Comparison between 3-T magnetic resonance imaging and multi-detector row computed tomography for the preoperative evaluation of rectal cancer.

OBJECTIVE: To compare prospectively between 3-T magnetic resonance imaging (MRI) and multidetector row computed tomography (MDCT) for the local staging of rectal cancer.

MATERIALS AND METHODS: During a recent 8-month period, both 3-T MRI with a phased array coil and MDCT scanner were used to preoperatively examine 31 consecutive patients. Preoperatively, the 3 experienced reviewers independently assessed the MRI and MDCT findings for the depth of tumor invasion into the rectal wall (T). Regional lymph node metastasis (N) was assessed by the 3 reviewers working in consensus. For T staging, we used a modified T staging (<or=T2, T3, and T4 staging). The results of the MRI and MDCT findings were compared based on the diagnosis of the resected specimens.

RESULTS: At histopathology, T1 was identified in 8 patients, T2 in 6, and T3 in 17 patients. The sensitivity, specificity, and accuracy for T2 staging or less between MRI and MDCT were 93% and 79%, 88% and 76%, and 91% and 77%, respectively. The sensitivity, specificity, and accuracy for T3 between MRI and MDCT were 92% and 73%, 93% and 83%, and 92% and 78%, respectively; there was a statistically significant difference for the T2 and T3 staging or less (P < 0.01). For N staging, MRI and CT can predict accurately in 88% and 77%, respectively (P > 0.05).

CONCLUSIONS: For local staging of rectal cancer, 3-T MRI is more accurate than MDCT for determining the depth of tumor invasion and the extent of lymph node metastasis.