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At least 541 records · Page 30Linked to original sources
PubMed2001

Statistical data evaluation in mobile gamma spectrometry: an optimization of on-line search strategies in the scenario of lost point sources.

There is a potential risk that hazardous radioactive sources could enter the environment, e.g., via satellite debris, smuggled radioactive goods, or lost metal scrap. From a radiation protection point of view there is a need for rapid and reliable methods for locating and identifying sources. The methods could also be used to locate hot spots after radioactive fallout. Carborne and airborne gamma spectrometry systems are suitable for the task. This work focuses on a situation where the radionuclide to search for is known, which is not an unlikely scenario. The possibility that the source is located near a road can be high, and thus motivating a carborne spectrometer system. The main object is to optimize on-line statistical methods in order to achieve a high probability for locating the point source and still have reasonably few false alarms caused by variations in the natural background radiation. Data were obtained from a carborne 3-L NaI(Tl) detector and two point sources located at various distances from the road. The nuclides used were 137Cs and 131I. Spectra were measured stationary on the road. From these measurements we have reconstructed counts in spectral windows applicable to different speed and sampling times; the time 3 s and speeds 32 and 54 km h(-1) are used in this work. The maximum distance a source can be located from the road and still be detected is estimated with four different statistical analysis methods. This distance is called the critical distance, CD. The method is applied on gross counts in the full energy peak spectral window. For each method alarm levels have been calculated from background data obtained in Scania (Skåne), in the south of Sweden. The results show large differences in CD. With the best approach, the two sources could be detected from about 180 m (137Cs, 6 GBq) and 170 m (131I, 4.5 GBq).

Automobiles↗
PubMedDate not supplied

Manipulation under anaesthetic of children's fractures: use of the image intensifier reduces radiation exposure to patients and theatre personnel.

During simulated manipulation of children's forearm fractures, levels of scattered radiation from both plain radiographs and an image intensifier in different modes were measured at various sites on the surgeon, anaesthetist, radiographer, and patient both with and without recommended shielding. By using fluoroscopy in the pulsed screening mode but allowing only single pulses to occur, radiation levels could be substantially reduced to the eye, thyroid, and gonads of all those exposed. The radiographer and the anaesthetist were so far from the source and guarded by various pieces of equipment that levels were almost unrecordable. Effective dose equivalent for the surgeon using pulsed mode, based on circa six pulses per manipulation, during 100 manipulations per year, would equate to 1 microSv even in the unshielded state (< 0.1 microSv shielded), which is approximately 1/1,000 of background radiation at sea level. Because the current dose limit is 50 mSv (50,000 microSv) per year for employees, we are many orders of magnitude in the safety zone.

Anesthesia↗
PubMedDate not supplied

[Radiation reactions and the possibilities for their modification in rats exposed in the area of the Chernobyl Atomic Electric Power Station].

A study was made of some embryological, hematological, cytogenetic and biochemical characteristics in Wistar rats exposed within the Chernobyl NPP zone over a period of 30 days (the average radiation background level, 75, and at the soil surface, 115 mR/h; a cumulative dose, 57 rad/30 days, and for pregnant rats, 36 rad/20 days). The quantity of chromosome aberrations in bone marrow metaphases and the embryonal death rate were invariable; some cases of teratogenesis were, however, observed. The total number of karyocytes in the brain and the leukocyte content in the peripheral blood sometimes decreased. The changes in certain characteristics (such as the content of endogenous amines and thiols in the liver and spleen) of the endogenous radioresistance background (ERB) and the normalization of the ERB by the radioprotective agent MIGI-K were found.

Accidents↗
PubMed2004

Dosimetric and epidemiological approaches to assessing radon doses--can the differences be reconciled?

A significant problem in internal radiation dosimetry is the discrepancy between the radiation dose from exposure to radon inferred from epidemiological studies and the higher dose calculated using the Human Respiratory Tract Model (HRTM) adopted by the International Commission on Radiological Protection (ICRP). The difference is a factor of about 3. The agreement between these two assessments by radically different approaches is surprisingly good. Nevertheless, there has been concern to understand fully the reasons for this discrepancy and to attempt to reconcile the two approaches. This is of importance because radon contributes about half of the total effective dose from natural background radiation. Furthermore, the HRTM was developed with application to radon exposure in mind, yet at present it is not used for risk assessment purposes although ICRP does suggest that it is useful for comparative dosimetry.

