Objective; To determine the accuracy of visual analysis and the retention index (RI) with dual-time point (18)FFDG PET/CT for the characterization of indeterminate pulmonary nodules (IPN) with low FDG uptake.
Materials and methods: A retrospective analysis was performed on 43 patients (28 men, 64 +/- 11 years old, range 36-83 years) referred for IPN characterization with F-18-FDG-PET/CT and maximum standard uptakevalue <= 2.5 at 60 minutes post-injection (SUVmax1). Nodules were analyzed by size, visual score for FDGuptake on standard (OSEM 2,8) and high definition (HD) reconstructions, SUVmax1, SUVmaxat 180 minutespostinjection (SUVmax2), and RI was calculated. The definitive diagnosis was based on histopathologicalconfirmation (n = 28) or >= 2 years of follow-up.
Results: Twenty-four (56%) nodules were malignant. RI >= 10% on standard reconstruction detected 18nodules that would have been considered negative using the standard SUVmax >= 2.5 criterion for malignancy. RI >= 10% had a sensitivity, specificity, PPV, NPV and accuracy of 75, 73.7, 78.3, 70, and 74.4%, respectively, while for FDG uptake > liver on HD these were 79.1, 63.2, 73.1, 70.6, and 72.1%, respectively. SUVmax1 >= 2, SUVmax2 > 2.5 and FDG uptake > liver on standard reconstruction had a PPV of 100%. FDGuptake > mediastinum on HD had a NPV of 100%.