Fluorine-18-labeled sodium fluoride

Last revised by Andrew Murphy on 3 Apr 2020

Fluorine-18-labeled sodium fluoride (also known as 18F-NaF or sodium fluoride) is a PET radiotracer used primarily for skeletal imaging.

Fluorine-18-labeled sodium fluoride is an ionic compound comprised of a single sodium atom bound to a positron-emitting isotope of fluorine. 

Sodium fluoride has a generalized distribution, but the non-absorbed tracer is quickly cleared from the body in less than an hour by renal clearance and bone absorption 1. Skeletal targeting occurs because of fluoride absorption directly onto the surface of the bone matrix, as hydroxyapatite is converted to fluorapatite 1.

Similar to conventional bone scintigraphy, which uses Tc-99m-labeled methylene diphosphate (MDP) as the radiotracer, skeletal sodium fluoride distribution corresponds to osseous blood flow and osteoblastic activity 2. However, there is significantly higher bone absorption with sodium fluoride versus MDP. Thus, the higher target signal yields images which are higher in contrast and spatial resolution.

Sodium fluoride PET has higher sensitivity and specificity in detecting and diagnosing bone diseases compared with conventional bone scintigraphy, even when the latter is supplemented with SPECT or SPECT/CT imaging 2.

The primary clinical use of sodium fluoride PET is in detection of osseous prostate cancer metastasis. It is FDA-approved for PET imaging in evaluation of metastatic bone disease and for evaluation of treatment response 2.

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