3.0T MR DWIBS in diagnosis of lymph nodes metastasis of malignant pelvic tumors

Objective: To evaluate the efficacy of diffusion-weighted imaging with background signal suppression (DWIBS) using 3.0T MR scanner for diagnosing lymph nodes metastasis in patients with pelvic malignant tumors. Methods: Totally 60 patients with pelvic malignant tumor underwent preoperative routine MRI+DWI examination and tumor dissection+pelvic lymph node dissection within 2 weeks. Metastatic and non-metastatic lymph nodes were confirmed by pathology after operation. ADC values, long-axis and short-axis diameters of lymph nodes were measured and statistical analyzed. Diagnostic efficacy of ADC values, long-axis and short-axis diameters in differentiating metastatic lymph nodes from non-metastatic lymph nodes by comparing area under curve (AUC) of ROC were assessed. Results: Eighty-two metastatic lymph nodes and 224 non-metastatic lymph nodes were identified. There was statistical difference in short-axis diameter (P=0.001) and short-long axis diameter ratio (P=0.008), but no statistical difference was found in long-axis diameter (P=0.480) between metastatic lymph nodes and non-metastatic lymph nodes. The ADC values of metastatic lymph nodes and non-metastatic lymph nodes were (0.86±0.20) × 10^-3 mm²/s and (1.05±0.30) × 10^-3 mm²/s, respectively (all P<0.001). The ADC values of non-metastatic lymph nodes are higher than metastatic lymph nodes in both short-axis diameter ≥10 mm or <10 mm group (P<0.01). AUC of short-axis diameter and short-long axis diameter ratio was 0.623 and 0.599, respectively. AUC of ADC values of all lymph nodes, short-axis diameter ≥10 mm and <10 mm lymph nodes was 0.740, 0.792 and 0.731, respectively. ADC value of short-axis diameter ≥10 mm lymph nodes got the highest value for diagnosing metastatic lymph node, its sensitivity was 90.5%, and specificity was 68.2%. Conclusion: DWIBS using 3.0T MR scanner has distinct advantages in detecting metastatic lymph nodes of pelvic malignant tumor. ADC value has significant accuracy, higher than lymph node diameters.