A METHOD TO IDENTIFY AND LOCALIZE A SINGLE HOT PARTICLE IN THE LUNGS USING AN ARRAY OF HIGH-PURITY GERMANIUM DETECTORS FOR IMPROVED ESTIMATE OF THE DEPOSITED ACTIVITY.

A new method has been developed to identify and localize a single hot particle in the lungs using an array of four high-purity germanium detectors. The method is based upon calculating a set of three count rate ratios (generated by each individual detector in the array) that are evaluated in sequence to designate whether the measured deposition can be associated with a hot particle rather than the default assumption of a uniform activity distribution. Identification and localization of the hot particle are determined from a single in vivo measurement in which detectors are positioned above and below the thorax. The method was tested using an anthropomorphic thorax phantom in which point sources of 241Am, 137Cs and 60Co were individually inserted in the lungs at 15 different locations and were measured using a scanning bed whole-body counter. Depending upon source location and photon energy, a bias of -35% up to +76% could be introduced by falsely assuming a uniform activity distribution in the lungs. This bias would directly translate to an erroneous dose estimate to the lungs. It was demonstrated that by using the appropriate detector efficiencies for the single hot particle, the bias associated with the activity determination is reduced to <10% and ~2% in average.

RETENTION OF 7Be IN THE LUNGS FOLLOWING INTAKE BY INHALATION.

Several workers were internally exposed to 7Be particles following their dispersion in air from a damaged electrodeposited source. A series of in vivo measurements performed with one worker up to 108 days post exposure determined that retention of 7Be in the thoracic region of the respiratory tract was best described by a two-component exponential function with half-lives of ~0.4 and ~109 days. The initial deposition in the thoracic region was estimated to be 6.8 kBq. The concentration of 7Be in single void urine samples collected from this worker up to 3 days post intake ranged from 1 to 10 Bq/l. In the absence of specific knowledge about the physical and chemical characteristics of the inhaled particles, the committed effective dose was estimated to be 0.3 µSv.

Characterization of internal exposure to enriched uranium at a former gaseous diffusion plant.

The National Institute for Occupational Safety and Health (NIOSH) is conducting a nested case-control study of mortality from multiple myeloma involving 581 subjects who worked at the Oak Ridge K-25 Gaseous Diffusion Plant. Internally-deposited uranium is the primary agent being considered in the exposure assessment. Routine operation and maintenance of the plant presented the potential for inhaling uranium of various enrichments. As part of the exposure assessment, records describing the various plant processes and procedures, documentation on the medical monitoring program, uranium urinalysis data, and procedures and analytical methods for monitoring uranium exposure were retrieved and reviewed. Uranium urinalysis data consisted of 161,055 uranium urinalysis results obtained by fluorometry and 171,914 results obtained by alpha particle counting. Approximately 20% of the workers were monitored for internal exposure using urine sampling. Mean and median uranium concentrations in urine for the monitored study subjects were slightly lower than for the entire population of monitored K-25 workers. The specific activity of uranium excreted in urine was determined by comparing results obtained using fluorometric and alpha activity measurements and indicate that the majority of internal exposure involved uranium that was depleted or enriched to no more than 4% U.

Estimating active bone marrow dose from occupational exposure to uranium at a former gaseous diffusion plant.

Active bone marrow absorbed doses were estimated for 581 workers as part of a nested case-control study of multiple myeloma mortality at the Oak Ridge Gaseous Diffusion Plant (K-25). Uranium urinalysis results obtained by fluorometric and gross alpha measurements were available for about 20% of the 581 study subjects. These data were used to determine intakes of uranium as a result of occupational exposure during operation of the K-25 facility. Uranium solubility was inferred from the observed urinary excretion rate, job titles, and department codes. Data suggest that most study subjects were exposed to uranyl fluoride, a relatively soluble uranium compound. The median cumulative bone marrow dose determined for subjects with bioassay data was 0.06 mGy with a geometric standard deviation of 4.48. Subjects without bioassay data were assigned cumulative bone marrow dose based upon job titles and department codes.

