Positron emission tomography radionuclides

A specialized application of microwave-assisted organic synthesis involves the preparation of radiopharmaceuticals labeled with short-lived radionuclides, particularly for use in positron emission tomography [70-72]. This represented an excellent application of microwave technology, where the products must be prepared quickly and in high radiochemical yield, on a small scale. 

Three new positron emitting generator systems have been described. The practical availability of these radionuclides could significantly broaden the potential applications of positron emission tomography. The next few years should see human clinical trials undertaken to fully evaluate their utility for nuclear medicine. 

Ultra short lived radionuclides, with a half-life of a few seconds to a few minutes are readily available from long-lived parent radionuclides adsorbed to an organic or inorganic ion exchange support matrix (1-3). These radionuclide generator systems are an inexpensive alternative to an on-site cyclotron, especially for positron emitters used for positron emission tomography (PET). 

Automated radionuclide generators capable of providing precise dose delivery of multi-millicurie amounts of short-lived positron emitters on demand from a safe and easily operated system are an attractive alternative to on-site cyclotrons for positron emission tomography. The availability of curie quantities of parent radionuclides from national laboratories and the development of microprocessor automation makes it feasible to utilize these generators in the clinical setting. 

Keywords Somatostatin Positron-emitting radionuclide Cancer therapy Diagnosis Positron emission tomography... 

Distribution in vivo could be studied by positron emission tomography (PET). Positron emission tomography is a sensitive and specific functional non invasive 3-D imaging method that permits rapidly and directly measurement of the total radioactivity from a drug labelled with a positron-emitting radionuclide (Gupta). 

However, positron emission tomography (PET) radiopharmaceuticals involve short-lived radionuclides (positron emitters) giving a double set of photons at 511 keV each. 

Positron emission tomography has become a widely used diagnostic technique in nuclear medicine. Ultrashort half-live radionuclides are used in these cases, and such radionuclides are mostly obtained in small cyclotrons with high yields and short irradiation times. The overall process will be described further in this chapter when PET radiopharmaceuticals are described. 

A relatively new technique that uses radioactivity to study body processes and diagnose malfunctions is commonly called positron emission tomography (PET). In this technique radionuclides that decay by positron emission are incorporated into compounds. For example, brain function can be studied by incorporating 1gC into glucose, which is the main source of energy for the brain. By studying how this labeled glucose is metabolized in the brain, doctors can discover abnormalities caused by diseases such as cancer, Parkinson s disease, and epilepsy. 

Several positron emitters are of practical importance in nuclear medicine for positron emission tomography (PET). Some are listed in Table 12.6. Protons or deuterons with energies varying between about 10 and 40MeV are available in small cyclotrons ( baby cyclotrons ) and are applied for the production of suitable radionuclides. 

Nowadays, nuclear medicine has become an indispensible section of medical science, and the production of radionuclides and labelled compounds for application in nuclear medicine is an important branch of nuclear and radiochemistry. The development of radionuclide generators made short-lived radionuclides available at any time for medical application. New imaging devices, such as single photon emission tomography (SPET) and positron emission tomography (PET) made it possible to study local biochemical reactions and their kinetics in the living human body. 

The production of short-lived positron emitters has been described in section 12.2. By interaction with electrons, the positrons are annihilated and two y-ray photons of 511 keV each are emitted simultaneously in opposite directions. By measuring these photons by means of a suitable arrangement of detectors, exact localization of the radionuclides in the body is possible. This is the basis of positron emission tomography (PET), which has found broad application in nuclear medicine. The most frequently used positron emitters are listed in Table 19.2. They are preferably produced by small cyclotrons in the hospitals or nearby. 

In positron emission tomography (PET) the two SllkeV y-ray photons emitted simultaneously in opposite directions are registered by y-ray detectors, indicating that the positron decay must have occurred somewhere along the line between these two detectors. The same holds for other events of positron decay, and the radionuclide can be localized at the intersection of these lines. 

Recently, a great demand for fast chemical synthesis has emerged in the clinical field. Positron emission tomography (PET) is a medical imaging technique that produces a three-dimensional image or map of functional processes in the body. The common PET probes contain radionuclides such as F, and Rb, the lifetimes of which are very short,... 

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