Air Pollutants, Radioactive↗
PubMed2005

Antioxidants, radiation and mutation as revealed by sperm abnormality in barn swallows from Chernobyl.

Reduced levels of antioxidants such as carotenoids and vitamins A and E can increase DNA damage caused by free radicals. Exposure to radiation has been proposed to reduce levels of antioxidants that are used for DNA repair and this reduction may be responsible for increased levels of mutation in radioactively contaminated areas. We test this hypothesis using field measures of antioxidants in blood, liver and eggs of the barn swallow Hirundo rustica while relating these to levels of mutation as reflected by the frequency of abnormal sperm. Antioxidant levels in blood, liver and eggs were reduced in Chernobyl, Ukraine, compared with an uncontaminated control area, and levels of antioxidants correlated negatively with levels of background radiation. The frequency of abnormal sperm was almost an order of magnitude higher in Chernobyl than in the control area and was negatively related to antioxidant levels in blood and liver. This is consistent with the hypothesis of a direct link between radiation and individual levels of antioxidants, suggesting that levels of mutation differ among individuals owing to individual differences in the abundance of antioxidants.

Animals↗
PubMedDate not supplied

Radioactivity in municipal sewage and sludge.

OBJECTIVE: To determine the environmental consequences of discharges of radioactivity from a large medical research facility into municipal sewage, specifically 131I activity in sewage sludge, and the radiation exposures to workers and the public when sludges are incinerated. METHODS: The authors measured radioactivity levels in the sludge at the Ann Arbor, Michigan, Waste Water Treatment Plant following radioiodine treatments of two patients at the University of Michigan hospital complex and performed a series of calculations to estimate potential radiation doses due to releases of 131I from incineration of sewage sludge. RESULTS: Approximately 1.1% of the radioactive 131I administered therapeutically to patients was measured in the primary sludge. Radiation doses from incineration of sludge were calculated to be 0.048 millirem (mrem) for a worker during a period in which the incinerator filtration system failed, a condition that could be considered to represent maximum exposure conditions, for two nine-hour days. Calculated results for a more typically exposed worker (with the filtration system in operation and a 22-week period of incineration) yielded a committed effective dose equivalent of 0.066 mrem. If a worker were exposed to both conditions during the period of incineration, the dose was calculated to be 0.11 mrem. For a member of the public, the committed effective dose equivalent was calculated as 0.003 mrem for a 22-week incineration period. Exposures to both workers and the public were a very small fraction of a typical annual dose (about 100 mrem excluding radon, or 300 mrem with radon) due to natural background radiation. Transport time to the treatment plant for radioiodine was found to be much longer than that of a normal sewage, possibly due to absorption of iodine by organic material in the sewer lines. The residence time of radioiodine in the sewer also appears to be longer than expected. CONCLUSION: 131I in land-applied sludge presents few health concerns because sufficient decay occurs before it can reach the public however, incineration, which is done in winter months, directly releases the 131I from sewage sludge to the atmosphere, and even though exposures to both workers and the public were found to be considerably lower than 1% of natural background, incineration of sludge in a pathway for public exposure. Although 131I was readily measurable in sewage sludge, only about 1% of the radioione administered to patients was found in the sludge. The fate of the remaining radioactivity has not been established; some may be in secondary and tertiary residuals, but it is quite likely that most passed through the plant and was discharged in dilute concentrations in plant emissions. The behavior of radioiodine and other radioactive materials released into municipal seweage systems, such as those from large medical facilities, is not yet well understood.

Air Pollutants, Radioactive↗
PubMed2004

Evaluation of indoor gamma radiation dose in dwellings.

The use of materials containing naturally occurring radionuclides for house construction may enhance the natural radiation background to which some population groups are exposed. External exposure results from gamma emitter radionuclides existing in the walls, floor and ceiling. Mathematical models can be used to predict external dose rates inside a room, provided the compartment geometry and the radionuclide concentration activities are known. This paper presents a methodology and a computer code for theoretical evaluation of indoor external gamma doses in the air. The room was modelled as three pairs of rectangular slabs of finite thickness. Doses were evaluated by applying a photon transport model, taking into account self-absorption and radiation build-up. Calculations were performed for 40K, 226Ra and 232Th, considering concrete walls. The results obtained show good agreement with those reported in the literature. Dose conversion factors are presented in a practical manner, ready to use for radiological impact screening.

