F-18 fluorodeoxyglucose

F-18 fluorodeoxyglucose (FDG) is the most common PET radiotracer.

Structure

The radiopharmaceutical consists of the fluorine-18 radionuclide substituting the hydroxyl group at the C-2 position of glucose. The IUPAC chemical name is 2-deoxy-2-[F-18]fluoroglucose.

Production

F-18 fluoride ion is created in a cyclotron and then converted via an automated chemistry module into F-18 FDG. Specifically, F-18 FDG is produced through a nucleophilic substitution reaction, using the F-18 fluoride by nuclear reaction ¹⁸O (p,n) ¹⁸F starting from water (H₂O) enriched with oxygen-18.

Pharmacokinetics

• physical half-life: 110 minutes

• excretion: renal

Biodistribution

Physiologic activity is commonly seen in the following organs:

• brain (especially in basal ganglia, posterior cingulate cortex and visual cortex) ¹

• heart (especially left ventricular myocardium)

• kidneys and bladder (due to urinary excretion)

• liver (often used as an internal reference standard on whole body scans)

Other sites of physiologic uptake are variable or less intense:

• skeletal muscle (in extremities after strenuous activity or exogenous insulin administration, in mouth and larynx after speech or chewing)

• brown fat (especially in the neck and mediastinum)

• gastrointestinal mucosa (associated with metformin use)

• hematopoietic/lymphoid tissue: Waldeyer ring, thymus, spleen, and bone marrow

• salivary glands

• breast tissue, with increased activity during lactation

• spinal cord: most commonly T11-L1 and C4 levels ³

Clinical uses

• brain

  • identification of foci associated with epileptic seizures

  • evaluation of suspected Alzheimer dementia

• whole body

  • cancer staging and surveillance

  • evaluation of patients with fever of unknown origin

• cardiac

  • identification of viable and ischemic myocardium

See also

• F-18 fluorodeoxyglucose (FDG) embolism