Evaluation Of Early Microcirculation Function Of Residual Tumor After Radiofrequency Ablation In Rabbit Liver VX2 Tumor By Dual-detector Based Spectrum CT And MR Functional Imaging

Objective:1.Establish residual tumor model of rabbit liver VX2 tumor after radiofrequency ablation,apply dual-detector based spectrum CT perfusion imaging and iodine quantitative to evaluate the early microcirculation status after radiofrequency ablation of residual tumor model,and evaluate the correlation between CT perfusion parameter values and iodine quantitative value,and the correlation of CT perfusion parameter with microvascular density.2.Apply IVIM-DWI and DCE-MRI function imaging parameters to evaluate early microcirculation status of residual tumor after radiofrequency ablation in rabbit liver VX2 tumor,analyze the correlation between IVIM-DWI and DCE-MRI,and correlation between the various parameters and MVD.3.Analyze the correlation of iodine quantitative,IVIM-DWI,classical CT perfusion and MR perfusion DCE-MRI in residual tumor after radiofrequency ablation in rabbit liver VX2.Methods:1.Establish rabbit liver VX2 tumor model and the model of residual tumor after radiofrequency ablation.New Zealand white rabbit liver VX2 tumor model were prepared using ultrasound-guided percutaneously implanted vx2 tumor masses.To make residual tumor model,the test group undergo ultrasound-guided radiofrequency ablation in 2 to 3 weeks after modeling,and the ablation range is about 2/3 of the maximum diameter of the lesion.While the control group only were underwent liver VX2 tumor implantation.2.Study of energy spectrum CT functional imaging of residual cancer of rabbit liver VX2 tumor after radiofrequency ablation.Iodine quantitative accuracy phantom test:In the part of spectral CT functional imaging,to choose the most suitable scanning conditions,we measure and evaluate the accuracy of iodine quantification using different radiation dose levels?CTDIvol?and different iterative recombination levels with an iodine phantom?Gammex RMI 472phantom?.The iodine quantitative phantom built-in insert using 7 different iodine concentrations?2.0,2.5,5.0,7.5,10.0,15.0,20.0 mg/mL?,repeatedly scanning 5 times at CTDIvol of 25,20,15,10,5 mGy with 120 kVp,140 kVp tube voltage.When tube voltage was 120 kVp,the tube current designated to be 142,163,122,82,and 41 mAs.When tube voltage was 120 kVp,the tube current designated to be 204,114,85,57,and29 mAs.The raw data were reconstructed as spectral-based images?SBI?by spectral iterative algorithms?spectral level 0,2,4,6?.The images were measured separately at three consecutive slices,take the mean.Record the iodine density values for each dose group and calculate the iodine quantitative standardized error values.Assessment of CT perfusion and iodine quantification:all the experimental animals,that meet the criteria of residual cancer model,underwent dynamic perfusion scanning using energy spectrum CT at before and after 1 week of radiofrequency ablation.The control animals were examined in the same way at 2 weeks and 3 weeks after VX2 tumor implantation in the liver.Use Function CT software to get liver perfusion parameters blood flow?BF?,peak enhancement intensity?PEI?,time to peak?TTP?,blood volume?BV?,hepatic artery perfusion?HAP?,hepatic portal perfusion?HPP?,total perfusion?TP?,hepatic perfusion index?HPI?.Restructure CT perfusion scan raw data into SBI images,get perfusion scanning SBI images of all phases,and generate iodine density images,measure respectively hepatic arterial and portal iodine density values?ICa,ICp?,calculate standardized iodine density values?iodine concentration in the region of interest/isotopic concentration of abdominal aorta in the same layer,NICa,NICp?and hepatic arterial enhancement index?AIF=ICa/ICp?.Data were measured by two abdominal radiologists.Two doctors read jointly all the images and determine the ROI selected location combined with gross pathology and HE staining,then measure separately CT perfusion parameters and iodine density values of residual tumor area,necrosis area,normal liver tissue and control group VX2 tumor.3.Study of MR functional imaging of early residual cancer after radiofrequency ablation of rabbit liver VX2 tumor.MR scans of all experimental animals were performed on the same day and more than 4 hours apart.MR scan use 3.0 T MR first conventional T1WI and T2WI imaging,then undergo IVIM-DWI and DCE-MRI imaging.IVIM-DWI select 7 b values?0,20,50,100,200,500,1000 s/mm2?,data use IVIM V3.2 software?provided by Philips company?to perform two-stage fitting linear calculation to get D value,D*value and f value.To DCE-MRI,after T1 mapping acquisition,we perform 90 dynamic acquisitions?the first two were baseline?after contrast injection?Gadopentetate dimeglumine,0.2 mmol/kg?.Measure parameters using MR Permeability software,get