Health Physics

This paper discusses the evaluation of dose-equivalent rates in mixed radiation environments such as are found, for example, around a high energy particle accelerator. It is shown that it is not possible to evaluate absorbed dose and dose-equivalent rates by any single measurement, in such complicated environments, with sufficient accuracy for purposes of radiation protection. This paper studies in detail the problems of evaluating dose equivalent from measurements of absorbed dose made with a tissue-equivalent ionization chamber. Our work supplements and is distinctly different from that of Shaw et al. They have shown that when a neutron spectrum is known one can use the ORNL (Oak Ridge National Laboratory) Monte Carlo calculation to calculate the dose equivalent and absorbed dose distributions in tissue and hence evaluate QF. On the other hand, in this paper we show that knowledge of the neutron spectrum is also necessary when one must choose an average "Quality Factor" to be applied to a single measurement of absorbed dose when only a table of (QF vs. neutron energy is available. Recently the U.S. Atomic Energy Commission has published a table of quality factors for monoenergetic neutrons as a function of neutron energy, and this has now appeared in National Bureau of Standards Handbook 107, but no values were given for the spectra spanning the large energy range typically found around high energy accelerators and reactors. By the use of the values of quality factor recommended for monoenergetic neutrons, the QF for a variety of typical neutron spectra was calculated. The neutron spectra studied include the Watt fission spectrum, the PuBe spectrum, the cosmic-ray neutron spectrum, and three typical accelerator spectra measured at CERN and the Lawrence Radiation Laboratory. In addition, calculations were made for a variety of spectra expressed in simple exponential form. These calculations indicate the quality factor to be an extremely sensitive function of neutron spectrum and maximum-energy cutoff in the range of practical interest-the average quality factor varies with these parameters by more than a factor of 3. This work indicates the potential errors in estimating dose equivalent when making absorbed dose measurements and assuming a single value of quality factor. Knowledge of such errors is a valuable guide to operational health physicists. (C)1971Health Physics Society

There are many conflicting data on the actual tumorigenicity of radon and its progeny with respect to indoor radon. Furthermore, although it was generally assumed that radon exposure causes a negligible radiation dose to bone marrow, some authors reported a radon related risk for leukemia (Henshaw et al. 1990; Alexander et al. 1990; Eatough and Henshaw 1993; Haque and Kirk 1992). Cytogenetic analyses in peripheral blood lymphocytes from radon-exposed subjects may provide further biological evidence of whether significant doses are received by target cells in the marrow. According to previously published data demonstrating an association between radon exposure and chromosomal aberrations, radon-induced chromosome aberrations significantly include inversions, translocations, dicentrics, and ring chromosomes (Brandom et al. 1978; Bauchinger et al. 1994). Furthermore, it was also found that subjects living in areas with low radon levels had unexpectedly high frequencies of chromosome aberrations in their lymphocytes (Pohl-Ruehling 1988). Therefore, we though it worthwhile to perform a cytogenetic and karyotypic investigation on a limited number of subjects who were included in other radon studies. If very low radon levels are able to induce chromosome aberrations this should also be seen in our subjects, whereas the karyotypic analysis may especially reveal the presence of stable aberrations. 14 refs., 2 tabs.

The quality factor, Q, is a dimensionless modifier used in converting absorbed dose, expressed in gray (or rad), to dose equivalent, expressed in sievert (or rem). The dose equivalent is used in radiation protection to account for the biological effectiveness of different kinds of radiation. The quality factor is related to both linear energy transfer (LET) and relative biological effectiveness (RBE). The RBE obtained from biological experiments depends in a complex way on the observed biological effect, the specific test organism and the experimental conditions. Judgment is involved, therefore, in the choice of Q. Questions regarding the adequacy of current Q values for neutrons were first raised in a 1980 statement by the National Council on Radiation Protection and Measurements (NCRP) and later in a 1985 statement by the International Commission on Radiological Protection (ICRP). In 1980, the NCRP alerted the technical community to the possibility of a future increase between a factor of 3 to 10 in the Q for neutrons, and in 1985, the ICRP suggested an increase by a factor of 2 in Q for fast neutrons. Both these advisory groups are now recommending essentially the same guidance with regard to Q for neutrons: an increase by a factor of 2. The Q for neutrons is based on a large, albeit unfocused, body of experimental data. In spite of the lack of focus, the data supporting a change in the neutron quality factor are substantial. However, the proposed doubling of Q for neutrons is clouded by other issues regarding its application. These issues are discussed, together with the current database for the neutron quality factor. Improvements are needed to provide better guidance with regard to both Q for neutrons and its application in radiation protection.

The objective of this study was to examine the feasibility of an accurate in situ measurement of radioactive hot spots by a HPGe detector located at a height of 0.1 m above the surface, thus sparing the awkward use of a heavy collimator required at the standard 1 m height. Radioactivity concentrations of primordial naturally occurring 40K, 232Th, 238U and of anthropogenic 137Cs in a sand plot were measured in situ at the two heights. Independently, six fractions of a soil profile collected in the site were measured in the laboratory. Good agreement was found between the results of the two geometries and the soil samples. Good agreement between measured and predicted radioactivity concentration values was obtained for hot spots simulated by uniform planar sources of 40K, 60Co and 137Cs having a circular pattern 0.5 m in diameter. The study shows that an in situ measurement without a collimator but close to a hot spot can provide a reliable result.

