Chemistry and Isotopes of Iodine
Erwin Regoeczi in Iodine-Labeled Plasma Proteins, 2019
The principle of electron capture has already been described in Figure 5. It is quite common among iodine isotopes, this being the sole mode of decay for 123I and 125I, and part of the decay scheme for the I nuclides with mass numbers 118,119, 120, 121, 124, 126, and 128. Because of the conversion of one proton to a neutron by this process, the atomic number of the daughter is one less than that of the parent, whereas the mass number remains the same. Therefore, each iodine isotope undergoing electron capture transforms to tellurium of the corresponding atomic mass, e.g., , or., . Tellurium is the next element to I in period 5, group VI of the periodic table.
Biomedical Imaging Molecular Imaging
Lawrence S. Chan, William C. Tang in Engineering-Medicine, 2019
EC is the second method by which unstable neutron deficient nuclides decay. In general, neutron deficient isotopes which are of high atomic number decay more predominantly by electron capture, whereas those with lower atomic numbers will decay primarily by β+ decay. During EC the positive charge in the nucleus is decreased when a K-shell electron is captured by the parent nucleus. This capture results in the conversion of a proton to a neutron and the ejection of a neutrino and can be represented by the equation:
Fundamental Concepts and Quantities
Shaheen A. Dewji, Nolan E. Hertel in Advanced Radiation Protection Dosimetry, 2019
This process is termed electron capture and results in the transformation of a proton into a neutron. Thus, the Z number is decreased by one. Since the result is the same as positron decay, it is a competing process for nuclei with high Z/A ratios, and is a more common decay mode. The innermost (e.g., K and L shell) electrons are most likely to be captured and, as a result, characteristic X-rays from orbital cascade may result as the shells are re-filled. The energy equation for electron capture is
9th international symposium on physical, molecular, cellular, and medical aspects of Auger processes: preface
Published in International Journal of Radiation Biology, 2023
Katherine A Vallis, Roger F. Martin, Nadia Falzone
Removal of an inner orbital electron through the photoelectric effect, electron capture, or internal conversion leads to a vacancy which is then filled by a cascade of electron transitions from the outer shells. These transitions are accompanied by the emission of low energy ‘Auger’ electrons or characteristic X-rays. Auger electrons have low energy (<25 keV), have a short track length and are densely ionizing. As a result, the absorbed radiation dose they deposit in biological material is extremely high but restricted to a nanoscale volume (a few nm3) around the decay site. These qualities mean that Auger electron emitting radionuclides are suited to the ultra-precise delivery of radiation to individual cells, organelles or even to specific molecular targets, and so hold promise as oncologic therapeutic agents.
GOLD: human exposure and update on toxic risks
Published in Critical Reviews in Toxicology, 2018
Alan B. G. Lansdown
At least 70 isotopes of gold are known, some with half lives of <10 milliseconds, but only one stable isotope of gold (197Au) is known (Shuh et al. 2012). Decay modes of the 36 radioactive isotopes include proton emission, alpha decay, or electron capture. Radioactive gold nanoparticles (AuNP) (198Au or 199Au) are potentially beneficial in experimental anti-cancer therapies, radiotherapy and diagnostic medicine (Chanda et al. 2010; Chithrani et al. 2010; Haume et al. 2016). Several cases have been reported where skin cancer has been associated with “radioactivity emitted by gold rings” (Baptiste et al. 1984; Callery 1989; Miller and Aldrich 1990). Thus, Baptiste evaluated 135 individuals exposed to radioactively contaminated rings and reported nine cases of squamous cell carcinoma on the fingers. Elsewhere, Callery emphasized that the radioactivity emitted from the rings was not attributable to any radioactive isotope of gold but probably to contamination with emissions of radon gas (Callery 1989). Miller and Aldrich estimated that skin cancer in a lady who wore one such radioactive gold ring for 37 years was due to a radiation dose equivalent to 240 Gy/week and a maximum dose of 4800Gy (Miller and Aldrich 1990). In the early days of radium therapy for cancer, small hollow “gold-seeds containing radioactive radon gas were implanted into solid tumors. As discussed below, there is no evidence that stable gold (197Au) is carcinogenic in humans. (Gold beads implanted into tumors are still used widely in diagnostic medicine.)
The effect of 111In radionuclide distance and auger electron energy on direct induction of DNA double-strand breaks: a Monte Carlo study using Geant4 toolkit
Published in International Journal of Radiation Biology, 2018
Behnaz Piroozfar, Gholamreza Raisali, Behrouz Alirezapour, Mohammad Mirzaii
More than half of radionuclides which decay by electron capture and/or internal conversion, emit Auger electrons with energies ranging from few eV to few keV. The Auger electrons’ range in water changes from a nanometer to several micrometers comparable with subcellular scale (Kassis 2003, 2004; Boswell and Brechbiel 2005; Nikjoo et al. 2008). The emitted Auger electrons lead to highly localized energy deposition (106–109 cGy) in an extremely small volume in the proximity of the decaying nucleus (Boswell and Brechbiel 2005; Balagurumoorthy et al. 2012). For many years, because of low energies and short range of Auger electrons, their biological effects and therapeutic applications were neglected (Kassis 2003, 2004), but based on the recent investigations and observed biological effects, Auger electron therapy and its therapeutic potential have increasingly been considered (Buchegger et al. 2006; Cai et al. 2010; Tavares and Tavares 2010; Pszona et al. 2012). In contrast to α and β-particles, Auger electrons with high linear energy transfer are much less radiotoxic to healthy cell while travelling in blood or bone marrow, and become highly efficient when incorporated into DNA of target cells (Buchegger et al. 2006; Emfietzoglou et al. 2008).
Related Knowledge Centers
- Atom
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- Beta Particle
- Gamma Ray
- Radioactive Decay
- Internal Conversion
- Characteristic X-Ray
- Atomic Nucleus
- Positron Emission
- Inverse Beta Decay