Applicational Research Of IVIM-DWI In Preoperative Predicting Simplified Pathological Classification Of Thymic Epithelial Tumors

Part 1 The value of conventional MRI in preoperative predicting simplified pathological classification of thymic epithelial tumorsPurpose To investigate the value of the conventional magnetic resonance imaging in the diagnosis of the TETs.Materials and Methods Seventy-seven patients with TETs confirmed by pathological analysis underwent a conventional magnetic resonance imaging,which included the T1WI,T2 WI,STIR sequences in axial,as well as T2 WI in coronal and sagittal.To investigate the conventional MRI features of TETs,including growth pattern,size,contour,homogeneity of intensity and the invasion of the adjacent structure.The conventional MRI features were compared for differences among low-risk thymomas(LRT),high-risk thymomas(HRT)and thymic carcinomas(TC)based on one-way ANOVA and independent sample t test,respectively.Results Conventional MRI features,including the growth pattern,the maximum diameter,homogeneity,invasion to the adjacent structures,have significant difference among the three groups(LRT,HRT and TC)(P<0.001).Unilateral growth pattern was common to see in LRT,while the bilateral growth pattern was more often to see in HRT and TC.The LRT was usually small than 6cm(56.5%),while the maximum diameter larger than 6cm was suggested the diagnosis of HRT(87.1%)or TC(91.3%).Most of the LRT were homogeneous,or there was the foci high intensity in the T2WI(73.9%);while it was usually to see heterogeneous in HRT or TC.It was rare to see the invasion of adjacent structures in LRT(8.7%),while 32.3% of the HRT and all of the TC invaded the adjacent structures.There were no significant differences in tumor mean diameter and shape among different subtypes of TETs(P = 0.056 and 0.742,respectively).Conclusion Conventional magnetic resonance imaging has a potential value in preoperative predicting the pathological classification of World Health Organization(WHO)in thymic epithelial tumors.Part 2 Application of IVIM-DWI in preoperative prediction of simplified pathological classification in thymic epithelial tumorsPurpose To evaluate the performance of intravoxel incoherent motion(IVIM)parameters in the preoperative predicting of the pathological classifications and Masaoka stages of TETs;Materials and Methods Seventy-seven patients with TETs confirmed by pathological analysis underwent a diffusion weighted(DW)magnetic resonance(MR)imaging sequence with 9 b values before any treatment.The conventional MRI features and IVIM parameters(slow diffusion coefficient(D),fast perfusion coefficient(D*)and perfusion fraction(f))and multi b-value fitted apparent diffusion coefficient(ADCmb)were compared for differences among low-risk thymomas(LRT),high-risk thymomas(HRT)and thymic carcinomas(TC)and for differences between early and advanced stage TETs based on one-way ANOVA and independent sample t test,respectively.Receiver operating characteristic curve(ROC)analyses were performed to determine optimum thresholds for differentiating the defined groups based on various parameters and to calculate sensitivity,specificity,and area under the curve(AUC)values.ICC was used to estimate the agreement between two readings.Results The conventional MRI parameters : The parameters of the maxmum diameter,homogeneity,pericardial or pleural effusion of the tumors have significant difference(LRT,HRT and TC)(P<0.01).The parameters of shape and mean diameter of tumors have no significant difference among the groups(the p valve was 0.742,0.056,respectively).The IVIM-DWI parameters : The ADCmb,D and D* values in LRT were significantly higher than the values from HRT and TC in both readings(the first reading: ADCmb,1.55,1.17 and 0.94 ×10-3 mm2 /sec;D,1.09,0.66 and 0.57 ×10-3 mm2 /sec;D*,10.06,4.93 and 3.35 × 10-3 mm2 /sec;all P<0.001),while there were no significant differences between the HRT and TC in both readings(P>0.05).The mean ADCmb,D and D* value in the early stage were significantly higher than in the advanced stages in both readings(the first reading: ADCmb,1.41,1.06 ×10-3 mm2 /sec;D,0.93,0.64 ×10-3 mm2 /sec;D*,8.19,4.34 × 10-3 mm2 /sec;all P<0.001).As for the f value,no significant differences were found among defined groups in both readings(P>0.05).Conclusions The magnetic resonance imaging has potential valve to predict the pathological classification and Masaoka stages of TETs preoperatively.