A Perspective from Ontario Tech University Industrial Research Chairs on 20 Years of Capacity Building in Health Physics and Radiation Science.

ABSTRACT: Ontario Tech University (University of Ontario Institute of Technology) is one of Canada's newest universities, having been incorporated in 2002. In 20 y, the University has increased enrollment from a few hundred students to over 10,000. The University was designed to be "market driven" and as such offered courses that had high market demand. The Faculty of Energy Systems and Nuclear Science was one of the first faculties to be established at the University, with the intent to fill a gap between personnel that were retiring out of the nuclear industry and the dearth of nuclear engineers and health physicists being educated in Canada. As such, the University established unique programs in both nuclear engineering and health physics/radiation science with strong input from industry stakeholders. This paper will discuss the evolution of the Health Physics and Radiation Science program at Ontario Tech from the teaching and capacity building perspective, and it provides insight regarding health physics and radiation science research at Ontario Tech under the industrial research chair program.

Electron paramagnetic resonance spectroscopy for the detection of radiation exposure in dreissenid mussels.

Electron paramagnetic resonance (EPR) spectroscopy, established for radiation measurements in calcified tissues, was identified as a methodology that merits investigation for the purpose of environmental radiation measurements using dreissenid mussels from the Great Lakes. With the refinement of sample preparation and measurement protocols, a linear relationship of dose with the peak-to-peak height of the radiation-induced signal at g = 2.0034 was established. A dedicated analysis algorithm was developed to process batches of samples, eliminating the need for manual peak-to-peak height measurement. Varying background EPR signals were identified in different sampling groups, with samples gathered in winter having a markedly lower background signal. Through optimisation of spectrum acquisition normalisation methods, it was possible to resolve doses as low as 0.2 Gy. This work provides further validation that EPR dosimetry of shelled species has the potential to contribute to better characterisation of absorbed doses in aquatic environments.

Local Dose Coefficients for Radionuclide Contamination in Wounds.

ABSTRACT: When a radiation accident has occurred that leads to radioactive material being imparted to a wound, this is treated as an internal contamination scenario. It is common for the material to transport throughout the body based upon biokinetics of the material in the body. While standard internal dosimetry approaches can be used to estimate committed effective dose from the insult, some material may get fixed for longer periods of time at the wound location, even after medical procedures such as decontamination and debridement have been applied. In this case, the radioactive material becomes a local dose contributor. This research was to generate local dose coefficients for radionuclide-contaminated wounds to supplement committed effective dose coefficients. These dose coefficients can be used to calculate activity limits at the wound site that could lead to a clinically significant dose. This is useful for emergency response to assist in decisions on medical treatment, including decorporation therapy. Wound models were created for injections, lacerations, abrasions, and burns, and the MCNP radiation transport code was used to simulate the dose to tissue considering 38 radionuclides. Biokinetic models accounted for biological removal of the radionuclides from the wound site. It was found that radionuclides that are not retained well at the wound site are likely of little concern locally, but for highly retained radionuclides, estimated local doses may require further investigation by medical and health physics personnel.

A Practical Method for EPR Dosimetry Using Alanine Powder.

ABSTRACT: This work investigates alanine powder, an inexpensive and versatile material compared to alanine pellets, as a standardized dosimeter for the alanine-EPR system using a Bruker EMX-Micro spectrometer. The feasibility of this method was investigated, and a calibration curve was produced using 40 dosimeters, which were prepared by tightly packing DL-alanine powder in polypropylene microcentrifuge tubes. The dosimeters were irradiated to doses ranging from 0.2-20 Gy using a 60 Co source. A dosimeter handling and measurement protocol was established for all dosimeters. The dosimetric signal was evaluated by measuring the peak-to-peak height of the central resonance peak, and the dose response of alanine powder dosimeters showed a linear behavior in the investigated dose range with relative errors below 13%. Measurement repeatability and reproducibility were tested to show the errors associated with sample placement in the cavity and with the overall measurement method, with both tests showing relative errors below 7%. As an inexpensive material compared to pellet dosimeters, alanine powder has a strong potential to be used as a standardized material for radiation dosimetry applications. The scope of this work is to present an effective and comprehensive methodology with accompanying analysis scripts for dosimetry with alanine powder that is useful in a wide range of applications and dose requirements.

Encapsulated Gamma Source Contact Dose Conversion Factors: Updating NCRP-40 Guidance.