In vivo measurements of 210Pb in skull and knee geometries as an indicator of cumulative 222Rn exposure in a underground coal mine in Brazil.

Cumulative exposure to radon can be evaluated by measuring 210Pb in bone. The skull and knee are two convenient parts of the skeleton for in vivo measuring 210Pb because these regions of the body present a high concentration of bone, the detectors are easily positioned and the likelihood of cross contribution from other organs or tissues is low. A radiological survey of non-uranium mines in Brazil indicated that an underground coal mine in Paraná, located in the south of Brazil, exhibited a high radon concentration. In vivo measurements of 32 underground coal miners were performed in the IRD-CNEN Whole Body Counter shielded room using an array of four high-resolution germanium detectors. Estimations of 210Pb in the total skeleton were determined from direct in vivo measurements of 210Pb in the head and knees. In vivo measurements of 210Pb in 6 out of 32 underground coal miners ranged from 80 to 164 Bq, suggesting that these workers were significantly exposed to 222Rn.

Response of a Shadow-Shield Whole-Body Counter to a Variety of Physical Phantoms.

The performance characteristics of a shadow-shield whole-body counter system with an array of four high-resolution germanium detectors using whole-body and organ-specific (lungs, liver, head, knee and thyroid) physical phantoms are described. Detection efficiency and minimum detectable activities for selected radionuclides and several measurement configurations are presented. Results demonstrate that the system meets the requirements for direct radio bioassay and that detection efficiency and minimum detectable activities are similar in magnitude to other whole-body (or organ) counting systems installed in fully shielded structures.

Assessment of plutonium exposures for an epidemiological study of US nuclear workers.

An ongoing case-control study evaluating the association between workplace external radiation exposures and leukaemia mortality required an assessment of internal plutonium exposures as a potential confounder. Of the study participants, 1,092 were employed at four Department of Energy sites where plutonium-bearing materials were processed or stored. Exposures were assessed by first categorising exposure potentials based on available bioassay data, then estimating doses for workers in the highest categories using recent recommendations of the International Commission on Radiological Protection. Given the aetiology of leukaemia, equivalent dose to active bone marrow was chosen as the exposure variable. There were 556 workers each with at least one plutonium bioassay result, assigned to one of three evaluation categories. Dose estimates were made for 115 workers resulting in a collective equivalent dose of 2.1 person-Sv for 2,822 exposure-years, compared with 29.8 person-Sv estimated from photon exposures. Modelling uncertainties were examined by comparison of results from independent analyses and by Monte Carlo simulation.

Nonprogression of coronary artery atherosclerosis in homozygous familial hypercholesterolemia after 31 months of repetitive plasma exchange.

The effects of plasma exchange performed every two weeks for 31 months in combination with diet and drug therapy were studied in a patient with receptor-defective homozygous familial hypercholesterolemia. Coronary angiography performed three years prior to commencing plasma exchange was compared to angiography 31 months after starting the program. Comparison of the angiograms taken six years apart showed no progression of coronary atheroma in the main left coronary artery in which a 30% narrowing was originally seen. An internal mammary artery-coronary artery bypass remained widely patent and showed no development of atherosclerosis. Plasma cholesterol levels were reduced 46% by plasma exchange, diet and drug compared to diet and drug alone. Achilles tendon xanthoma diminished significantly. It appears that plasma exchange combined with diet and drug therapy, while not producing regression of existing atheromatous lesions, does retard or prevent further progression.

Non-pelvic abdominal ultrasound: an overview for emergency physicians.

