Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Background Radiation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMedDate not supplied

Radiation therapy for oncological emergencies.

AIMS AND BACKGROUND: Radiation therapy holds a fundamental role in oncological emergencies such as superior vena cava syndrome, spinal cord compression and endocranial hypertension. The purpose of our study was, by comparing schedules of treatment, to confirm the efficacy of hypofractionated radiation therapy. METHODS: From January 1994 to December 1998, 43 patients with superior vena cava syndrome, 37 patients with metastatic spinal cord compression and 108 patients with endocranial hypertension secondary to metastasis were treated at our institution. In the group of patients with superior vena cava syndrome, radiotherapy schedules were: 4 Gy x 5 to a total dose of 20 Gy (23 patients) and 3 Gy x 10 to a total dose of 30 Gy (20 patients). In the group of patients with spinal cord compression, radiation schedules were: 3 Gy x 10 to a total dose of 30 Gy (15 patients); 4 Gy x 5 to a total dose of 20 Gy (12 patients); a single fraction of 8 Gy in 10 cases, repeated after 1 week in 7 responder cases to a total dose of 16 Gy. 5 out of 37 patients were underwent to laminectomy plus stabilization of the spine and post-operative radiotherapy. In the group of patients with endocranial hypertension, radiotherapy schedules were: 6 Gy x 2 to a total dose of 12 Gy (53 patients), repeated after 4 weeks in 34 responder patients and 3 Gy x 10 to a total dose of 30 Gy (55 patients). RESULTS: The patients with superior vena cava syndrome, revaluated after 4 weeks at the end of treatment, obtained a partial remission of symptomatology in 73.9% with 20 Gy and in 75% with 30 Gy. The patients with spinal cord compression obtained symptomatic relief in 73.3% with 30 Gy, in 66.6% with 20 Gy and in 70% of cases treated with 8 Gy. The patients with endocranial hypertension obtained symptomatic relief in 64.1% with 12 Gy and in 63.3% with 30 Gy. CONCLUSION: Histology, pretreatment and performance status were important prognostic factors for the response to therapy. Our results demonstrated no significant difference among different schedules of radiotherapy and confirmed the importance of radiotherapy for oncological emergencies: it improves the quality of life and, in responding patients, is associated with a longer survival time.

Adult↗
PubMed2005

Estimation of radiation levels by EPR measurement of tooth enamel in Indian populations.

Enamel from 34 molars from 22 individuals in the general population are used to evaluate the background radiation in six cities in India. The estimation of the background dose for each tooth is evaluated using two EPR methods: the calibration-curve method and the additive-dose method. The variation of the estimated EPR dose with tooth position is investigated by using eight teeth taken from the same person. Contribution of the dental X-ray treatments to the enamel-absorbed dose was evaluated using another 17 teeth exposed from 1 to 10 times.

Adult↗
PubMedDate not supplied

[Secondary biogenic radiation of human body].

It was shown that tissues of alive healthy hyman organism (hands, surface of breast, hair) permanently emitted secondary biogenous radiation (SBR), which was registered with biological detectors. The hypothesis was suggested that natural background radiation permanently excited biopolymers (proteins, nucleic acids) in condensed state and induced electromagnetic field of SBR which is vitally important for human organism. The field partly extends beyond the organism, where it is registered with sensitive biological detectors.

Background Radiation↗
PubMed1991

[Evaluation of the tracheobronchial clearance in patients with chronic bronchial infections by an integrated system using radioactive aerosol inhalation scintigraphy].

