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At least 1,441 records · Page 80Linked to original sources
PubMed1982

Toxicology of 85Kr: tissue distribution and retention in the rat.

Wistar rats were exposed to 85Kr gas atmospheres to determine saturation/desaturation kinetics in major tissues. Tissue partition coefficients [concentration 85Kr in tissue (muCi/g)/concentration of 85Kr in the atmosphere (muCi/cc)] were determined following equilibration with 85Kr gas. Tissue partition coefficients were highest for adrenals and fat; lowest for bone, heart and brain. Tissue partition coefficients for immature rats, 1-12 days of age, and for adults, were not significantly different. The highest concentrations of 85Kr were found in fatty tissues and in gas pockets in the intestinal lumen.

Aging↗
PubMed1983

Radiation absorbed dose estimates for positron emission tomography (PET): inert gases 19Ne and 77Kr.

Detailed estimates of radiation absorbed dose based on solubility data and the distribution of body water and fat are presented for 19Ne and 77Kr, useful PET rCBF imaging agents. The steady-state inhalation of 75 mCi of 19Ne and the bolus inhalation of 18 mCi of 77Kr should result in comparable imaging statistics for typical protocols and lung radiation absorbed doses less than approx. 0.5 rad. A model for both steady-state and bolus inhalation techniques for soluble gases used for these radiation absorbed dose calculations is also presented.

Adipose Tissue↗
PubMed1984

Toxicology of 85Kr: chronic exposure studies.

Male and female Wistar rats were exposed chronically to graded doses of 85Kr to determine long-term biological effects of simulated environmental exposure. Rats were exposed in 4 groups, including room air-exposed controls and 3 groups exposed to 85Kr concentrations equivalent to 10(2), 10(3) and 10(4) times the maximum permissible concentration (MPC) for the general population (3 X 10(-7) microCi/ml). Exposures continued 24 hr/day, 7 days/week for 808 days, until only approximately 10% of the original 400 rats were alive. No effect of 85Kr exposure was observed on weight gain or tumor incidence, including leukemias. The results support the adequacy of established 85Kr exposure limits for the general population in light of the absence of evidence of build-up in tissues after chronic exposure and the lack of exposure-related biological effects in rats after near-lifespan exposure to concentrations equivalent to 10,000 times the MPC.

Animals↗
PubMed1984

Disposition and effects of 85Kr in pregnant rats.

Pregnant rats were housed in 85Kr atmospheres at 10, 15, or 20 days of gestation (dg) and killed after 4 hr of exposure to 37-40 nCi/ml. The 85Kr was present in the components of the fetoplacental unit (FPU) at concentrations (nCi/g) equivalent to approximately 2% of the concentration (nCi/ml) in the exposure atmosphere. Tissue distribution of 85Kr and the distribution of radiation dose did not suggest any unusual hazard to the fetus associated with exposure of pregnant animals. This conclusion was tested using 5-day exposures to a 1000-fold increased concentration: 40 muCi/ml. The main effects observed in pregnant rats exposed to 85Kr from 7-12 or 12-17 dg (estimated radiation dose of 5 X 10(3) rad to maternal lung and 5 X 10(5) rad to maternal skin surface) were deaths, impaired weight gain and skin lesions. Secondarily, the maternal toxicity led to indications of embryotoxicity, although the incidence of malformations was not increased by the estimated 50-rad dose to the FPU.

Abnormalities, Radiation-Induced↗
PubMed1985

Toxicology of 85Kr: effects of whole-body immersion exposure on newborn rats.

Newborn rats exposed to 85Kr exhibited acute radiation effects, e.g. epilation, skin scaling and abnormal development of the extremities, at beta immersion doses in excess of 1000 rad to the skin surface. The incidence of skin tumors, principally basal-cell carcinomas, was increased at all dose levels over the range from 1000 to 4750 rad. The effective skin-surface dose to induce basal-cell carcinoma in the newborn Wistar rat is apparently less than 1000 rad, the lowest dose employed in this study. No lung tumors attributable to 85Kr exposure were observed in these rats.

Animals↗
PubMed1986

A Monte Carlo program to calculate the exposure rate from airborne radioactive gases inside a nuclear reactor containment building.

A program was developed to calculate the exposure rate resulting from airborne gases inside a reactor containment building. The calculations were performed at the location of a wall-mounted area radiation monitor. The program uses Monte Carlo techniques and accounts for both the direct and scattered components of the radiation field at the detector. The scattered component was found to contribute about 30% of the total exposure rate at 50 keV and dropped to about 7% at 2000 keV. The results of the calculations were normalized to unit activity per unit volume of air in the containment. This allows the exposure rate readings of the area monitor to be used to estimate the airborne activity in containment in the early phases of an accident. Such estimates, coupled with containment leak rates, provide a method to obtain a release rate for use in offsite dose projection calculations.