ABSTRACT: Secondary electron generation on the surface of encapsulated gamma sources can play a large role in the dose measured near the surface of the encapsulation. The National Council on Radiation Protection and Measurements Report No. 40 contains contact dose rate conversion factors for encapsulated gamma sources, along with recommended secondary electron correction factors. However, secondary electron correction factors were based on experiments performed in the 1930s and 1940s with encapsulated radium sources, and the correction factors for the other sources listed in the report were estimated based on these radium source measurements. Monte Carlo simulations were performed using the Particle and Heavy Ion Transport code System (PHITS) to calculate the contact dose rate conversion factors for each encapsulated gamma source presented in NCRP-40, taking into account the dose from both gamma rays and secondary electrons. These simulations showed that the contact dose rate conversion factors are much lower than those presented in NCRP-40, and the secondary electron contribution was much greater than the values proposed by NCRP-40. The original research used results from encapsulated 226Ra experiments to determine the secondary electron correction factors for NCRP-40. To support the current Monte Carlo calculations, experiments were conducted using an encapsulated 137Cs source, rare earth magnet, and ion chamber detector to show that the secondary electron correction factors presented in NCRP-40 were not applicable to the geometry of tissue in direct contact with the encapsulation. In this work, contact dose conversion factors for common encapsulated radionuclide sources are presented.

Meeting radiation dosimetry capacity requirements of population-scale exposures by geostatistical sampling.

BACKGROUND: Accurate radiation dose estimates are critical for determining eligibility for therapies by timely triaging of exposed individuals after large-scale radiation events. However, the universal assessment of a large population subjected to a nuclear spill incident or detonation is not feasible. Even with high-throughput dosimetry analysis, test volumes far exceed the capacities of first responders to measure radiation exposures directly, or to acquire and process samples for follow-on biodosimetry testing. AIM: To significantly reduce data acquisition and processing requirements for triaging of treatment-eligible exposures in population-scale radiation incidents. METHODS: Physical radiation plumes modelled nuclear detonation scenarios of simulated exposures at 22 US locations. Models assumed only location of the epicenter and historical, prevailing wind directions/speeds. The spatial boundaries of graduated radiation exposures were determined by targeted, multistep geostatistical analysis of small population samples. Initially, locations proximate to these sites were randomly sampled (generally 0.1% of population). Empirical Bayesian kriging established radiation dose contour levels circumscribing these sites. Densification of each plume identified critical locations for additional sampling. After repeated kriging and densification, overlapping grids between each pair of contours of successive plumes were compared based on their diagonal Bray-Curtis distances and root-mean-square deviations, which provided criteria (<10% difference) to discontinue sampling. RESULTS/CONCLUSIONS: We modeled 30 scenarios, including 22 urban/high-density and 2 rural/low-density scenarios under various weather conditions. Multiple (3-10) rounds of sampling and kriging were required for the dosimetry maps to converge, requiring between 58 and 347 samples for different scenarios. On average, 70±10% of locations where populations are expected to receive an exposure ≥2Gy were identified. Under sub-optimal sampling conditions, the number of iterations and samples were increased, and accuracy was reduced. Geostatistical mapping limits the number of required dose assessments, the time required, and radiation exposure to first responders. Geostatistical analysis will expedite triaging of acute radiation exposure in population-scale nuclear events.

Preliminary Determination of Activation Products for a Varian Truebeam Linear Accelerator.

Medical linear accelerators used to treat various forms of cancers are operated at a number of different energies. A by-product of the high-energy photons produced by accelerators is activation of components within the machine itself and its surrounding bunker. The activation products pose radiological and regulatory challenges during the operation of the accelerator as well as when it is time for final decommissioning. The Varian TrueBeam is a new state-of-the-art linear accelerator now operating in the Canadian market. There is currently limited information on the production of its activation products and the resulting impacts on operation and decommissioning. In this paper, activation products in the Varian TrueBeam accelerator are experimentally determined by performing gamma spectroscopy using a portable high purity germanium detector. A total of 10 isotopes are identified for the conditions tested, which include Na, Al, Mn, Ni, Cu, Cu, Br, Sb, Sb, W. The half-lives of these isotopes range from 2.3 min to 60.2 d. These preliminary results indicate that a decommissioning case similar to other radiotherapy accelerators can be made.

A simulator-based nuclear reactor emergency response training exercise.

