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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
Unlike SPECT, PET uses radiopharmaceuticals, commonly labeled with 18F, that decay and generate a positron. Individual positrons typically traverse short distances in the body and then are annihilated via interaction with an electron. Each annihilation yields two 511-keV photons that ideally move in anti-parallel directions and arrive, nearly simultaneously, at two detectors, as mentioned in Section 12.2.2.2 (Fig. 12.23a). The associated detection circuitry registers a coincidence event if certain energy and timing conditions are met (Fig. 12.23b).
Sol, Our Sun
Published in Thomas Hockey, Jennifer Lynn Bartlett, Daniel C. Boice, Solar System, 2021
Thomas Hockey, Jennifer Bartlett, Daniel Boice
Let us go through the complete p-p process. During the fusion of the two protons, one converts into a neutron. Two exotic byproduct particles are released: a neutrino [νe] and a positron [e+]. A neutrino is a neutral and nearly-massless particle that travels at almost the speed of light. A positron behaves like a positively-charged electron; it is called the antiparticle of the electron. Antimatter is real and is being produced in the Sun's core in large quantities. Unlike the ghostly neutrino that escapes directly to the ‘surface,’ the positron cannot survive in the crowded core. Antiparticles annihilate when they encounter their counterparts (in this case an electron) in a blinding flash of energy, resulting a two gamma-ray2 photons [γ]. A photon is a unit of electromagnetic radiation or light.
X-ray Interactions in Matter
Published in Ken Holmes, Marcus Elkington, Phil Harris, Clark's Essential Physics in Imaging for Radiographers, 2021
This process does not occur in diagnostic X-ray beams. The process only occurs with a photon energy of 1.02 MeV and above. The photon interacts with the nucleus of an atom and produces a positron and an electron. Positron annihilation is the basis of positron emission tomography (PET) scanning.
New Compact Neutron Generator System for Multiple Applications
Published in Nuclear Technology, 2020
For the production of the 6-MeV D-10B neutrons, pure 10B or its compound should be used as a thick target for the D− ion beam. The natural abundance of 10B is only 20%. For this reason, an efficient scheme such as the multi E × B filter system5 can be employed to produce enriched 10B for the target of the neutron generator. In the 10B(d,n)11C reaction, both the 6-MeV neutrons and the radioisotope 11C are produced simultaneously. The latter is commonly used in positron emission tomography (PET) imaging. Application of the 6-MeV neutrons is discussed in Sec. VI.
Nuclear Medicine in Oncology
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2018
Carla Oliveira, Rui Parafita, Ana Canudo, Joana Correia Castanheira, Durval C. Costa
PET is a tomographic imaging procedure that uses radiopharmaceuticals labelled with positron emitting isotopes. The emitted positrons, when combined with electrons, annihilate one another. The mass-energy conversion results in a pair of 511 keV gamma photons (two photons emitted simultaneously in opposite directions for each annihilation event) which are detected by the scanner. Presently, the majority of PET scanners feature a computerised tomography scanner component (CT) – hybrid equipment – to correct for photon attenuation and also for anatomical referencing of the lesions identified by the PET component.
Coexistence of positive and negative polarity solitons, double layers and supersolitons in electron-positron multi-ion plasmas
Published in Waves in Random and Complex Media, 2023
Debaditya Kolay, Debjit Dutta, Biswajit Sahu
The plasmas that have positrons act differently than usual plasma containing ions and electrons. The positrons are produced by the interplay of atoms and cosmic ray nuclei in the interstellar medium [1,2]. So in nature electron-positron-ion plasma appear in the early universe [3,4], pulsar magnetosphere [5], active galactic nuclei [6], neutron stars [7,8]) and solar atmosphere [9] etc. The electron's anti-particle is a positron that is positively charged and has equal mass and magnitude of charge as the electron. In very early universe [3,4] (when the temperature was nearly ), due to high temperature, photons had enough energy to produce electron-positron pairs. To be more precise, during the first second after the big-bang a huge number of electron-positron pair is created maintaining thermodynamic equilibrium. The electron-positron pair comes into exist in active galactic nuclei [6], when the gamma ray with energy interacts with soft photons of energy . In neutron star [7,8], the electron-positron pairs are formed during the magnetosphere filling period through curvature radiation which supplies electron-positron pairs to the neutron star's surroundings. In their paper, Dwyer et al. [10] suggested that the Earth's inner magnetosphere could be a new source of highly energetic electrons and positrons. According to new data from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), the Sun can emit positrons under specific circumstances, and solar flare-induced plasma collisions near the surface can provide enough energy to produce positron-electron pairs [11]. According to Greaves et al. [12], the modified positron trapping method have produced room-temperature plasmas containing positrons with s lifespan. Thus, majority of astrophysical and laboratory plasmas end up being an amalgam of electrons, positrons, and ions due to the long lifespan of positrons. Consequently, the e-p-i plasma has recently gained interest among plasma physicists.