Differentiation Of Recurrence Rectal Cancer And Benign Pelvic Lesions After Curative Rectal Operation With 3.0T MR

Objective To evaluate the value of T2WI,DWI and 3D-VBIE at 3.0T in differentiation of recurrence rectal cancer and benign pelvic lesions after curative rectal operation.Methods 28 patients with abnormal pelvic lesions confirmed by CT or MR during the period between April,2007 and march,2009 were evaluated with MR imaging.All of them received examinations of both T2WI and DWI,24 of them received extra examination of 3D-VIBE.13 patients with MR imaging in the same period who were confirmed as having no disease of rectum were accepted as a contrast group.The mean ADC values,the ratio of the signal intensity(SI) of the lesions to the gluteus muscles in T2WI(SI_L/SI_M) and the ratio of the signal intensity of the lesions to the signal intensity of the iliac artery(SI_L/SI_A) at the time of 35 seconds after the iliac artery achieved its highest intensity were measured and calculated.The type of the time-intensity curve(TIC) were overviewed and were classified as the benign type when the TIC is rising slowing or rising constantly and lasts for more than 90s;or the malignant type when the TIC is rising significantly but lasts less than 90s and then keep as a horizontal line for a period or descending slowly or rising slowly.Result There were 29 lesions of different final diagnosis,including 17 recurrence rectal cancers,4 fibrous masses,3 stoma inflammations,1 sinus,1 fist,1 abscess and 2 radiation changes.14 of them were confirmed by pathology results.The ratio of SI_L/SI_M has no statistics significance during the benign group,the malignant group and the contrast group.When the ADC value of 1.21×10^-3mm²/s was set as a diagnostic threshold,the sensitivity,specificity,accuracy and coherence for the diagnosis of the malignant lesions is 100%(17/17),91.7%(11/12),96.6%(28/29) and 0.928.When the SI_L/SI_A value of 0.28 was set as a diagnostic threshold,the sensitivity, specificity,accuracy and coherence for the diagnosis of the malignant lesions is 100%(13/13),58.3%(7/12),80.0%(20/25) and 0.593.When considering the TIC as the diagnostic standard,the sensitivity,specificity and accuracy for the diagnosis of the malignant lesions is 100%(13/13),83.3%(10/12) and 92.0%(23/25).Conclusion The signal intensity of T2WI has no specificity in differentiation of malignant lesions and benign lesions while the DWI and the 3D-VIBE have high values in it.