Training offsite emergency response personnel basic awareness of onsite control room operations during nuclear power plant emergency conditions was the primary objective of a week-long workshop conducted on a CANDU® virtual nuclear reactor simulator available at the University of Ontario Institute of Technology, Oshawa, Canada. The workshop was designed to examine both normal and abnormal reactor operating conditions, and to observe the conditions in the control room that may have impact on the subsequent offsite emergency response. The workshop was attended by participants from a number of countries encompassing diverse job functions related to nuclear emergency response. Objectives of the workshop were to provide opportunities for participants to act in the roles of control room personnel under different reactor operating scenarios, providing a unique experience for participants to interact with the simulator in real-time, and providing increased awareness of control room operations during accident conditions. The ability to "pause" the simulator during exercises allowed the instructors to evaluate and critique the performance of participants, and to provide context with respect to potential offsite emergency actions. Feedback from the participants highlighted (i) advantages of observing and participating "hands-on" with operational exercises, (ii) their general unfamiliarity with control room operational procedures and arrangements prior to the workshop, (iii) awareness of the vast quantity of detailed control room procedures for both normal and transient conditions, and (iv) appreciation of the increased workload for the operators in the control room during a transient from normal operations. Based upon participant feedback, it was determined that the objectives of the training had been met, and that future workshops should be conducted.

Operational Testing of a Combined Hardware-Software Strategy for Triage of Radiologically-Contaminated Persons.

After a radiological dispersal device (RDD) event, it is possible for radionuclides to enter the human body through inhalation, ingestion, and skin and wound absorption. The dominant pathway will be through inhalation. From a health physics perspective, it is important to know the magnitude of the intake to perform dosimetric assessments. From a medical perspective, removal of radionuclides leading to dose (hence risk) aversion is of high importance. The efficacy of medical decorporation strategies is extremely dependent upon the time of treatment delivery after intake. The "golden hour," or more realistically 3-4 h, is imperative when attempting to increase removal of radionuclides from extracellular fluids prior to cellular incorporation. To assist medical first response personnel in making timely decisions regarding appropriate treatment delivery modes, a software tool has been developed which compiles existing radionuclide decorporation therapy data and allows a user to perform simple triage leading to potential appropriate decorporation treatment strategies. Three triage algorithms were included: (1) multi-parameter model (MPM), (2) clinical decision guidance (CDG) model, and (3) annual limit on intake (ALI) model. A radiation triage mask (RTM) has simultaneously been developed to provide a simple and rapid hardware solution for first responders to triage internally exposed personnel in the field. The hardware/software strategy was field tested with a military medical unit and was found by end-users to be relatively simple to learn and use.

The role of the health physicist in nuclear security.

Health physics is a recognized safety function in the holistic context of the protection of workers, members of the public, and the environment against the hazardous effects of ionizing radiation, often generically designated as radiation protection. The role of the health physicist as protector dates back to the Manhattan Project. Nuclear security is the prevention and detection of, and response to, criminal or intentional unauthorized acts involving or directed at nuclear material, other radioactive material, associated facilities, or associated activities. Its importance has become more visible and pronounced in the post 9/11 environment, and it has a shared purpose with health physics in the context of protection of workers, members of the public, and the environment. However, the duties and responsibilities of the health physicist in the nuclear security domain are neither clearly defined nor recognized, while a fundamental understanding of nuclear phenomena in general, nuclear or other radioactive material specifically, and the potential hazards related to them is required for threat assessment, protection, and risk management. Furthermore, given the unique skills and attributes of professional health physicists, it is argued that the role of the health physicist should encompass all aspects of nuclear security, ranging from input in the development to implementation and execution of an efficient and effective nuclear security regime. As such, health physicists should transcend their current typical role as consultants in nuclear security issues and become fully integrated and recognized experts in the nuclear security domain and decision making process. Issues regarding the security clearances of health physics personnel and the possibility of insider threats must be addressed in the same manner as for other trusted individuals; however, the net gain from recognizing and integrating health physics expertise in all levels of a nuclear security regime far outweighs any negative aspects. In fact, it can be argued that health physics is essential in achieving an integrated approach toward nuclear safety, security, and safeguards.

Canadian Cardiovascular Society position statement on radiation exposure from cardiac imaging and interventional procedures.