Air Pollution, Indoor↗
PubMed2002

Portable chest radiographs in the intensive care units: referral patterns and estimated cumulative radiation exposures.

The objective of this article was to determine the frequency of referrals for portable chest radiographs from medical and (noncardiac) surgical intensive care units (NICU and SICU) and their respective stepdown units (NICA and SICA). Additionally, the cumulative entrance skin exposure (ESE) using an ion chamber was determined. We retrospectively reviewed the medical records of all adult patients admitted to the MICU, SICU, MICA, and SICA at a tertiary referral center during a 6-month interval. The duration of stay and the number of portable chest radiographs were determined for each patient. The measured ESEs from all portable radiography units ranged from 5 to15 mR (average: 10mR). The cumulative radiation exposure for each patient was calculated. There were 567 patients admitted to the units: 146 surgical and 421 medical. Their ages ranged from 15 to 87 years. The duration of stay varied from 1 to 68 days. A total of 3,794 portable chest radiographs were obtained. The number of radiographs per patient varied from 1 to 94. The number of radiographs and the corresponding cumulative radiation doses were as follows: 406 patients (72%) had fewer than five radiographs (<50 mR); 76 (13%) had five to 10 radiographs (<100 mR); 35 (6%) had 11 to 20 (<200 mR); and 50 (9%) had more than 20 chest radiographs (>200 mR). The cumulative ESE ranged from 10 to 940 mR. It exceeded 450 mR in only nine (1.5%) patients. Most (73%) patients undergoing intensive care undergo fewer than five radiographs during their stay in the units. Patient exposure from portable chest radiographs in this population is less than the average annual exposure from background radiation in the USA (450-500 mR), and is much less than the average annual exposure from teratogenic radiation.

Adolescent↗
PubMed1978

[Genetic radiation burden of the population in the canton Basel-City due to nuclear medicine].

The genetically significant radiation dose is defined as the gonadal dose which, if received by every member of the population, would produce the same genetic hazard to the population as do the actual doses received by the individuals. PORETTI et al. published a value of 42.9 mrad for Switzerland as the result of X-ray diagnostic examinations in 1971. The contribution from nuclear medicine was determined with reference to special circumstances in the Canton of Basle City: the annual genetically significant dose amounted to 0.5 mrad in 1976. This value represents about 0.5% of the annual annual background radiation.

Body Burden↗
PubMed1993

X-ray diagnostics in Poland--doses and risks.

This article refers to radiation risk resulting from X-ray diagnostics in the Polish population. Frequency of the examinations were reviewed on the basis of data from the national survey performed in 1986. The doses to patients at different age were evaluated taking into consideration the exposure parameters really used during particular examinations. The mean effective dose for a statistical patient in Poland was found to be 2.8 mSv. This denotes that all X-ray diagnostic examinations yield the mean effective dose of 1.6 mSv per capita, i.e. more than 60% of mean effective dose from natural background radiation.

Adolescent↗
PubMed1981

Health concerns in uranium mining and milling.

Mortality of uranium miners from both lung cancer and other respiratory diseases is strongly dependent on exposure to radon daughters, cigarette smoking and height. Lung cancer among 15 different mining groups (uranium, iron, lead, zinc) was analyzed to determine what factors influence incidence and the induction-latent period. At low exposure or exposure rates, alpha radiation is more efficient in inducing lung cancer, producing an upward convex exposure-response curve. The induction-latent period is shortened by increased age at start of mining, by cigarette smoking and by high exposure rates. For a follow-up period of 20 to 25 years, the incidence increases with age at start of mining, with magnitude of exposure and with amount of cigarette smoking. Instead of extrapolating downward from high exposures to estimate risk at low levels, it is suggested that it might be more appropriate to use cancer rates associated with background radiation as the lowest point on the exposure-response curve. Although health risks are much greater in uranium mines than mills, there is some health risk in the mills from long-lived radioactive materials.

Age Factors↗
PubMed2001

Impact of ionizing radiation and genetic background on mammary tumorigenesis in p53-deficient mice.