A whole-body tomographic model, called VIP-Man, was recently developed at Rensselaer Polytechnic Institute from the high-resolution color photographic images of the National Library of Medicine's Visible Human Project. An EGS4-based Monte Carlo user code, named EGS4-VLSI, was developed to efficiently transport electrons using the large image data set for VIP-Man. VIP-Man has been used to calculate doses for neutrons and photons. This paper presents a new set of fluence-to-absorbed-dose conversion coefficients for monoenergetic electron beams between 100 keV and 10 MeV for VIP-Man. Irradiation conditions include anterior-posterior, posterior-anterior, right lateral, left lateral, rotational, and isotropic source geometries. Comparisons between organ doses from VIP-Man, which is taller and heavier than the Reference Man, and existing data from mathematical models show significant discrepancies. It appears that even slight differences between body models can cause dramatic dosimetric deviations for low penetrating electron irradiation. This suggests that a single standard body model may poorly represent a large population and may not be acceptable for electron dosimetry.

Minimizing the x-ray radiation dose is an important aspect of patient safety during interventional fluoroscopy procedures. This work investigates the practical aspects of an additional 0.1 mm Cu x-ray beam spectral filter applied to cine acquisition mode imaging on patient dose and image quality. Measurements were acquired using clinical interventional imaging systems. Acquisition images of Solid Water phantoms (15-40 cm) were acquired using x-ray beams with the x-ray tube inherent filtration and using an additional 0.1 mm Cu x-ray beam spectral filter. The skin entrance air kerma (dose) rate was measured and the signal difference to noise ratio (SDNR) of an iodine target embedded into the phantom was calculated to assess image quality. X-ray beam parameters were recorded and analyzed and a primary x-ray beam simulation was performed to assess additional x-ray tube burden attributable to the Cu filter. For all phantom thicknesses, the 0.1 mm Cu filter resulted in a 40% reduction in the entrance air kerma rate to the phantoms and a 9% reduction in the SDNR of the iodine phantom. The expected additional tube load required by the 0.1 mm Cu filter ranged from 11% for a 120 kVp x-ray beam to 43% for a 60 kVp beam. For these clinical systems, use of the 0.1 mm Cu filter resulted in a favorable compromise between reduced skin dose rate and image quality and increased x-ray tube burden.

Estimates of the distribution of absorbed dose and dose equivalent with depth in a tissue slab have been made for irradiation by normally incident and also isotropically incident protons and neutrons with energies up to 2.0 GeV. The Monte Carlo calculations, based on a simplified model for nuclear interactions, take into account the production of pions as well as nucleons in nuclear interactions. The energy deposited due to ionization by charged particles is separated into LET ranges permitting different quality factors to be used. The total dose is broken down to show the contribution due to ionization by primary particles (in the case of incident protons), ionization by secondary particles, ionization by pions, excitation of residual nuclei following cascades, and the contribution from pions that stop within the tissue. Results are presented in the form of graphs showing the distribution of absorbed dose and dose equivalent with depth within the phantom for incident energies 0.6, 1.0, and 2.0 GeV. The results appear to be in reasonable agreement with experimental results. There is a rapid buildup of dose near the surface and then a more gradual buildup in the remainder of the 30 cm thick tissue slab. Pions are found to contribute less than 10% of the total dose. For normally incident neutrons, the quality factor decreases from near 10 at the surface from which the neutrons are incident to approximately 2.5 near the back of the slab. (C)1969Health Physics Society

Magnetic resonance, once a research tool limited to the basic sciences, has experienced an increase in popularity due to its unique ability to analyze certain living systems in vivo. Expanding applications in the biomedical sciences have resulted in magnetic sources being located in research institutions nationally. Space and resource limitations sometimes necessitate siting magnetic resonance units in proximity to other institutional operations. For magnetic field shielding and personnel protection considerations, the generally accepted 0.5 mT (milliTesla) limit for implanted cardiac devices is commonly used as the conservative basis for decisions. But the effects of magnetic fields on equipment can be easily observed at levels far below 0.5 mT, often resulting in concern and apprehension on the part of personnel in the surrounding areas. Responding to recurrent worker concerns spawned by noticeable effects on equipment at exposure levels <0.5 mT can strain finite radiation safety program resources. To enhance the ability to anticipate possible facility incompatibility issues associated with the installation of magnetic sources, a literature review was conducted to summarize documented equipment effects. Various types of equipment were found to be impacted at levels ranging down to perhaps 0.001 mT. Armed with this information, practicing radiation safety professionals can better anticipate facility incompatibility issues and improve their responses to worker concerns initiated by observed effects on equipment.

