Figure 2.

[¹⁸F]Fluorodeoxyglucose (¹⁸F-FDG) (a) and 16α-[¹⁸F]fluoro-17β-estradiol (¹⁸F-FES) (b) positron-emission tomography (PET) studies obtained in a patient with newly diagnosed metastatic recurrent breast cancer in the bones. The bone metastases are readily seen in both studies. Whereas ¹⁸F-FDG-PET images provide information about the metabolic activity of the metastases, ¹⁸F-FES images can demonstrate that the recurrent lesions still express high levels of estrogen receptors.