Radiation Environment and Medicine Vol.8, No.2
- Publisher : Hirosaki University press
- Language : English
- ISSN : 2423-9097 (PRINT), 2432-163X (ONLINE)
- Release : September 2019
- Issue : Hirosaki University Press
- pp. 39-132
Radiation Doses to Practitioners Caring for Victims of a Radiological Accident
- Introduction: Nuclear and Radiological incidents present unique patient care challenges.
Traditionally, the focus of radiological incident preparedness has been nuclear power plant
accidents. Emergency response planning now has a broader focus and addresses a range of
nuclear and radiological emergencies including acts of terrorism.
Basic actions of responders to radiological emergencies should not differ, in general, from those
taken in response to emergencies involving other hazardous material. The purpose of this project
was to model the potential radiation exposure to first responders and in receiving healthcare
- Methods: Radiation doses to medical personnel were modeled both empirically and via computer
modeling. Simulated isotopes were selected based on their likelihood of being present during
a radiological incident, as well as their radiological characteristics. Working backward from a
regulatory dose limit, the amount of material on or in a victimʼs body needed to produce such a
dose was determined.
- Results: Calculations estimate a dose rate of 0.67 mSv h-1 to a practitioner caring for a Chernobyl
accident victim with 1,400 MBq of I-131 in the thyroid. A practitioner caring for a hypothetical
patient uniformly contaminated with 60Co, 137Cs, or 192Ir would be able to stay in close proximity to
the patient for 18.1, 33.7, or 54.7 hours, respectively, before they reached the IAEA threshold dose
for lifesaving activities.
- Conclusion: Information presented here may be used to educate healthcare workers on the
relative risk of lifesaving activities following a radiological or nuclear incident. The research
presented here can also be used to provide additional information that an Incident Commander
can use to make more informed decisions about evacuation, sheltering-in-place, defining radiation
hazard boundaries, and in-field radiological dose assessments of the radiation workers, responders, and members of the public.
Key words: emergency response, accident, dose assessment
Validation of Popular Models Used in the Analysis of Specific Activity of Primordial Radionuclides in Environmental Samples through 1-D Analytical Modeling
A scientific model may be considered agreeable if it conforms to given scientific laws, in addition to being able to procure data that can be replicated to an acceptable level when other time-tested and proven methodologies are applied. For first-time researchers such as graduate students, choosing the right model is not always easy and some may opt for a particular model not because they are assured of its correctness, but because it has been used by peers before them. Such tendencies can inadvertently lead to the propagation of flawed models across generations of researchers. In the field of environmental radioactivity, the “comparison” and “conventional” models are frequently used in the evaluation of specific activity of primordial radionuclides in solids. Through one-dimensional (1-D) analytical modeling, this paper shows that while the conventional model conforms to given scientific laws, the comparison model does not since it wrongly assumes a linear between the intensity of gamma radiation through a solid and mass of the solid. A modified version of the comparison model that corrects for difference in mass between the solids being compared (sample of interest and certified reference material) is advanced.
Key words: 1-D modeling, model, conventional model, one-dimensional modeling
Radiation Induced by Stander Signalling
Radiation induced bystander effects are effects observed in unirradiated cells which receive signals
from irradiated cells. Bystander effects include DNA damage, chromosomal aberrations, changes
in gene expression, oncogenic transformation and cell death. Bystander signals can be transferred
to surrounding cells either by gap junctional intercellular communication or by the production of
soluble extracellular factors released from irradiated cells. Recently, exosomes have been shown
to play a role in transferring signals from irradiated to non-irradiated cells. This review summarises
a recent body of work on radiation induced bystander signalling, focusing on calcium, reactive
oxygen and nitrogen species and on membrane signalling.
Key words: Radiation induced bystander effects, signalling, calcium, reactive oxygen 32 species, reactive nitrogen species, membrane signalling
Current Status of Dosimetry Tools for Clinical Proton Beams
The use of proton beams is increasing in radiation therapy due to the physical characteristics of
the Bragg curve, offering dosimetric advantages over conventional radiation. However, dosimetric
measurements are necessary for safe and accurate irradiation with clinical proton beams. The
accuracy of dosimetry should be considered in terms of the required dose at the target volume,
which in general, requires standard uncertainty levels of 3%–5%. Reference dosimetry should thus
be done with uncertainties well below those levels, typically better than 1%, by using cylindrical
ionization chambers. By contrast, for non-reference measurements, the use of other dosimeters
should be considered provided that the energy and linear energy transfer (LET) dependence of
the detector response has been checked against the ionization chambers. The response of films,
silicon diodes, and other available solid-state detectors exhibits strong energy or LET dependence,
and their use is limited to conditions with nearly constant LET. This review is described current
dosimetric tools and methods for use with proton beams in routine clinical practice.