Ultrasound scanning is a very useful technique for diagnosing emergent abdominal conditions and diseases. Of the two types of scanning that can be done, real-time imaging is more useful under emergency conditions than static imaging. Real-time scanning equipment is portable, easy to operate, and can be used on acutely ill and poorly cooperative patients. Real-time scanners readily image fixed organs as well as mobile structures and substances in the abdomen. Scanning is very accurate in the diagnosis of cholelithiasis, common hepatic duct obstruction, pancreatic pseudocyst, obstructive uropathy, and aortic aneurysms. It has also been found to be of value in recognizing acute cholecystitis, pancreatitis, and renal transplant rejection. Although it is not currently a common practice, emergency physicians can be trained to perform this diagnostic procedure and interpret the resulting scanning images.

Effect of leachability on environmental risk assessment for naturally occurring radioactive materials in petroleum oil fields.

Elevated concentrations of naturally occurring radioactive material (NORM), including 238U, 232Th, and their progeny found in underground geologic deposits, are often encountered during crude oil recovery. Radium, the predominant radionuclide brought to the surface with the crude oil and produced water, co-precipitates with barium in the form of complex compounds of sulfates, carbonates, and silicates found in sludge and scale. These NORM deposits are highly stable and very insoluble under ambient conditions at the earth's surface. However, the co-precipitated radium matrix is not thermodynamically stable at reducing conditions which may enable a fraction of the radium to eventually be released to the environment. Although the fate of radium in uranium mill tailings has been studied extensively, the leachability of radium from crude oil NORM deposits exposed to acid-rain and other aging processes is generally unknown. The leachability of radium from NORM contaminated soil collected at a contaminated oil field in eastern Kentucky was determined using extraction fluids having wide range of pH reflecting different extreme environmental conditions. The average 226Ra concentration in the samples of soil subjected to leachability testing was 32.56 Bq g(-1) +/- 0.34 Bq g(-1). The average leaching potential of 226Ra observed in these NORM contaminated soil samples was 1.3% +/- 0.46% and was independent of the extraction fluid. Risk assessment calculations using the family farm scenario show that the annual dose to a person living and working on this NORM contaminated soil is mainly due to external gamma exposure and radon inhalation. However, waterborne pathways make a non-negligible contribution to the dose for the actual resident families living on farmland with the type of residual NORM contamination due to crude oil recovery operations.

Statistical analysis of real-time, environmental radon monitoring results at the Fernald Environmental Management Project.

A comprehensive real-time, environmental radon monitoring program is being conducted at the Fernald Environmental Management Project, where a large quantity of radium-bearing residues have been stored in two covered earth-bermed silos. Statistical analyses of radon measurement results were conducted to determine what impact, if any, radon emitted by the radium bearing materials contained in the silos has on the ambient radon concentration at the Fernald Environmental Management Project site. The distribution that best describes the outdoor radon monitoring data was determined before statistical analyses were conducted. Random effects associated with the selection of radon monitoring locations were accommodated by using nested and nested factorial classification models. The Fernald Environmental Management Project site was divided into four general areas according to their characteristics and functions: 1) the silo area, where the radium-bearing waste is stored; 2) the production/administration area; 3) the perimeter area, or fence-line, of the Fernald Environmental Management Project site; and 4) a background area, located approximately 13 km from the Fernald Environmental Management Project site, representing the naturally-occurring radon concentration. A total of 15 continuous, hourly readout radon monitors were installed in these 4 areas to measure the outdoor radon concentration. Measurement results from each individual monitor were found to be log-normally distributed. A series of contrast tests, which take random effects into account, were performed to compare the radon concentration between different areas of the site. These comparisons demonstrate that the radon concentrations in the production/administration area and the perimeter area are statistically equal to the natural background, whereas the silo area is significantly higher than background. The study also showed that the radon concentration in the silo area was significantly reduced after a sealant barrier was applied to the contents of the silos.

The U.S. Transuranium Registry report on the 241Am content of a whole body. Part III: Gamma-ray measurements.

