L2 of group C has the strongest positive correlation with CD11b(r =0.93,p<0.001).Group A(r=0.81,p<0.01)and Group C(r=0.90,p<0.01)had a strong positive correlation between the WC value in the L2 and the water content of brain tissue.Conclusion 1.The iodine concentration value and the slope of the spectral curve in the solid tumor area have a strong correlation with the tumor VEGF and Ki-67 proliferation index.It is inferred that the Spectral CT can also non-invasively reflect the state of C6 glioma microvessels and tumor cell proliferation.2.There is a strong correlation between the water concentration value of C6 glioma and CD11 b.It is inferred that the water concentration value of the Spectral CT quantitative parameter can reflect the changes of the tumor immune microenvironment after radiotherapy combined with dexamethasone in C6 glioma to a certain extent.3.The Spectral CT quantitative parameters iodine concentration value,water concentration value,and the slope of the spectral curve are expected to realize the dynamic monitoring of the tumor microscopic information under different intervention measures for C6 glioma.It provides a new exploration method for animal experiments and clinical research of glioma.