This article distills from available data descriptions of typical human symptoms in reaction to prompt total-body ionizing radiation in the dose range 0.5 to 30 Gy midline body tissue. The symptoms are correlated with dose and time over the acute postexposure period of 6 wk. The purpose is to provide a symptomatology basis for assessing early functional impairment of individuals who may be involved in civil defense, emergency medical care and various military activities in the event of a nuclear attack. The dose range is divided into eight subranges associated with important pathophysiological events. For each subrange, signs and symptoms are designated including estimates of symptom onset, severity, duration and incidence.

Geiger-Müller counters are often used in mixed-field dosimetry to determine the photon dose fraction. For accurate dose specification, their neutron sensitivities must be known. The pulsed beam time-of-flight method was used to determine the neutron sensitivities of an energy-compensated type ZP1320/PTFE Geiger-Müller counter in the 0.5-8-MeV region. The flux of monoenergetic neutrons from the T(p,n)3He and D(d,n)3He reactions, which were used in these measurements, was determined from time-of-flight spectra with an NE213 scintillation counter of known efficiency.

A recently developed source of intermediate energy neutrons was used to calibrate two commercial versions of the Andersson Braun wide range rem response survey meter and a standard de Pangher long counter.The source, which emits a broad spectrum of neutrons centred on 0.5 keV, allowed an investigation of the response of these instruments in a hitherto unexplored energy region. The survey instruments were shown to be oversensitive to these neutrons, whereas the sensitivity of the long counter was shown to be relatively energy independent.

Hematopoietic growth factors (HGF) are recommended therapy for high dose radiation exposure, but unfavorable administration schedules requiring early and repeat dosing limit the logistical ease with which they can be used. In this report, using a previously described murine model of H-ARS, survival efficacy and effect on hematopoietic recovery of unique PEGylated HGF were investigated. The PEGylated-HGFs possess longer half-lives and more potent hematopoietic properties than corresponding non-PEGylated-HGFs. C57BL/6 mice underwent single dose lethal irradiation (7.76-8.72 Gy, Cs, 0.62-1.02 Gy min) and were treated with various dosing regimens of 0.1, 0.3, and 1.0 mg kg of analogs of human PEG-G-CSF, murine PEG-GM-CSF, or human PEG-IL-11. Mice were administered one of the HGF analogs at 24-28 h post irradiation, and in some studies, additional doses given every other day (beginning with the 24-28 h dose) for a total of three or nine doses. Thirty-day (30 d) survival was significantly increased with only one dose of 0.3 mg kg of PEG-G-CSF and PEG-IL-11 or three doses of 0.3 mg kg of PEG-GM-CSF (p ≤ 0.006). Enhanced survival correlated with consistently and significantly enhanced WBC, NE, RBC, and PLT recovery for PEG-G- and PEG-GM-CSF, and enhanced RBC and PLT recovery for PEG-IL-11 (p ≤ 0.05). Longer administration schedules or higher doses did not provide a significant additional survival benefit over the shorter, lower dose, schedules. These data demonstrate the efficacy of BBT's PEG-HGF to provide significantly increased survival with fewer injections and lower drug doses, which may have significant economic and logistical value in the aftermath of a radiation event.

The (241)Am contents in the United States Transuranium and Uranium Registries' (USTUR) case 0102 leg phantom were previously estimated to be 1,243 ± 11 Bq. Recent analysis of the computed tomography images of the phantom revealed multiple bone structures missing from various regions of the phantom skeleton including: posterior ilium, anterior ilium, ischium, femur proximal end, femur middle shaft, femur distal end, patella, tibia distal shaft, fibula distal shaft, and fibula distal end. Additionally, the fifth metatarsal and all of the fifth-digit phalanges were found to be completely missing from the foot. A three-dimensional (3D) model of the leg phantom was created using 3D-Doctor software. Volumes of missing bone structures were outlined separately based on the anatomical assessment of those structures. Weights of the missing bone samples were calculated. Consequently, the value of total( 241)Am activity in the USTUR leg phantom is 1,218 ± 11 Bq. This activity is about 2.0% less than the previously published value of 1,243 ± 11 Bq. External gamma detector response was simulated considering both activity values (1,243 and 1,218 Bq) across the five different locations along the USTUR leg phantom: foot, middle leg, knee, middle thigh, and hip. Each counting position was chosen such that it was above the missing bone structure locations. The highest difference observed between the two counting efficiencies (each corresponding to the two different quantities of estimated activity) was 8.2% and 9.4% for locations above the foot and middle thigh, respectively. Other counting locations (middle leg, knee, and hip) showed efficiency variations of about 1%.

