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Health Physics - Current Issue

Health Physics - Current Issue
  1. ICRP 67 Biokinetic Models for AM-241 Applied to Nonhuman Primates
    imageAbstract: Between 1960 and 1985, Patricia Durbin and colleagues performed studies on the distribution of intravenously and intramuscularly injected 241Am citrate with dosages ranging from 16 to 32 kBq kg−1 in 30 male and female non-human primates (NHP). Dr. Durbin died unexpectedly in March of 2009, leaving much of the extensive serial blood, bioassay, and autopsy data from these NHP studies unanalyzed. As part of the experimental design, serial blood samples were taken, and urine and feces samples were collected separately for the duration of the study. The measurements of urine, fecal excretion, blood samples, and organ burden data obtained from the animals were used to evaluate the transfer rates of the ICRP 67 biokinetic model for 241Am. Seven cases, in which the primates were administered 241Am citrate by intravenous injection, were evaluated using the ICRP 67 systemic model. There were differences ranging from 51.4% underestimated to 102.7% overestimated activity between the predicted intake, which was calculated using IMBA Professional Plus software and based upon the urine bioassay data and the actual activity. The difference between the predicted activity at the time of death in the liver and skeleton using IMBA professional software and the value of the measured activity at the time of death were also compared. Generally, the ratios of predicted activity in the liver and skeleton at the time of death to the measured activity were consistently more than 1. However, the ratios were less than 1 in the skeleton for animals that were sacrificed 2,199 and 973 d post injection. The posterior probability distributions for model parameters derived using WeLMoS method were inconsistent with the ICRP 67 default parameters. The prediction made based on the posterior probability distributions for model parameters derived using WeLMoS gave the best fit to these data; however, the modified parameters overestimated the activity in almost all cases. The difference between the predicted Am activity and the value of the measured activity may be due to the physiological age-related characteristics relative to the age of the animal at the time of the injection and early and long scarified time.

  2. Monte Carlo Simulations Comparing the Response of a Novel Hemispherical Tepc to Existing Spherical and Cylindrical Tepcs for Neutron Monitoring and Dosimetry
    imageAbstract: Neutron dosimetry in reactor fields is currently mainly conducted with unwieldy flux monitors. Tissue Equivalent Proportional Counters (TEPCs) have been shown to have the potential to improve the accuracy of neutron dosimetry in these fields, and Multi-Element Tissue Equivalent Proportional Counters (METEPCs) could reduce the size of instrumentation required to do so. Complexity of current METEPC designs has inhibited their use beyond research. This work proposes a novel hemispherical counter with a wireless anode ball in place of the traditional anode wire as a possible solution for simplifying manufacturing. The hemispherical METEPC element was analyzed as a single TEPC to first demonstrate the potential of this new design by evaluating its performance relative to the reference spherical TEPC design and a single element from a cylindrical METEPC. Energy deposition simulations were conducted using the Monte Carlo code PHITS for both monoenergetic 2.5 MeV neutrons and the neutron energy spectrum of 252Cf-D2O moderated. In these neutron fields, the hemispherical counter appears to be a good alternative to the reference spherical geometry, performing slightly better than the cylindrical counter, which tends to underrespond to H*(10) for the lower neutron energies of the 252Cf-D2O moderated field. These computational results are promising, and if follow-up experimental work demonstrates the hemispherical counter works as anticipated, it will be ready to be incorporated into an METEPC design.

  3. A Posting Peculiarity
    imageAbstract: The definitions of “radiation area,” “high radiation area,” and “very high radiation area,” provided by the U.S. Department of Energy in 10 CFR Part 835.2, and by the Nuclear Regulatory Commission in 10 CFR Part 20.1003, appear to require redundant posting. This is counterintuitive and would be confusing if the regulations were followed as currently written. We suspect that this is unintentional. However, until the relevant regulations are revised, it is recommended that licensees request written clarification from the regulators to ensure that they are able to demonstrate regulatory compliance.

