IVIM-DWI Evaluation The Tumor Microvascular Changes After TACE Treatment In A Rabbit VX2 Tumor Model

Objective:In order to explore the changes of tumor microvessels after transarterial chemoembolization（TACE）in a rabbit VX2 liver tumor model,a non-invasive imaging detection technology based on pathological evaluation was performed.The diagnostic value of weighted imaging（IVIM-DWI）on microcirculation and angiogenesis after TACE.Methods:VX2 liver tumor model was established by ultrasound-guided percutaneous puncture combined with gelatin sponge injection.Ultrasound was performed weekly after modeling,and the tumor formation rate,tumor growth,ectopic implantation rate and mortality were recorded after modeling.After successful modeling,all rabbits were randomly divided into experimental group and control group.Interventional therapy was performed within 2-3 weeks after modeling.The femoral artery approach was adopted,and a microcatheter was placed in the proper hepatic artery under DSA equipment fluoroscopy.The experimental group was treated with 5%glucose injection to dissolve pyrrolidone for injection at a concentration of 2 mg/ml.Bixing was mixed with poppy lipiodol at a ratio of 2:1 to prepare an embolization emulsion,and then the emulsion was slowly injected through a microcatheter for intrahepatic tumor chemoembolization.All rabbits underwent IVIM-DWI examination 2 weeks after operation,and the scanned images were analyzed and processed by the post-processing workstation to obtain the corresponding apparent diffusion coefficient（ADC）,apparent diffusion coefficient（ADC）,pure Diffusion coefficient（D）and pseudo-diffusion coefficient（D*）and perfusion fraction（f）.After the IVIM-DWI examination was completed,blood was collected from the ear artery,and serum samples were collected by centrifugation,and blood biochemical indicators such as aspartate aminotransferase（AST）were detected.All experimental rabbits were sacrificed 4 hours after the above-mentioned examinations,and specimens were taken from the central area of the tumor,the junction area between the tumor and the liver parenchyma,and the area of the liver parenchyma.Pathomorphological changes were evaluated;CD31,CD34,and CD105 immunohistochemical examinations were performed to evaluate tumor microvessel density（MVD）.Statistical analysis The independent samples t test was used to compare the experimental group with the control group,and the pearson correlation test was used for the correlation between the MVD of the tumor junction and the magnetic resonance IVIM DWI parameters ADC,D,D*and f.Results:VX2 liver tumor model was established by ultrasound-guided percutaneous coaxial technology combined with gelatin sponge injection technology.All 20experimental rabbits were successfully modeled,and the modeling success rate was100%.Pathology confirmed that the tumor formation rate was 100%,and the intrahepatic tumors were all located in the extrahepatic lobe.Two of them had extrahepatic implantation,and the ectopic implantation rate was 10%.Eighteen rabbits who met the experimental criteria and were included in the follow-up experiments were randomly divided into the experimental group（n=9）and the control group（n=9）.After surgery,the success rate was 100%,and there was no death or serious complications.The rabbits in the experimental group started to eat actively 3 days after the operation,and the control group resumed eating the day after the operation.Both the experimental group and the control group completed the IVIM-DWI scan 2 weeks after the operation,and the liver parenchyma,tumor and tumor junction area were measured at the same level respectively.The average size of the region of interest（ROI）was 10-30mm ².The signal intensity（SI）of the three parts decreased with the increase of b value.The ADC value(2.340±0.255×10^-3mm²/s)and D value(2.146±0.238×10^-3mm²/s)in the experimental group were higher than those in the control group ADC value:(91.410±0.803×10^-3mm²/s),D value was(1.24±0.124×10^-3mm²/s),the difference was statistically significant（both P<0.001）,the median D*value and f value of the experimental group were 13.580（31.353）×10^-3mm²/s and0.050（0.046）,and the control group were 189.500（207.900）×10^-3mm²/s and0.120（0.119）respectively.It can be seen that the D*and f values of the experimental group were lower than those of the control group.The difference was statistically significant（P=0.001,P=0.004）.The ADC value,D value and D*value in the tumor junction area of the experimental group were 1.565±0.207×10^-3mm²/s and0.951±0.301×10^-3mm²/s,respectively,82.042±69.561×10^-3mm²/s,the control group were 1.805±0.14610^-3mm²/s,1.422±0.264×10^-3mm²/s,181.281±51.650×10^-3mm²/s,it can be seen that the experimental group is significantly lower than the control group,the difference is statistically significant（P value:0.008,0.002,0.002）,the f value of the experimental group（0.345±0.085）is significantly higher than that of the control group（0.173±0.025）increased,the difference was statistically significant（P<0.001）.Compared with the control group,the ADC value,D value,D*and f value in the liver region of the experimental group had no statistical significance（all P>0.05）.The ALT,AST,Cr and BUN of the control group were 47.6±13.29U/L,28.98±10.70U/L,68.94±7.19umol/L and 18.34±2.64mg/d L and the experimental group was110.28±67.10U/L,108.29±53.34U/L,78.95±13.97umol/L and 22.34±6.07mg/d L,it can be seen that the experimental group is higher than the control group,among which ALT and AST have statistical differences between the two groups（both P=0.002）,BUN and Cr was not statistically different between the two groups（P=0.098,P=0.074）.HE staining under light microscope showed a large number of necrotic cells in the tumor area of the experimental group,and extensive edema of hepatocytes around the tumor.CD31,CD34,CD105 immunohistochemical staining was used to mark the distribution of MVD.It can be seen that the MVD in the tumor junction area of the experimental group increased significantly.The corresponding MVD counts were CD31-MVD:62.60±8.18,CD34-MVD:63.50±11.56,CD105-MVD:50.10±13.34,the control group was CD31-MVD:46.60±8.73,CD34-MVD:25.40±6.88,CD105-MVD:21.90±5.99,the experimental group CD31,CD34,CD105 were higher than the control group,the difference was statistically Academic significance（P values are:0.001,<0.001,<0.001）.The MVD counts of CD31,CD34 and CD105 in the tumor border region were correlated with IVIM-DWI parameters ADC,D,D*and f.The results showed that ADC value,D value,D*value and f value were all correlated with MVD.Among them,f value is positively correlated with MVD（in order:r=0.6,P<0.005,r=0.725,P<0.001,r=0.711,P<0.001）,ADC value,D value,D*value are negatively correlated with MVD（ADC value:r=-0.803,P<0.001,r=-0.613,P=0.004,r=-0.665,P=0.001;D value:r=-0.741,P<0.001,r=-0.611,P=0.004,r=-0.665,P=0.003;D*values:r=-0.603,P=0.005,r=-0.619,P=0.004,r=-0.055,P=0.044）.Conclusions:Rabbit liver VX2 tumor treated with TACE can induce increased neovascularization in the junction area between tumor and liver parenchyma.Magnetic resonance IVIM-DWI can be used to evaluate the changes of tumor microvascular after TACE treatment in a rabbit liver VX2 tumor model.