It is widely accepted that the impairment of tracheobronchial clearance (TBC) are closely related to the development and the progression of chronic bronchial infections. We investigated TBC in patients with chronic bronchial infections (bronchiectasis; 11 cases, diffuse panbronchiolitis; 9 cases and primary ciliary dyskinesia; 3 cases) and also in 6 healthy subjects by a radioactive aerosol (99mTc-human serum albumin, 4.4 +/- 1.4 microns in diameter) inhalation scintigraphy with cough control in order to elucidate the relationships between impaired TBC and chronic bronchial infections. All subjects were not current smokers. After 4-minutes inhalation of radioactive aerosols (tidal volume: 500 ml x 20/min.), radioactivities in whole right lung were measured every 20 seconds for 2 hours serially and then measured at the time of 6 and 24 hours after inhalation. Immediately after the serial recording for 2 hours, single photon emission computed tomography (SPECT) was performed to assess the deposition pattern of radioactive aerosols. During the first 2 hours, all the subjects were instructed to avoid coughing as much as possible to evaluate the mucociliary clearance without cough effect. And then the subjects were allowed to cough between 2 and 24 hours after inhalation. All radiation counts were corrected for background radiation and physical decay of 99mTc. Because it is considered that the deposited aerosols are eliminated much more slowly in alveoli (biological half life: several months) than in airways (biological half life: several hours), the radioactivity remaining at the time of 24 hours was defined as alveolar deposition (ALV). Initial bronchial deposition (Br0) was defined as initial whole lung deposition (L0) minus ALV. We evaluated the TBC with following parameters; 1) Br0/L0 (%):ratio of initial bronchial deposition to initial lung (bronchial and alveolar) deposition. 2) Br2/Br0 (%), Br6/Br0 (%):bronchial retention ratio; the ratio of bronchial deposition at the time of 2 and 6 hours after inhalation to initial bronchial deposition, respectively. 3) TMV (mm/min.):tracheal mucus velocity (rate of shift of radioactive bolus on tracheal mucosa), which was measured during the period of first 2 hours under prohibition of cough. The patients (23 cases) were divided into two groups with regards to cough control for the first two hours of the scintigraphy:cough-controlled group (19 cases) and cough-uncontrolled group (4 cases). The cough-controlled group was subdivided into two subgroups (group A and group B) according to Br0/L0:group A less than 47.9% (mean + SD of Br0/L0 in healthy control) less than or equal to group B.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Inhalation↗
PubMed1982

Radiation safety.

Radiation safety is rapidly becoming a major concern of every patient. Poor understanding of ionizing radiation and its effects frequently heightens anxiety. The average United States resident receives about 125 mrem of radiation per year from natural background radiation and another 120 mrem from man-made sources. The 240 million x-ray procedures performed annually contribute 90 percent of the man-made portion. It is assumed that the risks of medical radiation are outweighed by the benefits gained from the information obtained. If present in sufficiently high dosage, radiation can have harmful effects, such as induction of leukemia and thyroid malignancy. No deleterious effects have been shown to have been caused by diagnostic radiation. It is reassuring that the risks of medical radiation appear to be quite small compared with other common hazards most people face daily. Careful attention to the use of radiographic safety and protective technique will ensure the lowest possible radiation dose. The physician's discretion in ordering only appropriate and indicated x-ray films will ensure the patients are exposed to the lowest possible amount of radiation.

Female↗
PubMed2004

Effect of high-level natural radiation on chromosomes of residents in southern China.

To study the effect of low-dose (rate) radiation on human health, we analyzed chromosomes of peripheral lymphocytes of residents in a high background radiation area (HBRA) and compared the results with those obtained from residents in a control area (CA) in Guangdong Province, China. Unstable types of chromosome aberrations (dicentrics and rings) were studied in 22 members of eight families in HBRA and 17 members of five families in CA. Each family consists of three generations. On average 2,600 cells per subject were analyzed. 27 adults and six children in HBRA and 25 adults and eight children in CA were studied with respect to translocations. On average 4,741 cells per subject were examined. We found an increase of the frequency of dicentrics and rings in HBRA, where the natural radiation level is three to five times higher than in the control area. But the increase of translocations in HBRA was within the range of individual variation in the controls.

Adult↗
PubMed1992

Terrestrial gamma radiation dose in Hong Kong.

The first reactor of the Daya Bay nuclear power plant, 30 km from Hong Kong, is expected to begin operation in 1992. As a result, residents in Hong Kong are concerned with potential exposure to man-made and natural radiation. Therefore, the Radioisotope Unit of the University of Hong Kong performed studies to estimate Hong Kong's natural background radiation and the potential exposure to local residents, the results of which are presented here.

Background Radiation↗
PubMed1987

Environmental radiation and cancer in India.

The hormesis hypothesis, which suggests that ecologically realistic low levels of ionising radiations may be beneficial to humans, seems to be substantiated significantly by the data available on cancer incidence/mortality rates and environmental radiation levels in various cities and states of India. Where the radiation level is greater, cancer risk is invariably less. The annual cancer incidence rate (per 100,000 population) seems to decrease by 0.03/microSv increase in the external background radiation dose from a hypothetical incidence level of 79 per 100,000 corresponding to "zero environmental radiation".

Background Radiation↗
PubMed1994

Trends and geographical distribution of childhood leukemia in Greece in relation to the Chernobyl accident.

