Fluorodeoxyglucose uptake in absence of CT abnormality on PET-CT: What is it?

Figure 13 Lymphomatous disease of bone. A 28-year-old man with disseminated B-cell lymphoma had fluorodeoxyglucose positron emission tomography-computer tomography (PET-CT) for initial staging. Sagittal PET image shows foci of intense uptake in the vertebral bodies of the upper thoracic spine, but the CT is unremarkable in the corresponding sites. Repeated scan 3 mo after chemotherapy demonstrate resolution of uptake in the bones as well as lungs and lymph nodes.