18FNaF

18FNaF, or fluorine-18 sodium fluoride (18F-NaF), is a radiopharmaceutical used in positron emission tomography (PET) imaging to visualize bone metabolism. It consists of fluoride-18 ions bound to sodium fluoride and localizes in regions of active bone formation, providing high-contrast skeletal images.

Production and administration: 18F is produced in a cyclotron by proton irradiation of 18O-enriched water and is subsequently prepared as 18F-NaF for intravenous injection. Typical activity for an adult PET bone study is about 185–370 MBq (5–10 mCi), with scanning starting roughly 60 minutes after administration to allow adequate bone uptake and clearance from blood.

Mechanism and imaging: Fluoride-18 ions exchange with hydroxyl groups in hydroxyapatite of bone, concentrating at sites of osteoblastic activity. 18F-NaF PET offers rapid blood clearance and high bone uptake, enabling whole-body imaging with greater sensitivity and spatial resolution than conventional bone scintigraphy. This can improve detection of small or early metastatic lesions and other abnormalities of bone metabolism.

Clinical uses and advantages: 18F-NaF PET is primarily used to detect bone metastases, evaluate unclear osseous lesions, and assess metabolic activity in various bone disorders. Compared with Tc-99m–based bone scintigraphy, 18F-NaF PET generally provides higher sensitivity and resolution, potentially allowing shorter imaging protocols and more accurate staging.

Limitations and considerations: Availability requires a cyclotron and specialized radiochemistry facilities, which can limit access and increase cost. Radiation dose is comparable to other PET tracers, and uptake can occur in inflammatory or infectious processes, necessitating careful interpretation within clinical context. Safety considerations apply for pregnancy and other standard radiopharmaceutical precautions.