18FFET

18F-fluoroethyl-L-tyrosine, commonly abbreviated 18F-FET, is a radioactive tracer used in PET imaging. It is an analog of the amino acid tyrosine labeled with fluorine-18. 18F-FET is transported into cells by amino acid transport systems, especially LAT1, and accumulates in cells with increased transport activity, a characteristic of many malignant tumors. It is designed to reflect transport rather than protein incorporation, aiding tumor visualization in the brain.

Clinically, 18F-FET PET is most used for brain tumors, particularly gliomas. It assists in detecting lesions, delineating tumors for biopsy or radiotherapy planning, and monitoring treatment response. It can help distinguish tumor progression from treatment-related changes, though results vary. Quantification uses standardized uptake values or tumor-to-brain ratios, with dynamic protocols sometimes employed to improve diagnostic accuracy.

Production relies on cyclotron-produced 18F, introduced into a tyrosine precursor via radiochemical synthesis to yield 18F-FET. Typical synthesis times and yields support routine hospital radiopharmacy workflows, and the tracer has a half-life of about 110 minutes, enabling distribution to PET centers.

Regulatory status varies by region. 18F-FET is widely used in Europe, Asia, and other regions, often within clinical protocols or research settings. In the United States, use is more limited and primarily within trials or off-label contexts. Safety follows standard PET radiopharmaceutical guidelines.

Historical development began in the 1990s, with researchers pursuing amino acid–based tracers to improve brain tumor imaging compared with glucose PET or MRI alone.