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At least 397 records · Page 22Linked to original sources
PubMed1985

Dental radiologic survey of Virginia and Florida.

The results of a survey of 2,257 dental offices recording dental radiology practices are presented and compared to earlier surveys. In many practices patients were exposed to radiographs at predetermined intervals; the variables of manual processing are not well controlled, and darkrooms had excessive light.

Adult↗
PubMed1993

Radiation exposures around a panoramic dental x-ray unit.

To evaluate the radiation hazard in the vicinity of a panoramic x-ray unit, Ektaspeed periapical films were placed in an array behind and to the side of the unit. They were left in place for 7 months, during which 1414 examinations were carried out. The maximum exposure at 80 cm from the patient was determined to be about 1 mGy in 7 months with a heavy workload. This shows clearly that no special environmental shielding barriers are necessary around this unit.

Dental Staff↗
PubMed1985

Reducing radon exhalation from covered tailings: optimization or cost effectiveness?

Reduction of radon exhalation from uranium tailings as a function of the number of radon diffusion lengths in cover materials is discussed, based on dimensionless mathematical functions. Cost effectiveness is examined to determine the least expensive cover with a preselected number of radon diffusion lengths (i.e., a preselected level of radiation protection), and to find the maximum attainable reduction in radon flux with a predetermined cost (i.e., a fixed amount of money). Cost effectiveness rather than optimization through cost benefit analysis can be used advantageously in these cases.

Cost-Benefit Analysis↗
PubMed1985

A framework for a limitation policy of the population exposure to natural radiation in Belgium.

The conclusions are put forward that are adopted by a discussion group preparing the framework for a limitation policy of the radon problem in Belgium. Existing and future situations are treated in a coherent policy that is adequate for practical implementation. An action level is defined, together with a hierachy of levels for new constructions. The decision logic for the acceptance of building materials is explained.

Belgium↗
PubMed1985

Limitation of exposure to natural radioactivity in Canada.

The jurisdictional responsibility for natural radioactivity in Canada is divided between the federal and provincial governments. The desire for uniform standards has resulted in the formation of a scientific group to advise governments concerning the desirability of standards for exposure to natural radioactivity. The various types of exposure are reviewed with emphasis on naturally occurring radon in homes. The scientific Committee could not agree either philosophically or practically on the control level for radon in homes. To resolve this impasse, it undertook a calculation designed to illustrate for Canada, the potential cancers saved each year compared to the actual lung cancer rate, with an estimate of the cost for each limit derived. A second calculation reviewed the cost of modifying the building code and estimated the long term effect by comparing avoided cancers and cost. The calculations are based on cross-Canada surveys, intensive long term investigation of smaller groups of homes and national housing statistics. The results are discussed and serve to illustrate development of the proposed policy.

Canada↗
PubMed1985

The control of indoor radiation exposure.

Surveys of natural radiation indoors permit improved estimates to be made of exposures nationally and of regional variations. In the UK, there are clear indications that individual doses from radon decay products can be more than two orders of magnitude above the national average. A reliable risk factor for lung cancer allows the risks to individuals to be determined, and some members of the public are seen to be exposed to relatively high risks. The feasibility of reducing such risks requires a knowledge of the costs and effectiveness of remedial and preventive measures. There are also social and administrative considerations. The form of standards and the means of implementating them require careful consideration. A systematic approach to these issues is discussed in this paper.

Air↗
PubMed1995

Methodology for assessment of exposure to environmental factors in application to epidemiological studies: assessment of exposure to natural ionizing radiation.

This paper reviews the recent progress of passive measurement methods of gamma radiation and radon. Relatively cheap and reliable dosimeters are now available. Results from national and world-wide surveys of natural radiation in bedrock and soils and indoor radon concentrations exist. These can be used to more precisely indicate areas with enhanced exposure to gamma radiation, indoor radon levels and radium and radon in household water. Besides direct measurements of the radiation intensity, additional information (e.g., history of residence, house ventilation habits) is required to reconstruct historical exposure levels for epidemiological investigations. The availability and correctness of this information may influence the validity of exposure estimates.

Carcinogens, Environmental↗
PubMed1988

Radiation dose and shielding for the Space Station.