Key words: proton beam, dosimetry, measurement, detector
Preliminary Study of Expression of γ -H2AX and 53BP1 in Medical Radiation Workers
Currently a huge number of professional and technical personnel in medicine, dentistry,and veterinary medicine are exposed to radiation while administering various radiologic procedures such as diagnostic, therapeutic, interventional, and nuclear medicine. The radiation workers in medical area have risks to be exposed to ionizing radiation that also potentially cause DNA damage. In this study, 43 blood samples were taken from medical radiation workers in three hospitals (Hasan Sadikin, Medistra, and Betsaida Hospitals) and administrative staff served as control. They were grouped according to gender (man and woman) and duration of working time (0 – 20 and > 20 years). The expression of γ-H2AX and 53BPI foci was detected by using antibody of γ-H2AX Ser-139 and 53BPI under fluorescence microscope observation. The mean γ-H2AX and 53BPI foci in medical radiation worker and control were 0.22 and 0.12 and 0.38 and 0.17 respectively (P > 0.05). There was correlation between γ-H2AX foci and 53BP1 (P < 0.0001) and no statistically significant of γ-H2AX and 53BP1 foci in behalf on gender and duration of working time of radiation workers (P > 0.05). It can be concluded that potency of DNA damaged that detected by γ-H2AX and 53BP1 foci between medical radiation worker and administrative staff and their duration of working time was not different.
Key words: γ-H2AX, 53BP1, DNA damage, medical radiation worker
An Alternative Method for Screening Liquid in Bottles at Airports Using Low Energy X-ray Transmission Technique
Since August 2006, each airline passenger has been allowed to carry only a maximum of 100 ml liquid in each container and a total of not more than 1,000 ml in carry-on luggage. This measure was adopted to prevent bringing sufficient amount of deleterious liquids such as flammable, combustible and explosive liquids into the aircraft. Several methods have been investigated and tested to screen liquids in bottles at airports but none of them has been accepted as a routine inspection method. This research introduces low energy X-ray/gamma-ray transmission technique using a small 238Pu isotopic source and a compact 25 mm3 CdTe detector. The linear attenuation coefficients of various kinds of liquids contained in bottles having different sizes and thickness at 13.6 – 43.5 keV were determined without measurement of transmitted X-rays from an empty identical container or the empty portion of the container. Attenuation factor of the container was obtained from the estimated or measured container thickness and the predetermined linear attenuation coefficient of the container material. The technique introduced here could clearly distinguish alcohol, fuel oil and other kinds of liquid from water contained in bottles and cans while its sensitivity is dependent upon radiation energy and diameter of the bottle. It could be concluded that the proposed method has potential application in screening liquids contained in bottles for aviation security but further investigation on using other X-ray sources and X-ray detectors is recommended.
Key words: X-ray, gamma-ray, liquid, airport security, aviation security, explosive
Apoptotic Induction Mechanism of X-ray Irradiation Combined with Hydrogen Peroxide
Kochi oxydol-radiation therapy for unresectable carcinomas (KORTUC) is a clinical therapy, that combines X-ray irradiation and localized hydrogen peroxide. However few studies have reported the basic biological mechanism of action of KORTUC. Therefore we examined the effects of using a combination of hydrogen peroxide and X-ray irradiation on cell death. Cell viability of DU145, SAS, and HL60 cells decreased upon X-ray irradiation combined with exposure to hydrogen peroxide, compared to that on X-ray irradiation alone. DNA fragmentation of HL60 cells increased when cells were exposed to the combination treatment in comparison to X-ray irradiation, and apoptosis was considered to have increased. Abasic sites by DNA oxidative damage were observed early during X-ray irradiation, but no such increase was observed with hydrogen peroxide treatment. Caspase-3 and caspase-9 activities increased with all the three types of treatment, whereas caspase-8 showed high activity on treatment with hydrogen peroxide and the combination. The appearance of Bax and cytochrome c on X-ray irradiation and western blot analysis indicated the involvement of caspase-9 activation. Thus, cytochrome c was released via Bax, and the pathway leading directly from caspase-8 to caspase-3 was inferred to be induced with hydrogen peroxide treatment. The results suggested that hydrogen peroxide treatment induces apoptosis through a cascade that is different from that induced by irradiation, and combination with hydrogen peroxide is considered to enhance the effect of irradiation.
Key words: radiation, hydrogen peroxide (H2O2), apoptosis, caspase, KORTUC (Kochi oxydolradiation therapy for unresectable carcinomas)
Radon Priority Areas and Radon Extremes −−Initial Statistical Considerations
Radon is acknowledged an important health hazard. Indoor radon is believed to be the second cause of lung cancer after smoking. Therefore, indoor Rn has increasingly been subject to regulation for the last years; in Europe, the EU directive on basic safety standards for protection against ionizing radiation. Among other, it requires delineation of radon priority areas, i.e. areas in which action related to prevention and remediation of high indoor radon concentrations should be taken with priority. Whatever the exact definition of these areas, also in those not declared priority areas, high radon concentrations can occur, if with lower frequency. Arguing that also scattered instances of high radon, which are too scarce to justify declaring an area radon priority, deserve mitigation attention, a particular label might be given to these areas, indicating the presence of extremes within an otherwise non-priority area. First statistical considerations about radon extremes and anomalies are presented in this paper.
