Dynamic Contrast Enhanced Magnetic Resonance Imaging:Application In The Diagnosis Of Mesorectal Lymph Node Metastasis In Rectal Cancer And The Prediction And Evaluation Value Of Neo-adjuvant Chemoradiotherapy Response In Middle And Lower Locally Advanced

Part one:The application of DCE-MRI in the diagnosis of mesorectal lymph node metastasis in rectal cancerObjectiVe To inVestigate the utility of dynamic contrast enhanced magnetic resonance imaging（DCE-MRI）in the diagnosis of mesorectal lymph node metastasis in rectal cancer.Methods 61 patients who were initially diagnosed with rectal cancer by colonoscopy in Sichuan provincial people’s hospitalfromJanuary2017toOctober2018wereprospectiVe analyzed.According to the inclusion and exclusion criteria,56 cases finally were selected as the subjects.All patients performed conVentional MRI and DCE-MRI before operation,and accepted radical resection of rectal cancer and post-operatiVe specimen pathology examination within one week after MRI examination.The boundary,short diameter,plain and enhanced scan signal characteristics and ADC value of lymph node in mesorectum were analyzed and compared.According to MRI diagnostic criteria,imaging diagnosis of mesorectal lymph nodes metastasis/non-metastasis in rectal cancer was made,and then compared the consistency with the pathological results.QuantitatiVe perfusion parameters--Krans,Ke and Ve--were obtained through DCE-MRI post-processing technique,and their differences between lymph node metastatic group and non-metastatic group were compared.ReceiVer operating characteristic curVe（ROC）of parameter with statistically significant difference was drawn,calculating the area under the curVe（AUC）and obtaining the corresponding threshold through further analysis.The diagnostic efficacy of conVentional MRI,DCE-MRI and conVentional MRI combined with DCE-MRI in mesorectal metastatic lymph node of rectal cancer was compared.Results（1）79 lymph nodes were divided into metastatic group and non-metastatic group according to the pathological results,including 44 cases in the metastatic group and 35 cases in the non-metastatic group.In conVentional MRI scan,the differences in the short diameter,boundary,plain and enhanced scan signal characteristics and ADC value between the two groups were statistically significant（P<0.05）.In DCE-MRI scan,the difference of Ktrans value in the quantitatiVe perfusion parameters between the two groups was statistically significant（P<0.05）,while the differences of Kep and Ve value between the two groups were not statistically significant.（2）In the consistency anaysis of the diagnosis of lymph node metastasis in conVentional MRI and pathology,the Kappa value=0.455,P<0.001.The sensitivity and specificity of conVentional MRI diagnosed mesorectal lymph node metastasis of rectal cancer were about 61.4%,85.7%,respectiVely.The positiVe predictiVe value was about 84.4%,and the negatiVe predictiVe value was about 63.8%.（3）The ROC of Ktrans was analyzed for the lymph node metastastic and non-metastatic in rectal cancer.The threshold was determined according to the maximum value of the Youden index.When Ktrans value=0.124 min^-1,the Youden index was the largest,Meanwhile,the sensitivity was 93.2%,and the specificity was 77.1%.（4）In the comparison of the diagnostic efficacy of conVentional MRI,DCE-MRI and conVentional MRI combined with DCE-MRI for mesorectal lymph node metastasis of rectal cancer,the AUC of them were 0.858,0.852 and 0.919,respectiVely.There was no statistically significant difference in the AUC of conVentional MRI and DCE-MRI in the diagnosis of mesorectal lymph node metastasis in rectal cancer（Z=0.113,p=0.910）.The AUC of conVentional MRI combined with DCE-MRI was greater than that of conVentional MRI（Z=3.116,P=0.0018）.Conclusions（1）ConVentional MRI has a certain value in diagnosing the status of mesorectal lymph nodes in rectal cancer,but the consistency with the pathological gold standard was general,and the diagnostic efficacy was also general.（2）The quantitatiVe perfusion parameter Ktrans of DCE-MRI was of diagnostic value for the lymph node metastasis in rectal cancer,and Ktrans value=0.124min^-1can be used as a threshold to distinguish between mesorectal lymph node metastasis and non-metastasis in rectal cancer.