Beta-particle Dose Research Articles

Thermoluminescence properties of Er-doped borophosphate glass for beta radiation

The thermoluminescence (TL) dosimetric properties of metaphosphate glass system were investigated. The glass system of (Er2O3)1-(SrO)24-(B2O3)25-(P2O5)50 was prepared using a melt quenching technique. The glass system was characterized using different techniques. The internal structure of the system was probed with XRD and FTIR technique was used to identify the types of bonds between the involved atoms. The analysis of TL glow curve was studied by different methods and was found to be composed of six trap peaks at energies 0.817, 0.846, 0.958, 1.190, 1.248, and 1.347 eV. The TL dose–response signal was found to be linear in the range of 0.22–55 Gy. The activation energies were determined by three methods: glow curve deconvolution (CGCD), Tmax-Tstop method and Peak shape (PS) methods. The results of the three methods exhibited a good agreement with each other. Highlights The thermoluminescence properties of metaphosphate glass were investigated. The glass samples were irradiated to different doses of beta particles. The deconvolution indicated the presence of six overlapping glow peaks. The activation energies were determined by three methods and the results of all the methods exhibited a good agreement.

TL and OSL analysis of natural orange calcite crystal

The study presents TL and OSL characterization of orange calcite. It is known that calcite exhibits TL however its OSL emission is unwell studied. The morphological characterization was done by means of X-rays diffraction (XRD) technique and it was confirmed that the sample is a pure calcium carbonate. Total and traces elements were determined using Total Reflection X-Ray Fluorescence (TXRF) technique and several impurities were found as P (53070 mg/kg), S (877 mg/kg), K (442.1 mg/kg), Ca (118290 mg/kg), Fe (330.4 mg/kg), Cr (101.19 mg/kg), and Ni (115.01 mg/kg), also some trace impurities, as Cu (1.96 mg/kg) and Zn (1.30 mg/kg), Mn (57.21 mg/kg) were determined and they may have important role in the luminescent emission. Sample in powder form was irradiated with crescent doses of beta particles, in an interval of 5–25 Gy and showed TL peaks at approximately 93, 125, 162, 189 and 227 °C. An OSL response was verified and can be fitted using 3 components with decay constant values of 2.3, 10.0 and 77.4 s.

Study of the thermoluminescence kinetic parameters of a β-irradiated natural calcite

The current study was going to investigate the thermoluminescence properties of brownish calcite of sedimentary origin in Gebel El Galala, Egypt. The analytical characteristics of the calcite samples were performed using XRD and atomic spectroscopy techniques. The samples were irradiated to different doses of beta particles from 0.11 Gy up to 330 Gy. The TL glow curves of the samples were deconvoluted using new TL software. The deconvolution indicated the presence of 6 overlapping glow peaks. The kinetic parameters were obtained using different methods and their results were in a good agreement with each other. The samples exhibited sensitivity in average of 322.356 Gy−1 mg−1 and a minimum detectable dose of 976.221 μGy. The samples exhibited a long range of linearity from 1.1 up to 330 Gy responding to beta particles irradiation. The fading results recommended to start the measurements of the calcite samples after 2 days to give established measurements.

Structural and optical properties of sol-gel derived α-Fe2O3 nanoparticles

α-Fe2O3 nanoparticles of crystallite size between 3.9 and 9.5nm were synthesized by a simple sol-gel method using iron (III) nitrate nonahydrate (Fe(NO3)3·9H2O) as a precursor. Polyvinyl alcohol (PVA) was added as a capping agent to avoid agglomeration of the nanoparticles. A single pure phase was obtained when the sample was annealed at 300°C and 600°C. The purity was further confirmed with the Fourier Transform Infrared Spectroscopy. The energy band gap of the materials was extrapolated from the Kubelka-Munk relation and it ranges between 1.8 and 2.3eV. The Photoluminescence of the 3 samples shows a broad emission spectrum centered at about 422nm when excited by a 336nm lamp. The emission peaks intensities increased with an increase in the annealing temperature, accept for the 576nm peak, which was quenched as the temperature increased from 300°C to 600°C. The thermoluminescence glow curves were carried out at different heating rates and the samples were exposed to different beta particle doses (82–1315Gy). The activation energy of the trapped electrons was determined.

