Simplified and automatic one-pot synthesis of 16α-[18F] fluoroestradiol without high-performance liquid chromatography purification

16 alpha-[F-18] Fluoroestradiol (16 alpha-[F-18]FES, 1) is known as a valuable tracer in molecular imaging as estrogen receptor (ER) ligand for investigation of primary and metastatic breast cancer. ER concentration in human breast tumor cells is a significant indicator for the degree of disease and is often monitored by immunoassays or in vitro ligand binding of a tumor biopsy sample. More preferable non-invasive diagnosis is accessible using 16a-[18F] FES (1) as PET tracer. Our aim was to develop a reliable, easy-to-use, remotely controlled synthesis for non carrier added (n.c.a.) 16 alpha-[F-18]FES (1) by nucleophilic substitution using a disposable cassette for GE TRACERlab (R) MXFDG. Purification of the crude product using solid phase extraction (SPE) cartridges, Oasis (R) WAX, HLB Plus, Sep-Pak (R) C18 and Light Alumina N, allows abandonment of an HPLC purifying system. Formulation of the final product is included in the automatic synthesis. The experimental conditions for this easy-to-use synthesis for routine production of 16 alpha-[F-18] FES (1) are given in detail. Within 75 min 16 alpha-[F-18]FES (1) is produced in typically 20% n.c.a., radiochemical yield (non decay corrected). Chemical and radiochemical purity is > 95% and > 99%, respectively.