Differentiation of recurrent rectal cancer and scarring with dynamic MR imaging.

The accuracy of dynamic contrast enhanced magnetic resonance (MR) imaging in the differentiation of malignant and benign pelvic lesions during follow-up of patients with treated colorectal tumours was evaluated prospectively. 19 patients (11 men, 8 women; age range 35-70 years; mean 57 years) with suspected local recurrence of colorectal malignancy were evaluated with MR imaging. Dynamic MR imaging with axial Turbo-FLASH gradient echo imaging and bolus injection of contrast medium was performed. Dynamic images, each consisting of one slice in the same location, were acquired at 5, 10, 15, 20 and 30 s, and at 1, 2, 3, 4, 5 and 10 min. The maximum change in signal intensity (Emax), the acceleration rate of the time-intensity curve (TIC) and the ratio of the signal intensity of the lesions to the signal intensity of the iliac artery (SIL/SIA) were used as the enhancement parameters. The TIC and SIL/SIA ratio at 60 s were found to be valuable in the differential diagnosis; Emax had no significance in differentiating benign and malignant lesions. Sensitivity was 83% for each calculated parameter. SIL/SIA has the highest specificity and accuracy among the parameters.