Optical absorption in LiF, LiF:Mg, LiF:Mg,Cu,P irradiated with high gamma and beta doses

We examine the optical absorption spectra of a variety of LiF materials, variously doped with Mg, Cu and/or P. Both single crystal LiF (from various sources) and LiF:MCP-N sintered pellets are examined. We follow the growth of the individual absorption bands as a function of high, gamma-photon doses and high, beta-particle doses. Detailed deconvolution of the spectra, measured at room temperature following irradiation also at room temperature, allows for the behavior of the individual OA peaks to be analyzed. We also examine the post-irradiation step annealing of the spectrum by progressively heating the samples to high temperatures. We compare the data so obtained with the shape of the thermoluminescence glow curve recorded from these same materials. F, F2, F3,F3+, F3− and F4 centers are identified, along with impurity-related and possible Li-colloid absorption features. The various OA bands grow with dose (1 kGy–700 kGy) and the annealing behaviors of the various absorption features are discussed.

Carbon nanotubes buckypaper radiation studies for medical physics applications

Graphite ion chambers and semiconductor diode detectors have been used to make measurements in phantoms but these active devices represent a clear disadvantage when considered for in vivo dosimetry. In such circumstance, dosimeters with atomic number similar to human tissue are needed. Carbon nanotubes have properties that potentially meet the demand, requiring low voltage in active devices and an atomic number similar to adipose tissue. In this study, single-wall carbon nanotubes (SWCNTs) buckypaper has been used to measure the beta particle dose deposited from a strontium-90 source, the medium displaying thermoluminescence at potentially useful sensitivity. As an example, the samples show a clear response for a dose of 2Gy. This finding suggests that carbon nanotubes can be used as a passive dosimeter specifically for the high levels of radiation exposures used in radiation therapy. Furthermore, the finding points towards further potential applications such as for space radiation measurements, not least because the medium satisfies a demand for light but strong materials of minimal capacitance.

Mathematical study of the thermoluminescence process in K2YF5:Tb(3+).

This paper presents results of studying the simulated thermoluminescence (TL) glow curve in potassium-yttrium double fluoride doped with trivalent optically active Tb(3+) ions (K2YF5:Tb(3+)). Samples have been irradiated with different doses (0.24, 2.4 and 24 Gy) of beta particles. Four trapping states and one kind of recombination-centre model have been used in this simulation. The activation energy and order of kinetics are determined using the general-order kinetic model. The results obtained using the authors' proposed models were tested and compared with the experimental glow curve of K2YF5:Tb(3+). The comparison has shown that the proposed model can predict more accurately and easily the behaviour of the TL glow curve at three different doses.

High dosage thermoluminescence diamond dosimeters

Diamond thin films have been irradiated with high doses (up to 12.8 kGy) of 90Sr beta particles. The diamond thin films have been synthesized from commercial Tequila as a precursor using Pulsed Liquid Injection by the Chemical Vapor Deposition (PLICVD) technique reported recently. Thermoluminescence (TL) phenomena at these doses exhibit peak curve shift to higher temperatures (from 370 to 440 K) in the glow curve and the integrated TL curve show a linear behavior. Therefore, it has been considered that diamond thin films could be used as high doses dosimeters.

Characteristics of spontaneously transformed human endothelial ECV304 cell line: II. Functional responses of ECV304 cells

The functional peculiarities of spontaneously transformed human endothelial ECV304 cell line were studied to estimate its adequacy as an endothelial cell model for studying angiogenesis and signal transduction. The dependence of the proliferative activity of this line on the presence of growth factors was shown. The absence of serum in the nutrition medium leads to the blockage of cells in the G1 phase of cell cycle, which is not characteristic of tumor cell lines. Low doses of beta particles emitted during the decay of the [3H]-thymidine blocked, dose-dependent proliferation of these cells in the G2/M phase. The incubation of the cells in medium with another source of β particles, 3H2O, resulted in the predominant accumulation of cells in the S phase under conditions of equal specific tritium activities. The different efficiency of β particles of tritium as a part of the H2O molecule or thymidine demonstrates that different mechanisms are responsible for different checkpoints. The checkpoint of G1/S is absent, which agrees with the presence of the deletion of chromosome 9 at locus p21. The level of NO produced by the constitutive form of NO synthase in ECV304 cells was relatively low and not modified by inducible NO-synthase inhibitors. The data obtained suggest that the ECV304 line cells retained properties of the initial spontaneously transformed cell line obtained from the human umbilical vein (HUVEC) and can be used as a model system for further studies of properties of the vascular endothelium.