Ktrans,Kep,Ve,Vp maps and quantitative values respectively.ROI is sketched at the maximum level or two continuous adjacent maximum levels of tumor lesions,which is consistent with the position on the CT image.Two groups of experimental animals were euthanized after completing all the experiments,liver VX2 tumor tissue and surrounding normal liver tissue were anatomized acquisition.Select the largest level of tumor and cut open the tumor in the same direction as CT scan axis,undergo HE staining and immunohistochemistry CD34staining,count microvascular density?MVD?at 400x field of view.Use ICC to conduct consistency check of liver CT perfusion,iodine quantitative value,IVIM-DWI parameters and DCE-MRI parameters obtained by two measurers.Comparison within groups use Wilcoxon rank sum test.Comparison between groups use Kruskal-Wallis rank sum test.Spearman correlation analysis was performed for the correlation among CT perfusion,iodine quantitative value,IVIM-DWI parameters and DCE-MRI parameters,also the correlation with microvascular density.Result:1.Experimental results of iodine quantitative phantom.At CTDl_vol levels of 25,20,15,10 mGy,radiation doses had no effects on the accuracy of iodine quantitation;at CTDl_vol level of 5 mGy,the accuracy of iodine quantification was the lowest,with the mean APB of 4.33%?P<0.05?.There was no significant difference in the accuracy of iodine quantitation between 120 and 140 kVp?3.42%vs.3.01%,P=0.648?.IR levels did not affect the accuracy of iodine quantification?P=0.998?.2.Pathology result.29 experimental animals and 15 control animals meet the experimental inclusion criteria,undergo data analysis.HE staining:experimental group arranged outward from the focus of the lesions were followed by coagulation necrosis area,some small focal residual tumor cells can be seen;junction area of necrosis area and residual tumor area,where necrosis and residual cancer coexist,infiltrated inflammatory cell and little hyperplastic fibrous tissue can be seen;residual tumor area,a large number of tumor cells can be seen,which has clear boundary with the normal liver parenchyma;normal liver parenchyma area.CD34 staining:the VX2 tumor nucleus is dark blue,the CD34 specific staining is mainly expressed in vascular endothelial cells of rabbit liver VX2 tumor lesion,which is brown or tan,mainly focus on the residual area of cancer,uneven distribution and more messy,performed uneven lumen or cluster distribution,while center necrosis area of tumor almost no expression.The rabbit liver VX2 tumors in control group were grayish fishlike,have clear boundary with dark red normal liver tissue,no envelope,focal fluid necrosis at tumor lesion can be seen.At HE staining,the tumor nuclear is large,deep stained,arranged disorderly.3.Evaluation result of spectral CT functional imaging.Two measuring evaluators measure separately CT perfusion each parameters iodine density value of two groups of experimental animals before and after surgery,after intraclass correlation coefficient,two evaluators have good consistency to the measure result of CT perfusion parameters.Comparison of CT perfusion parameters:in necrosis area,the perfusion parameters of one week after radiofrequency ablation of rabbit liver VX2 tumor,except TPP,were obviously reduced than those of pre-operation,the difference was statistically significant?P<0.01?.In residual tumor area,the perfusion parameters compared with preoperative,except TPP and HPP,the difference was statistically significant?P<0.01?.The BF,BV and PEI of the residual tumor area were higher than the control group,the difference was statistically significant?P<0.01?.The perfusion parameters in necrosis area compared with those in residual tumor area,the difference was statistically significant?P<0.01?.Comparison of iodine density quantitative values:in necrosis area,the ICa,ICp,NICa,NICp value of one week after radiofrequency ablation of rabbit liver VX2 tumor is obviously reduced than those of pre-operation,the difference was statistically significant?P<0.01?.In residual tumor area,the perfusion parameters have no obvious change compared to those of pre-operation.The parameters of the necrosis area,except AIF,were lower than those of the residual cancer area,the parameters of the necrosis area were lower than those of normal liver area and control group,the difference was statistically significant?P<0.01?.Undergo Spearman correlation analysis of CT perfusion parameters and iodine density values with MVD in residual tumor area.Among them,CT perfusion parameter values BF?r_s=0.664,P<0.001?,HAP?r_s=0.575,P<0.001?,HPI?r_s=0.751,P<0.001?have correlation with MVD,BV?r_s=0.428,P<0.001?and TP?r_s=0.508,P<0.001?have correlation with MVD,NICa value?r_s=0.634,P<0.001?and AIF value?r_s=0.702,P<0.001?have correlation with MVD.Undergo Spearman correlation analysis of