The Value Of Multimodal Magnetic Resonance Imaging Based Quantitative Parameters In Differentiating Benign And Malignant Renal Tumors

BackgroundsThe clinical characteristics of renal tumor are not characteristic,and also lack of specific tumor markers.So it is difficult to differentiate between benign and malignant tumor preoperatively.However,the treatment and prognosis are different.There are clinical significance on therapeutic strategy,the reduction of unnecessary nephrectomies,the improvement the survival and living quality,only if accurate diagnosis between benign and malignant diagnosis could be completed before surgery.At present,renal biopsy pathology is the gold standard for preoperative diagnosis of benign and malignant tumors,but it is not only invasive but also causes unnecessary complications.Therefore,the preoperative diagnosis of renal tumors can be completed by imaging examination.MRI is a non-invasive examination with no radiation damage and high soft tissue resolution.In particular,the development and utilization of functional sequences of MRI in recent years has greatly improved the preoperative diagnosis of renal tumors.The sequences of diffusion weighted imaging（DWI）,intravoxel incoherdent motion（IVIM）,diffusion kurtosis imaging（DKI）and dynamic contrasted enhanced magnetic resonance imaging（DCE-MRI）have been used in the differential diagnosis among different subtypes of renal cell carcinoma and grading diagnosis of clear renal cell carcinoma.However,there are few studies focused on the differential diagnosis between benign and malignant renal tumors.In view of this,this study aims to explore the value of the above quantitative parameters in differentiating benign and malignant renal tumors by comparing the differences of DWI,IVIM,DKI and DCE-MRI quantitative parameters,as well as the additional value of combining quantitative parameters to improve the preoperative diagnostic efficiency between benign and malignant renal tumors.ObjectivesTo compare and analyze the quantitative parameters(ADC,D,D^*,F,MD,MK,K^trans,K_ep,V_e)of DWI,IVIM,DKI,DCE-MRI between benign and malignant renal tumors,and evaluate the diagnostic efficacy of each parameter and multiple sequences combination in differentiating benign and malignant renal tumors.MethodsThe MRI data of 104 patients with renal tumors confirmed by surgery and pathology were retrospectively collected.All patients underwent unenhanced and dynamic contrasted enhanced MRI scans 1 week before surgery,including DWI,IVIM,DKI and DCE-MRI sequences.Two readers analysis the tumor size,location,signal intensity,cystic degeneration,hemorrhage,capsule and other conventional MRI features independently with double-blind method.The ADC,D,D^*,f,MD,MK,K^trans,K_ep,V_evalues and other quantitative parameters were measured on ADC and DCE-MRI kinetics maps.The differences of thesesparameters and features between benign and malignant tumors were compared.The diagnostic efficacy of quantitative parameters were evaluated by（ROC）and the area under the curve（AUC）.The differences of AUCs was evaluated by De Long test.Results1.Totally 104 patients was enrolled.According to surgical pathology,19 cases were benign tumors（benign group）and 85 cases were malignant tumors（malignant group）;All the tumors,whether benign or malignant,presented heterogeneous T1WI isosignal/hyposignal signal intensity,heterogeneous T2WI hypersignal intensity,and showed varying degrees of cystic necrosis.The capsule was identified in 85.88%cases,which was found in renal cell carcinoma.There were no significant differences in age,lesion location and size between the two groups.2.Differences in quantitative parameters of multi-modal MRI between the two groups:（1）The average ADC of benign tumor group was 1.78（0.94,2.98）×10^-3mm~2/s,which was higher than that of malignant tumor group 1.04（0.51,2.27）×10^-3mm~2/s,the difference was statistically significant（Z=-5.060,P<0.05）.