Fluorine radionuclides

An electrochemical cell [93,94] was used to obtain an efficient anodic deposition of no carrier added F-fluoride solubilized in the target water. The radioisotope is electrochemically adsorbed on the anode (glassy carbon electrode) and can be easily dried. An opposite electrical field releases the radionuclide directly into a solution of a phase transfer catalyst in dipolar aprotic solvents. The nucleophilic fluorination can be performed simultaneously if the electrochemically and thermally induced desorption of radioactivity is done in the presence of the precursor. However, the yields remain poor (3 % in the electrochemical n.c.a [ F]fluorination of anisole). 

The radionuclide fluorine-18 and some general considerations concerning short-lived positron emitters... 

THE RADIONUCLIDE FLUORINE-18 AND SOME GENERAL CONSIDERATIONS CONCERNING SHORT-LIVED POSITRON EMITTERS... 

Fluorine-18 is an artificial radionuclide, discovered in 1937. It decays with a half-life of 109.8 min for 97% by positron emission and for 3% by electron capture to the stable isotope oxygen-18. The maximum jS+-particle energy is 0.635 MeV [4],... 

The choice of the radionuclide and the position of the labelling are generally determined by the chemical structure of the target molecule to label and the ease of introduction of the radionuclide from a chemical point of view. The physical half-life of the radionuclide should however match the timescale of the studied process. For example, in repeated blood flow measurements, oxygen-15 in the form of p Ojwater is ideal, while carbon-11 and especially fluorine-18 are preferable in the study of slower processes. 

Many radionuclides can be produced in cyclotrons, thus avoiding the use of more costly nuclear reactors. Many research hospitals now have cyclotrons to provide shortlived radionuclides of carbon, nitrogen, oxygen, and fluorine. The longer-lived products are produced commercially or in government laboratories.25,26 28A list of major isotopes and their uses is shown in Table 21.9,... 

Some Positron Emitters of Clinical Interest Fluorine-18 is undoubtedly the most widely used positron-emitting radionuclide. This is mainly due to the wide use of 18FDG, the PET radiopharmaceutical that has permitted PET to become an everyday clinical tool. With the exception of 18FDG and probably 18FDOPA, the use of other 18F-labeled radiopharmaceuticals is very limited. However, the chemical and physical characteristics of 18F are excellent ... 

When the short-lived, positron-emitting radionuclide [ F]fluorine must be introduced in an organic framework, fluorination via acid decomposition of 3,3-dialkyItriazenes (Section... 

In the field of radiochemistry, and particularly with the use of high-specific-activity radionuclides, syntheses are almost uniformly done with an excess of unlabeled precursor and reagents with respect to the radionuclide, in this review fluorine-18. For that reason the efficiencies of reactions are generally given in terms of radiochemical yields instead of... 

Liquid targets are used in the production of many PET radionuclides, particularly 18F and 13N. Fluorine-18 is produced by using a liquid target of lsO-enriched water and so is 13N by using 5 nM ethanol in water. The target volume is small in the range of 3-15 ml under high pressure. Since lsO-water is expensive, it is customary to recover it for subsequent irradiation and the method of recovery is described in the later section. 

---