Application Research Of Magnetic Resonance Imaging In Diagnosis And Preoperative Staging Of Rectal Cancer

BackgroundRectal cancer is one of the most common gastrointestinal carcinoma and has been a serious public health issue. It has been a ascension of morbidity of rectal cancer at home and abroad. In recent years,its incident in our country is higher than that in other nations. Successful tumor resection mainly depends on moderately accurate staging of the disease and appropriate surgical techniques. Thus accurate preoperative staging is significant for clinical decision-making in rectal caner treatment for individual patients. Imaging findings, particularly magnetic resonance imaging (MRI) is essential for evaluation of preoperative staging. MRI with high soft tissue resolution could better differentiation of rectal wall layers and adjacent tissues or organs. MRI has significant value in evaluation of staging of rectal cancer, which has been emphasized by more and more clinical doctors in recent years.ObjectiveThe aim of this study was to evaluate the accuracy of 3.0T magnetic resonance imaging (MRI) for preoperative TN staging of rectal cancer and distance from the anal verge to the tumor. The final diagnosis was proved by pathological staging which was taken as golden standard and surgical findings respectively.MethodsBetween 2009.9 and 2011.1 ,53 patients with surgically and pathologically proven primary rectal cancer who all underwent 3.0T MRI. MRI study include TSE T1-WI,TSE T2-WI (some patients also using SPIR sequence) us and DWI on axial, sagittal and coronal sections, while some patients were also examined by GD-DTPA enhanced T1WI. The size and signal intensity of tumor, transmural invasion depth, lymph nodes metastasis and distance from the anal verge to tumor were assessed. Using the results of pathology as the golden standard, to compare the imaging findings with those observed from surgery and pathology. Statistical analysis was performed with the SPSS 13.0 software. To evaluate accuracy, sensitivity, specificity, a positive predictive value, and a negative predictive value of 3.0T MRI in T N staging were calculated. In addition, to analysis the correlation between MRI and surgery in respect of measuring the distance from tumor to anus margin by using the paired t-tests.ResultsMRI T-staging agreed with pathological T-staging in 44 of 53. The under-staging and over-staging were 4, 5 cases respectively. The overall accuracy of T-staging was 83. 1% (44/53), and diagnosis accuracy of T1-T4 was 66.7%(2/3),77.8%(14/18), 88.9% (24/27), and 80%(4/5). There were no obvious difference between the result of T Stage with MRI and postoperative histological T Stage (Kappa=0.713,P=0.000). Regarding lymph nodes involvement, the accuracy for N-staging was 67.9%. And the agreement between pathological and MRI N-stages was reported to be excellent(Kappa=0.516,P=0.000). There was no significant statistical difference between MRI and resected specimens in determining the distance from the anal verge to tumor(t=1.845,P=0.077).ConclusionsMRI is highly accurate for diagnosis and preoperative TN-staging of rectal cancer. MRI could accurately evaluate the local lesion and adjacent tissues invasion, assess the distance between the anal verge and the carcinoma. Therefore MRI is more reliable for planning the treatment and selecting the optimum surgical modality for individual patient.