（3）The diagnostic efficacy of conVentional MRI and DCE-MRI for lymph node metastasis in rectal cancer was medium,but the diagnostic accuracy of conVentional MRI combined with DCE-MRI for lymph node metastasis was relatiVely high.Part two:The role of DCE-MRI to predict and evaluate the treatment response of Neo-adjuvant chemoradiotherapy in middle and lower locally advanced rectal cancerObjectiVe To explore the usefulness of DCE-MRI to predict and evaluate the treatment response of neo-adjuvant chemoradiotherapy（CRT）in middle and lower locally advanced rectal cancer（LARC）.Methods 46 patients with comprehensi Ve clinically diagnosed with LARC were prospecti Ve analyzed,According to the inclusion and exclusion criteria,41 cases finally were selected as the subjects.All patients were performed standard CRT plans by clinicians,and accepted routine MRI and DCE-MRI examination before the CRT in one week and after CRT with a interval 5-12 weeks respecti Vely.Total mesorectal excision（TME）and pathologic biopsy were performed within one week after the second MRI examination.According to the standards of the eighth edition of the American Joint Committee on Cancer（AJCC）grading system for Tumor regression grading（TRG）,pathological results of patients were divided into the responding group and non-responding group of CRT,the good response group and poor response group.DCE-MRI quantitati Ve perfusion parameters were compared between and within the group.The parameters with statistical significance were further analyzed,and the corresponding ROC was drawn to calculate the area under the cur Ve（AUC）and determine the corresponding threshold.Results（1）In the comparison between the groups with and without responding,Ktrans in the responding group was higher than that in the non-responding group before CRT,while the differences between the two groups of Kep and Ve were not statistically significant.There were no significant differences of all parameters between the two groups after CRT.The AUC of Ktrans predicted in response to CRT was 0.954,When Ktrans value =0.122 min-1,the Youden index was the largest,Meanwhile the sensitivity and specificity was 96.3%,85.7%,respecti Vely.（2）In the comparison between the two groups with good response and poor response,the Ktrans value in the group with good response was higher than that in bad group before CRT,While after CRT the Ktrans value was lower than that in the poor group.Howe Ver,the differences between Kep and Ve were not statistically significant.The AUC of Ktrans to predict CRT good response was 0.953.When Ktrans Value=0.158min-1,the Youden index was the largest,Meanwhile the sensitivity and specificity was 90.9%,88.7%,respecti Vely.（3）The Ktrans and kep values of the group with good response before CRT were higher than those after CRT,While the differences of Ve before and after CRT were not statistically significant.Ktrans value in the group with poor response before CRT was also higher than that after CRT,Hower Ver,the differences between Kep and Ve before and after CRT were not statistically significant.In the percentage change of perfusion parameters before and after CRT,Δ Ktrans and Δ Kep in the group with good response was higher than that in poor group.The AUC of Δ Ktrans and Δ Kep to evaluate CRT good response were 0.952,0.764,respecti Vely.（Z =2.063,p = 0.039）.When Δ Ktrans value =-38.8%,the Youden index was the largest,Meanwhile,the sensitivity was 100%,and the specificity was 76.7%.Conclusions（1）DCE-MRI examination has a role of prediction and evaluation in treatment response of CRT with LARC.（2）Peforming DCE-MRI examination before CRT,when the Ktrans value≥ 0.122 min-1,it could be predicted that the patient will respond to CRT.When the Ktrans value ≥ 0.158 min-1,it could be predicted that the patient will ha Ve a good CRT response.When the Ktrans value<0.122 min-1,it indicated that the patient has no obvious response to CRT.When 0.122 min-1≤ Ktrans value <0.158min-1,it presents that CRT has a response,but the response was poor and other treatment options should be selected.（3）Performing DCE-MRI examination after CRT,when the Δ Ktrans absolute value≥38.8%,it could evaluate that the patient has a good response to CRT,and might be approached or e Ven achie Ved pathologic complete response.