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OBJECTIVE. The purpose of this study was to use quantitative dynamic contrast-enhanced MRI (DCE-MRI) to evaluate mesorectal microcirculation in patients with rectal cancer. MATERIALS AND METHODS. A total of 53 patients with semicircular rectal tumors underwent DCE-MRI with a 3-T MRI system before surgery. ROIs 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 val ues than mesorectum that surrounded normal rectal wall (mean, 0.069 ± 0.035 [SD] 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 K trans 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.

Background: To determine whether magnetic resonance imaging (MRI)-detected extramural vascular invasion (mrEMVI) status is associated with quantitative perfusion parameters derived from dynamic contrast-enhanced MRI (DCE-MRI) in rectal cancer., Methods: Seventy-two patients with rectal adenocarcinoma who underwent curative surgery alone within 2 weeks following rectal MRI were enrolled in this retrospective study. mrEMVI status was determined based on high-resolution MRI. The quantitative perfusion parameters (K trans , k ep and v e ) derived from DCE-MRI were calculated from all sections containing tumours. DCE-MRI parameters and clinicopathological variables in patients with different mrEMVI statuses were compared., Results: For patients who were mrEMVI positive, the tumours demonstrated significantly lower k ep values (P = 0.012) and higher v e values (P = 0.021) than tumours of patients who were mrEMVI negative, while the K trans value displayed no significant difference (P = 0.390). The patients who were mrEMVI positive had larger tumour size, higher pathological tumour stage and increased regional nodal metastases compared to those who were mrEMVI negative (2.9 cm vs. 3.5 cm, P = 0.011; 63.8% vs. 92.0%, P = 0.010; 36.2% vs. 76.0%, P = 0.001; respectively)., Conclusions: This study demonstrated for the first time that tumour microcirculation is altered in mrEMVI-positive patients with rectal adenocarcinoma, as evidenced by significantly lower k ep and higher v e values. In addition, these patients were more likely to have a larger tumour size, a higher pathological tumour stage and regional nodal metastases than mrEMVI-negative patients.

Background: To investigate the application value of fat-suppressed gadolinium-enhanced isotropic high-resolution 3D-GRE-T1WI in regional nodes with different short-axis diameter ranges in rectal cancer, especially in nodes ≤5 mm., Methods: Patients with rectal adenocarcinoma confirmed by postoperative histopathology were included, and all the patients underwent preoperative 3.0 T rectal magnetic resonance imaging (MRI) and total mesorectal excision (TME) within 2 weeks after an MR scan. The harvested nodes from specimens were matched with nodes in the field of view (FOV) of images for a node-by-node evaluation. The maximum short-axis diameters of all the visible nodes in the FOV of images were measured by a radiologist; the morphological and enhancement characteristics of these nodes were also independently evaluated by two radiologists. The χ 2 test was used to evaluate differences in morphological and enhancement characteristics between benign and malignant nodes. The enhancement characteristics were further compared between benign and malignant nodes with different short-axis diameter ranges using the χ 2 test. Kappa statistics were used to describe interobserver agreement., Results: A total of 441 nodes from 70 enrolled patients were included in the evaluation, of which 111 nodes were metastatic. Approximately 85.5 and 95.6% of benign nodes were found to have obvious enhancement and homogeneous or mild-heterogeneous enhancement, respectively, whereas approximately 89.2 and 85.1% of malignant nodes showed moderate or mild enhancement and obvious-heterogeneous or rim-like enhancement, respectively. The area under the receiver operating characteristic (ROC) curve (AUC) values of the enhancement degree for identifying the overall nodal status, nodes ≤5 mm and nodes > 5 mm and ≤ 10 mm were 0.887, 0.859 and 0.766 for radiologist 1 and 0.892, 0.823 and 0.774 for radiologist 2, respectively. The AUCs of enhancement homogeneity were 0.940, 0.928 and 0.864 for radiologist 1 and 0.944, 0.938 and 0.842 for radiologist 2, respectively. Nodal border and signal homogeneity were also of certain value in distinguishing metastatic nodes., Conclusions: Enhancement characteristics based on fat-suppressed gadolinium-enhanced isotropic high-resolution 3D-GRE-T1WI were helpful for diagnosing metastatic nodes in rectal cancer and were a reliable indicator for nodes ≤5 mm.