Parts of Greece have been exposed to fallout radiation from the Chernobyl accident as much as any of the countries boardering with the former Soviet Union, because of the direction of the prevailing winds after the accident. Although fallout radiation did not reach levels expected to be associated with measurable effects, there is widespread concern in Greece that the incidence of childhood leukemia may be rising in the more heavily affected parts of Greece. Patient discharge data from all Greek hospitals treating childhood leukemia were used to calculate the annual incidence of the disease from January 1980 to June 1986 (preaccident period), from July 1986 to June 1988 (immediate postaccident period) and from July 1988 to June 1991 ("relevant" post-accident period, that accommodates the presumed latent period of the disease). Fallout radiation measurements (in Bq/kg Cs-137) were used to create 17 regions of similar (within regions) but highly variable (between regions) levels of fallout deposition. Background radiation (in Bq/kg Ra-226) and annual incidence of childhood leukemia by region were also estimated. There was no evidence of increased incidence of childhood leukemia during the immediate or the "relevant" post-Chernobyl period in any part of the country. Furthermore, regression analyses did not show any significant or suggestive association of childhood leukemia by region with either background or fallout radiation. These results indicate that the Chernobyl accident did not affect noticeably the incidence of childhood leukemia in Greece during the five-year post accident period.

Accidents↗
PubMed2004

The annual effective dose from natural sources of ionising radiation in Canada.

A review and analysis of published information combined with the results of recent gamma ray surveys were used to determine the annual effective dose to Canadians from natural sources of radiation. The dose due to external radiation was determined from ground gamma ray surveys carried out in the cities of Toronto, Ottawa, Montreal and Winnipeg and was calculated to be 219 microSv. A compilation of airborne gamma ray data from Canada and the United States shows that there are large variations in external radiation with the highest annual outdoor level of 1424 microSv being found in northern Canada. The annual effective inhalation dose of 926 microSv from 222Rn and 220Rn was calculated from approximately 14,000 measurements across Canada. This value includes a contribution of 128 microSv from 222Rn in the outdoor air together with 6 microSv from long-lived uranium and thorium series radionuclides in dust particles. Based on published information, the annual effective dose due to internal radioactivity is 306 microSv. A program developed by the Federal Aviation Administration was used to calculate a population-weighted annual effective dose from cosmic radiation of 318 microSv. The total population-weighted average annual effective dose to Canadians from all sources of natural background radiation was calculated to be 1769 microSv but varies significantly from city to city, largely due to differences in the inhalation dose from 222Rn.

Background Radiation↗
PubMed2002

Current concepts in radiation enteritis and implications for future clinical trials.

BACKGROUND: Radiation enteritis is one of the most feared complications of abdominal and pelvic radiation. Once its occurs, the process is relentless and may result in the patient's death. Available treatment is only supportive. Recent progress in molecular biology has shed some light on the pathogenesis of radiation enteritis and other diseases that are characterized by excessive fibrosis. New treatment modalities may be devised to improve the outcome of patients who are affected with this complication. METHODS: A literature search was used to identify the common denominator between many radiation-induced fibrotic conditions and other sclerotic diseases. Factors that affect the disease process and possible therapeutic interventions were evaluated. RESULTS: The hyperstimulation of transforming growth factor beta1 (TGF-beta1) leads to increased fibrosis and, ultimately, organ failure. Interferon gamma (IFN-gamma) inhibits the effects of TGF-beta1 in the nucleus. The fibrotic process may be reverted by IFN-gamma in various pathologic conditions. CONCLUSIONS: Radiation enteritis and other radiation-induced, long-term complications are characterized by excessive stimulation of TGF-beta1. Preliminary studies suggest that IFN-gamma may be effective in the treatment of patients with radiation-induced cutaneous fibrosis. IFN-gamma should be considered in Phase I-II studies to assess its toxicity and efficacy in the treatment of patients with radiation enteritis.

Abdominal Neoplasms↗
PubMed2006

Expression profiling of radiation-induced genes in radiodermatitis of hairless mice.

