Abstract: Objective To explore the application value of 3.0 T MRI in the preoperative staging and assessment of rectal cancer. Methods Data of 103 patients with rectal cancer diagnosed by biopsy was collected. The T staging, situations of paracolic lymphatic metastasis and fascia involvement, and distance of tumor edge to anal verge were estimated by preoperative MRI. The stage and assessment of preoperative MRI and postoperative pathology were compared. Results MRI showed that there were 5 patients with stage T1-2, 72 patients with stage T3, and 26 patients with stage T4. And pathological diagnosis showed that there were 5 patients with stage T1, 16 patients with stage T2, 60 patients with stage T3, and 22 patients with stage T4. The sensitivity and specificity of stage T1-2, T3, and T4 were 23.8% and 100%, 96.7% and 67.4%, 90.9% and 92.6%, respectively. Results of MRI were broadly consonant with the results of pathology (Kappa=0.748, P＜0.01). MRI showed that there were 74 patients with paracolic lymphatic metastasis. Pathological diagnosis after surgery showed that there were 66 patients with paracolic lymphatic metastasis. The sensitivity and specificity for MRI diagnosis were 92.4% and 64.9%, respectively (Kappa=0.601, P＜0.01). Among the 18 patients received anal resection, the different value of distance of tumor edge to anal verge was less than or equal to 6 mm between MRI and postoperative specimen, with no significant difference (P＞0.05). Totally 65 patients without fascia involvement diagnosed by MRI were consonant with the results of postoperative pathology. Among the 38 patients with fascia involvement diagnosed by MRI, 12 patients were false-positive. The sensitivity and specificity were 100.0% and 84.4%, respectively (Kappa=0.732, P=0.000). Conclusion 3.0 T MRI can provide accurate preoperative staging and evaluation for patients with rectal cancer before the operation, and help in clinical diagnosis and treatment.

Key words: rectal neoplasms, magnetic resonance imaging, rectal cancer, T staging, preoperative assessment, pathology