Loss of p53 function is known to compromise cell cycle regulation, inductionof apoptosis, and DNA damage repair and can facilitate neoplastic transformation of cells. Mutations in the p53 gene are identified frequently in breast carcinomas. Li-Fraumeni patients inheriting a mutant p53 allele have an increased risk for developing tumors including breast cancer. Although mouse lines carrying mutations in the p53 gene have been generated, they die primarily of lymphoma and thus to date provide a limited model for the study of this disease and the role of p53 in nonfamilial breast cancer. An increasing body of literature suggests that the incidence of various tumors is determined largely by the genetic background on which mutations are studied. In addition, population studies and studies in animals suggest that environmental factors, together with genetic factors, determine overall risk for development of specific types of tumors. We therefore examined the impact of genetic background together with exposure to ionizing radiation on the development of tumors, particularly mammary tumors, in p53-deficient animals. We report here that modifier alleles present in the BALB/c strain increase the incidence of hemangiosarcomas [15 of 53 (28.3%); P = 0.0007] in p53(-/-) mice above rates reported previously in p53(-/-) mice on a mixed background as compared to the incidence observed in DBA/p53(-/-) mice. However, no increase in the frequency of mammary tumors is seen in these mice or in p53(-/-) DBA/2 animals, nor was an increase in mammary tumors observed in the DBA/2 p53(+/-) mice, even after exposure to 5 Gy of whole-body ionizing radiation. In contrast, a significant increase in the incidence of mammary tumors was observed in similarly treated BALB/c p53(+/-) mice (37.3% versus 6.8%; P = 0.0007). This was accompanied by a comparable decrease in the incidence of lymphomas. These results show that environmental agents together with genetic factors can increase the frequency and decrease the latency of mammary tumors, leading to an incidence similar to that observed in Li-Fraumeni syndrome. Furthermore, it suggests that the risk of development of a particular type of tumor by individuals deficient in p53 after exposure to damaging agents can be influenced by modifier alleles.

Alleles↗
PubMed2006

Evaluation of a radiation protection cabin for invasive electrophysiological procedures.

AIMS: Complex invasive electrophysiological procedures may result in high cumulative operator radiation exposure. Classical protection with lead aprons results in discomfort while radioprotection is still incomplete. This study evaluated the usefulness of a radiation protection cabin (RPC) that completely surrounds the operator. METHODS AND RESULTS: The evaluation was performed independently in two electrophysiology laboratories (E1-Leuven, Belgium; E2-Bordeaux, France), comparing operator radiation exposure using the RPC vs. a 0.5 mm lead-equivalent apron (total of 135 procedures). E1 used thermoluminiscent dosimeters (TLDs) placed at 16 positions in and out of the RPC and nine positions in and out of the apron. E2 used more sensitive electronic personal dosimeters (EPD), placed at waist and neck. The sensitivity thresholds of the TLDs and EPDs were 10-20 microSv and 1-1.5 microSv, respectively. All procedures could be performed unimpeded with the RPC. Median TLD dose values outside protected areas were in the range of 57-452 microSv, whereas doses under the apron or inside the RPC were all at the background radiation level, irrespective of procedure and fluoroscopy duration and of radiation energy delivered. In addition, the RPC was protecting the entire body (except the hands), whereas lead apron protection is incomplete. Also with the more sensitive EPDs, the radiation dose within the RPC was at the sensitivity threshold/background level (1.3+/-0.6 microSv). Again, radiation to the head was significantly lower within the RPC (1.9+/-1.2 microSv) than with the apron (102+/-23 microSv, P<0.001). CONCLUSION: The use of the RPC allows performing catheter ablation procedures without compromising catheter manipulation, and with negligible radiation exposure for the operator.

Arrhythmias, Cardiac↗
PubMedDate not supplied

Low-dose ionizing radiation exposure: understanding the risk for cellular transformation.

Radiation is energy transfer. When radiation has sufficient energy to remove an orbital electron from its atom, an ionized atom is formed, and radiation with the capacity to do this is called ionizing radiation. The primary effect of radiation is the induction of free radicals and Reactive Oxygen Species (ROS). All the molecules in every cell of the body are potential targets, but the final effect of radiation will be mainly of concern if the molecule impaired is a molecule critical for life. ROS are also generated as a result of the aerobic respiration (metabolic ROS) in much larger quantity than from the natural radiation background. During evolution, life has developed powerful control and repair mechanisms that greatly contribute to minimize the risks associated with the generation of free radicals and ROS. At low irradiation doses the probability of the risk is therefore proportional to the dose, and the ALARA (As Low As Reasonable Achievable) principle seems to be a valuable goal in radioprotection policies.

