To evaluate the efficacy of MRI of high resolution layer in rectal cancer at 3.0T magnetic resonance (MR) for diagnosing rectal cancer, and analyze the relationship between apparent diffusion coefficient (ADC) values and pathological results of tumor.

We retrospectively analyses 75 patients with radical surgical and pathological proved rectal cancer. All patients received high resolution layer rectal 3.0T MRI, to evaluate the correlation between MRI and pathology by estimating invasive depth and measuring the ADC value in different type of group.

The diagnostic accuracy of high resolution layer rectal MRI for pathological changes in T1, T2, T3, and T4 was 0%, 38.1%, 72%, 14.3% in the group of non-preoperative therapy, and 50%, 33%, 75%, 0% in the group of preoperative therapy. There was poor consistency between T stage of MRI and pathology whether in group of non-preoperative therapy (κ=0.200) or preoperative therapy (κ=0.270). There was no significant correlation between the ADC value of tumors and groups of various T stage. There was also no significant correlation between the ADC value of tumors and groups of various differentiation grades. Non-preoperative therapy group (F=0.074, P=0.929; F=0.737, P=0.496) and preoperative therapy group (F=1.889, P=0.783; F=4.385, P=0.627). There was a significant difference between the patients with lymph metastasis and those without lymph metastasis in non-preoperative therapy group (F=0.073, P=0.012), and there was no significant difference in preoperative therapy group (F=0.035, P=0.793).

The diagnostic accuracy of high resolution layer rectal MRI for pathological changes in T3 is high, but the overall accuracy rate is low. ADC value of high resolution layer rectal MRI has some value in evaluated the lymph metastasis and need further study.