| Objective:To analyze the difference of the tumor volume,the radiological findings of diffusion weighted imaging(DWI)and proton magnetic resonance(~1H-MRS)of rabbit VX2 transplanted tumor in radiation group and control group at different observed day.And to analyze the role of DWI and~1H-MRS examnations in evaluating the sensitivity of early radiotherapeutic effects by comparing the features of DWI and ~~1H-MRS with pathological changes in VX2 transplanted tumor.Methods:Sixty New Zealand white rabbits were implanted XV2 tumor in unilateral thigh muscle to establish the experimental models.2 weeks later,the rabbits were randomly divided into10 groups according to the radiation group and control group and the observed day.There were group A0、A1、A3、A5、A7、B0、B1、B3、B5 and group B7(A accepted radiation,B received no treatment,0、1、3、5 and 7 represent the observed day).There were 6 rabbits in every group.Group A0 and group B0 were performed MR scans 1day before radiation on a SIEMENS 3.0T scanner.The rest groups were performed MR scans 1day、3days、5days and 7days after radiation.MR scans including T1 WI,T2WI,DWI and~1H-MRS.The tumor volume was calculated on T2 WI.3 continuous regions of interest(ROI)were positioned on the tumor parenchyma to get the average ADC values.The Cho/Cr ratios and the Lip/Cr ratios were get from ~~1H-MRS.The rabbits were executed soon after the scans for immunohistochemical examinations.The tumor volume,the ADC values,the Cho/Cr ratios and the Lip/Cr ratios of rabbit VX2 transplanted tumor in radiation group and control group at different observed day were analyzed using a factorial designstatistical method.The correlation between radiological features and pathological changes were analysed with pearson or spearman statistical method.All data were analyzed with SPSS 21.0 software package.Results:1.There was no significant difference in tumor volume in radiation group [(2.05±0.09)cm~3 ] and control group[(2.02±0.07)cm~3 ] before radiation.The tumor volume in radiation group increased 1day after radiation(P<0.05).In day 3 、day 5 and day 7 tumor volume was statistically smaller than the volume in day 1(P<0.05).Tumor volume in control group increased gradually(P<0.05).Tumor volume in control group was larger than radiation group at the same observed day after radiation(P<0.05).2.The VX2 tumor was obviously hyperintense in DWI and hypointense in ADC maps comparing with surrounding normal muscle.ADC values in radiation group[(0.80±0.01)×10~﹣3mm~2/s ] and control group [(0.80±0.02)×10~﹣3mm~2/s ]were not statistically different before radiation.After radiation,ADC values in radiation group increased gradully(P<0.05).ADC values in control group showed no significant changes at different observed day(P>0.05).The ADC values in radiation group were statistically greater than control group at the same observed day after radiation.3.There were mainly Cho peak、Lip peak and Cr peak in ~1H-MRS and Cho peak was the first peak.Cho peak tended to descende and the Lip peak tended to climbe in radiation group after radiation.There were no statistically difference in Cho/Cr ratios(1.76±0.07,1.77±0.09)and Lip/Cr ratios(1.20±0.08,1.21±0.06)of the tumor between control group and radiation group before radiation.There were statistically changes of Cho/Cr ratios in radiation group.There were no statistically difference of Cho/Cr ratios in control group.Cho/Cr ratios in radiation group were statistically higher than control groups at the same observed day after radiation.Lip/Cr ratios in radiation group gradually increased after radiation(P<0.05).The Lip/Cr ratios in radiation group were larger than control group after radiation(P<0.05).The Lip/Cr ratios in control group were not statistically different before and after radiation.4.The expression of the bax gene in radiation group tended to increase gradually.5.There were some correlations between the tumor volume and the ADC values、Cho/Cr ratios and Lip/Cr ratios(r=﹣0.516、P<0.001,r=0.558、P<0.001,r=﹣0.692、P<0.001,respectively).There were obviously negative correlations between ADC values and Cho/Cr ratios(r=﹣0.918,P<0.001).The Lip/Cr ratios increased as the ADC values increased(r=0.968,P<0.001).There were also correlations between the expression of bax gene and the ADC values、Cho/Cr ratios and Lip/Cr ratios(r=0.900、P<0.001,r=﹣0.816、P<0.001,r=0.798、 P<0.001,respectively).Conclusions:1.DWI and~1H-MRS could detect the internal structure changes of tumor early after radiation in the level of molecule and biochemistry.2.There were some correlations between the tumor volume and the ADC values、Cho/Cr ratios and Lip/Cr ratios early after radiation,DWI and ~~1H-MRS may be somewhat valuable in predicting early radiotherapeutic sensitivity.3.There were correlations between the expression of bax gene and the ADC values、Cho/Cr ratios and Lip/Cr ratios,cell apotosis might be one of the mechnisms for ADC values、Cho/Cr ratios and Lip/Cr ratios changes. |
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