BACKGROUND: Radiation induces many cellular events leading to radiodermatitis. OBJECTIVES: The aim of this study was to establish a radiodermatitis model using experimental animals, and to examine the expression profile of radiation-induced genes. METHODS: Hairless mice were irradiated on the dorsal skin; then total RNAs were isolated and microarray hybridizations were performed. RESULTS: Irradiation with a total of 40 Gy (10 Gy day-1 for four consecutive days) provokes radiodermatitis in the hairless mouse. After microarray analysis, 130 genes that showed upregulation by radiation were selected and organized into four different clusters, depending on the time-kinetic pattern. Classification of these genes into several functional categories revealed that various biological processes were globally affected by radiation. These include transcription regulation, signal transduction, cell communication, cell death regulation and metabolism. CONCLUSIONS: These results demonstrate the complexity of the transcriptional profile of the radiation response, providing important clues on which to base further investigations of the molecular events underlying radiodermatitis.

Animals↗
PubMed2006

Intercellular adhesion molecule-1: a consistent inflammatory marker of the cutaneous radiation reaction both in vitro and in vivo.

BACKGROUND: Radiation damage to skin is a key diagnostic and prognostic parameter for patients accidentally exposed to radiation. Moreover, skin is a target organ for crucial side-effects of routine radiotherapy. The pathophysiology of the cutaneous radiation reaction is in many respects still unknown. The acute inflammatory radiation reaction of skin has been shown to involve alterations in cell-cell and cell-matrix interactions, which are mediated by cellular adhesion molecules. OBJECTIVES: To evaluate the effect of ionizing radiation on intercellular adhesion molecule-1 (ICAM-1) expression in human skin cells. METHODS: Dermal monolayer cells, a three-dimensional skin model and skin biopsies were investigated for ICAM-1 expression after ionizing radiation using flow cytometry, quantitative reverse transcription-polymerase chain reaction and immunohistochemistry. ICAM-1 expression in monolayer cells pretreated with protein kinase inhibitors and dexamethasone prior to irradiation was analysed by flow cytometry. RESULTS: Using different sources of skin cells, we demonstrated a consistent upregulation of both ICAM-1 mRNA and protein expression by ionizing radiation. Blocking experiments revealed that tumour necrosis factor-alpha, another ICAM-1 inducer, does not account for the effect of radiation. Radiation-induced upregulation of ICAM-1 expression was significantly attenuated by inhibitors to protein kinase C, mitogen-activated protein (MAP) ERK kinase, p38 MAP kinase and phosphatidylinositol 3-kinase. The anti-inflammatory agent dexamethasone suppressed the effect of radiation on ICAM-1 expression, suggesting its usefulness to treat the cutaneous radiation reaction. CONCLUSIONS: Our data suggest that ICAM-1 is a consistent inflammatory parameter of the cutaneous radiation reaction both in vitro and in vivo that might provide new therapeutic options for diagnosis and treatment of effects of radiation.

Aged↗
PubMed1998

Radiation-Induced Sarcoma Following Treatment of Breast Cancer.

BACKGROUND: Radiation therapy (XRT) is an important modality in the treatment of cancer, and XRT is now commonly utilized in the treatment of early-stage breast cancer. However, its use has occasionally resulted in the development of secondary malignancies. We present a critical review of radiation-induced sarcoma (RIS) that develops after irradiation for the treatment of breast cancer. METHODS: The case of a patient who developed sarcoma after radiation for breast cancer is presented, and current literature on RIS is reviewed. The role of XRT in the development of RIS is examined, and the evaluation and treatment of these malignancies are reviewed. Results: RIS occurs in 0.2% of patients following treatment of breast cancer. The role of radiation in the development of RIS has been clearly demonstrated. Clinical presentation varies, and diagnosis is commonly delayed. Treatment consists of wide surgical excision. The role of chemotherapy is controversial. CONCLUSIONS: The occurrence of RIS following treatment of breast cancer is rare. Its development has an average latency of over 10 years and likely correlates with the dose and technique of the radiation treatment. The prognosis of patients with RIS following treatment for breast cancer is poor predominantly due to a delay in diagnosis. However, the benefit derived by breast cancer patients from XRT far outweighs the risk of RIS and should not affect the decision to treat these patients with this modality.

Journal Article↗
PubMed2006

Radiological studies in the hot spring region of Mahallat, Central Iran.

Five hot springs called 'Abegarm-e-Mahallat', located in the central part of Iran, have a mean water temperature of 46 +/- 1 degrees C and are used by visitors as spas. This is an area of high natural radiation background due to the presence of (226)Ra and its decay products in the deposited travertine (CaCO(3)). The mean concentration of (226)Ra in these hot springs, measured by the emanation method, ranged from 0.48 +/- 0.05 to 1.35 +/- 0.13 Bq l(-1). (222)Rn concentrations measured in the hot springs using a liquid scintillation counter ranged from 145 +/- 37 to 2731 +/- 98 Bq l(-1). Mean radon concentrations in air were 487 +/- 160 and 15.4 +/- 2.7 Bq m(-3) for indoor and outdoor, respectively. Radiation levels above that of normal background ( approximately 100 nGy h(-1)) were mainly limited to the Quaternary travertine formations in the vicinity of the hot springs. The results of environmental radiological studies in this region are presented and discussed.

