[MRT and dynamic CT in the diagnosis of a recurrence of rectal carcinoma]

A prospective study on 29 patients with presacral lesions after operation of rectal cancer was performed to define the accuracy of CT using a dynamic contrast study and MRI for detection of tumour recurrence (sensitivity) and differentiation from scar formation (specificity). In dynamic CT sensitivity was 88% and specificity was 100%. In MRI the respective data were 94% (sensitivity) and 92% (specificity). Additionally 14 patients with primary rectal cancer were included to define standards for dynamic CT; no differences between primary tumour and relapse were found. In MRI the assessment of signal intensities in T2w images permits differentiation between tumour relapse and scar tissue. In dynamic CT automatically calculated time-density graphs enable differentiation of presacral lesions and the initial increase of density after standardised bolus application was shown to be the most reliable parameter.