Fig. 1: Axial CT image of a 70-year-old woman shows a well-defined, lobulated nodule in the left upper lobe.
Fig. 2: Axial FDG-PET image at the corresponding level to CT shows increased uptake of the nodule (relative to normal mediastinal uptake). The nodule was found to be adenocarcinoma.
- PET has sensitivity of 97% and specificity of 78% for the diagnosis of malignant solitary pulmonary nodule (this conclusion was drawn from a meta-analysis of nodules of any size but predominantly >1 cm)
- Pulmonary nodules negative on PET most likely benign, but further evaluation should be based on CT appearance (likelihood of cancer such as bronchioloalveolar carcinoma, carcinoid that are usually negative on PET) and clinical scenario.
- Dual time point PET (scan at 70 and 120 minutes after FDG injection) increases sensitivity, specificity and accuracy of PET for the detection of malignant nodule.
- Ability of PET to detect malignant nodule depends on the size of lesion and degree of uptake. Small lesions with high uptake may be shown on PET.
1. Gilman MD, Aquino S. State-of-the-art FDG-PET imaging of lung cancer. Sem Roentgenol 2005;40:144.
2. Gould MK, et al. Accuracy of positron emission tomography for diagnosis of pulmonary nodules and mass lesions. JAMA 2001;285:914.