Dosimetry for a Study of Low-Dose Radiation Cataracts among Chernobyl Clean-up Workers

A cohort of 8,607 Ukrainian Chernobyl clean-up workers during 1986-1987 was formed to study cataract formation after ionizing radiation exposure. Study eligibility required the availability of sufficient exposure information to permit the reconstruction of doses to the lens of the eye. Eligible groups included civilian workers, such as those who built the "sarcophagus" over the reactor, Chernobyl Nuclear Power Plant Workers, and military reservists who were conscripted for clean-up work. Many of the official doses for workers were estimates, because only a minority wore radiation badges. For 106 military workers, electron paramagnetic resonance (EPR) measurements of extracted teeth were compared with the recorded doses as the basis to adjust the recorded gamma-ray doses and provide estimates of uncertainties. Beta-particle doses to the lens were estimated with an algorithm devised to take into account the nature and location of Chernobyl work, time since the accident, and protective measures taken. A Monte Carlo routine generated 500 random estimates for each individual from the uncertainty distributions of the gamma-ray dose and of the ratio of beta-particle to gamma-ray doses. The geometric mean of the 500 combined beta-particle and gamma-ray dose estimates for each individual was used in the data analyses. The median estimated lens dose for the cohort was 123 mGy, while 4.4% received >500 mGy.