Air Pollutants, Radioactive↗
PubMed2005

Terrestrial gamma radiation dose study to determine the baseline for environmental radiological health practices in Melaka state, Malaysia.

Environmental terrestrial gamma radiation dose rates were measured throughout Melaka, Malaysia, over a period of two years, with the objective of establishing baseline data on the background radiation level. Results obtained are shown in tabular, graphic and cartographic form. The values of terrestrial gamma radiation dose rate vary significantly over different soil types and for different underlying geological characteristics present in the study area. The values ranged from 54 +/- 5 to 378 +/- 38 nGy h(-1). The highest terrestrial gamma dose rates were measured over soil types of granitic origin and in areas with underlying geological characteristics of an acid intrusive (undifferentiated) type. An isodose map of terrestrial gamma dose rate in Melaka was drawn by using the GIS application 'Arc View'. This was based on data collected using a NaI(Tl) scintillation detector survey meter. The measurements were taken at 542 locations. Three small 'hot spots' were found where the dose rates were more than 350 nGy h(-1). The mean dose rates in the main population areas in the mukims (parishes) of Bukit Katil, Sungai Udang, Batu Berendam, Bukit Baru and Bandar Melaka were 154 +/- 15, 161 +/- 16, 160 +/- 16, 175 +/- 18 and 176 +/- 18 nGy h(-1), respectively. The population-weighted mean dose rate throughout Melaka state is 172 +/- 17 nGy h(-1). This is lower than the geographical mean dose rate of 183 +/- 54 nGy h(-1). The lower value arises from the fact that most of the population lives in the central area of the state where the lithology is dominated by sedimentary rocks consisting of shale, mudstone, phyllite, slate, hornfels, sandstone and schist of Devonian origin which have lower associated dose rates. The mean annual effective dose to the population from outdoor terrestrial gamma radiation was estimated to be 0.21 mSv. This value is higher than the world average of 0.07 mSv.

Background Radiation↗
PubMed1983

Demonstration of a biological effect of natural ionizing radiations.

The blue-green alga, Synechococcus lividus, was grown under various levels of radiations. Shielding of cultures with lead resulted in a lower cell growth rate: the reduction disappeared when a normal radiation level was restored in the lead chamber. Irradiations from a thorium source at a dose-rate 14 times higher than that of natural irradiation stimulated the growth of the algae. These results are a new demonstration of a biological effect of background radiations.

Background Radiation↗
PubMed2001

Radium-226, 232Th, and 40K distribution in the environment of Kaiga of south west coast of India.

Systematic studies on gamma radiation level and the distribution of natural radionuclides were carried out under a pre-operational survey for the establishment of baseline data on background radiation level and the distribution of radio-nuclides in the environment of Kaiga, in the south west coast of India, where a nuclear power reactor of 235 MWe has just been commissioned. The external gamma absorbed dose rates prevailing in the region were measured using a portable plastic scintillometer. Soil samples from 18 stations were collected from depth intervals of 0-5, 5-10, and 10-25 cm and analyzed for their 226Ra, 232Th, and 40K activity concentrations by gamma spectrometry employing a 90 cc PGT HpGe detector coupled to an EG&G ORTEC 8K multichannel analyzer. The activity of 226Ra was found to vary between 15.5-61.2 Bq kg(-1) with a mean value of 31.3 Bq kg(-1), that of 232Th varies between 11.4-41.9 Bq kg(-1) with a mean value of 27.5 Bq kg(-1) and of 40K between 78.3-254.8 Bq kg(-1) with a mean value of 159.9 Bq kg(-1) in 0-5 cm soil profiles of the region. The contributions of 238U, 232Th, and 40K to the total gamma absorbed dose rate were 39.9%, 40.7%, and 16.0%, respectively. The gamma absorbed dose rate in air estimated using the results of activity concentration of 226Ra, 232Th, and 40K are found to compare well with that of the direct measurement. The results of the study were compared with the literature values reported for other environs of the country as well as the world, and conclusions are drawn.

Background Radiation↗