Evaluation of Mesorectal Microcirculation With Quantitative Dynamic Contrast-Enhanced MRI

OBJECTIVE. The purpose of this study was to use quantitative dynamic contrast-enhanced MRI (DCE-NIRI) to evaluate mesorectal microcirculation in patients with rectal cancer. MATERIALS AND METHODS. A total of 53 patients with semicircular rectal tumors underwent DCI-MRI with a 3-T MRI stem before surgery. ROI s were manually delineated in the mesorectum that surrounded the tumor and the mesorectum that surrounded the normal rectal wall. DCE-MRI parameters including forward volume transfer constant (K-trans), reverse volume transfer constant (k(ep)), and fractional extravascular extracellular space volume (V-e) were estimated using computer software. Histopathologic analysis served as the standard reference. RESULTS. Mesorectum that surrounded the tumor showed significantly higher K trans values than mesorectum that surrounded normal rectal wall (mean, 0.069 +/- 0.035 1SD] vs 0.039 0.020 min(-1) ; p < 0.001). The tumor-surrounding mesorectum also showed higher V-e values than normal mesorectum (p < 0.001). An opposite trend was observed for k(ep), but this was not significant (p = 0.077). A lower Kraus of the tumor-surrounding mesorectum was observed in patients with malignant lymph nodes compared with those with benign lymph nodes (mean, 0.054 +/- 0.027 vs 0.076 +/- 0.036 min(-1) ; p = 0.034). Although k(ep) values for the tumor-surrounding mesorectum were higher in patients with tumors categorized as pathologic Tis (pTis) to pT2 than in those with pT3 tumors, the p value was close to 0.05 (p = 0.047). The tumor-surrounding mesorectum showed no significant differences in the aforementioned parameters between patients with positive MRI-detected extramural vascular invasion (mrEMVI) and those with negative mrEMVI. CONCLUSION. Mesorectum that surrounded rectal tumor had a higher blood flow than that close to the normal rectal wall. The blood flow decreased in the tumor-surrounding mesorectum when there was nodal involvement.