Fluorodeoxyglucose F18 Humans Lymph Nodes/*diagnostic imaging/pathology Lymphatic Metastasis/diagnosis/*diagnostic imaging/pathology Neoplasm Staging/methods Positron Emission Tomography Computed Tomography/*methods ROC Curve Sensitivity and Specificity Urinary Bladder Neoplasms/*diagnostic imaging/pathology/surgery Bladder cancer F-18 fluorodeoxyglucose Lymph node Positron emission tomography/computed tomography Staging