Exposure to ionizing radiation is a consequence of many diagnostic and interventional cardiac procedures. Radiation exposure can result in detrimental health effects because of deterministic (eg, skin reaction) and stochastic effects (eg, cancer). However, with the levels experienced during cardiac procedures these risks can be difficult to quantify. Healthcare providers and patients might not fully appreciate radiation-related risks. Though in many cases radiation exposure cannot be avoided, a practice of minimizing exposures to levels "as low as reasonably achievable" (ALARA principle) without compromising the utility of the procedure is encouraged. The purpose of this document is to inform health care providers on the key concepts related to radiation risk from common cardiac procedures and provide specific recommendations on ensuring quality of care.

Combined hardware--software considerations for triage of internally contaminated personnel.

Medical response to a radiological emergency involves first assessing, triaging and treating trauma, followed by determining potential hazard from radiological intake. A combined hardware-software strategy is required for this mission. The hardware strategy should consist of a dedicated detector suite capable of alpha, beta and gamma radiation detection, identification and quantification suitable for order of magnitude dose assessment. The hardware platform should provide a simple user interface suitable for field deployment. The software should provide first-on-the-scene responders with the ability to perform radiological triage in a mass casualty type event, physicians with the ability to assign treatment regimes, and long-term care medical personnel with information to provide continual risk reassessment of the patient taking into account toxicology of the decorporation therapy and dose aversion. The software should be rich in data, yet accessible through a simple user interface. Practicing in a radiological emergency exercise environment with the equipment is crucial to its efficacy in a real emergency.

First response considerations for children exposed to a radiological dispersal device.

Children are considered a vulnerable population during an accidental or deliberate release of radioactive material to the environment due to the fact that they have more active cell division compared with the adult population and therefore detrimental effects promulgate very quickly. Additionally, physical and social characteristics of children make them more prone to internalise a toxin (for example, children are closer to the ground where heavy aerosols can collect; children also have more relaxed sanitary habits compared with the adult population, which aids in hand-to-mouth transfer of contaminants). To confound matters, many emergency protocols are based upon a reference as opposed to a child. Although numerous radiological response exercises have been conducted in the years post 9/11, very few have utilised children actively in the scenarios. This paper considers observations made during a NATO exercise with scenarios covering radiological releases and which utilised a variety of children as exercise participants.

Radiation protection issues related to Canadian museum operations.

Museums in Canada have been found to possess radioactive items. The origin of the radiation can be broadly categorized as either natural (generally, radioactive ores) or anthropogenic (generally, luminous gauges). Radioluminescent gauges, especially bearing radium (226Ra), can also generate significant radiation fields. This is especially true if many gauges are located in close proximity. In addition, the radon may out-gas from these gauges, and generate a loose contamination problem in enclosed spaces (such as display cases). Radioactive ores, bearing naturally occurring uranium and thorium, can generate radiation fields many times greater than the ambient background levels. In addition, they will increase the ambient radon level and potentially generate loose contamination. In this paper, we discuss the specific results of radiological decommissioning at three museums: the National Air Force Museum of Canada (Trenton, Ontario); the Quebec Air and Space Museum (Montreal, PQ); and the Canadian Museum of Nature (Aylmer, PQ). In addition, a radiological survey performed at Canadian Forces Detachment Mountain View (Mountain View, Ontario) of surplus aircraft is included. The primary conclusion is that museums holding radioactive materials may have detectable levels of loose Ra and progeny contamination. They, therefore, have a requirement to be surveyed for loose contamination periodically with the potential for periodic decontamination caused by radon out-gassing. In addition, public access to displays bearing radioactive material should generally be restricted, and comprehensive radiation safety and security programs at museum facilities should be developed and enacted.

The inhibitory receptor LILRB1 modulates the differentiation and regulatory potential of human dendritic cells.

Dendritic cells (DCs) link innate and adaptive immunity, initiating and regulating effector cell responses. They ubiquitously express members of the LILR (ILT, LIR, CD85) family of molecules, some of which recognize self-HLA molecules, but little is known of their possible functions in DC biology. We demonstrate that the inhibitory receptor LILRB1 (ILT2, LIR1, CD85j) is selectively up-regulated during DC differentiation from monocyte precursors in culture. Continuous ligation of LILRB1 modulated cellular differentiation, conferred a unique phenotype upon the resultant cells, induced a profound resistance to CD95-mediated cell death, and inhibited secretion of cytokines IL-10, IL-12p70, and TGF-beta. These features remained stable even after exposure of the cells to bacterial LPS. Ligated DCs exhibited poor stimulatory activity for primary and memory T-cell proliferative responses, but this was substantially reversed by blockade of CD80 or its preferred ligand CTLA-4, or by depleting CD4(+) CD25(+) CD127(lo) regulatory T cells. Our findings suggest that ligation of LILRB1 on DCs by self-HLA molecules may play a key role in controlling the balance between the induction and suppression of adaptive immune responses.