Skin penetration by radionuclide contaminants serves as a route of entry into the body and may pose a serious health risk to humans depending on the magnitude of intake. The United States Transuranium and Uranium Registry whole body Case 0262 was involved in a wound intake of plutonium at the Hanford Site. The registrant died about 33 years later. Results were initially reported in 2007 regarding the deposition and retention of plutonium in various tissues, including the wound site. However in 2009, an additional (previously unrecorded) sample of the wound tissue was located in the National Human Radiobiological Tissue Repository. The new sample was analyzed using inductively coupled plasma-mass spectrometry (ICP-MS), and the results were used to calibrate the measurement of emitted Pu x-rays from the original wound tissue sample made in 2007. In the present study, the analysis of Pu absorption rates from the wound and axillary lymph node from the initial study is repeated using the additional wound activity data and ICP-MS calibration. This new analysis is carried out using the Weighted Likelihood Monte Carlo Sampling (WeLMoS) method and code, which applies Bayesian inference to calculate the posterior probability distribution of intake and wound absorption parameters directly from the observed data and the assumed biokinetic model structure. The resulting central estimates of empirical wound absorption parameters and their associated uncertainties are here compared with the empirical values recommended in NCRP Report No. 156 for plutonium and with the maximum likelihood point estimates derived in the initial study from the Case 0262 data available at the time.

Exercise Initial Thunder (ExIT-08) was the fourth in a series of four emergency response exercises sponsored by the Chemical, Biological, Radiological, Nuclear and Explosives Research and Technology Initiative (CRTI). It was designed to test the Canadian Federal, Provincial and Municipal response to a terrorist attack using radioactive materials. The complexity of this exercise had been increased over previous exercises to now include provincial and municipal players. As a result about 350 persons participated as players in the 4-day exercise that was held in two locations in the western part of Canada. This paper summarizes the experiences and the lessons learned of the Health Canada (HC) team.

The attenuation of 60 Co gamma rays and photons of 4, 10, and 18 MV x-ray beams by concrete, steel, and lead has been studied using the Monte Carlo technique for angles of incidence 0, 30, 45, 60, and 70 degrees. Transmission factors have been determined down to <2x10(-5) in all cases. The results show that deviation from the obliquity factor increases with angle but is not significant for angles <45 degrees. At a 70 degree angle of incidence and a transmission factor of 10(-5), the obliquity factor varies between 1.2 and 1.9 for concrete, between 1.4 and 1.7 for steel, and between 1.4 and 1.5 for lead for the range of energies investigated. This amounts to an additional 86 and 50 cm of concrete, 25 and 23 cm of steel, and 8 and 14 cm of lead for 60 Co and 18 MV x rays respectively. The results for 60 Co in concrete and lead are in good agreement with previously published experimental work. Fits to the data using mathematical models allow reconstruction of all data curves to better than 1% on average and 7% in the worst single case.

Intoxication with uranium compounds is both an occupational risk for the workers engaged in the different processes of the elaboration of nuclear fuel and a risk for the population at large in terms of contaminated water and food. The toxic effects of uranium can be reduced by the administration of a biphosphonate, ethane-1-hydroxy-1,1-biphosphonate (EHBP), subcutaneously or intraperitoneally. The aim of the present work was to examine whether orally administered EHBP reduces the lethal effect of a single orally administered toxic dose of uranyl nitrate. Nine groups of 20 male Balb-c mice were used. Five groups received 350 mg kg(-1) of uranyl nitrate orally administered by gavage, four were co-treated 20 min later with EHBP either by gavage (350, 500, or 700 mg kg(-1)) or by subcutaneous injection (50 mg kg(-1)), and one group was not treated. Four groups of animals received only EHBP in doses and routes the same as those used in the intoxicated animals. Survival was assessed for 14 d. On day 14 the surviving animals of all groups were killed. An additional group of uranium intoxicated animals was killed on day 2 after the start of the experiment. Kidneys were examined histologically. On day 3 all the animals treated with uranyl nitrate alone and 20% of the animals treated with 700 mg kg(-1) of EHBP alone were dead. Survival at day 14 of the groups of mice intoxicated with uranyl nitrate and treated with EHBP (50 mg kg(-1) orally or 50 mg kg(-1) subcutaneously) was 45.0 and 49.6%, respectively. Tubule necrosis lesions were present in kidneys of mice intoxicated with uranyl nitrate, whereas lesions were less severe in mice treated with EHBP. Oral administration of EHBP is effective for reducing the lethal effect of uranium, and it is at least as useful as subcutaneous administration for prompt therapy of oral uranium exposure, achieving a survival rate of almost 50%.

