Fluorine-18, radioactive isotope

The choice of an isotope for tracer studies requires an appreciation of not only the radiochemical properties of the element, but also the effects that they might have both biochemically and analytically. The isotope should have a half-life that is long enough for the analysis to be completed without any significant fall in its activity. Occasionally this might present a problem in that some elements only have radioactive isotopes with very short half-lives, e.g. fluorine-18 has a half-life of 111 min. Conversely, isotopes with very long half-lives should not be used for in vivo studies because accumulation in the tissues of the recipient is unacceptable. 

For decades, fluorine was a laboratory curiosity and it was studied mainly by mineral chemists. As is often the case, it was coincidence and not planned research that gave rise to fluorine chemistry. The development of the organic chemistry of fluorine is a direct consequence of the Manhattan Project in order to build nuclear weapons, the isotopic enrichment of natural uranium into its radioactive isotope was needed. For this purpose, the chosen process involved gas diffusion, which required the conversion of uranium into gas uranium hexafluoride (UFs) was thus selected. In order to produce UFe gas on a large scale, fluorhydric acid and elemental fluorine were needed in industrial quantities. This was the birth of the fluorine industry. 

The halogens will be restricted to chlorine, bromine and iodine since fluorine, as the most electronegative element, does not function as the central atom in a complex and astatine has only short-lived, radioactive isotopes, so that very little of its coordination chemistry has been investigated.2 ... 

Tritium is also one of the products obtained by bombardment of fluorine, beryllium, antimony, copper, or silver with deuterons, or the bombardment of boron and nitrogen with neutrons. Tritium is the simplest known radioactive isotope. It decays by emission of beta particles to form an isotope of helium and has a half-life of about 12 years. 

Fluorine is a chemical element that in pure form occurs as a dimer of two fluorine atoms, F2. The fluorine atom has the ground state electron configuration ls22s22p5. There is only one stable, naturally occurring isotope of fluorine 19F. However, the radioactive isotopes 17F, 18F, and 20F are known. The inclusion of the isotope 18F (half-life 110 minutes) in bioor-ganic molecules is an important noninvasive technique used in the study of living tissue by positron emission tomography. 

Fluorine possesses one radioactive isotope that is observable in the explosions of novae. This l8F has a halflife of 110 minutes, and the positrons that its decay ejects... 

In addition, 10 artificial radioactive isotopes of fluorine are known. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive. 

One radioactive isotope, fluorine-18, is sometimes used for medical studies. It is combined chemically with glucose (blood sugar) molecules and injected into the body. It then travels to cancer cells, which reproduce rapidly and use glucose very quickly. The presence of fluorine-18 can be detected in these cells because of the radiation it gives off Using this method, medical workers can determine the location, size, and other properties of cancerous cells in the body. 

One of the major goals of research in nuclear medicine is a drug that can be used to demonstrate the brain blood flow pattern. To do this job, a drug should demonstrate four properties. First, it must carry a radioactive isotope that is a positron emitter (best, a fluorine or an iodine atom, for use with the positron camera) that can be put onto the molecule quickly, synthetically, and which will stay on the molecule, metabolically. Second, as to brain entry, the... 

That is where we are headed now. In our lab at UCLA, for example, we conducted studies using PET scans for predicting the effectiveness of each of the major classes of cytotoxic chemotherapy agents used to fight breast, as well as many other, cancers. We tagged each of these drugs with a radioactive isotope of fluorine so that we could... 

All the stable isotopes of boron, carbon, nitrogen, oxygen, and fluorine are shown in the chart in the right hand column (in red), along with their radioactive isotopes with ti/2 > 1 min (in blue), (a) Write the chemical symbols, including mass and atomic numbers, for all of the stable isotopes, (b) Which radioactive isotopes are most likely to decay by beta emission (c) Some of the isotopes shown are used in positron emission tomography. Which ones would you expect to be most useful for this application (d) Which isotope would decay to 12.5%... 

Fluorine-18 is an artificially produced radioactive isotope. It decays by emitting a single positron. Write the nuclear equation for this decay. 

Owing to the short half-lives of the radioactive isotopes involved (e.g., t n of carbon-ll=20min, ty-i of fluorine-18 = 110min), radiopharmaceuticals for PET (and related SPECT) imaging are typically produced on-site daily or at facilities in close proximity to the PET imaging center. Radiopharmaceutical production typically requires trained radiochemists, with specific and expensive facilities. Moreover, the short-lived radionuclides involved means that radiochemical reactions must be fast, efficient, and amenable to automation, and new techniques that facilitate radiopharmaceutical production and the ability to meet clinical demand for PET tracers are in demand. Solid-phase synthesis is an attractive synthetic technique to the radiochemist as it bears many of these desirable characteristics. Despite this, solid-phase organic radiosynthesis (SPOR) is a relatively new... 

Although many fluorocarbon polymers are commercially available (Appendix 16.H), poly(tetrafluoroethylene) (PTFE) is estimated to command about 90% of the market. This polymer, under DuPont s trade name. Teflon, has been made since the early 1940s. Both PTFE and poly(chlorotrifluoroethylene) were developed to meet wartime demands, especially for the corrosive processes involving separation of radioactive isotopes. Many other fluorinated polymers have been commercialized over the years. 

ISOTOPES There are a total of 16 isotopes of fluorine. Only one, F-19, is stable. It makes up 100% of the fluorine found on Earth. All the others are radioactive with half-lives ranging from 2.5 milliseconds to 4.571 OOxlO years. 

The artificial radioactive fluorine isotope F-18 emits positrons (positive electrons) that, when injected into the body, interact with regular negative electrons, and they annihilate... 

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