Release limits and decontamination efficacy for tritium: lessons learned outside nuclear power operations.

Various pieces of equipment in use by the Canadian Department of National Defence (DND) contain radiation-emitting components. One such piece is a sight knob used on light artillery. At the request of the DND's Director General Nuclear Safety (DGNS-DND's internal nuclear regulatory agency), the authors were contacted to remove the luminous tritium-impregnated paint strip from over 300 sight knobs. This paper discusses the physical description of the sight knobs, the protocol developed for decontaminating the sight knobs, the rationale for the release limits used, and experience gained in using and modifying the decontamination protocol.

Differential costimulation through CD137 (4-1BB) restores proliferation of human virus-specific "effector memory" (CD28(-) CD45RA(HI)) CD8(+) T cells.

In healthy carriers of human cytomegalovirus (HCMV), the virus-specific memory CD8(+) T-cell population is often dominated by CD28(-) CD45RA(hi) cells that exhibit direct ex vivo cytotoxicity but whose capacity for proliferation and generation of further memory cells has been questioned. We show that when highly purified CD28(-) CD45RA(hi) CD8(+) T cells are stimulated with viral peptide presented by autologous monocytes, the virus-specific T cells show early up-regulation of CD137 (4-1BB) and CD278 (ICOS), re-express CD28, and proliferate with similarly high cloning efficiency in limiting dilution analysis as CD28(+) CD45RO(hi) cells or CD28(-) CD45RO(hi) cells. Using peptide-pulsed autologous fibroblasts transfected with individual costimulatory ligands as antigen presenting cells, we showed CD137L to be a key costimulatory ligand for proliferation of CD28(-) CD45RA(hi) CD8(+) T cells and not CD80, CD86, or CD275 (ICOSL). Therefore, CD28(-) CD45RA(hi) CD8(+) T cells were not terminally differentiated but required a specific costimulatory signal for proliferation.

Rapid CD8+ T cell repertoire focusing and selection of high-affinity clones into memory following primary infection with a persistent human virus: human cytomegalovirus.

To investigate the mechanism of selection of individual human CD8+ T cell clones into long-term memory following primary infection with a persistent human virus (human CMV (HCMV)), we undertook a longitudinal analysis of the diversity of T cell clones directed toward an immunodominant viral epitope: we followed this longitudinally from early T cell expansion through the contraction phase and selection into the memory pool. We show that following initial HCMV infection, the early primary response against a defined epitope was composed of diverse clones possessing many different TCR Vbeta segments. Longitudinal analysis showed that this usage rapidly focused predominantly on a single TCR Vbeta segment within which dominant clones frequently had public TCR usage, in contrast to subdominant or contracted clones. Longitudinal clonotypic analysis showed evidence of disproportionate contraction of certain clones that were abundant in the primary response, and late expansion of clones that were subdominant in the primary response. All dominant clones selected into memory showed similar high functional avidity of their TCR, whereas two clones that greatly contracted showed substantially lower avidity. Expression of the IL-7R is required for survival of murine effector CD8+ T cells into memory, but in primary HCMV infection IL-7R was not detected on circulating Ag-specific cells until memory had been established. Thus, the oligoclonal T cell repertoire against an immunodominant persistent viral epitope is established early in primary infection by the rapid selection of public clonotypes, rather than being a stochastic process.

Neutron production associated with radiotherapy linear accelerators using intensity modulated radiation therapy mode.

A number of experiments were conducted on a Clinac 21EX radiotherapy accelerator using an IMRT treatment plan to determine neutron dose equivalent as a function of both patient dose delivered and machine workload. It was determined that IMRT mode is more neutron dose intensive as a function of patient dose when compared to a similar standard non-IMRT treatment. It was found that when the neutron production is normalized to workload, the measured neutron dose equivalents are similar. It is therefore recommended that neutron production be reported as a function of workload when considering IMRT treatment modes.