Key words: Radon priority area, anomaly, extreme
Extended Ordered-subsets Expectation-maximization Algorithm with Power Exponent for Noise-robust Image Reconstruction in Computed Tomography
The maximum-likelihood expectation-maximization (ML-EM) algorithm is the most popular iterative reconstruction method in emission-computed tomography with a noise model based on the Poisson distribution. The ordered-subsets EM (OS-EM) algorithm is known owing to accelerating the convergence of the ML-EM algorithm with the drawback of slow convergence. In this paper, we propose an extended OS-EM algorithm with a power exponent. We theoretically prove the asymptotic stability of an equilibrium corresponding to the solution of the nonlinear hybrid dynamical system whose numerical discretization based on multiplicative calculus coincides with the extended OS-EM algorithm. We provide a numerical experiment to demonstrate the effectiveness of the proposed system and confirm the acceleration of the proposed method and the robustness against noise. The reconstruction of high-quality images made by the method even when the projection data is noisy allows patient dose reduction in clinical practice.
Key words: Computed tomography, Iterative reconstruction, Ordered-subsets expectation maximization algorithm, Continuous-time image reconstruction, Noise-robust image, reconstruction, Dose reduction
Determination of Radon Mass Exhalation Rate in the Region of Highest Lung Cancer Incidence in India
Radon mass exhalation rate and radon flux from the soil are measured using Smart RnDuo detector in Saiha and Lawngtlai District of Mizoram, India during 2015-2016. Seasonal collection and analysis of soil samples were done from the study area under or near the dwellings. Inspite of being the region of highest lung cancer incidence area in India, the average mass exhalation rate and radon flux from the soil were found to be low, being 89.59 ± 1.83 mBq/kg/h and 66.66 ± 3.69 Bq/m2/h respectively. Soil type and its grain size which are important factors in determining the radon mass exhalation rate were further analysed and it was found that the soil was sandy type where larger grain sizes (mesh number 60-120) were dominant. Mizoram has high percentage (67%) of tobacco user from the population. Large consumption of tobacco and its products along with the life style of the people rather than radon are attribute to the high cancer incidence in these areas. In spite of lower than global average radon flux in the study area, effect of inhalation of the gas to cause lung cancer cannot be ignored.
Key words: Radon Mass exhalation rate, radon flux, Smart RnDuo detector, High lung cancer
Experience in Individual Dose Estimation after the Fukushima Nuclear Accident Using Self-administered Questionnaires ─ Activities to Encourage Responses to the Questionnaires and Resulting Response Rate ─
Following the Fukushima Daiichi Nuclear Power Plant accident, individual external doses have been estimated by obtaining information on peopleʼs behavior at an initial stage after the accident and combining it with ambient dose rate maps. Residents in Fukushima Prefecture were asked to fill in their behaviors on self-administered questionnaires. The rate of response to the questionnaires was in the 20% range several months after sending out the questionnaire by mail. However, the rate did not subsequently increase by much after that, so various activities were taken to raise the response rate. Major activities were (1) creating a questionnaire that was simpler to fill out, (2) approaching Fukushima residents directly at various venues to help them fill out questionnaires, and (3) using the mass media to encourage people to submit questionnaires. While these activities, carried out primarily from FY2012 to FY2015, helped increase the number of responses, the response rate for the entire prefecture did not increase by much, and was at 27.6% as of March 31, 2018. However, rates exceeded 50% in most municipalities of the Soso region, where the damaged nuclear power plant is located. It appears that the response rate roughly reflected the ambient dose rate level.
Key words: Fukushima accident, individual external dose, behavior survey, self-administered, questionnaire, response rate
Introduction of the Radiation Emergency Medicine Course at REAC/TS and Impressions of It from the Viewpoint of Medical Students
Since 2008, Hirosaki University has been running several projects on radiation emergency medicine for the preparedness in radiation and nuclear accidents. Within the framework of these projects, staff members of Hirosaki University have participated in the Radiation Emergency Medicine Course at the Radiation Emergency Assistance Center/Training Site (REAC/TS) in the USA since 2009. In 2019, some medical students of Hirosaki University got the first opportunity to attend the training course conducted by REAC/TS. Radiation Emergency Medicine course was mainly emphasized on the practical aspects of initial hospital management for the patients who were exposed and/or contaminated through lectures and hands-on practical exercises. In addition to radiation knowledge, having the same training with people from different occupations, languages and cultures gave us valuable experiences in deepening communication abilities. All of us had a very exciting and fulfilling time during our stay in REAC/TS.
Key words: radiation emergency medicine, training course, REAC/TS, medical student, Hirosaki University