Exposure to uranium is a risk for the workers involved in uranium mining, purification, and manufacture, principally by its ingestion or inhalation. It is also a risk for the population at large in case of intake of contaminated water or food. Uranium induces nephropathy that is characteristic of heavy metals, which can lead to death. The toxic effects of uranium can be prevented by a biphosphonate, ethane-1-hydroxy-1,1-bisphosphonate (bisodic etidronate), administered orally or subcutaneously. Employing bisodic etidronate, our laboratory obtained satisfactory results in terms of survival in adult mice, adult rats, and suckling rats. The aim of the present study was to evaluate the efficacy of bisodic etidronate for preventing renal dysfunction induced by a lethal dose of uranyl nitrate, employing serum levels of urea and creatinine as end-points. Two experiments were performed over different time periods, i.e., Experiment A: 48 h, Experiment B: 14 d. Each experiment was performed with 4 groups of 20 male Balb/c mice each, 25 g average body weight. Three of these groups received 350 mg kg(-1) of body weight of uranyl nitrate by gavage (forced oral administration). Two of the three exposed groups were treated with bisodic etidronate either by gavage in a dose of 500 mg kg(-1) body weight or with a subcutaneous injection of 50 mg kg(-1) body weight. The fourth group served as control. Survivors of the experimental groups were sacrificed at the end of the experiment by overdose of inhalation anesthetic (ether). The kidneys were routinely processed for histological analysis. Blood samples were taken by cardiac puncture to assess urea and creatinine serum levels. Urea and creatinine serum levels were markedly lower at 48 h in exposed animals treated with bisodic etidronate than in untreated exposed animals. On day 14 these values in exposed and treated animals did not differ significantly from control values. The renal function of animals treated with orally or subcutaneous bisodic etidronate that survived uranyl nitrate exposure was markedly improved compared to the controls of untreated exposed animals at 48 h. At 14 days, treatment with bisodic etidronate averted renal damage. At this time, the histologic study of kidneys showed images of tissue recovery. These results suggest that the use of EHBP may be of great value in reducing the renal damage.

The processes of uranium extraction, purification, and manufacture involve the risk of chemical intoxication. Acute uranium poisoning elicits renal failure which in turn may lead to death. Great efforts have been put into the search for a protective agent for acute uranium poisoning. Several chelating agents such as EDTA, Tiron, DTPA, or aminosalicylic acid have been experimentally assayed. However, even when these agents are able to reduce the mortality none of them achieve 100% survival. We herein present the use of EHBP to prevent mortality due to uranium poisoning. Rats weighing 14 g were employed in two different experiments: A) The surviving animals were killed on the 60th day; and B) The animals were killed on the 9th day. In both experiments 4 groups were considered: 1. untreated control; 2. one intraperitoneal (IP) injection of uranyl nitrate (2 mg kg-1 of body weight); 3. 1 IP injection of EHBP (10 mg kg-1 of body weight); and 4. treatments 2 and 3 combined. In both experiments 50% of the animals in group 2 died on the eighth day. All the animals of the other groups were alive at the end of the experiment. Histological analysis of the kidneys of the animals of experiment B revealed renal damage in the exposed animals, whereas no structural alterations were detected in the kidneys of the other three groups, including those given uranyl nitrate and treated with EHBP. These results show the efficiency of only one injection of EHBP to avoid renal damage and to counteract the mortality due to uranium poisoning with a success rate of 100%.

The authors have assembled a compilation of exposure rate constants, ƒ-factors, and lead shielding thicknesses for more than 1,100 radionuclides described in ICRP Publication 107. Physical data were taken from well established reference sources for mass-energy absorption coefficients in air, attenuation coefficients, and buildup factors in lead and other variables.The data agreed favorably for the most part with those of other investigators; thus this compilation provides an up-to-date and sizeable database of these data, which are of interest to many for routine calculations. Emissions were also segregated by emitting nuclide, and decay product emissions were emitted from the calculated coefficients, thus for the first time providing for the calculation of exposure rates from arbitrary mixtures of nuclides in arbitrary equilibrium states.

The threat of a dirty bomb or other major radiological contamination presents a danger of large-scale radiation exposure of the population. Because major components of such contamination are likely to be actinides, actinide decorporation treatments that will reduce radiation exposure must be a priority. Current therapies for the treatment of radionuclide contamination are limited and extensive efforts must be dedicated to the development of therapeutic, orally bioavailable, actinide chelators for emergency medical use. Using a biomimetic approach based on the similar biochemical properties of plutonium(IV) and iron(III), siderophore-inspired multidentate hydroxypyridonate ligands have been designed and are unrivaled in terms of actinide-affinity, selectivity, and efficiency. A perspective on the preclinical development of two hydroxypyridonate actinide decorporation agents, 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO), is presented. The chemical syntheses of both candidate compounds have been optimized for scale-up. Baseline preparation and analytical methods suitable for manufacturing large amounts have been established. Both ligands show much higher actinide-removal efficacy than the currently approved agent, diethylenetriaminepentaacetic acid (DTPA), with different selectivity for the tested isotopes of plutonium, americium, uranium and neptunium. No toxicity is observed in cells derived from three different human tissue sources treated in vitro up to ligand concentrations of 1 mM, and both ligands were well tolerated in rats when orally administered daily at high doses (>100 micromol kg d) over 28 d under good laboratory practice guidelines. Both compounds are on an accelerated development pathway towards clinical use.

