Applicated Study Of MR Imaging For The Preoperative Evaluation Of Rectal Cancer

Objective To study the value of conventional MRI combined with diffusion weighted imaging(DWI)(b=800s/mm2) in preoperative staging of rectal cancer, as well as the value of MRI signs and ADC value for T staging.Materials and methods During Jun.2010 to Feb.2011, Sixty-eight patients with rectal cancer confirmed by the colonoscopy were studied. All patients underwent conventional MRI and DWI examination. Inclusion criterias:no radiotherapy or Neoadjuvant therapy were performed before examination. Operated successfully and obtained specimens within two weeks. MR images were clear enough for assessment. Fifty-eight patients met the standards and enrolled in this study. Among them,30 males,28 females, aged 26 to 78 years, averaged 54.4 years.MR scan were performed in PHILIPS Achieval 1.5T superconductical scanner with 8 channel phased-array surface coil pairs. Feet-first way were applied and all sequences were as follows:axial TSE-T1WI, T2WI, and T2WI SPAIR (FOV: 210x210mm, matrix:349×333, slice thickness:4mm); sagital TSE-T2WI; axial small-FOV T2WI (FOV:210×210mm, matrix:349×333, slice thickness:4mm); coronal small-FOV T2WI(FOV:200×200mm, matrix:286×264, slice thickness: 4mm); axial small-FOV DWI (FOV:210×210mm, matrix:128×128, slice thickness: 4mm, b=800s/mm2).The accuracy, sensitivity, specificity, positive predictive value(PPV), negative predictive value(NPV) and the consistency with pathological results of preoperative rectal cancer prognosised by MRI of all datas were statistical analysed.The correlation between MRI T3 rectal cancer signs and pathological results, accuracy, specificity, sensitivity of all datas were statistical analysed.The ADC values of tumor, paratumor fiber and lymph node were measured, while measured the ADC value of gluteal muscle at the same slice to calculate the rADC values of all of above. The ADC and rADC values for tumor of different differentiated group were analyzed by Analysis of variance(ANOVA) anlysis. The ADC values differences between benign and malignant paratumor fiber, benign and metastatic lymph nodes were compared, respectively. All datas applied Independent sample t test, significance level a=0.05, there were statistically differences when P <0.05 (a=0.05, P<0.05).Results Conventional MRI combined with DWI diagnosing rectal cancer revealed 91.4% accuracy in T staging, 75.9% accuracy in N staging. The consistency between T staging and pathological results were perfect (Kappa=0.82). The consistency between N staging and pathological results were moderate (Kappa=0.63). The relationship between the MRI signs of rectal cancer and the pathological T staging was strong positive(rs=0.874,P<0.01).The total T3 stagging accuracy of lateral rectal wall fiberal strip,disrupted rectal muscular layer, tumor node-like evagination and blurry mesenterium were 67.2%,93.1%,84.5%,72.4%, the sensitivity were 64.5%, 93.5%,70.9%,77.4%, the specificity were 70.4%,92.6%,100%,66.7%, respectively. The accuracy of lateral rectal wall fiberal strip and disrupted rectal muscular layer were 37.9%and 48.3%respectively, when only single sign exist. The sensitivity, specificity and accuracy of Lateral rectal wall fiberal strip combined with blurry mesenterium were 48.3%,77.7%and 62.1%respectively, that of disprupted rectal muscular layer combined with blurry mesenterium were 77.4%,92.6%and 84.5%. while that of lateral rectal wall fiberal strip combined with discontinued hypointensity muscular layer were 58.1%,96.3%, and 75.8%. When three signs above coxisted, that were 48.4%,96.3%and 70.7%.ADC and rADC values varied among different differented tumors as the tumor, and the discrepancies of the ADC values between different tumor degrees were statistically different(P=0.000). The discrepancies of ADC values between benign and malignant paratumor fibers were statistically different(P=0.016,0.007). The ADC and rADC values of benign lymph nodes were larger than malignant lymph nodes, and the discrepancies were statistically different(P=0.001).Conclusions Conventional MRI combined with DWI had a agreat role in preoperative T stagging of rectal cancer, on the contrary, had an unsatisfied role in N stagging. The measurement of ADC value was useful for differentiating the degrees of rectal cancer and judge the malignancy of peritumoral fibers and lymph nodes, while the rADC values were effective supplement for ADC values.