Significant differences in dose prediction for Space Station arise depending on whether or not the magnetic field model is extrapolated into the future. The basis for these calculations is examined in detail, and the importance of the residual atmospheric layer at altitudes below 1000 km, with respect to radiation attenuation is emphasized. Dosimetry results from Shuttle flights are presented and compared with the computed results. It is recommended that, at this stage, no extrapolation of the magnetic field into the future be included in the calculations. A model adjustment, to replace this arbitrary procedure is presented. Dose predictions indicate that, at altitudes below 500 km and at low inclination, and with nominal module wall thickness (0.125 in. aluminum), orbit stay times of 90 days in Space Station would result in quarterly radiation doses to the crew, which are well within present limits both for males and females. Countermeasures would be required for stay times of a year or more and the measure of increasing shielding is examined.

Aluminum↗
PubMedDate not supplied

Radiation protection of astronauts in LEO.

Radiological protection for space flights is often perceived as a technico-scientific problem. All this is the result of the effects of radiation encountered in space and manned flight conditions. The main characteristics of this radiation come from its complex composition and its large energy spectrum which must be taken into account as well as flux variations by both solar activity and the vehicle position on orbit. Inside a vehicle, structures constitute irregularly distributed shields and lead to a specific dose at each location. To be able to protect the crew, it is first necessary to understand the threat and therefore to identify the radiation environment: extraterrestrial and orbital. As the environment varies with both the orbit position and time, the dose received in each critical organ during missions must be determined and compared with acceptable limits. To counter the threat, which may exceed acceptable limits, a strategy is required, including the complementary aspects of prevention, detection, protection and possibly treatment.

Atlantic Ocean↗
PubMed1991

Radiological health risks for exploratory class missions in space.

Crewmembers on missions to the Moon or Mars will be unavoidably exposed to ionizing radiation as they pass through the Van Allen belts and the Galactic Cosmic Ray (GCR) flux. There is the possibility for exposure to proton radiation from Solar Particle Events (SPE). Using absorbed doses and ICRP 26, Linear Energy Transfer (LET) -dependent quality factors, the following dose-equivalents are estimated: In a spacecraft with 0.75 cm aluminum walls (2 g/cm2) at solar minimum, the lunar round trip dose-equivalent is less than 0.05 Sv. During a Mars mission the estimated dose-equivalents are: outbound (Van Allen Belts) <0.02 Sv; Earth to Mars (205 days exposure to free space GCR) 0.32 Sv; 30 days on the Martian surface (GCR) 0.023 Sv; Mars to Earth (225 days exposure to free space) 0.35 Sv; and through the Van Allen Belts 0.02 Sv. Conventionally, the total of 0.73 Sv over 460 days could be expected to increase the risk of cancer mortality in a 35-year old male astronaut by about one percent. However three-fourths of the dose-equivalent in free space is contributed by high LET heavy ions (Z > or = 3) and target fragments with average quality factors of 10.3 and 20 respectively. The biological effectiveness of these radiations is poorly understood; so the quality factors are set at conservatively very high values. The entire concept of absorbed dose/quality factor/dose-equivalent as applied to GCR must be reconsidered.

Animals↗
PubMed1994

Space radiation dosimetry.

In this report dosimetric measurements are presented which were performed during the missions Spacelab 1, D 1, Biocosmos 8 and Biocosmos 9. Detector packages consisting of plastic nuclear track detectors, nuclear emulsions and thermoluminescence dosimeters were exposed at different locations inside and outside spacecrafts behind more or less well defined shielding thicknesses. These detector systems which supplement each other in their registration characteristic allow to record all biological relevant portions of the radiation field separately. Dose equivalents for the astronauts have been calculated from the measurements using the quality factors as defined in the old and the new recommendations of the International Commission on Radiation Protection (ICRP).

Cosmic Radiation↗
PubMedDate not supplied

Dosimetric measurements in manned missions.

Detector packages consisting of thermoluminescence detectors (TLDs), nuclear emulsions and plastic nuclear track detectors were exposed in different sections of the MIR space station, inside the Spacelab during the IML1 mission, and inside Spacelab module and tunnel during the D2 mission. This report concentrates on total dose measurements with TLDs during these mission. The results are discussed and compared to results of former missions and to calculations. Finally, dose equivalents and mean quality factors for each mission are presented which are derived from the TLD results and results obtained from the other detector systems. Dose equivalents range between 200 microSvd-1 and 700 microSvd-1.

Aerospace Medicine↗