Accidents↗
PubMed1997

Applications of a self-collimating BGO detector system to radiological emergency response.

The capability of a recently developed BGO detector system featuring a "self-collimating" structure to locate a point source was established by Monte Carlo simulations and by laboratory scale experiments. The detector system's capability to determine the direction of a nuclear plume resulting from a PWR1 or PWR2 type accident in stable atmospheric conditions by airborne monitoring of the 2.4 MeV photons emitted by 88Kr was established by Monte Carlo simulations.

Bismuth↗
PubMed1997

Calibration of a portable tritium-in-air monitor for various radioactive gases.

A commercially available portable tritium-in-air monitor was calibrated for detecting the concentration of tritium-in-air, 14C-in-air, and various radioactive noble gases. Calibrations were performed both experimentally, using assayed quantities of the calibration gases, and theoretically, by simulating the monitor's response using Monte Carlo code. The experimental and theoretical calibrations agreed within +/- 10% for all gases tested with the exception of 41Ar-in-air where the agreement was approximately 20%. The results show that, although the monitor can be used to measure a wide range of radioactive gases, if more than one gas is present the monitor can not be used to accurately determine the concentration of, and hazard posed by, these gases. It is also shown that the monitor's ability to accurately assess tritium-in-air hazards would be seriously compromised by the presence of other radioactive gases.

Air Pollutants, Radioactive↗
PubMed1977

Dynamic positron emission tomography for study of cerebral hemodynamics in a cross section of the head using positron-emitting 68Ga-EDTA and 77Kr.

Dynamic positron emission tomographic studies were performed on over 120 patients with occlusive cerebrovascular disease, arteriovenous malformations, and brain tumors, using the positron section scanner, consisting of a ring of 32 scintillation detectors. The radiopharmaceuticals were nondiffusible 68Ga-EDTA for transit time and uptake studies and the diffusible tracer, 77Kr, for quantitative regional cerebral blood flow studies in every square centimeter of the cross section of the head. The results of dynamic positron emission tomography in correlation with the results from the gamma scintillation camera dynamic studies and computed tomography (CT) scans are discussed.

Adult↗
PubMed1982

Tomographic study of regional cerebral blood flow in ischemic cerebrovascular disease by 81mKr intraarterial infusion and HEADTOME.

The single photon mode of a hybrid emission tomograph, HEADTOME, was used to appraise cerebral blood flow (CBF) by the continuous infusion of 81mKr into the internal carotid artery or the ascending aorta. The study was performed on 32 patients with ischemic cerebrovascular disease. The results of the tomographic CBF study were compared with the findings of X-ray computed tomography (CT) and carotid angiography. Twenty-nine patients in the present series showed ischemic areas that correlated better with the localization suggested by the clinical rather than the CT findings. In two patients, CT was negative, whereas the CBF tomogram clearly revealed an ischemic focus. In most of the patients (90.6%), regional ischemia was seen to extend to the normodense brain tissue surrounding the low density areas. Although the method has some limitations, such as its invasiveness, it may be an economical and practical technique for tomographic CBF studies.

Adult↗
PubMed1985

Oesophageal transit of liquid: effects of single or multiple swallows.

The effects of single and multiple swallowing on oesophageal transit have been evaluated in healthy subjects. It was shown that the transit patterns observed after multiple swallowing were different from that observed after a single swallow. It was concluded that for the detection of oesophageal transit abnormalities, the test should be performed using a single swallowed bolus.

Deglutition↗
PubMed1986

Oesophageal transit patterns in healthy subjects.

Oesophageal transit was studied in 49 healthy volunteers. When a good quality bolus was reached, the tracer passed through the oesophagus leaving no residual activity. The mean time of transit of the total oesophagus was 4.5 +/- 1.3 s. In cases of fragmented bolus, residual activity was found in about 80% of the cases giving rise to a prolonged transit time. When using 81Krm, artefacts due to fragmented bolus can easily be overcome by repeating the test as often as necessary.

Adult↗
PubMed1987

Measurement of lung volume with 81Krm in a dynamic scintigram.

The meaning of 81Krm counts obtained in a dynamic series of gated lung ventilation scans was evaluated in terms of flow rate, lung volume, or the flow/volume ratio. Flow and volume signals were recorded together with scintigraphic events in 29 subjects breathing 81Krm and after its decay, 127Xe as a tracer of lung volume. Gated ventilation scans and respiratory signals were reconstructed. Statistical analyses were carried out for linear regressions between total normalized counts detected by the gamma camera and (1) flow rate, (2) lung volume and (3) flow/volume ratio. Inspiration and expiration were analysed separately. For both isotopes, the best correlation was obtained between counts and lung volume (r greater than 0.93). No correlation was obtained between counts and flow rate or flow/volume ratio. Thus, we conclude that 81Krm count variations in gated scans correlate well with tidal volume.

Humans↗