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Planar Scintigraphy and Emission Tomography
Published in Bethe A. Scalettar, James R. Abney, Cyan Cowap, Introductory Biomedical Imaging, 2022
Bethe A. Scalettar, James R. Abney, Cyan Cowap
Many radioactive nuclei occur naturally. However, medicine relies primarily on the use of radioactive nuclei that are generated artificially in one of three ways – using a cyclotron, a nuclear reactor, or a radionuclide generator. Here we summarize the cyclotron and generator approaches because these are the sources of two of the most prominent radionuclides used in medical imaging, 18F and Tc-99m.
Chemical Aspects of Nuclear Processes
Published in Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff, Radiation and Radioactivity on Earth and Beyond, 2020
Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff
In the laboratory, the most common device for the preparation of radioisotopes with accelerated particles is the cyclotron. This is a circular type of accelerator in which the ions describe a spiral trajectory and attain energies up to 100 megaelectronvolts. Current intensities are typically of the order of a milliampere, which corresponds to a flow of 6×1015 particles per second. Machines of more compact form, called “baby cyclotrons” are increasingly being used in hospitals for medical applications of short lived nuclides.
Radioactive Materials and Radioactive Decay
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
There are about 40 radioisotopes that are made in nuclear reactors by having an existing isotope absorb a neutron, and there are about a dozen additional radioisotopes that are created from the fission products—that are the by-products of the fission reaction itself. Table 6.4 lists some of these isotopes as well as their half-lives and medical applications. Notice that almost all of the isotopes listed in the following are produced in fission reactors from the nuclear fission of uranium fuel. Most of these isotopes are β− or electron emitters because the nuclei that they are emitted from are neutron rich. These isotopes also correspond to the pink dots that are shown in the Chart of the Nuclides or the Segre chart (see Figure 6.14). In contrast to nuclear fission reactors, cyclotrons and nuclear accelerators are used for producing radioisotopes that are proton rich (or neutron poor).
Development of an Experimentally Validated MCNP6 Model for 11C Production via the 14N(p,α) Reaction Using a GE PETtrace Cyclotron
Published in Nuclear Technology, 2020
Amy Hall, Daniel A. Gum, Richard Ferrieri, John Brockman, James E. Bevins
A major concern associated with gaseous cyclotron target systems is the effective dissipation of heat within the target.4 When heat builds up within a target, it leads to gas expansion, which results in a nonuniform density distribution throughout the target volume. Higher cyclotron beam currents are ideal for producing greater amounts of radioisotopes because they allow for increased interactions per unit time.4 However, higher beam currents also result in higher temperatures within the production targets and more pronounced gas density reduction effects. When the production target gas heats up, the density decreases, and the gas spreads out from the heat source, which is generally in the center of the gas region. The target gas becomes more dense on the edges of the target where the gas has reduced interaction with the cyclotron beam. This results in decreased overall efficiency of radioisotope production within the target.4
SRIM and FLUKA simulation for target design
Published in Radiation Effects and Defects in Solids, 2019
S. A. Kandil, D. Krupp, U. W. Scherer
There is an increasing demand for radionuclides for diagnostic and therapeutic Nuclear Medicine. The number of cyclotrons has increased grossly over the last 20 years, but they cannot cover the consumption, in particular, of longer-lived radionuclides for which larger cyclotrons are frequently required. Moreover, ‘non-organic’ metallic radionuclides have been recognised in their diagnostic and therapeutic value. Frequently, the so-called theranostic couples of radionuclides have been identified, where one isotope of an element is used for diagnosis and another one for therapy in nuclear medicine (1). In many cases, it is advantageous or even required to produce these radionuclides with medium-energy cyclotrons which are not generally available. This also means, to provide a reasonable supply, the production yields need to be high to cover at least the regional demand.
Development of Tracer Particles for Positron Emission Particle Tracking
Published in Nuclear Science and Engineering, 2023
Thomas Leadbeater, Andy Buffler, Michael van Heerden, Ameerah Camroodien, Deon Steyn
The University of Birmingham benefits from access to daily cyclotron beams for PEPT isotope production,47 but at iThemba LABS and elsewhere, access is much more restrictive. In such cases radioisotopes can be acquired indirectly from cyclotron produced radioisotope generators (Sec. V.A), which have immediate benefits in producing the required high specific activity and short-lived isotope without the need for daily activation by an accelerator. A further alternative being occasionally explored makes use of daily activation used in the production of medical positron emitters (e.g., 18F, Sec. V.C), but these have scientific and political complications in maintaining sustained and frequent use.