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Basics of Radiation Interactions in Matter
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
There are also some differences in the naming of photons. Gamma rays are those photons emitted as a result of the decay of a nucleus, and which therefore originate from the nucleus. X-rays that are emitted as a result of energy loss when electrons, accelerated in the vicinity of the atomic nucleus, are named ‘bremsstrahlung photons’ (sometimes also ‘braking radiation’). When a positron is close to an electron, and both particles are close to rest, a transformation of the two electron masses to energy in the form of electromagnetic radiation is possible with the result of two annihilation photons. A vacancy in an electron shell, caused by, for example, photoelectric absorption of an incoming photon, is called a ‘characteristic X-ray’ because the energies of these emitted X-ray photons are characteristic of the energy levels of the different electron shells and thus of the element. It is therefore recommended to follow these naming conventions because they provide information about the underlying interaction process.
Prompt Gamma Detection for Proton Range Verification
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Paulo Magalhaes Martins, Riccardo Dal Bello, Joao Seco
Prompt gamma-rays have an energy spectrum that goes up to 10 MeV. Gamma quanta with energies greater than 1 MeV interact with materials preferentially through Compton scattering or pair production. The photoelectric effect, which is usually exploited for imaging at lower photon energies, plays here only a minor role. It is therefore likely for a single prompt gamma to undergo multiple interactions with partial energy deposition before being fully absorbed. This has an impact both on the transport of the gamma radiation from the nucleus to the detector as well as on the interactions within the detector.
Particle Interactions with Matter
Published in Eric Ford, Primer on Radiation Oncology Physics, 2020
Further details about the underlying physics of LET can be found in the video, but a few key concepts are the following:LET depends strongly on the type of radiation (e.g. X-ray vs. light charged particle vs. heavier charged particle).LET is relatively low for X-rays, gamma rays, and electrons (<few keV/μm).LET is much higher for more massive charged particles (up to >100 keV/μm). This can be seen in Equation 7.3, which shows a z2 dependence for collisional stopping power. Note that neutrons are a high-LET modality because the products they produce (protons and various nuclei) are high-LET.
LDR-adapted liver-derived cytokines have potential to induce atherosclerosis
Published in International Journal of Radiation Biology, 2023
Eunguk Shin, Dahye Kim, You Yeon Choi, HyeSook Youn, Ki Moon Seong, BuHyun Youn
It should be noted that there is a potential difference in biological effectiveness in our in vivo and in vitro experimental data using different types of radiation, gamma ray and X-ray. RBE (Relative Biological Effectiveness) has been used to describe the effectiveness of different types of radiation on the same specified end-point as cancer development or other health effects. Although gamma ray and x-ray are usually regarded as the same type of radiation, low energy photons with a weighting factor (wR) of 1 for simple comparison to other higher LET radiation, the biological effectiveness of lower-energy of low LET radiation may be more than two times greater than for higher-energy of low-LET (ICRP publication 92 and NCRP Report No.181). Also, RBE generally increases with decreasing dose and dose rate (Barendsen 1992; Sørensen et al. 2021). Conventional 200kV x-rays are considered to be about twice as effective at low doses compared to gamma rays in some in vitro studies, including chromosomal aberrations in human lymphocytes, and killing of mouse oocytes (National Research Council Board on Radiation Effects R 1998). Therefore, our mechanistic results in the irradiated cells should be carefully interpreted for the enhanced understanding of physiological response in the radiation-exposed mice, considering dose rate, fractionation and energy quantity of radiation.
Radiosensitivity of seedling traits to varying gamma doses, optimum dose determination and variation in determined doses due to different time of sowings after irradiation and methods of irradiation in faba bean genotypes
Published in International Journal of Radiation Biology, 2023
Rajdeep Guha Mallick, Subhradeep Pramanik, Manas Kumar Pandit, Akhilesh Kumar Gupta, Subhrajit Roy, Sanjay Jambhulkar, Ashutosh Sarker, Rajib Nath, Somnath Bhattacharyya
To initiate an induced mutagenesis programme the first step is to select a suitable mutagen. A long-held idea, which probably has been influencing the choice of mutagen (chemical vs. physical) is that the chemical mutagens more favorably induce point mutations, whereas physical mutagens encourage gross lesions, such as chromosomal aberration and rearrangement. The chemical mutagens are said to be highly toxic. On the other hand, the side effects on the health caused by physical mutagens are considerably less. The choice of mutagen completely depends on its availability, allied expenditures and existing infrastructures. Gamma rays are quite easy in application; it penetrates easily due to their non-particulate nature and causes higher mutation frequency. In this experiment, gamma rays have been used for seed irradiation.
Assessment of chromosome aberrations in large Japanese field mice (Apodemus speciosus) in Namie Town, Fukushima
Published in International Journal of Radiation Biology, 2022
Yohei Fujishima, Akifumi Nakata, Risa Ujiie, Kosuke Kasai, Kentaro Ariyoshi, Valerie Swee Ting Goh, Kojun Suzuki, Hirofumi Tazoe, Masatoshi Yamada, Mitsuaki A. Yoshida, Tomisato Miura
As for the soil samples, five surface soil samples of 5 cm depth were collected at each sampling point. The soil samples were completely dried at 120 °C for 20 h before measurement. Each sample was transferred into separate plastic containers (U-8 container, SANPLATEC Co., Ltd., Osaka, Japan). The activity concentration for the collected samples was determined by gamma-ray spectrometry using a hyperpure germanium (HPGe) detector (ORTEC GEM-40190, SEIKO-EG&G Co., Ltd., Tokyo, Japan). 134Cs and 137Cs were detected using 604.6 and 661.6 keV gamma-ray energies respectively for 1,000–80,000 s to satisfy measurement errors from counting to below 5% of the corresponding activity concentration. Activity was decay corrected to the sampling date, and activity concentration was calculated as per kilogram of dry weight of the soil samples.