Physics for radiation protection: a handbook

Preface. 1 Atoms and Energy. 1.1 Structure of Atoms. 1.2 Nuclide Chart. 1.3 Atom Measures. 1.4 Energy Concepts for Atoms. 1.5 Relativistic Energy. 1.6 Electron Volt (eV). 1.7 Binding Energy of Nuclei. 1.8 Summary and Checkpoints. 2 Major Discoveries in Radiation Physics. 2.1 Great Discoveries from Simple Tools. 2.2 First Concept of the Atom. 2.3 Theory of Electromagnetic Radiation: the Quantum. 2.4 Discovery of the Atom's Structure. 2.5 Wave Mechanics: a Necessary Theory. 2.6 Atom Systems. 2.7 Summary. 3 Radioactive Transformation. 3.1 Processes of Radioactive Transformation. 3.2 Decay Schemes. 3.3 Rate of Radioactive Transformation. 3.4 Radioactivity Calculations. 3.5 Activity-mass Relationships. 3.6 Radioactive Series Transformation. 3.7 Radioactive Equilibrium. 3.8 Total Number of Transformations (Uses of &tau and &lambda Eff ). 3.9 Discovery of the Neutrino. 4 Interactions. 4.1 Production of X-rays. 4.2 Characteristic X-rays. 4.3 Nuclear Interactions. 4.4 Alpha Particle Interactions. 4.5 Transmutation by Protons and Deuterons. 4.6 Neutron Interactions. 4.7 Activation Product Calculations. 4.8 Medical Isotope Reactions. 4.9 Transuranium Elements. 4.10 Photon Interactions. 4.11 Fission and Fusion Reactions. 4.12 Summary. 5 Nuclear Fission and its Products. 5.1 Fission Energy. 5.2 Physics of Sustained Nuclear Fission. 5.3 Neutron Economy and Reactivity. 5.4 Nuclear Power Reactors. 5.5 Light Water Reactors (LWRs). 5.6 Heavy Water Reactors (HWRs). 5.7 Breeder Reactors. 5.8 Gas-cooled Reactors. 5.9 Reactor Radioactivity. 5.10 Radioactivity in Reactors. 5.11 Summary. 6 Naturally Occuring Radiation and Radioactivity. 6.1 Discovery and Interpretation. 6.2 Background Radiation. 6.3 Cosmic Radiation. 6.4 Cosmogenic Radionuclides. 6.5 Naturally Radioacitve Series. 6.6 Singly Occuring Primordial Radionuclides. 6.7 Radioactive Ores and Byproducts. 6.8 Radioactivity Dating. 6.9 Radon and its Progeny. 6.10 Summary. 7 Interactions of Radiation with Matter. 7.1 Radiation Dose and Units. 7.2 Radiation Dose Calculations. 7.3 Interaction Processes. 7.4 Interactions of Alpha Particles and Heavy Nuclei. 7.5 Beta Particle Interactions and Dose. 7.6 Photon Interactions. 7.7 Photon Attenuation and Absorption. 7.8 Energy Transfer and Absorption by Photons. 7.9 Exposure/Dose Calculations. 7.10 Summary. 8 Radiation Shielding. 8.1 Shielding of Alpha-Emitting Sources. 8.2 Shielding of Beta-Emitting Sources. 8.3 Shielding of Photon Sources. 8.4 Gamma Flux for Distributed Sources. 8.5 Shielding of Protons and Light Ions. 8.6 Summary. 9 Internal Radiation Dose. 9.1 Absorbed Dose in Tissue. 9.2 Accumulated Dose. 9.3 Factors In The Internal Dose Equation. 9.4 Radiation Dose from Radionuclide Intakes. 9.5 Operational Determinations of Internal Dose. 9.6 Bioassay Determination Of Intake. 9.7 Summary. 10 Environmental Dispersion. 10.1 Atmospheric Dispersion. 10.2 Nonuniform turbulence: Fumigation, Building Effects. 10.3 Puff Releases. 10.4 Sector-Averaged &Chi /Q Values. 10.5 Deposition/Depletion: Guassian Plumes. 10.6 Summary. 11 Nuclear Criticality. 11.1 Nuclear Reactors and Criticality. 11.2 Nuclear Explosions. 11.3 Criticality Accidents. 11.4 Radiation Exposures in Criticality Events. 11.5 Criticality Safety. 11.6 Fission Product Release in Criticality Events. 11.7 Summary. 12 Radiation Detection and Measurement. 12.1 Gas-Filled Detectors. 12.2 Crystalline Detectors/Spectrometers. 12.3 Semiconducting Detectors. 12.4 Gamma Spectroscopy. 12.5 Portable Field Instruments. 12.6 Personnel Dosimeters. 12.7 Laboratory Instruments. 13 Statistics in Radiation Physics. 13.1 Nature of Counting Distributions. 13.2 Propagation of Error. 13.3 Comparison of Data Sets. 13.4 Statistics for the Counting Laboratory. 13.5 Levels of Detection. 13.6 Minimum Detectable Concentration or Contamination. 13.7 Log Normal Data Distributions. 14 Neutrons. 14.1 Neutron Sources. 14.2 Neutron Parameters. 14.3 Neutron Interactions. 14.4 Neutron Dosimetry. 14.5 Neutron Shielding. 14.6 Neutron Detection. 14.7 Summary. 15 X-rays. 15.1 Producing and Shaping the X-ray Beam. 15.2 X-ray Image Information. 15.3 Capture of the X-ray Image. 15.4 Image Processing. 15.5 Radiation Protection from X-rays. 15.6 X-ray Shielding. 15.7 Summary. Appendix A. Appendix B. Appendix C. Appendix D. Appendix E. Appendix F. Index.

Relative Toxicity of Chronic Irradiation by45Ca β Particles and242Cm α Particles with Respect to the Production of Lung Tumors in CBA/Ca Mice

