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Cervical Cancer
Published in Pat Price, Karol Sikora, Treatment of Cancer, 2020
Georgios Imseeh, Alexandra Taylor
There is an ongoing debate about the optimal schedule for intrauterine brachytherapy.51 Low dose rate (LDR) systems with cesium-137 were radiobiologically ideal, as they allowed ongoing repair of radiation damage to normal tissues. However, these machines are no longer manufactured and are being replaced by high dose rate (HDR) systems delivering rates in excess of 1 Gy/min, and the most common radioactive source is iridium-192. The short treatment time allows more geometrical stability of the applicator during treatment and more rapid patient throughput, but there is considerably less time for repair of radiation damage. Therefore, such treatments are fractionated over several days, and the dose is adjusted for this difference in dose rate. Pulsed dose rate brachytherapy (PDR) uses an HDR source but delivers multiple small fractions over 2 days for a single insertion to reproduce LDR radiobiology.52 In order to be able to compare outcomes for these different dose rates and fractionation regimens, it is now standard to report 2 Gy equivalent (EQD2) total doses.
Dose Coefficients
Published in Shaheen A. Dewji, Nolan E. Hertel, Advanced Radiation Protection Dosimetry, 2019
Nolan E. Hertel, Derek Jokisch
Due to its valence electron structure, cesium exhibits biochemistry similar to potassium. Due to the body’s widespread use of potassium, cesium tends to accumulate in a variety of tissues but will favor skeletal muscle, as shown in Figure 8.27 (ICRP 2017). Cesium-137’s progeny is barium-137m whose half-life (2.25 min) is short, but long enough to allow for migration out of the tissue it is created in and back to the bloodstream. Given the distribution of muscle throughout the body, and the long-range nature of 137mBa’s 661.6 keV gamma ray, the dose to tissues ends up more uniformly distributed than the other examples in this chapter, as seen in Figure 8.28 .
Radionuclides in water *
Published in Jamie Bartram, Rachel Baum, Peter A. Coclanis, David M. Gute, David Kay, Stéphanie McFadyen, Katherine Pond, William Robertson, Michael J. Rouse, Routledge Handbook of Water and Health, 2015
Cesium-137 is an anthropogenic radionuclide, with a 30 year half-life, produced during nuclear fission (i.e., the splitting of a nucleus into at least two other nuclei) of various isotopes of uranium, plutonium, and thorium. Cesium-137 decays by β decay that is shortly followed by the emission of a γ ray from its short lived decay product, barium-137m (the “m” indicates it is a metastable nuclear isomer that decays very quickly). Two other isotopes of cesium, cesium-135 and cesium-134, are often considered less of a health concern because of their decay characteristics. For example, cesium-135, a β emitter, with a half-life of 2.3 million years has very low specific activity (i.e., number of decays per unit mass or volume). Cesium-134, a β emitter, has a half-life of 2.1 years so does not persist in the environment as long as cesium-137. However, determining cesium-137/cesium-134 ratios may help to identify the source and age of cesium in water.
A review of the impact on the ecosystem after ionizing irradiation: wildlife population
Published in International Journal of Radiation Biology, 2022
Georgetta Cannon, Juliann G. Kiang
Twenty-one years later after the Chernobyl power plant explosion, various isotopes of plutonium, strontium-90, americium-241, and cesium-137 were still detected at high levels causing adverse biological effects across the nearby areas (Voitsekhovych et al. 2007). Wildlife continued to be exposed to substantial radiation doses after humans were evacuated from these areas. The half-life of cesium-137 is approximately 30 years and it decays by β emission to a metastable isomer of barium-137. The half-life of barium-137 isomer is 2 minutes. Subsequently, the metastable isomer emits γ radiation and becomes ground state barium (Baum et al. 2002). Food or water contaminated with cesium-137 that are ingested lead to internal β and γ radiation doses in addition to external radiation doses. The half-life of cesium-134 is about 2 years. Cesium-134 emits β particles. The half-life of strontium-90 is approximately 29 years. Strontium-90 emits pure β radiation. Most of the plutonium isotopes emit α particles, which are ionizing and harmful, but have a short penetration distance. The half-life of plutonium-241 is approximately 14 years. It emits β radiation to become americium-241. The half-life of americium-241 is 432 years, and it emits α particles to become neptunium-237, with a by-product of γ emissions (Baum et al. 2002). This is the composition of radiation released and retained in the soil, water and air across the Chernobyl landscape. In addition to external radiation exposure, ingestion of contaminated food and water by wildlife occurred from the beginning of the disaster and continues to the present.
Consequences of a large-scale nuclear accident and guidelines for evacuation: a cost-effectiveness analysis
Published in International Journal of Radiation Biology, 2020
Moshe Yanovskiy, Ori Nissim Levi, Yair Y. Shaki, Yehoshua Socol
Radiation contamination decreases with time due to radioactive decay. In case of NPP accident, many radionuclides are released. The longest-living relevant radionuclide—cesium-137 (Cs-137)—has a half-life of 30 years; thus, its radioactivity decreases rather slowly: 50% of the initial level after 30 years, 25% of the initial level after 60 years and so on. However, many short-living isotopes are also released, so the initial radiation level decreases rather rapidly during the first year. There is also another mechanism of radiation rate decrease—the migration of radionuclides from the contaminated surface due to rain, wind, road traffic etc. The data for Chernobyl and Fukushima is fairly consistent (Balonov 2016; IRSN 2016; Zoriy et al. 2016; WNA 2018b) and shown in Figure 1. As a result, radiation dose absorbed in 10 years is only twice higher than the first-year dose, and the lifetime dose is approximately equal to three first-year doses (UNSCEAR 2013, p. 209). Although this fact is well known, it is not always considered in the radiation-protection context. One year after the accident and onwards the dose-rate R(t) can be approximately described by R(t) = R(0)/(1 + 0.75 × t) where t – time in years. This approximation is illustrated in Figure 1. Table 1 summarizes doses absorbed during different periods of time after the accident relative to the dose absorbed during the first 12 months.
Isolation of the effects of alpha-related components from total effects of radium at low doses
Published in International Journal of Radiation Biology, 2022
Chandula Fernando, Soo Hyun Byun, Xiaopei Shi, Colin B. Seymour, Carmel E. Mothersill
In the analysis data from the gamma irradiation experiments (through acute exposure to Cs-137) were subtracted from data generated from experiments with mixed alpha, beta and gamma irradiation (through chronic exposure to Ra-226 and its progeny). The data were analyzed to see the actual effect of caesium-137 exposure in directly exposed and distant progeny versus chronic exposure to radium assuming a dose and dose rate effectiveness factor (DDREF) value of 1 (Rühm et al 2016; Hoel 2018). In the second approach a Monte Carlo model was used to determine the contributions of alpha, beta and gamma decays to the total effect of the radium exposure in the directly exposed and progeny cells.