Evolution of Radiation Protection and Radiation Risk Concepts
K. N. Govinda Rajan in Radiation Safety in Radiation Oncology, 2017
Tolerance dose and MPBB implied that there is a threshold for harmful effects of radiation and that the cells would be able to repair any damage below this tolerance dose or MPBB. Since such thresholds are common in biological systems while dealing with toxic agents, few believed it could be any different with X-rays or gamma rays. However, growing evidence, particularly the studies of Herbert J. Muller on the mutations induced in fruit flies by X-rays, showed there was no such threshold for this effect. There was a direct proportion between the quantity of radiation and the number of mutations, without any threshold limit. This seemed to suggest that perhaps the so-called tolerance might mean detriment at a more subtle level and not detectable, such as with the skin injury. In any case, Muller’s results and its implications for germ cells led to a reconsideration of the tolerance dose, to set a lower value for it. It also created an opinion in the scientific committee that perhaps there is no real threshold for some of the radiation effects, though there could be a threshold for noncancer somatic effects such as skin injuries or eye cataracts. This led to changing the terminology from tolerance dose to maximum permissible dose (which may not be tolerable but the harm is acceptable).
Radiographic Applications in Forensic Dental Identification
Michael J. Thali M.D., Mark D. Viner, B. G. Brogdon in Brogdon's Forensic Radiology, 2010
Recent research simulating morgue usage in a mass fatality setting has proven the safety of those working within the dental operating area. A study simulating doses to that received by a dental team over a 2-week disaster deployment (5760 exposures) showed that the team member receiving the highest dose was at a position 60� to the side of the emanating beam, and received an exposure of 0.253 mSv.19 This dose corresponds to 1/200th of the annual occupational maximum permissible dose (MPD) of 50 mSv and approximately 3.5 weeks of the U.S. average background radiation.20 Another study simulated the dose received at numerous operator body locations during 915 exposures. Extrapolating the data as an expression of average annual operator exposure resulted in a whole body dose of 0.4536 or 0.9% of the annual MPD.21
The Physical Environment
Vilma R. Hunt, Kathleen Lucas-Wallace, Jeanne M. Manson in Work and the Health of Women, 2020
The recent concern arises from a recommendation made several years ago by the NCRP7 that during the entire gestation period the maximum permissible dose equivalent to the fetus from occupational exposure of the expectant mother should not exceed 0.5 rem, i.e., one tenth the maximum permissible dose allowed the worker — 5 rem. The following is the comment that went with the recommendation: The need to minimize exposure of the embryo and fetus is paramount. It becomes the controlling factor in the occupational exposure of fertile women. In effect, this implies that such women should be employed only in situations where the annual dose accumulation is unlikely to exceed 2 or 3 rems and is acquired at a more or less steady rate. In such cases, the probability of the dose to a fetus exceeding 0.5 rem before a pregnancy is recognized is negligible. Once a pregnancy is known, the actual approximate dose can be reviewed to see if work can be continued within the framework of the limit set above…the method of application (of the recommendation) is speculative and needs to be tested for practicality in a wide range of occupational circumstances. For conceptual purposes, the chosen dose limit essentially functions to treat the unborn child as a member of the public involuntarily brought into controlled areas. The NCRP recommends vigorous efforts to keep exposure of an embryo or fetus to the very lowest practicable level.
Tamoxifen citrate loaded chitosan-gellan nanocapsules for breast cancer therapy: development, characterisation and in-vitro cell viability study
Published in Journal of Microencapsulation, 2018
Pankaj Kumar Kathle, Nivedita Gautam, Karthikeyan Kesavan
Worldwide, about one-fifth of cancer patients suffer from breast cancer and this is a common cause of death in women (Malik et al.2012, Rugo 2014). The proliferative effects of oestrogen (female hormones) on breast glandular cells have been proved to be the major cause in mechanism of breast cancer (Lin et al.2016). Several therapeutic methods for breast cancer in clinical practice are available such as curative surgery, chemotherapy, radiation, hormonal therapy, and biologically targeted therapy. The available chemotherapeutic agents do not significantly differentiate between the normal and cancerous cells, which results in systemic toxicity and side effects. This significantly limits the maximum permissible dose of the drug. The convectional formulations have very poor drug permeation into the cancer cells due to less distribution and quick elimination (Maji et al.2014).
Flying rats and microbeam paths crossing: the beauty of international interdisciplinary science
Published in International Journal of Radiation Biology, 2022
In clinical radiotherapy, the maximum permissible dose prescribed to treat the tumor is always determined by the tolerance of the normal tissue in the vicinity of the tumor. One of the most important advantages of MRT, which has been demonstrated continuously during the decades of microbeam research in small animal studies, is the extremely high functional tolerance of normal brain tissue with respect to microbeams. Based on those data, it is expected that MRT, delivered as single fraction radiosurgery or as simultaneously integrated boost (SIB), should allow to administer X-ray doses sufficiently high to control malignant tumors which are considered radioresistant with the available radiotherapy techniques.
A review of studies of childhood cancer and natural background radiation
Published in International Journal of Radiation Biology, 2021
Gerald M. Kendall, Mark P. Little, Richard Wakeford
The National Council on Radiation Protection and Measurements has recently published a review of the implications of epidemiologic studies for the linear-non-threshold model and radiation protection (NCRP 2018). This covered very much more than just studies of childhood cancer and natural background radiation. The potential problems that NCRP identified for studies of childhood leukemia generally were:
Related Knowledge Centers
- Ionizing Radiation
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- Threshold Model
- Radiation Hormesis
- Effective Dose
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