  4. Tritium ( 3 H) Retention In Mice: Administered As HTO, DTO or as 3 H-Labeled Amino-Acids
    imageAbstract: The objective of this study was to compare the biokinetics of injected 3H-labeled light (HTO) and heavy (DTO) water in CBA/CaJ mice and to compare the organ distribution and/or body content of 3H administered by chronic ingestion for 1 mo to C57Bl/6J mice, as either 3H-labeled water or 3H-labeled amino acids (glycine, alanine and proline). HTO and DTO were administered to CBA/CaJ mice by single intraperitoneal injection and body retention was determined for up to 384 h post-injection. Tritium-labeled water or 3H-labeled amino acids were given to C57Bl/6J mice ad libitum for 30 d in drinking water. Body content and organ distribution of 3H during the period of administration and subsequent to administration was determined by liquid scintillation counting. No differences were found between the biokinetics of HTO and DTO, indicating that data generated using HTO can be used to help assess the consequences of 3H releases from heavy water reactors. The results for 3H-water showed that the concentration of radionuclide in the mice reached a peak after about 10 d and dropped rapidly after the cessation of 3H administration. The maximum concentration reached was only 50% of that in the water consumed, indicating that mice receive a significant fraction of their water from respiration. Contrary to the findings of others, the pattern of 3H retention following the administration of a cocktail of the labeled amino acids was very little different from that found for the water. This is consistent with the suggestion that most of the ingested amino acids were rapidly metabolized, releasing water and carbon dioxide.

  5. Change
    No abstract available

  6. Gamma-Ray Dose From an Overhead Plume
    imageAbstract: Standard plume models can underestimate the gamma-ray dose when most of the radioactive material is above the heads of the receptors. Typically, a model is used to calculate the air concentration at the height of the receptor, and the dose is calculated by multiplying the air concentration by a concentration-to-dose conversion factor. Models indicate that if the plume is emitted from a stack during stable atmospheric conditions, the lower edges of the plume may not reach the ground, in which case both the ground-level concentration and the dose are usually reported as zero. However, in such cases, the dose from overhead gamma-emitting radionuclides may be substantial. Such underestimates could impact decision making in emergency situations. The Monte Carlo N-Particle code, MCNP, was used to calculate the overhead shine dose and to compare with standard plume models. At long distances and during unstable atmospheric conditions, the MCNP results agree with the standard models. At short distances, where many models calculate zero, the true dose (as modeled by MCNP) can be estimated with simple equations.

  7. THE HEALTH PHYSICS SOCIETY: An Affiliate of the International Radiation Protection Association (IRPA)
    No abstract available

  8. Rapid Analysis of 239,238Pu, 241Am, and 90Sr for Nasal Smear Samples in Radiation Emergency and Evaluation of Intake Retention Fraction
    imageAbstract: The efficiency of the nasal smear method was reviewed to perform a method of sample collection, analysis and initial dose estimation. The screening method of alpha-emitting radionuclides using chemical separation and alpha spectrometry was also studied. To rapidly conduct the appropriate response to victims, special monitoring for 239,238Pu, 241Am, and 90Sr using sequential analysis was established, and the method was successfully validated through participation in an international inter-comparison program. The duration of the analysis method was evaluated with regard to application in emergency situations because of its relatively rapid treatment and counting time. The intake retention fraction was calculated and evaluated to review the characteristics of each radionuclide in the anterior nasal passage of the extra-thoracic region. No large difference was observed among the four radionuclides. However, the values of the intake retention fraction were affected by age groups because of the different respiratory rates. The effects of the 90Y ingrowth and particle size were also discussed.

  9. RF Safety Analysis of a Novel Ultra-wideband Fetal Monitoring System
    imageAbstract: The LifeWave Ultra-Wideband RF sensor (LWUWBS) is a monitoring solution for a variety of physiologic assessment applications, including maternal fetal monitoring in both the antepartum and intrapartum periods. The system uses extremely low power radio frequency (RF) ultra-wide band (UWB) signals to provide continuous fetal heart rate and contractions monitoring during labor and delivery. Even with the incorporation of three very conservative assumptions, (1) concentration of the RF energy in 1 cm3, (2) minimal (2.5 cm) maternal tissue attenuation of fetal exposure, and (3) absence of normal thermoregulatory compensation, the maternal whole body spatial-averaged specific absorption rate (WBSAR) would be 34,000 times below the FCC public exposure limit of 0.08 W kg−1 and, at 8 wk or more gestation, the peak spatial-averaged specific absorption rate (PSSAR) in the fetus would be more than 160 times below the localized exposure limit of 1.6 mW g−1. Even when using very conservative assumptions, an analysis of the LWUWBS’s impact on tissue heating is a factor of 7 lower than what is allowed for fetal ultrasound and at least a factor of 650 compared to fetal MRI. The actual transmitted power levels of the LWUWBS are well below all Federal safety standards, and the potential for tissue heating is substantially lower than associated with current ultrasonic fetal monitors and MRI.

