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Basic Radiobiology
Published in Kwan Hoong Ng, Ngie Min Ung, Robin Hill, Problems and Solutions in Medical Physics, 2023
Kwan Hoong Ng, Ngie Min Ung, Robin Hill
There has been a lot of discussion about the linear no-threshold model for determination of radiation risks at low doses. Why is the scientific information on radiation effects of low radiation doses (e.g., dose < 20 mSv) limited?
Theoretical Background to Radiation Protection
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Mike Rosenbloom, W. P. M. Mayles
Because of the low incidence of radiation-induced cancer compared with the natural incidence of the disease, there is little direct evidence of the magnitude of the risk for doses below 200 mSv. The possibility of a threshold below which radiation is not harmful is a subject of much controversy. Studies of large cohorts, such as the study of British radiologists, have failed to show any increased risk associated with the low doses they received (Berrington et al. 2001). Some have argued that very small doses of radiation may even be beneficial (so-called radiation hormesis) (Cameron and Moulder 1998; Siegel et al. 2017a), bearing in mind the existence of natural background radiation. BRER (2006), ICRP (1990, 2007a) and the radiation protection community have, however, taken the view that in the absence of clear evidence to the contrary, a linear no-threshold model should be assumed. An excellent review of these issues is given by Johansson (2003). There is also a view that the effect of radiation at low doses is underestimated by the linear model (Hall et al. 2004), although the latest evidence from the LSS (Grant et al. 2017) does not support this. The majority view of the Committee Examining Radiation Risks of Internal Emitters (CERRIE 2004) is that the linear no-threshold model is the most appropriate.
Augmented Reality for Reducing Intraoperative Radiation Exposure to Patients and Clinicians during X-Ray Guided Procedures
Published in Terry M. Peters, Cristian A. Linte, Ziv Yaniv, Jacqueline Williams, Mixed and Augmented Reality in Medicine, 2018
Nicolas Loy Rodas, Nicolas Padoy
X-ray-based medical imaging has revolutionized the diagnosis of diseases and the practice of numerous surgical treatments in the past few decades. It also has been a key factor in the paradigm shift from traditional surgery to minimally invasive surgery. X-ray imaging has become fundamental in several fields of medicine, such as interventional radiology/cardiology, orthopedics, urology, neuroradiology, and radiation therapy. However, the use of x-rays for medical purposes carries with it the risk of exposing patients, surgeons, and supporting medical staff members to harmful ionizing radiation. Studies have reaffirmed the hypothesis of a linear no-threshold model of radiation risk, namely that any amount of exposure increases the risk of radiation-induced tissue reactions (epilation, skin necrosis, cataract etc.) and of stochastic effects (cancers) (Roguin et al. 2013). While a patient’s exposure can be justified by medical indication and usually occurs in a single episode, medical staff providing patient care may be exposed on a daily basis. The repetitive nature of such an exposure, even when the dose is low, increases the risk of developing negative biological effects, and this risk increases with the dose accumulated over time (Kirkwood et al. 2014). Furthermore, as can be seen in Figure 15.1, when x-ray imaging is used for guidance, such as during interventional procedures, clinicians are obliged to remain next to the patient during the procedure, and their exposure cannot be completely avoided (Nikodemová et al. 2011). Indeed, reports have documented the dosage of radiation among interventional physicians as the greatest registered among any medical staff working with x-rays (Roguin et al. 2013).
Establishing a communication and engagement strategy to facilitate the adoption of the adverse outcome pathways in radiation research and regulation
Published in International Journal of Radiation Biology, 2022
Vinita Chauhan, Nobuyuki Hamada, Jacqueline Garnier-Laplace, Dominique Laurier, Danielle Beaton, Knut Erik Tollefsen, Paul A. Locke
Over the past few decades a vast amount of biological data has been generated to understand mechanisms of radiation-induced health effects (for humans and non-human species). These data complement the extensive information that has been gleaned from epidemiological studies and other evaluations that now create a robust framework on which to base decision making. However, at present there is no effective tool for collating and evaluating this extensive body of new evidence and identifying an optimal way of integrating it so that the most relevant scientific knowledge can be deployed to support radiation risk assessments. Additionally, radiation protection is confronted with a challenge to better understand health risks from low dose and low dose rate radiation exposures (<100 mGy and <5 mGy/h for low linear energy transfer radiation) to reduce the uncertainty related to the linear-no-threshold model (LNT) that constitutes one of the main assumptions underlying the international radiation protection system (ICRP 2007; NCRP 2020).
Low dose ionizing radiation and the immune response: what is the role of non-targeted effects?
Published in International Journal of Radiation Biology, 2021
Annum Dawood, Carmel Mothersill, Colin Seymour
Radiation risk in the low dose zone remains uncertain where models such as Linear-Non-Threshold Model (LNT) are currently used to make assessments about the carcinogenic effect of radiation. Many reviews have been written to discuss this model and how its applicability in the low dose zone may need reevaluation (Clarke 2000; Prise et al. 2003; Little 2010; Calabrese 2017; Calabrese 2018). The anti-tumor effect of LDIR has been reported by many (Portess et al. 2007; Csaba 2019), potentiating it as a viable immunotherapeutic treatment option (Janiak et al. 2017). Scott (2017) asserted that in addition to cancer, LDIR may also impart protection against other life-threatening conditions. Some suggested LDIR induced stimulation of a protective biological mechanism by way of adaptive or hormesis responses, (Feinendegen 2005; Scott 2008; Jargin 2012) such as activating bone marrow cells to differentiate into dendritic cells, thereby enhancing DC cells’ antigen uptake capacity and cytokine release (Chun et al. 2012).
Prolonged effect associated with inflammatory response observed after exposure to low dose of tritium β-rays
Published in International Journal of Radiation Biology, 2020
Yi Quan, Zhaoyi Tan, Yang Yang, Bing Deng, Long Mu
For low dose exposure, the estimation of health risk is extrapolated from the Linear No-Threshold model which is deduced from the epidemiological and statistical data of acute and high dose exposure (Brenner and Sachs 2006). While, limited informative epidemiological data can be used to explore health risk of low dose radiation induced by tritium exposure (Little and Lambert 2008; UNSCEAR 2017). For example, in most studies it is not possible to analyze the risk alone contributed by tritium as tritium exposure generally mixes with other type of radiation in occupational exposure (Snigireva et al. 2011; Schubauer-Berigan et al. 2015). To overcome this shortage, animal models and cellular experiments in vitro are carried out to provide plentiful data for the health risk estimation of tritium exposure. Recently, Canadian Nuclear Laboratories (CNL, Canada) and the Institute de Radioprotection et de Sûreté Nucléaire (IRSN, France) conducted a series of experiments on large scale in vivo mice to elucidate the biological effects induced by chronic internal exposure of tritium β-rays to low dose (Priest et al. 2017; Guéguen et al. 2018; Bertho et al. 2019). They conclude that HTO can produce protective or detrimental cellular responses, but the damage is less severe than organically bound tritium (OBT). However, fewer studies are performed to investigate the mechanism involved with the possible pathological process induced by tritium. As the genetic damage plays a critical role in pathological consequences of ionizing irradiation (Sia et al. 2020), in present work the gene toxicity and physiological effects were studied to recognize the subsequent effects caused by tritium β-rays of low dose. In brief, the lethal DNA damage, DNA double strand breaks (DSBs), was measured through γH2AX immunofluorescence staining. Then, changes of cellular behaviors and differences in gene expression after long incubation were analyzed. To clarify the involved mechanism, the associated regulated pathways were assessed by Ingenuity Pathway Analysis (IPA) based on the results of RNA sequencing.