Local recurrence of rectal cancer: MR imaging before and after oral superparamagnetic particles vs contrast-enhanced computed tomography

The aim of this study was to compare three ig strategies for the diagnosis of local recurrence of rectal cancer: (a) MR imaging; (b) MR imaging after administration of enteral superparamagnetic particles (Ferristene); and (c) contrast-enhanced CT. Seventeen patients with previous surgery for rectal cancer were examined, 12 patients with local tumour recurrence in the pelvi s and 5 patients with postoperative changes. Pelvic multi-coil MR imaging b efore and after oral administration of superparamagnetic contrast, medium [ Abdoscan (Ferristene USAN), Nycombed-Amersham, Lidingo, Sweden] as well as abdominal and pelvic CT was performed in all patients. The examinations wer e independently evaluated by three different radiologists. The general effe ct of the II MR contrast medium, the delineation of normal pathological str uctures as well as confidence in diagnosis were registered on a visual anal og scale (VAS). The diagnosis according to MR before and after oral contras t medium, and CT, was compared, in patients, with the final diagnosis which was verified by biopsy (n = 3), surgery (n = 6), clinical follow-up (n = 4 ) and by follow-up with MR or CT (n = 3). No significant improvement in MR image quality was found after enteral contrast medium. post-contrast MR dia gnosis was not changed in any of the patients. The diagnosis on MR correlat ed with the final diagnosis in 12 of 16 patients (sensitivity 91%, accuracy 62%) and the diagnosis on CT in 11 of 16 patients (sensitivity 82%, accura cy 56%), The radiologists' "confidence" in the diagnosis and the degree of accordance with the final diagnosis did not score higher on MR after than b efore oral contrast ministration; however, the accordance with the final di agnosis scored better on MR than on CT. No advantages of orally administere d superparamagnetic contrast medium were observed in the examination patien t group. Magnetic resonance is preferable to CT in diagnosing local tumour recurrence.