The Value Of Diffusion Kurtosis Imaging (DKI) In The Study Of Intramedullary Invasion Of Malignant Bone Tumors In Rabbits And The Its Correlation With Pathological Parameters

Objective:To investigate the value of diffusion kurtosis imaging(DKI)in evaluating the margin of intramedullary invasion in malignant bone tumors of rabbit models and its ability in distinguishing the simple edema from microscopic invasion area in the tumor transitional area.The correlation between parameters of DKI and pathology is also studied.Material and Methods:VX2 malignant tumor tissue was implanted in the right upper tibia of 33 male New Zealand white rabbits.After 15 days of growth,routine MRI and DKI were performed.HE staining and immunohistochemistry were performed on the largest sagittal section of the gross tumor specimens.Using pathological findings as the golden standard and combining them with MRI data,strict point-to-point control was performed to delineate regions of interest(ROIs)in the micro-infiltration and simple-edema areas of bone tumors for quantitative measurement of MD value(average diffusion coefficient)and MK value(average kurtosis).The density of tumor cells(CD),micro-vessel density(MVD)and vascular endothelial growth factor(VEGF)in solid and microinvasive areas of bone tumors were counted.MD and MK values between micro-infiltration and simple-edema areas were compared using an independent sample t-test,and the diagnostic values were evaluated by receiver operating characteristic(ROC)curve analysis.Independent sample t-test was also used to analyze the differences of tumor cell density(CD),micro-vessel density(MVD),vascular endothelial growth factor(VEGF)between solid and micro invasive areas.The correlation between DKI parameters and pathological indexes was evaluated by Spearman analysis.The difference was statistically significant when P<0.05.Results:(1)Of the 33 New Zealand rabbits,28 model rabbits were successfully prepared,and 5 died or failed in tumor implantation.Pathological examination showed that the boundary of bone tumor was not clear and there were micro infiltration areas in 25 cases,which were included in the study.(2)There were significant differences in MD and MK values between micro-infiltration area and simple edema area(t=5.630;2.358,P<0.05);In comparison with the simple-edema area,the micro-infiltration area demonstrated significantly smaller MD values and larger MK values(P<0.05),and MD showed a better area under the curve(AUC)than MK(AUC?=?0.884 vs.AUC?=0.690)for distinguishing the micro-infiltration area from the simple-edema area.The sensitivity and specificity of MD value were 84% and 84%,respectively.The sensitivity and specificity of MK value were 52%and 92%,respectively.MD value was more effective than MK value in differential diagnosis.The optimal cut-off MD value was 1108.5mm~2/s.When MD value was more than 1108.5mm~2/s,it could be considered as the simple edema area of VX2 bone tumor.(3)There were significant differences in CD,MVD and VEGF between solid and micro-infiltration areas.A significant negative correlation was found between MD and CD count(r=-0.821、-0.775,P<0.05)and VEGF count(r=-0.814、-0.702,P<0.05),respectively,but no correlation was found between MD and MVD(r=-0.140,P=0.506;r=-0.088,P=0.677)in solid and micro-infiltration areas.There was no statistical correlation between MK value in tumor solid area and microinfiltration area with CD,MVD and VEGF count(r=-0.209,-0.215;-0.259,-0.064;0.364,-0.214,P>0.05).Conclusion:This study shows that MD has a high value in judging the range of malignant bone tumors,especially in the differential diagnosis of microscopic infiltration area and simple edema area.MD value is negatively correlated with CD and VEGF counts in tumor infiltrating area.