（2）Comparison of IVIM parameter values:the mean D value of benign tumor group was 0.98（0.32,1.56）×10^-3mm~2/s,which was lower than that of malignant tumor group 1.12（0.65,1.89）×10^-3mm~2/s),and the difference was not statistically significant（Z=-1.545,P>0.05）;The mean D^*of benign tumor group was23.56（11.45,56.20）×10^-3mm~2/s,which was lower than that of malignant group 43.22（0.08,76.84）×10^-3mm~2/s,the difference was statistically significant（Z=-3.571,P<0.05）;The mean f of the benign tumor group was 34.53（22.76,56.33）,higher than that of the malignant group 34.22（21.34,45.33）,and the difference was not statistically significant（Z=-0.200,P>0.05）;（3）Comparison of DKI parameters:the mean MD of benign tumor group was 1.99（1.65,2.45）×10^-3mm~2/s,which was higher than that of malignant tumor group 1.54（0.68,2.72）×10^-3mm~2/s),and the difference was statistically significant（Z=-4.156,P<0.05）;The mean MK of benign tumor group was 0.55（0.33,0.78）,which was lower than that of malignant tumor group 0.65（0.38,1.45）,andthe difference was statistically significant（Z=-3.231,P<0.05）;（4）Comparison of DCE-MRI parameters:the mean K^transof benign tumor group was 0.42（0.10,0.54）min^-1,which was lower than that of malignant group 0.44（0.77,0.98）min^-1,and the difference was statistically significant（Z=-1.903,P<0.05）;The mean K_epof benign tumor group was 0.65（0.13,0.88）min^-1,which was higher than that of malignant tumor group 0.54（0.19,1.76）min^-1,and the difference was not statistically significant（Z=0.632,P>0.05）;The mean V_ein benign tumor group was 0.68（0.09,0.89）,higher than 0.45（0.09,0.99）in malignant tumor group,and the difference was not statistically significant（Z=-1.801,P>0.05）.3.The diagnostic efficacy of quantitative parameters in differentiating benign and malignant tumors:（1）The AUC of ADC in differentiating benign and malignant renal tumors was 0.872,the optimal threshold was 0.045,and the sensitivity and specificity were90.59%and 68.42%,respectively;（2）The AUC of D^*was 0.763,the best threshold was0.055,the sensitivity and specificity were 65.88%and 78.95%,respectively;（3）The AUC of MD in differentiating benign and malignant renal tumors was 0.806,the optimal threshold was 0.042,and the sensitivity and specificity were 72.94%and 94.74%,respectively.The AUC of MK was 0.738,the optimal threshold was 0.063,the sensitivity and specificity were 80.00%and 73.68%,respectively.;（4）The AUC of K^transwas 0.693,the optimal threshold was 0.067,the sensitivity and specificity were 91.76%and 42.11%,respectively;（5）Combined sequence diagnostic efficiency results:The AUC of DKI combined with DCE-MRI was 0.936,the sensitivity and specificity were 82.35%and 94.74%,respectively.The AUC of DKI combined with IVIM was 0.941,and the sensitivity and specificity were 84.71%and 94.47%,respectively.（6）the AUC of combining D^*and DKI for the discrimination between benign and malignant tumors was statistically higher than that of D^*、Ktrans MD、MK（Z=3.420,4.753,3.372,3.730,all P<0.001）;the AUC of combining K^transand DKI for the discrimination between benign and malignant tumors was statistically higher than that of D^*、K^transMD、MK（Z=2.603,4.629,3.616,2.904,all P<0.01）,but there is no significant differences of AUC between D^*+DKIand K^trans+DKI（Z=0.171,P=0.864）.ConclusionsThe quantitative parameters of MRI functional sequence are helpful for differentiating benign and malignant renal tumors.ADC has the highest efficacy for tumors with more solid components.D^*has the best efficacy in IVIM sequence.MD and MK have good stability.K^transhas high specificity but with a low sensitivity.However,each functional sequence still has its limitations,so the combination of multiple sequences would further improve its differential ability,and DKI combined with IVIM is superior to DKI combined with DCE because IVIM can be acquired without the need for exogenous contrast agents.In conclusionmultimodal MRI can provide a new diagnostic mode and quantitative tool for higher efficacy of preoperative diagnosis of benign and malignant renal tumors.