Approximately 1800 female CBA/Ca mice were exposed by inhalation at three dose levels to beta particles from (45)Ca-labeled fused aluminosilicate particles (FAP), to alpha particles from (242)Cm-labeled FAP, or to carrier control FAP. Another group of mice inhaled no FAP and were designated as untreated cage controls. The FAP in combination with these radionuclides was used to achieve the same spatial and temporal distribution of alpha- and beta-particle dose within the irradiated mice. Some mice were killed to determine the clearance of radiolabeled FAP from their lungs, and the remainder were allocated to a life-span study. All animals were subjected to a detailed necropsy. To facilitate the identification of small tumors, the lungs were rendered transparent in methyl salicylate and examined under back illumination for the presence of lesions. Lung nodules and other microscopic lesions were excised for histological examination. The median survival of mice in all groups was approximately 910 days. The control animals lived longer than those that were irradiated, but it was difficult to determine a dose-response relationship for survival among the exposed mice. Benign adenomas and, less frequently, malignant adenocarcinomas were identified in all animal groups. The prevalence of these tumors was approximately 28.8% in the control mice, which is consistent with the results of other studies using the same strain of mouse. After exposure to radionuclide-labeled FAP, there was a significant dose-related increase in the prevalence of lung tumors in (242)Cm- (peak prevalence 55%) and (45)Ca-exposed (peak prevalence 48.6%) mice. The prevalence of tumors in the mice that received (242)Cm-labeled FAP was approximately twice that in the mice that inhaled (45)Ca-labeled FAP within the range of doses employed (0.55-4.69 Gy). Using the ratio of the slope of the linear component of the dose-response curves, the toxicity of the alpha particles relative to the beta particles was 1.5 (90% CI: 0.7, 9.0) for all adenomas and 9.4 (90% CI: 5.0, 23.0) for the less frequent adenocarcinomas. The relative toxicity for adenocarcinomas was found to decrease with increasing dose.

Accurate calibration of a laboratory beta particle dose rate for dating purposes

This paper describes a novel method for calibration of the dose rate provided by a beta source used for luminescence dating. The calibration has been performed using an in-house calibration quartz that is given a dose in a Co-60 gamma ray facility. The gamma dose to the calibration quartz was calculated using Fricke dosimetry on simultaneously irradiated Fricke solution and Monte-Carlo simulations. An overall uncertainty in the dose to quartz of 0.6% (1 sigma) was achieved. The single aliquot regenerative dose (SAR) procedure was used to determine the irradiation time of the beta source needed to deliver the same dose to the sample. Results for a range of doses were combined by plotting irradiation time versus dose. A fit through the data points yielded the dose rate provided by the beta source at the sample position. This procedure resulted in an overall uncertainty in the beta dose rate of 0.9% (1 sigma). The beta dose rate was found to be in perfect agreement with an independent calibration using irradiated quartz provided by the Nordic Laboratory for Luminescence dating.

Assessment of90Sr Concentration in Dental Tissue using Thin-Layer Beta-Particle Detectors and Verification with Numerical Calculations

Electron paramagnetic resonance (EPR) measurements of tooth enamel can be used as an individual biological dosimeter for external dose assessment. However, the presence of 90Sr in the tooth tissues makes the task of interpreting EPR tooth dosimetry more complicated. The determination of the dose contribution of incorporated 90Sr in calcified tissue to the total dose measured by EPR is one of the main aspects of correct interpretation of EPR tooth dosimetry. In this work, experimental and numerical calculations were performed to convert the measured beta-particle dose rate to 90Sr concentration in calcified tissue. The cumulative beta-particle dose was measured by exposing artificially contaminated dentin and enamel to thin-layer alpha-Al2O3:C detectors in two different exposure geometries. Numerical calculations were performed for experimental exposure conditions using calculations of electron transport and secondary photons [Monte Carlo n-Particle Transport code version 4C2 (MCNP)]. Numerical calculations were performed to optimize the sample size and exposure geometry. The applicability of two different exposure conditions to be used in routine analysis was tested. Comparison of the computational and experimental results demonstrated very good agreement.

A mouse model for calculating the absorbed beta-particle dose from (131)I- and (90)Y-labeled immunoconjugates, including a method for dealing with heterogeneity in kidney and tumor.

