Diffuse bone marrow uptake on whole-body F-18 fluorodeoxyglucose positron emission tomography in a patient taking recombinant erythropoietin.

F-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET) is used extensively in oncology to diagnose, stage, and restage patients with various malignancies. Many patients treated for malignancies develop neutropenia secondary to marrow suppressive chemotherapy and are subsequently treated with synthetic hematopoietic growth factors (HGF), both granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte-colony-stimulating factor (G-CSF). Patients taking HGF can present a diagnostic challenge for those interpreting PET because they can demonstrate diffuse marrow uptake on FDG-PET scans, mimicking diffuse bone marrow metastases. It has not been reported whether bone marrow uptake is affected on PET scans in patients taking erythropoietin, the erythroid-specific cell-line stimulator. We report a case of extensive diffuse bone marrow uptake in a 77-year-old man with a history of colon cancer who began taking erythropoietin 3 weeks before his PET scan. This case demonstrates the need to consider erythropoietin in the differential diagnosis of possible etiologies causing diffuse bone marrow uptake on PET scans.

An introduction to PET-CT imaging.

Cancer is one of the leading causes of morbidity and mortality in developed countries such as the United States. Complex clinical decisions about treatment of oncologic patients are largely guided by imaging findings, among other factors. Most radiologic procedures map the anatomy and morphology of tumors with little or no information about their metabolism. Positron emission tomography (PET) performed with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) has proved valuable in providing important tumor-related qualitative and quantitative metabolic information that is critical to diagnosis and follow-up. PET-computed tomography (CT) is a unique combination of the cross-sectional anatomic information provided by CT and the metabolic information provided by PET, which are acquired during a single examination and fused. FDG PET-CT offers several advantages over PET alone; the most important is the ability to accurately localize increased FDG activity to specific normal or abnormal anatomic locations, which may be difficult or even impossible with PET alone. Understanding the principles of FDG PET-CT and the optimal scanning techniques and recognizing the potential pitfalls and limitations are important for advantageous use of this imaging modality.