New source of random telegraph signal in CMOS image sensors

We report a new source of dark current random telegraph signal in CMOS image sensors due to meta-stable Shockley-Read-Hall generation mechanism at oxide interfaces. The role of oxide defects is discriminated thanks to the use of ionizing radiations

Knowledge, attitude and perception on radiation imaging among children's caregivers in the pediatric dental clinic

OBJECTIVE: Nuclear medicine provides important clinical information for diagnostic and therapeutic purposes. Use of medical imaging has gradually increased in the United States and this has raised health concerns about the potential future risks associated with radiation exposure in children. While studies have evaluated the adverse effects of imaging procedures, there is insufficient evidence about communicating radiation risks. The overall purpose of this paper is to review radiation risks in pediatric imaging using published evidence by the World Health Organization and to evaluate the knowledge and attitude of caregivers towards radiation risks in pediatric imaging. Specifically, we aim to determine whether an educational brochure improves parental knowledge of radiation and/or changes in attitude and perception to allow their children to undergo dental radiographs. METHODS: A prospective sample survey was performed of caregivers who presented with their child to the Boston University Pediatric Oral Healthcare Center. Parents or legal guardians (18 years or older) who accompanied a child were eligible for inclusion and approached for enrollment. Pre- and post-survey questionnaires were used to evaluate parents’ or guardians’ level of knowledge and attitude about the risks and benefits of dental radiographs. Parents were also asked their comfort level to allow their child to undergo dental radiographs. After completing the pre-survey questionnaire, parents were asked to read the English-language informational handout. Statistical analysis was performed through Microsoft Excel 2013. Descriptive analysis was conducted to summarize the survey responses. RESULTS: Among 30 parents who were surveyed, a small proportion (30%) of parents were very comfortable with dentist using dental radiographs on their child, versus 57% after reading the handout. Results showed that the informational handout improved the parental knowledge of risks and benefits of ionizing radiation. Most parents indicated that the handout was helpful and they reported increased level of comfort and willingness in their children receiving radiation imaging during dental treatment procedures. DISCUSSION: Educating parents or caregivers through an informational handout is a helpful resource in improving their knowledge and in relieving their concerns. Informing parents about the risks of ionizing radiation does not change parental willingness for their children to undergo dental radiographs

Hazards to space workers from ionizing radiation

A compilation of background information and a preliminary assessment of the potential risks to workers from the ionizing radiation encountered in space is provided. The report: (1) summarizes the current knowledge of the space radiation environment to which space workers will be exposed; (2) reviews the biological effects of ionizing radiation considered of major importance to a SPS project; and (3) discusses the health implications of exposure of populations of space workers to the radiations likely to penetrate through the shielding provided by the SPS work stations and habitat shelters of the SPS Reference System

His+ reversions Caused in Salmonella typhimurium by different types of ionizing radiation

The yield of his+ reversions in the Ames Salmonella tester strain TA2638 has been determined for 60Co γ rays, 140 kV X rays, 5.4 keV characteristic X rays, 2.2 MeV protons, 3.1 MeV α particles, and 18 MeV/U Fe ions. Inactivation studies were performed with the same radiations. For both mutation and inactivation, the maximum effectiveness per unit absorbed dose was obtained for the characteristic X rays, which have a dose averaged linear energy transfer (LET) of roughly 10 keV/μm. The ratio of the effectiveness of this radiation to γ rays was 2 for inactivation and about 1.4 for the his+ reversion. For both end points the effectiveness decreases substantially at high LET, i.e., for the α particles and the Fe ions. The composition of the bottom and the top agar was the one recommended by Maron and Ames [Mutat. Res. 113, 173-215 (1983)] for application in chemical mutagenicity tests. The experiments with the less penetrating radiations differed from the usual protocol by utilization of a technique of plating the bacteria on the surface of the top agar. As in an earlier study [Roos et al., Radiat. Res. 104, 102-108 (1985)] greatly enhanced yields of mutations, relative to the spontaneous reversion rate, were obtained in these experiments by performing the irradiations 6 h after plating, which differs from the conventional procedure to irradiate the bacteria shortly after plating

DOES STILL EXIST A CORRELATION BETWEEN X-RAYS OCCUPATIONAL EXPOSURE AND BENIGN NODULAR THYROID DISEASE?