In this study the radionuclide databases for two versions of the Clean Air Act Assessment Package-1988 (CAP88) computer model were assessed in detail. CAP88 estimates radiation dose and the risk of health effects to human populations from radionuclide emissions to air. This program is used by several U.S. Department of Energy (DOE) facilities to comply with National Emission Standards for Hazardous Air Pollutants regulations. CAP88 Mainframe, referred to as version 1.0 on the U.S. Environmental Protection Agency Web site (http://www.epa.gov/radiation/assessment/CAP88/), was the very first CAP88 version released in 1988. Some DOE facilities including the Savannah River Site still employ this version (1.0) while others use the more user-friendly personal computer Windows-based version 3.0 released in December 2007. Version 1.0 uses the program RADRISK based on International Commission on Radiological Protection Publication 30 as its radionuclide database. Version 3.0 uses half-life, dose, and risk factor values based on Federal Guidance Report 13. Differences in these values could cause different results for the same input exposure data (same scenario), depending on which version of CAP88 is used. Consequently, the differences between the two versions are being assessed in detail at Savannah River National Laboratory. The version 1.0 and 3.0 database files contain 496 and 838 radionuclides, respectively, and though one would expect the newer version to include all the 496 radionuclides, 35 radionuclides are listed in version 1.0 that are not included in version 3.0. The majority of these has either extremely short or long half-lives or is no longer in production; however, some of the short-lived radionuclides might produce progeny of great interest at DOE sites. In addition, 122 radionuclides were found to have different half-lives in the two versions, with 21 over 3 percent different and 12 over 10 percent different.

Extruded LiF chips were irradiated in a scanning electron microscope (SEM) with electron energies of 1.0, 2.0 or 4.0 keV. The LiF chips were irradiated at several electron currents to deliver doses over the range of 5-1200 krads. The average dose, D, over the depth of electron penetration was determined in rads. The thermoluminescence produced by the electrons was compared with that produced by 137Cs gamma-rays. The sensitivity of the LiF to electrons was found to be 0.2-0.4 times its sensitivity to 137Cs gamma-rays. This indicates that thermoluminescence in LiF is produced with remarkable efficiency even at low electron energies provided the electrons reach the LiF. (C)1975Health Physics Society

Nucleon-meson cascade calculations have been carried out for monoenergetic neutrons and protons in the energy range from 3.5 GeV to 1.0 TeV normally incident on a semi-infinite slab of tissue 30 cm thick. The absorbed dose and dose equivalent as a function of tissue depth are presented, and analytic expressions for the resulting maximum and average fluence-to-absorbed-dose and fluence-to-dose-equivalent factors are given as a function of incident neutron or proton energy. The calculations were performed by using Monte Carlo methods in conjunction with theoretical nuclear-interaction models. (C)1973Health Physics Society

Data was collected to determine dose build-up in tissue resulting from beams of high energy protons and pions. Using the external momentum-analyzed beams of the Argonne 12.5 BeV Zero Gradient Synchrotron, depth-dose measurements were made in beams of positive particles with momenta of 1.0, 1.5, 2.5, 4.0, 5.0 and 10.0 BeV/c; and in beams of negative particles with momenta of 1.0, 1.5, 2.0, 3.0, 4.0 and 5.0 BeV/c. Measurements were made using a tissue-equivalent integrating ionization chamber. These measurements were normalized to a graphite integrating ionization chamber beam monitor. Data was collected at 1-in. intervals through a 10-in. thick Plexiglas phantom. The resulting depth-doses were normalized to the entrance dose for each momentum. Results show that in both the positive and negative beams the dose build-up factors decreased within the momenta range from 1.0 BeV/c to about 2.0 BeV/c, but then increased with higher momenta. For a given particle momentum, the dose build-up factor in the negative beams exceeded that obtained in the positive beams. At 5.0 BeV/c, a maximum build-up factor of 1.45 was obtained with negative particles as opposed to a build-up factor of 1.19 with positive particles. The results of this study are discussed in terms of values of stopping power for protons and pions in the BeV region, proton-pion ratios, muon contamination, cross-section data and production of cascade particles. (C)1966Health Physics Society

The 2.0-Mev Van de Graaff accelerator facility at USNRDL has been used ; as a source of high-intensity x radiation for a large number of experiments over ; the past several years. In order to explore the feasibility of using this ; radiation source in an even wider variety of situations, it was considered ; necessary to determine the exact spectrunn of bremsstrahlung produced by the ; bombardment of thick metallic targets by the monoenergetic electrons accelerated ; in the Van de Graaff. While a gold target is usually used as the bremsstrahlung ; target for high-intensity work, it was decided to explore the bremsstrahlung ; emerging from targets having a wide range of Z values, thus providing a more ; widely usable fund of information. Thus, the experiment described in this report ; consisted of the measurement of the 0° bremsstrahlung spectrum emerging ; from thick targets of polystyrene, aluminum, copper, silver, and gold bombarded ; by monoenergetic electrons at 2.0, 1.6, and 1.0 Mev. (auth);

Mass absorption coefficients have been measured for scandium, titanium, vanadium, iron, cobalt, nickel and zinc for photon energies from 1.49 to 15.77 keV with an average standard deviation of the mean of 1.2 per cent. A high intensity X-ray beam was provided by a partially evacuated, Bragg-crystal spectrometer. The absorbers were cold-rolled from spectroscopic grade material with thickness determined by the weight-area measurement method. An empirical equation relating photon energy and mass absorption coefficient is proposed for photon energies between the L- and K-absorption energies of the absorber. This equation is used to predict values of mass absorption coefficients for lead, tin, copper and calcium and the results compared with the values found in the Norelco Reporter. (C)1967Health Physics Society