  10. Effects of Medical Diagnostic Low-dose X Rays on Human Lymphocytes: Mitochondrial Membrane Potential, Apoptosis and Cell Cycle
    imageAbstract: Low-dose radiation is widely used across the world for the diagnosis of many diseases by means of a variety of imaging technologies. However, the harmful effects of exposure to low-dose radiation during medical examination remain controversial. The authors studied the effects of medical diagnostic low-dose x rays (i.e., 0.03, 0.05, or 0.1 mGy) after an in vitro exposure of human lymphocytes. Cells with no irradiation served as the non-irradiated control group. Three biological indicators were used to determine the effects of medical diagnostic low-dose x rays at 4, 8, 24, 48, and 72 h post-irradiation. These biological endpoints were mitochondrial membrane potential (ΔΨm), cell cycle, and apoptosis. Results indicated no changes in the ΔΨm, number of apoptotic cells, and cell cycle in lymphocytes exposed to these low doses of radiation, as compared to the corresponding non-irradiated lymphocytes at all harvest time-points. These results suggested that there were no harmful effects of the diagnostic low-dose x rays when human lymphocytes were exposed in an in vitro condition.

  11. RSO Interview with Miguel de la Guardia
    imageNo abstract available

  12. Interpretation of Nasal Swab Measurements Following Suspected Releases of Actinide Aerosols
    imageAbstract: For radionuclides such as plutonium and americium, detection of removable activity in the nose (i.e., nasal swab measurements) are frequently used to determine whether follow-up bioassay measurements are warranted following a potential intake. For this paper, the authors analyzed 429 nasal swab measurements taken following incidents or suspicious circumstances (such as an air monitor alarming) at Los Alamos National Laboratory (LANL) for which the dose was later evaluated using in vitro bioassay. Nasal swab measurements were found to be very poor predictors of dose and should not be used as such in the field. However, nasal swab measurements can be indicative of whether a reliably detectable committed effective dose (CED) occurred. About 14% of nasal swab measurements between 1.25 and 16.7 Bq corresponded to CEDs greater than 1 mSv, so in general, positive nasal swabs always indicate that follow-up bioassay should be performed (positive nasal swabs less than 1.25 Bq are considered separately). This probability increased significantly for nasal swabs greater than 16.7 Bq. Only about 3% of nasal swabs with no detectable activity (NDA) corresponded to reliably detectable CEDs. A nasal swab with NDA is therefore necessary, but not sufficient, to negate the need for a follow-up bioassay if it was collected following other workplace indicators of a potential intake.

  13. A Useful Gadget to Reduce the Radiation Dose of Interventionist's Hands
    imageAbstract: Increased demand for interventional radiology techniques has interventionists performing a large number of these procedures. Measurements and calculations have shown that the radiation doses received by these specialists can exceed the threshold of radiation-induced deterministic effects unless radiation protection procedures and devices are used. Proper usage of radiation protection devices can protect them from radiation-induced effects, even with a high workload. Occupational radiation protection entails proper training of interventionists to increase their awareness about available appropriate protection tools and equipment, and devices that can be used to minimize exposure, such as needle holders, tubing extensions, and injectors. This study introduces a device that can be used to fix the catheter to prevent the physician from holding the catheter by hand. The authors, also, discuss the importance of radiation protection training along with the training on new medical equipment, which can be applied to reduce the radiation dose.

  14. Dose Conversion Coefficients Based on Taiwanese Reference Phantoms and Monte Carlo Simulations for Use in External Radiation Protection
    imageAbstract: Reference phantoms are widely applied to evaluate the radiation dose for external exposure. However, the frequently used reference phantoms are based on Caucasians. Dose estimation for Asians using a Caucasian phantom can result in significant errors. This study recruited 40 volunteers whose body sizes are close to the average Taiwanese population. Magnetic resonance imaging was performed to obtain the organ volume for construction of the Taiwanese reference man (TRM) and Taiwanese reference woman (TRW). The dose conversion coefficients (DCC) resulting from photo beams in anterior-posterior, posterior-anterior, right-lateral, left-lateral, and isotropic irradiation geometries were estimated. In the anterior-posterior geometry, the mean DCC differences among organs between the TRM and ORNL phantom at 0.1, 1, and 10 MeV were 7.3%, 5.8%, and 5.2%, respectively. For the TRW, the mean differences from the ORNL phantom at the three energies were 10.6%, 7.4%, and 8.3%. The DCCs of the Taiwanese reference phantoms and the ORNL phantom presented similar trends in other geometries. The torso size of the phantom and the mass and geometric location of the organ have a significant influence on the DCC. The Taiwanese reference phantoms can be used to establish dose guidelines and regulations for radiation protection from external exposure.

    No abstract available

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