Objective: The prevalence of benign nodular thyroid disease in the general population is high, as shown by various studies, and the diagnosis is eased by the improved diagnostic capacity of the instruments used. The aim of the present study is the evaluation of occupational exposure to ionizing radiation as a possible significant risk factor in the determinism of this pathology. Method: A cross-sectional observational study in “A category” X-ray exposed workers (doctors, nurses, technicians) of the University Hospital of Palermo, compared with a sample of the general population, was carried out from June 2016 to June 2017. We evaluated data obtained from the Personal Health Records, including thyroid sonographic reports, assessed by 10-MHz neck ultrasonography: then were analyzed on the basis of statistical significance (p-value < 0.05, Odd ratios and 95% confidence interval), in order to identify possible relations with conditions who may become real risk factors, such as: occupational exposure, considering years and accumulated dose, age, gender, smoking habit. Result: Nodules were detected in 32/85 (37.6%) workers and in 31/90 (34.4%) subjects of the control group. None of the parameters examined in the two groups reached statistical significance as a risk factor, therefore not playing major role in the determinism of thyroid nodularitye. Conclusion: In this study, X-rays work-related exposure does not represent a risk factor of thyroid nodularity, although it would be opportune to know the reasons of the high prevalence of this pathology in general population

Mathematical methods and models for radiation carcinogenesis studies

Research on radiation carcinogenesis requires a twofold approach. Studies of primary molecular lesions and subsequent cytogenetic changes are essential, but they cannot at present provide numerical estimates of the risk of small doses of ionizing radiations. Such estimates require extrapolations from dose, time, and age dependences of tumor rates observed in animal studies and epidemiological investigations, and they necessitate the use of statistical methods that correct for competing risks. A brief survey is given of the historical roots of such methods, of the basic concepts and quantities which are required, and of the maximum likelihood estimates which can be derived for right censored and double censored data. Non-parametric and parametric models for the analysis of tumor rates and their time and dose dependences are explained

Historical Development of the Linear Nonthreshold Dose-Response Model as Applied to Radiation

[Excerpt] Despite the nearly universal adoption of the linear nonthreshold dose response model (LNT) as the primary basis for radiation protection standards for the past half century, the LNT remains highly controversial and a contentious topic of discussion among health physicists, radiation biologists, and other radiological scientists. Indeed, it has been pointed out that the LNT has assumed the status of a paradigm, synonymous with an ideal, standard, or paragon or perhaps to some, a sacred cow. Reduced to its very basics, the LNT postulates that every increment of ionizing radiation dose, however small, carries with it a commensurate increase in the chance or risk that the exposed individual will suffer some undesirable radiation effect, and that the risk thus incurred is directly proportional or linearly related to the dose. The specific effects are termed “stochastic,” which has been defined as “of a random or statistical nature.” Stochastic or probabilistic effects of radiation may occur as a result of low doses and are generally taken to be cancers (including leukemias) and genetic defects in the progeny. The severity of these radiation-induced stochastic effects, should they occur, are independent of the dose that produced them; thus, even though the likelihood or probability of an occurrence may be small to negligible, any and all manifestations of a radiation induced stochastic effect will have equal severity. By contrast, higher doses of radiation are known to produce characteristic somatic or deterministic effects including erythema, epilation, sterility, diminution of blood cell counts, cataracts and, in very high exposures, acute and chronic radiation syndromes. Such frank biological effects are nonstochastic in nature (in fact, they were at one time termed “nonstochastic effects”) and will always be manifested once a particular minimum dose – i.e., a “threshold” – has been received. The severity of the effect is related to the dose. Below the threshold dose there will be no demonstrable effect; as the dose increases beyond the threshold, so does the severity of the effect, or the degree of harm. … The purpose of the above discussion is to illustrate the underlying controversy and confusion that surrounds the LNT today, as well to underscore the lack of precision that sometimes accompanies the arguments of both the proponents and opponents of the LNT. Given that the LNT is a low dose phenomenon, there needs to at least be consensus on what is low dose, and such a consensus needs also to include consideration of other relevant and important factors such as the dose rate and specific stochastic end point (i.e., type of cancer or mutation). With this as a backdrop, the historical development and gyrations that led to the LNT as it is currently applied (or, some would say, misapplied) in radiological protection can be examined in the context of current scientific thinking with respect to radiation effects. It is not the purpose of this paper to endorse any particular position or to take sides but rather to present the story in a factual and fair minded manner. Hopefully, what follows will successfully achieve this goal. Thus, this paper will briefly review the scientific bases and supporting studies that led to the development and acceptance of the LNT in health physics. It will briefly touch on such topics as hormesis and other studies, such as the classic work of the late Robley Evans, that clearly demonstrate a threshold and nonlinear response for certain stochastic effects such as osteogenic sarcoma, along with the plethora of studies that suggest or have been interpreted to indicate that for at least some end points (i.e., cancers), response to ionizing radiation is consistent with the LNT model