A computer code was developed to simulate the bremsstrahlung dose rate distribution patterns produced by the CAMD electron storage ring. These bremsstralung dose rate distributions were measured along the interior surface of the shield walls (short walls perpendicular to the bending magnets) with TLD chips. Electron losses for each specific magnet was determined by running the computer code and varying the electron loss parameters to fit the measured dose rate distributions. It was determined that (1) bending magnet No. 1 (closest to the injection septum) loses 2.7 x 1010 electrons per minute during electron injection. The loss rate for each of the subsequent seven bending magnets during injection varies from about 25% to 33% of this number; (2) the magnet immediately subsequent to the bending magnet loses more electrons than the magnet immediately prior to the bending magnet does; and (3) the computer code may be used to predict potential problems such as misalignment.

A Monte Carlo code EGS4 expanded for low energy photon transport was validated by measuring absorbed doses in a phantom for 30 and 10 keV monoenergetic photons from synchrotron radiation. Using the EGS4 code, depth doses at 0.07 mm, 0.02 to 0.1 mm, and 10 mm in the ICRU slab phantoms were calculated for 1.5 to 50 keV photons using the updated photon cross section data PHOTX. The results show that the doses at 0.02 to 0.1 mm below 10 keV are practical indices of effective dose as calculated by others, based on the 1990 ICRP recommendations (1991).

The endothelial injury threshold was determined in rabbit for an 11-s exposure to 1.54 micro m radiation from an Erbium fiber laser. The beam was Gaussian with a 1/e diameter of 7 mm. Cell damage was detected with a wet staining technique. The threshold dose for these conditions is 4.4 x 10(5) J m(-2) (44 J cm) and is only 9% greater than the threshold for epithelial damage for the same exposure conditions. Exposures just above the threshold caused substantial endothelial damage, including loss of cells. The calculated endothelial temperature increase at the threshold is similar to that calculated for the epithelium at its injury threshold for the same exposure conditions. The results suggest that endothelial damage can be correlated with a critical temperature damage model with a critical temperature increase near 40 degrees C. The results also suggest that if a person were to receive an exposure only slightly above the epithelial injury threshold from a beam having a diameter of 7 mm (which is the diameter of the exit pupil of 7 x 50 binoculars) he or she would risk sustaining substantial endothelial damage.

Corneal epithelial injury thresholds have been determined for exposures to 1.54 mum infrared radiation from an Erbium fiber laser. Thresholds were determined for beam diameters from 0.05 to 0.7 cm for exposures having durations from approximately 1 to 100 s and for a fixed beam diameter of 0.1 cm for exposures with durations between 0.036 and 0.26 s. Near-threshold damage appeared within 30 min post-exposure. There was no evidence of latent damage from lesser exposures appearing up to 24-48 h post-exposure. The dependence of the threshold radiant exposures on laser beam diameter for exposures >1 s provides strong evidence supporting a critical temperature damage model. However, the shorter exposures are not in accord with a critical temperature damage model. Thresholds for exposures longer than 1 s are greater than 10 times the maximum permissible exposure (MPE) in ANSI Z-136.5-2000; however, the safety factor decreases to less than 10 for exposures less than 0.1 s with a 0.1-cm-diameter beam.

Gamma-ray kermas from the Hiroshima atomic bomb were measured by a thermoluminescence (TL) method using tile specimens collected from five locations on the rooftop of a building (Postal Saving Bureau), 1,591-1,635 m from the hypocenter. Four tile specimens each from five locations were sampled and quartz grains were extracted from them. TL of these grains were analyzed by the high temperature TL method and gamma-ray kermas were obtained. The results in tissue kerma, on average, are 21% higher (standard errors are 4.3-7.3%) than the DS86 estimation. The present data and the reported TL results indicate that the measured gamma-ray kermas begin to exceed the DS86 values at about 1.3 km and the discrepancy between them increases with ground distance. This discrepancy is attributed to errors in the DS86 neutron source spectrum and is supported by previous neutron activation measurements.

This paper presents the development of an in vivo exposure system for exposing small rodents. The system consists of four identical cylindrical waveguide chambers, each with a plastic cage for housing the animal. The chamber is fed by circularly polarized radiofrequency power in the 1.9 GHz cellular frequency band and is vertically mounted so that the long axis of the animal is co-planar with the rotating incident electric field. Power sensors were used along with directional or hybrid couplers and a digital voltmeter for data acquisition for real-time dose rate monitoring. The system was tested to evaluate its dose rate performance when a mouse phantom or a mouse cadaver was inside the cage. The dose rate was quantified in terms of whole-body-average (WBA) specific absorption rate (SAR) per input power using both measurement and computational methods. The exposures of the mouse phantom and cadaver were evaluated for various possible postures and positions. The measurement results showed that the highest WBA-SAR was 16.9 W kg per 1 W incident power when the cadaver was lying prone against the cage wall and the lowest WBA-SAR was 10.4 W kg per 1 W incident power when the cadaver was standing upright in the cage center. These results were found to be in good agreement with those obtained from the computational method.