Flynn, A. A., Green, A. J., Pedley, R. B., Boxer, G. M., Boden, R. and Begent, R. H. J. A Mouse Model for Calculating the Absorbed Beta-Particle Dose from (131)I- and (90)Y-Labeled Immunoconjugates, Including a Method for Dealing with Heterogeneity in Kidney and Tumor. Radiat. Res. 156, 28-35 (2001). Conventional internal radiation dosimetry methods assume that the beta-particle energy is absorbed uniformly and completely in the source organ and that the radioactivity is distributed uniformly in the source. However, in mice, a considerable proportion of the beta-particle energy can escape the source organ, resulting in large cross-organ doses. Furthermore, the distribution of radioactivity is generally heterogeneous in kidney and tumor. Therefore, a model was developed to account for cross-organ doses and for the effects of heterogeneity in kidney and tumor in mice for two of the most important radionuclides used in therapy, (131)I and (90)Y. Most mouse organs were modeled as single-compartment ellipsoids or cylinders, while heterogeneity in kidney and in tumor was addressed by using two compartments to represent the cortex and the medulla and viable and necrotic cells, respectively. The dimensions of these models were taken from previous studies, with the exception of kidney and tumor, which were defined using radioluminography and mosaics of high-power microscopy images. The absorbed fractions in each compartment were calculated using beta-particle point dose kernels. The self-organ dose was significantly higher for (131)I compared to (90)Y in all compartments, but a considerable amount of beta-particle energy was shown to escape the source organ for both radionuclides, with as much as 85% and 36% escaping the marrow for (90)Y and (131)I, respectively. The cortex was found to occupy a greater proportion of the total kidney volume than the medulla, and consequently the self-dose was higher in the cortex. In addition, the thickness of the viable shell in the tumor increased with tumor size, as did the self-dose fractions in both necrotic and viable areas. This dosimetry model improves dose estimates in mice and gives a conceptual basis for considering dosimetry in humans.

Skinflint dating

When a piece of flint is broken to form an artifact, and then buried in sediment at a site, its outer surface is exposed to a higher beta-particle dose rate than is experienced by the interior of the flint. A layer about 2 mm thick on each freshly broken surface receives an excess β-dose. The difference between the internal accumulated dose and that in the skin can be used to estimate the time elapsed since formation and burial of the artifact.

Induction and repair of DNA double-strand breaks under irradiation and microgravity.

The influence of microgravity on induction and repair of double-strand breaks was studied in the yeast mutant rad54-3, which is temperature-conditional for the repair of DNA double-strand breaks. The experiment was performed on the shuttle Atlantis flight STS-84. Cell samples were kept at 0-4 degrees C until they reached orbit, where they were transferred to 22 (permissive temperature for repair) and 37 degrees C (restrictive temperature). They were exposed to graded doses of beta particles from an in-built (63)Ni source during the repair period. After 152 h in microgravity, the radiation exposure was stopped, and the samples were returned to low-temperature conditions, where they remained until final evaluation in the home laboratory. The amount of double-strand breaks remaining was estimated from the differences in survival after plating and incubation at the restrictive temperature. The results show that there is no significant difference for both the induction and the repair of double-strand breaks between microgravity and terrestrial conditions.

Time- and Dose-Related Changes in the Thickness of Skin in the Pig after Irradiation with Single Doses of Thulium-170 Beta Particles

Time-related changes in skin thickness have been evaluated in the pig using a noninvasive ultrasound technique after exposure to a range of single doses of 0.97 MeV beta particles from (170)Tm plaques. The reduction in relative skin thickness developed in two phases; the separation into two phases was statistically justified only after 120 Gy (P = 0.04). The first phase was between 12 weeks and 24 weeks after irradiation. No further changes were seen until 48-60 weeks after irradiation, when a second phase of skin thinning was observed. No further changes in relative skin thickness were seen in the follow-up period of 104 weeks. The timing of these phases of relative skin thinning was totally independent of the radiation dose; however, the severity of each phase of radiation-induced skin thinning was related to the dose. The pattern of changes was similar to that reported previously after irradiation with 2.27 MeV beta particles from (90)Sr/(90)Y, but the degree of dermal thinning was less for a similar skin surface dose. From a comparison of the depth-dose distribution of the beta particles from the two radionuclides, it was concluded that the target cell population responsible for both the first and second phase of skin thinning in pig skin after irradiation may be located at approximately 800 microm depth. This corresponds to an area in the reticular dermis in pig skin and may be the appropriate site at which to measure the average dose to the dermal tissue.