The 241Am measurements on the donor's body, followed by an analysis of each bone of the skeleton, have provided the best available calibration factors for measuring the 241Am content in the skeletons of the living. These calibration factors have already been useful in measuring the skeletal burden of several workers in the nuclear industry. This study has shown that differential linear scanning provides good results on the content of various parts of the skeleton. Previously used methods of head or leg counting for estimating total skeletal content of 241Am were also found to provide good results. These studies confirm previous recommendations that in-vivo measurement of the skull probably provides the best estimate of 241Am in the skeleton; however, other positions such as the knee are also found to be bilaterally symmetrical for identical bones on the right and left sides of the body. A comparison of measurements on the donor's body with those of other people with skeletal burdens of 241Am shows that differences in skeletal distribution do exist and are probably due to the age of the person, the duration of the skeletal 241Am burden,and perhaps the physical activity of the person. Additional measurements and studies are planned on the remaining half of the skeleton and they should further improve the accuracy of in-vivo measurements of 241Am in the human skeleton.

A new method for analyzing high-resolution spectra from whole-body counter in-vivo measurements.

A new method has been developed at the Pacific Northwest Laboratory to analyze pulse-height energy spectra from whole-body counter in-vivo examinations that use high-resolution Ge detectors. A simple data transformation and smoothing function is used to calculate background and identify photopeaks for isotopic analysis. This technique is beneficial for routine in-vivo measurement programs because it avoids dependence upon complex spectrum deconvolution, stripping, or other least-squares fitting techniques that complicate the assessment of measurement reliability. An in-vivo measurement spectrum is analyzed by first applying the variance stabilizing transformation to the data in each channel, which results in a variable with unit variance. A background spectrum is then determined by smoothing the transformed data. Finally, peaks are identified whenever the difference between the background spectrum and the transformed measurement spectrum exceeds 2.57 standard deviations. This method of spectrum analysis is especially suited to whole-body counting because background spectra are calculated as an integral part of the analysis procedure. This new technique has been applied successfully to routine in-vivo measurements of Pu, Am, and U. The computations for this new pulse height-energy spectrum analysis procedure are easily programmed on a desk-top or analyzer-based computer. The simplicity of the computational technique is also attractive because of the ease with which results can be verified.

Analysis of coal slag for naturally occurring radioactive material.

Samples of aerosolized coal slag were collected during an abrasive blasting operation to determine the concentration of naturally occurring radioactive materials (NORM) in the respirable and nonrespirable fractions. Each slag fraction was analyzed using alpha and gamma spectrometry. Since the slag is insoluble, it was necessary to dissolve samples completely by fusion with potassium fluoride and, after additional transposing and separation, mount the precipitate containing radium (Ra), the main radioactive component in NORM, on a membrane filter for alpha counting. The concentration of 226Ra in coal slag was independent of the particle size fraction and equal to 2.28 picocuries/gram (pCi/g) +/- 0.43 pCi/g, which is approximately twice the typical concentration of NORM in uncontaminated soil. Analysis of NORM by gamma spectrometry identified low concentrations of uranium, thorium, and potassium, all primordial radioactive materials that are commonly encountered in normal background soil. Integral exposure to workers from inhalation of NORM during abrasive blasting with coal slag is extremely low and could be essentially eliminated by use of appropriate respiratory protection. External radiation exposure to workers handling large quantities of NORM-contaminated coal slag during shipping or storage is also low, but would vary depending on the concentration of NORM in the slag.

Rectus sheath hematoma.

Two patients who developed rectus sheath hematoma while on anticoagulants are presented. Ultrasound was the definitive method of establishing the diagnosis.

The hypoechoic caudate lobe: an ultrasonic pseudolesion.

The hypoechoic caudate lobe may occur as a normal variant because of acoustic shadowing in patients with more than the usual amounts of fat or fibrous tissue along the fissure of the ligamentum venosum. The use of a lower frequency transducer may cause the shadowing to decrease or disappear and the caudate lobe to appear more normal. The problem may also be resolved by angling the static scanner from the side or by using a real-time scanner. If pathologic lesions are still suspected, correlation with computed tomography is recommended.