Efficacy of 18-FDG PET-CT Dual-phase Scanning for Detection of Lymph Node Metastasis in Gynecological Cancer

AIM: This study investigated whether dual-phase scanning (DPS) with 18-fludeoxyglucose positron emission tomography -computed tomography (FDG PET-CT) improves diagnosis of lymph node metastasis (LNM) in gynecologic malignancies, compared to mono-phase scanning (MPS). PATIENTS AND METHODS: The study included 139 patients who underwent PET-CT followed by systemic lymph node dissection. PET-CT scans were obtained twice. The maximum standardized uptake value (SUVmax) was measured and the retention index (RI) was calculated as the % change from the early to the delayed scan. The optimal threshold of RI was determined using a receiver operating characteristic (ROC) curve. Diagnostic efficacies were calculated for MPS and DPS using pathological results. RESULTS: In total, 1,879 regions were dissected. The optimal RI was 9%. The sensitivity, specificity and accuracy were 35.8%, 99.0% and 96.8% for MPS and 26.9%, 99.6% and 97.0% for DPS, respectively. Specificity was significantly improved by DPS and accuracy was also improved, but not significantly. CONCLUSION: DPS had an unsatisfactory impact on the diagnostic efficacy for LNM.