The 59Fe uptake system was used to estimate the dose distribution throughout sham-operated and splenectomized rats exposed to whole-body 1000 kVp X-irradiation. The marrow in the splenectomized animals was found to be slightly more radiosensitive. However, the difference between the two groups of rats was not significant. The dose distributions throughout the marrow of both groups were the same. It was concluded that splenectomy had no effect on the usefulness of this method. The method of measuring 59Fe uptake in this study used the uptake of radioiron at 6 hr post-injection and the deduction of the activity due to circulating iron. This resulted in a technique capable of measuring changes in iron uptake with midline-air-exposures of 25 R. (C)1977Health Physics Society

The uptake of 59Fe citrate in the bones of control and irradiated dogs has been used as an index of the distribution of hematopoietic function. An animal exposed to 100 R whole-body 1000 kVp X-irradiation shows a shift in 59Fe uptake from the ribs to the long bones. This finding is in agreement with previous dosimetric studies. Similarly, those dogs subjected to partial-body irradiations show a decreased 59Fe uptake in directly exposed bones with increased uptakes in shielded bones which depend upon the distance of such bones beyond the edge of the shield, again in agreement with dosimetric studies. It is suggested that variations of this method may be useful in using the exposed animal as his own dosimeter. (C)1969Health Physics Society

Studies have been performed in which intramedullary doses have been measured throughout a large dog cadaver. These data will be used as the basis for live animal studies in which hematopoietic function will be measured using radioactive tracers. In the partial-body studies, it was noted that intramedullary dose beyond the edge of the shield is a function of distance from the shield and is unrelated to the type of bone involved. (C)1969Health Physics Society

A method has been described which utilizes glass microdosimeter rods in the determination of dose and an estimate of the effective energy at a point within tissue. Lead "absorption sleeves" containing 0, 0.5 and 1.0 mm of metal were designed to hold three rods and to produce differential responses dependent upon the incident energy. These sleeves were calibrated in air and tested within a presswood phantom. As designed, this technique was found to be of practical value between energies of 150 and 400 keV. Such absorption sleeves were placed within selected organs of a beagle cadaver which was exposed to whole-body- 1000 kVp X-radiation. A bilateral exposure was compared with a unilateral exposure of either side and was found to produce a more uniform irradiation with regard to both dose and energy. The midline tissue dose throughout the torso of the animal was found to be approximately 93 per cent of the midline air dose, and the mean effective energy throughout the same region was 282 keV (compared to an incident energy of 385 keV). (C)1965Health Physics Society

It cannot be assumed that the whole body irradiation of a group of beagles to the same midline air exposure results in the same stress to each animal. Previous phantom studies have demonstrated that the average exposure measured through the beam center is significantly less for larger dogs. Body contour and tissue composition may make similar measurements extended throughout the whole body of the dog differ from those found in a homogeneous rectangular phantom. Five beagle cadavers of varying sizes were exposed to 1000 kVp X-radiation and the effective photon energies and exposures were measured at twenty-three selected organ locations throughout each animal. Data are presented which demonstrate the relationship between animal size and average organ exposure. One difference noted between these cadaver measurements and previous theoretical or phantom studies was the levelling off of both photon energy and average organ exposures with increasing thickness in the upper torso. This is thought to be due to the increasing lung volume in the larger dogs which, relatively speaking, decreases the scattering and absorbing mass within this segment. Total body average exposure for various animal thicknesses was compared with survival data and, from this, the dependence of expected lethality vs. size for three midline air exposures was determined. (C)1967Health Physics Society

The distribution of radioactivity and the associated doses were evaluated postmortem for USUR Case 1001, a female who had been injected with Thorotrast some 36 y prior to death. The distribution was determined for four nuclides: 232Th and its decay products, 228Ra and 228Th; and 230Th, a contaminant associated with Thorotrast. More than 90% of the activity was associated with the reticuloendothelial system. Approximately 32% of the total activity was found in the total skeleton (mineral bone and bone marrow), which is somewhat higher than expected from the literature. The 44% found in the liver and 12% in the spleen were somewhat lower than expected. This difference may be attributable, in part, to the initial deposition as influenced by colloidal particle size and to the radiation-induced hyposplenism, splenic atrophy, and slight hepatic atrophy observed at autopsy. In addition, roughly 3% of the activity was found in the Thorotrastoma and surrounding carotid artery tissue. Estimated lifetime absorbed doses from the 232Th series were 15 Gy to the liver, 121 Gy to the spleen, 4 Gy to the skeleton, and 16 Gy to the Thorotrastoma. Comparable dose equivalents to these tissues are 300, 2420, 80, and 320 Sv, respectively, assuming a quality factor of 20 for alpha irradiation.