CT perfusion parameters with iodine density values in residual tumor area.Among them,CT perfusion parameters HAP have correlation with ICa and NICa?r_s=0.723,P<0.001;r_s=0.556,P<0.001?,AIF have correlation with HPI?r_s=0.818,P<0.001?.4.Evaluation result of MR functional imaging.Two measuring evaluators measure separately IVIM-DWI and DCE-MRI parameters of two groups of experimental animals before and after surgery,after intra-class correlation coefficient,two evaluators have good consistency to the MR functional imaging parameters measurement results.Comparison of IVIM-DWI:the f value of 1 week after radiofrequency ablation of rabbit liver VX2 tumor is higher than those of pre-operation,the difference was statistically significant?P=0.023?.In necrosis area,the D value is higher than those of pre-operation,while D*value and f value is decreased,the difference was statistically significant?P<0.001?.In residual tumor area,the D value is lower than that of necrosis area,while f value is higher than that of necrosis area,the difference was statistically significant?P=0.030,0.007?.Comparison of DCE-MRI:the Ktrans values of 1 week after radiofrequency ablation of rabbit liver VX2 tumor in residual area is higher than that of pre-operation,the difference was statistically significant?P<0.001?;the Ktrans,Kep,Ve,Vp value in necrosis area were decreased compared with those of pre-operation,the difference was statistically significant?P<0.001?;the Ktrans,Kep,Ve,Vp value in necrosis area were lower than those in residual tumor area,the difference was statistically significant?P<0.001?;the Ktrans,Kep in residual tumor area were higher than those of control group,the difference was statistically significant?P<0.05?;in residual tumor area,the indicators compared with those of normal liver,except Ktrans,the difference was statistically significant?P<0.001?.Undergo Spearman correlation analysis of IVIM-DWI parameters and DCE-MRI parameters in residual tumor area with MVD.Among them,the correlation coefficient of IVIM-DWI parameters value D,D*,f with MVD is respectively r_s=0.105?P=0.589?,-0.046?P=0.813?,0.481?P=0.008?;the correlation coefficient of DCE-MRI parameters value Ktrans,Kep,Ve,Vp with MVD is respectively r_s=0.718?P<0.001?,0.148?P=0.443?,0.325?P=0.086?,0.021?P=0.915?.Undergo Spearman correlation analysis of IVIM-DWI parameters and DCE-MRI parameters in residual tumor area.The results show that there were no correlation among parameters,except that Ktrans value and f value have general correlation?r_s=0.445,P=0.016?.5.The correlation among iodine quantitative parameters,IVIM-DWI,classic CT perfusion and DCE-MRI.Undergo correlation analysis among iodine quantitative parameters ICa,NICa,AIF and CT perfusion parameters BF,BV,HAP,HPI and classic DCE-MRI parameters Ktrans,Kep,Ve.There is correlation between ICa,NICa and HAP?r_s=0.723,P<0.001;r_s=0.556,P=0.002?and correlation between AIF and HPI?r_s=0.818,P<0.001?.Undergo correlation analysis among IVIM-DWI parameters D value,D*value,f value and classic CT perfusion parameters and DCE-MRI parameters.There is correlation between Ktrans value and f value?r_s=0.445,P=0.016?.Conclusion:1.At the condition of 120 kVp and 140 kVp,CTDIvol dose level below 5mGy affects the accuracy of iodine quantitation,iterative reconstruction have no significant effect on the accuracy of iodine quantitation.When doing quantitative analysis,moderate radiation dose level and iterative reconstruction level can be taken.2.The energy spectrum CT based on double-layer detector can simultaneously obtain quantitative data of CT perfusion and energy spectrum imaging through one-stop scanning.CT perfusion parameters and iodine quantitative parameters were contributed to the assessment of microcirculation status of residual cancer in the early stage after radiofrequency ablation.Among them,there have good correlation between perfusion parameters BF,HAP,HPI and iodine quantitative parameters NICa value,AIF,MVD,which is a good indicator to evaluate the microcirculation status of the new blood vessels in residual cancer.AIF has strong correlation with HPI and can be obtained from spectroscopic imaging at conventional radiation doses,which is expected to become a new parameter for assessing the hemodynamics of residual tumor.3.To some extent,IVIM-DWI and DCE-MRI can reflect the microcirculatory status of residual tumor after radiofrequency ablation.Among them,f value of IVIM-DWI and Ktrans value of DCE-MRI are better indicators that reflect the changes of microcirculation of residual tumor.4.Compared with classic CT perfusion and DCE-MRI imaging,IVIM-DWI without the need for contrast media and energy spectrum CT iodine quantitative imaging with low radiation dose all have certain application prospects in assessing microcirculation status of residual tumor after radiofrequency ablation.