Cell Transformation, Neoplastic↗
PubMed1991

[The estimation of the effective dose in bone mineral measurements with photon absorptiometry and computed tomography].

There is still some uncertainty in the assessment and comparison of patient dose which results from bone mineral measurements on the lumbar spine by photon absorptiometry and x-ray computed tomography (CT). In the literature, skin dose values are offered in almost all cases. These are not meaningful, however, as the size of the irradiated volume and the radiation sensitivities of the respective organs are not taken into account. Here, the concept of effective dose has to be applied. An assessment of effective dose resulted in approximately 1 mu Sv for absorptiometry and approximately 30 mu Sv for computed tomography with low kV and mAs values. For lateral lumbar spine films which are often taken in connection with absorptiometry, at least 700 mu Sv have to be added. In CT, additional 30 mu Sv result from the lateral topogram which is required for positioning. The concept of effective dose, the data and assumptions used in its assessment and a comparison to other risk factors, as for example natural background radiation of approximately 2400 mu Sv per year, are discussed in detail.

Absorptiometry, Photon↗
PubMed1983

Radiation doses to neonates requiring intensive care.

Radiological investigations have become accepted as an important part of the range of facilities required to support severely ill newborn babies. Increasing numbers of these very small premature babies now survive although they may undergo a considerable number of diagnostic X-ray examinations within the first few weeks of life. Since the infants are so small, many of the examinations are virtually "whole-body" irradiations and it was thought that the total doses received might be appreciable. A group of such babies admitted to the Neonatal Intensive Care Unit in Sheffield over a six-month period have been studied. X-ray exposure factors used for each examination have been noted and total skin, gonad and bone marrow doses calculated, supplemented by measurements on phantoms. It is concluded that in most cases the doses received are of the same order as those received over the same period from natural background radiation and probably less than those received from prenatal obstetric radiography, so that the additional risks from the diagnostic exposure are small. The highest doses are received in CT scans and barium examinations and it is recommended that the need for these should be carefully considered and requests for such examinations only made by experienced staff.

Birth Weight↗
PubMed2001

Improved X-ray Spectrum Simulation for Electron Microprobe Analysis.

The accurate calculation of characteristic peak intensity is essential for interpreting X-ray spectra in electron microprobe analysis. Conventionally, the measured intensity from a standard of known composition is used as a reference to simplify the calculation. However, if no such standard is available, then all factors influencing X-ray generation and X-ray detection efficiency must be included. If the intensity and energy distribution of the background radiation can also be calculated, the investigator can simulate an entire spectrum from an assumed composition, gaining powerful benefits in setting up an experiment and in confirming the results. The study presented here demonstrates a fast method of spectrum simulation, suitable for energy-dispersive spectroscopy (EDS), and assesses the accuracy using 309 spectra from samples of known composition. These include K, L, and M lines from elements of atomic number 6-92, excited by beam energies in the range of 5-30 keV. The RMS error between 360 measured and calculated peak intensities was found to be 7.1%. Central to the method is the use of the ratio of peak intensity/total background intensity, which allows spectra to be compared from instruments of differing collection efficiency, thereby easing the collection of data over a wide range of conditions.

Journal Article↗
PubMed1997

Performance study of a miniature gamma ray scintillation vivo probe for tumor localization.

UNLABELLED: We have developed a miniature gamma-ray endoscopic probe consisting of dual BGO detector probes for tumor detection inside the body cavities. The dual detector system was coupled with random coincidence to decrease the distant background radiation and to improve its spatial resolution for tumor localization. METHOD: The performance of the probe was investigated with a point source and a water phantom. A solution of positron emitting 18F isotope was used as the source. Clinical trials of the probe were done to localize tumors on the skin surface of four subjects carrying tumors close to the body surfaces, into whom 67Ga-citrate and 18F-FDG radiopharmaceuticals were injected. RESULTS: Measurements indicated that the spatial resolution of the dual detector probes is around 1.5 times better than the single detector probe, and both single and dual detector endoscopic probe systems are capable of localizing a tumor on a large photon background. CONCLUSION: The endoscopic probe may be easier to insert inside body cavities due to the small crystal size and the flexible light guides. A single detector probe with higher sensitivity may be useful in searching for tumors over a wide intracavity area but a dual detector probe can be used for precise tumor localization. The detector probe may also be suitable for intraoperative observation.

Adult↗