| Objective:To investigate the value of mono-exponential,bi-exponential and stretched exponential models in differentiating benign and malignant rectal tumors,and to analyze the correlation between each parameter value and Ki-67 expression in patients with rectal adenocarcinoma,as well as the value of evaluating extramural vascular invasion of rectal adenocarcinoma.Material and Methods:The clinical and imaging data of 82 patients with rectal tumors confirmed by surgery and pathology were analyzed retrospectively,the patients were admitted to Anqing Municipal Hospital from January 2020 to January 2022,of which 23 were benign and59 were malignant;In malignant group,35 cases were negative and 24 cases were positive for extramural vascular invasion.All patients underwent 3.0T MRI scanning of the rectum within one week before operation.The examination sequence included conventional T1 weighted imaging（T1WI）,high-resolution T2 weighted imaging（HR-T2WI）,conventional diffusion weighted imaging（DWI）（b=0,1000 s/mm2）and axial intravoxel incoherent motion magnetic resonance imaging（IVIM-MRI）【12 groups of different b values and average times were 0（1）,20（1）,50（1）,100（2）,150（2）,200（2）,400（2）,600（4）,800（4）,1000（6）,1500（6）,2000（6）s/mm2 respectively】.The patients were fasting for 4～6 hours before scanning;After the scanning,two senior doctors imported the original IVIM data of the lesions into the post-processing workstation,and delineated the region of interest（ROI）of the tumor in the axial position.The ROI was selected as the solid part at the largest level of the tumor,and its contour was manually marked according to the shape of the lesion.Attention should be paid to avoiding the necrotic cystic zone,intestinal gas and fecal stone.The ROI was measured three times at different times,and the final average value was taken.The parameters of mono-exponential,bi-exponential and stretched exponential models of the lesions were measured,including:standard ADC（apparent diffusion coefficient）;Slow ADC;Fast ADC;f（perfusion fraction）;DDC（distribution diffusion coefficient）;Alpha（Diffusion Heterogeneity Index）.The independent sample t-test was used to compare the differences of various parameters between benign and malignant rectal tumors.For indicators with statistical differences,the receiver operating characteristic（ROC）curve was used to evaluate the effectiveness of various parameters in the differential diagnosis of benign and malignant rectal tumors.The IVIM-DWI parameters of 59 patients with rectal adenocarcinoma with extramural vascular invasion（EMVI）confirmed by postoperative pathology were analyzed,and the value of IVIM-DWI parameters in preoperative evaluation of EMVI of rectal adenocarcinoma was discussed.All measurement data were subjected to S-W normality test and variance homogeneity analysis.The correlation between Ki-67 expression level and the quantitative parameter values of mono-exponential,bi-exponential and stretched exponential in patients with rectal adenocarcinoma was compared by using Spearman correlation analysis,and the value of evaluating the extramural vascular invasion of rectal adenocarcinoma was evaluated.P<0.05 was statistically significant.Result:There are significant differences in standard ADC,slow ADC,f,DDC and Alpha between the two groups for benign and malignant rectal tumors（P<0.05）,but there is no significant difference in fast ADC between the two groups（t=0.122,P=0.904）.Alpha value has the highest diagnostic efficiency in differentiating benign and malignant rectal tumors.The area under the ROC curve is 0.915,the sensitivity is 0.957,and the specificity is 0.833.Standard ADC,slow ADC,f,DDC and alpha have negative correlation with Ki-67,and alpha has the strongest correlation with Ki-67（r=-0.540）.Among 59 cases of rectal adenocarcinoma,24 cases were EMVI positive group and 35cases were negative group.The parameters of slow ADC,fast ADC,f and DDC in the positive group were（0.653±0.088）×10-3mm2/s、（6.461±1.639）×10-3mm2/s、0.357±0.047、1.390（1.120,1.710）×10-3mm2/s,all of them were higher than the parameters of slow ADC,fast ADC,f and DDC in the negative group[（0.583±0.080）×10-3mm2/s、（4.037±0.649）×10-3mm2/s、0.281±0.040、1.110（1.000,1.420）×10-3mm2/s],the difference between the two groups was statistically significant（P<0.05）;The standard ADC and alpha values of EMVI positive group of rectal adenocarcinoma were 0.892（0.822,0.932）×10-3mm2/s,0.682±0.065.The negative group standard ADC,alpha value were 0.843（0.812,0.956）×10-3mm2/s,0.661±0.050.There was no significant difference between the two groups（P>0.05）.When evaluating the EMVI positive of rectal adenocarcinoma,the area under the ROC curve of fast ADC is the largest（0.818）,with high diagnostic accuracy,when 5.045×10-3mm2/s is the diagnostic threshold,its sensitivity and specificity are 87.5%and 94.3%respectively.Conclusion:The mono-exponential,bi-exponential and stretched exponential models are helpful to differentiate the benign and malignant rectal tumors,and the alpha value is the most valuable for clinical differential diagnosis.In addition,the alpha value has a significant negative correlation with Ki-67 expression,which can indirectly provide help for the differential evaluation of benign and malignant rectal tumors.The bi-exponential model and the stretch exponential model have certain value in evaluating EMVI of rectal cancer,and the fast ADC of bi-exponential model has the highest diagnostic accuracy. |
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