Finger doses received during 153Sm injections.

This study was undertaken to determine the dose received by the skin of the fingers of clinical and laboratory staff during injections of 153Sm. The use of 153Sm, chelated with ethylenediaminetetramethylene phosphonic acid (153Sm-EDTMP), is coming into more frequent use in radionuclide therapy since its approval by the U.S. Food and Drug Administration in March 1997. 153Sm emits a range of medium-energy therapeutically useful beta particles that have been found beneficial in the palliation of metastatic bone cancer pain. It also emits a range of gamma rays. Calculations have been undertaken to provide the beta-particle and gamma-ray dose rates, at a depth within the skin corresponding roughly to the basal cell layer, when the finger is placed in direct contact with the external surface of a syringe containing 153Sm. The beta-particle dose rates were modeled using an empirically based Monte Carlo approach previously described by Beddoe and Kelly. The gamma-ray dose rates were modeled using a distributed point source approach previously reported by Pattison et al. In the calculations it is assumed that a typical administered activity is 2.6 GBq, with a finger-syringe contact time of 30 s. The skin dose, due to both beta particles and gamma rays when the finger is centrally placed over an active volume of 0.3 mL in a 1-mL syringe, is calculated to be 77 mGy per injection. Similarly, for an active volume of 1.0 mL in a 2.5-mL syringe, the dose is calculated to be 10 mGy per injection. In view of the ICRP recommended weekly skin dose limit of 10 mGy, both of the above two doses are excessive. If, however, the fingers are placed at the rear end of the syringe barrel, where they are only exposed to the gamma rays, the above two doses are reduced to 0.069 and 0.139 mGy per injection, respectively. Both of these two doses are well within the recommended weekly dose limits for the skin. It is found that the weekly dose limit for the skin is readily exceeded if the fingers are in direct contact with the external surface of the syringe and located over the active volume. However, if handled at the rear end of the syringe barrel, a typical weekly workload can be managed without exceeding the recommended dose limits.

Pulmonary Carcinogenicity of Relatively Low Doses of Beta-Particle Radiation from Inhaled 144 CeO 2 in Rats

This study was conducted to examine the carcinogenic effects of inhaled beta-particle-emitting radionuclides, particularly in lower dose regions in which there were substantial uncertainties associated with available information. A total of 2751 F344/N rats (1358 males and 1393 females) approximately 12 weeks of age at exposure were used. Of these, 1059 rats were exposed to aerosols of 144CeO2 to achieve mean desired initial lung burdens (ILBs) of 18 kBq (low level), 247 rats to achieve mean ILBs of 60 kBq (medium level) and 381 rats to achieve mean ILBs of 180 kBq (high level). Control rats (total of 1064) were exposed to aerosols of stable CeO2. Based on the 95% confidence intervals of the median survival times and the cumulative survival curves, there were no significant differences in the survival of groups of female and male exposed rats relative to controls. The mean lifetime beta-particle doses to the lungs of the rats in the four groups were: low level, 3.6 +/- 1.3 (+/-SD) Gy; medium level, 12 +/- 4.5 Gy; and high level, 37 +/- 5.9 Gy. The crude incidence of lung neoplasms increased linearly with increasing doses to the lungs (controls, 0.57%; low level, 2.0%; medium level, 6.1%; and high level, 19%). The estimated linear risk coefficients for lung neoplasms per unit of dose to the lung were not significantly different for the three dose levels studied. The risk coefficient at the lower level was 39 +/- 14 (+/-SE) excess lung neoplasms per 10(4) rat Gy; at the medium level the risk was 47 +/- 12; and at the higher level the risk was 50 +/- 9.0. The relationship of beta-particle dose to the lung and the crude incidence of lung neoplasms was described adequately by a linear function. We concluded that the risk of lung neoplasms in rats per unit of radiation dose did not increase with decreasing mean beta-particle dose to the lung over the range of 3.6 to 37 Gy. The weighted average of these three values was 47 +/- 6.4 (+/-SE) excess lung neoplasms per 10(4) rat Gy. To extend the risk coefficients for lung neoplasms to lower doses by experimentation will require much larger numbers of rats than used in this study.