Magnetic Resonance Imaging Rectal Neuroendocrine Neoplasm And Rectal Carcinoma

Part I Rectal neuroendocrine neoplasm:Correlation between MRI and pathological classificationPurpose:To analyze the MRI features of neuroendocrine neoplasm(NEN)and discuss the correlation with pathological grade.Methods:The clinical,pathological and pelvic MRI data of patients with pathologically confirmed rectal neuroendocrine tumors were retrospectively analyzed.Histological analysis was used as a reference standard for MRI evaluation.MRI assessment of tumor location,size,the degree of arterial phase enhancement,pelvic lymph node metastasis and other conditions.Pathological grade refers to the 2010 WHO Classification of Digestive Neuroendocrine Neoplasms.Results:Among the 33 cases of rectal NENs,there were 24 cases with grade G1,4 cases with G2 and 5 cases with G3.The size of Gland G2 tumors were all<20 mm,and the size of G3 were>20 mm,the difference of the tumor size between different grades was statistically significant(?2=14.48,p<0.001),and there was a positive correlation between the tumor size and the pathological grade(rs=0.654,p<0.001).In the arterial phase,G1 grade rectal NENs were mainly hypovascular while G2-G3 grade rectal NENs were mostly hypervascular,the degree of arterial phase enhancement was associated with pathological grade(p<0.001).G1-G3 grade rectal NENs were all hyperenhancement in the venous phase.13 cases were located in the lower rectum,and 20 were located in the middle and upper rectum,the tumor height was not correlated with pathological grade(p=0.774).There were 8 cases with pelvic lymph node metastases,including 2 cases of G1,3 cases of G2,and 3 cases of G3,there was a positive correlation between pelvic lymph node metastasis and pathological classification(p<0.001).Conclusion:The most common grade of rectal NENs is G1.Low-grade NEN is mostly manifested as intraluminal or submucosal nodules,the diameter usually less than 2cm,and the signal is generally homogeneous,with necrosis occasionally.Higher grade tumors are generally larger,invasive growth,and relatively more prone to cystic or necrosis.The increase of tumor size,increase of arterial phase enhancement,and enlargement of lymph nodes in pelvic cavity suggest that pathology may be of high grade.Part II Diagnostic performance of MRI in assessing rectal cancer:a retrospective single center studyPurpose:To analyze the diagnostic performance of MRI in assessing rectal cancer by using a large sample size data from one clinical center.Methods:A retrospectively analysis of image data from the picture archiving and communication system(PACS)in accordance with the clinical data was conducted between February 2008 and April 2014.Histological analysis was used as a reference standard for MRI evaluation.Kappa statistics was used for assessing the agreement of two readers.Receiver operating characteristic(ROC)curve was used to assess the diagnostic performance of MR imaging.Results:A total of 672 patients were enrolled in this study.There was no difference of the sensitivity between 1.5T and 3.0T MR system in T staging(Reader 1,p=0.752;Reader 2,p=0.948),N staging(Reader 1,p=0.865;Reader 2,p=0.917),and tumor height(Reader 1,p=0.202;Reader 2,p=0.236).And no difference in the specificity was found between 1.5T and 3.0T MR system in T staging(Reader 1,p=0.651;Reader 2,p=0.923),N staging(Reader 1,p=0.846;Reader 2,p=0.796),and tumor height(Reader 1,p=0.376;Reader 2,p=0.463).Moreover,for T staging,N staging and tumor height,no differences were found in PPV and NPV between 1.5T and 3.0T MR system(Reader 1 and reader 2,p>0.05 for all).For reader 1,the AUROCs for MR T staging,N staging,and tumor height were 0.645(95%CI 0.600-0.690,p<0.001),0.369(95%CI 0.325-0.414,p<0.001),and 0.615(95%CI 0.568-0.662,p<0.001),respectively.Moreover,for reader 2,the AUROCs of MR T staging,N staging,and tumor height were 0.589(95%CI 0.539-0.639,p<0.001),0.382(95%CI 0.335-0.429,p<0.001),and 0.581(95%CI 0.530-0.632,p<0.001),respectively.The Kappa values for two readers in T staging,N staging,and tumor height were 0.581,0.760and 0.632,respectively.Conclusion:MRI is a valuable and reliable tool in assessment of rectal cancer,with higher sensitivities in stage T2,T3,and N0,and without any improvement of diagnostic performance by using higher field strength of 3.0 Tesla.Higher agreement between two readers was found in MR N staging and tumor height.Rectal MR imaging is recommended as first choice in staging rectal cancer.