A Comparative Study Of DCE-MRI And Pathology For Evaluation Of Curative Effect After Radiotherapy On Rabbit VX2 Bone Tumor Model

Objective:To compare the changes of DCE-MRI quantitative parameters before and after radiotherapy on rabbit VX2 bone tumor model and to analyze the correlation between DCE-MRI quantitative parameters and MVD and VEGF,and to explore the value of DCE-MRI in reflecting the microvascular changes of tumors and noninvasive evaluation of the curative effect of early radiotherapy.Methods: The rabbit VX2 malignant bone tumor models were divided randomly into experimental group(n=20)and control group(n=20)two weeks later.The experimental group received radiotherapy at a single dose of 10 Gy.DCE-MRI scanning was performed before one day of treatment and after three days of treatment.The control group received DCE-MRI scanning at the same time points without any treatment.The hemodynamic parameters in the solid,transitional and necrotic areas of the tumor were obtained through the hemodynamic two-compartment model: Ktrans,Kep,Ve and Vp.After the second DCE-MRI scanning,the tumor was dissected in order to detect the MVD and VEGF expression levels.The changes of quantitative parameters and correlation between quantitative parameters and MVD and VEGF were statistically analyzed.Results :(1)Comparison of DCE-MRI quantitative parameters before and after radiotherapy in different tumor regions between the experimental group and the control group.In the experimental group,the Ktrans were all lower after radiotherapy than those before in the solid,transitional and necrotic area.The Ktrans was statistically differences before and after radiotherapy in the experimental group(P<0.05).In the control group,the Ktrans were all higher than after radiotherapy than those before in the solid and transitional area,while the Ktrans were all lower than those before radiotherapy in the necrotic area.The Ktrans was also statistically differences before and after radiotherapy in the control group(P<0.05).There were no statistically differences in Kep,Ve and Vp before and after radiotherapy in the experimental group and the control group(P>0.05).(2)The contrast results of MVD and VEGF in the experimental group and the control group after radiotherapy in different tumor regions.The MVD in the solid,transitional and necrotic areas of the tumors in the experimental group were26.47±5.65,18.38±6.99,10.66±4.33 respectively after radiotherapy.The MVD in above areas of the tumors in the control group were 35.82±6.07,27.12±3.73,16.29±7.25 respectively after radiotherapy.The VEGF in the solid,transitional and necrotic areas of the tumors in the experimental group were 4.56±3.46,3.62±2.36,1.99±1.84 respectively after radiotherapy.The VEGF in above areas of the tumors in the control group were6.68±2.82,4.83±1.17,3.19±1.19 respectively after radiotherapy.The difference of MVD and VEGF between the two groups was statistically differences after radiotherapy(P<0.05).(3)The correlation analysis of DCE-MRI quantitative parameters with MVD and VEGF in the experimental group and the control group after radiotherapy.There was a positive correlation between MVD and Ktrans in the solid areas of the experimental group and the control group(r=0.751 and r=0.823,P<0.05),and between VEGF and Ktrans(r=0.701 and r=0.824,P<0.05).There was a positive correlation between MVD and Ktrans in the transitional areas of the experimental group and the control group(r=0.820 and r=0.765,P<0.05),and between VEGF and Ktrans(r=0.823 and r=0.740,P<0.05).There was a positive correlation between MVD and Ktrans in the necrotic areas of the experimental group and the control group(r=0.842 and r=0.717,P<0.05),and between VEGF and Ktrans(r=0.814 and r=0.722,P<0.05).There was no significant linear correlation between MVD and Kep,Ve and Vp in the experimental group and the control group in the three regions(P>0.05).There was also no significant linear correlation between VEGF and Kep,Ve and Vp between the two groups in the three regions(P>0.05).Conclusion : DCE-MRI quantitative parameters Ktrans has a significant positive correlation with MVD and VEGF of VX2 malignant bone tumor,which can reflect the tumor angiogenesis.It can be used to evaluate the efficacy of early radiotherapy for bone tumors,so as to provide a theoretical basis for formulation and adjustment of treatment programs.