Feasibility study of computational occupational dosimetry: evaluating a proof-of-concept in an endovascular and interventional cardiology setting.

Individual monitoring of radiation workers is essential to ensure compliance with legal dose limits and to ensure that doses are As Low As Reasonably Achievable. However, large uncertainties still exist in personal dosimetry and there are issues with compliance and incorrect wearing of dosimeters. The objective of the PODIUM (Personal Online Dosimetry Using Computational Methods) project was to improve personal dosimetry by an innovative approach: the development of an online dosimetry application based on computer simulations without the use of physical dosimeters. Occupational doses were calculated based on the use of camera tracking devices, flexible individualised phantoms and data from the radiation source. When combined with fast Monte Carlo simulation codes, the aim was to perform personal dosimetry in real-time. A key component of the PODIUM project was to assess and validate the methodology in interventional radiology workplaces where improvements in dosimetry are needed. This paper describes the feasibility of implementing the PODIUM approach in a clinical setting. Validation was carried out using dosimeters worn by Vascular Surgeons and Interventional Cardiologists during patient procedures at a hospital in Ireland. Our preliminary results from this feasibility study show acceptable differences of the order of 40% between calculated and measured staff doses, in terms of the personal dose equivalent quantity Hp(10), however there is a greater deviation for more complex cases and improvements are needed. The challenges of using the system in busy interventional rooms have informed the future needs and applicability of PODIUM. The availability of an online personal dosimetry application has the potential to overcome problems that arise from the use of current dosimeters. In addition, it should increase awareness of radiation protection among staff. Some limitations remain and a second phase of development would be required to bring the PODIUM method into operation in a hospital setting. However, an early prototype system has been tested in a clinical setting and the results from this two-year proof-of-concept PODIUM project are very promising for future development.

Structural and biochemical characterization of SpoIIIAF, a component of a sporulation-essential channel in Bacillus subtilis.

Environmental stress factors initiate the developmental process of sporulation in some Gram-positive bacteria including Bacillus subtilis. Upon sporulation initiation the bacterial cell undergoes a series of morphological transformations that result in the creation of a single dormant spore. Early in sporulation, an asymmetric cell division produces a larger mother cell and smaller forespore. Next, the mother cell septal membrane engulfs the forespore, and an essential channel, the so-called feeding-tube apparatus, is formed. This assembled channel is thought to form a transenvelope secretion complex that crosses both mother cell and forespore membranes. At least nine proteins are essential for channel formation including SpoIIQ under forespore control and the eight SpoIIIA proteins (SpoIIIAA-AH) under mother cell control. Several of these proteins share similarity with components of Gram-negative bacterial secretion systems and the flagellum. Here we report the X-ray crystallographic structure of the soluble domain of SpoIIIAF to 2.7 Šresolution. Like the channel components SpoIIIAG and SpoIIIAH, SpoIIIAF adopts a conserved ring-building motif (RBM) fold found in proteins from numerous dual membrane secretion systems of distinct function. The SpoIIIAF RBM fold contains two unique features: an extended N-terminal helix, associated with multimerization, and an insertion at a loop region that can adopt two distinct conformations. The ability of the same primary sequence to adopt different secondary structure conformations is associated with protein regulation, suggesting a dual structural and regulatory role for the SpoIIIAF RBM. We further analyzed potential interaction interfaces by structure-guided mutagenesis in vivo. Collectively, our data provide new insight into the possible roles of SpoIIIAF within the secretion-like apparatus during sporulation.

Structural characterization of SpoIIIAB sporulation-essential protein in Bacillus subtilis.

Endospore formation in the Gram-positive bacterium Bacillus subtilis initiates in response to nutrient depletion and involves a series of morphological changes that result in the creation of a dormant spore. Early in this developmental process, the cell undergoes an asymmetric cell division that produces the larger mother cell and smaller forespore, the latter destined to become the mature spore. The mother cell septal membrane then engulfs the forespore, at which time an essential channel, the so-called feeding-tube apparatus, is thought to cross both membranes to create a direct conduit between the cells. At least nine proteins are required to form this channel including SpoIIQ under forespore control and SpoIIIAA-AH under the mother cell control. Several of these proteins share similarity to components of Type-II, -III and -IV secretion systems as well as the flagellum from Gram-negative bacteria. Here we report the X-ray crystallographic structure of the cytosolic domain of SpoIIIAB to 2.3 Šresolution. This domain adopts a conserved, secretion-system related fold of a six membered anti-parallel helical bundle with a positively charged membrane-interaction face at one end and a small groove at the other end that may serve as a binding site for partner proteins in the assembled apparatus. We analyzed and identified potential interaction interfaces by structure-guided mutagenesis in vivo. Furthermore, we were able to identify a remarkable structural homology to the C-subunit of a bacterial V-ATPase. Collectively, our data provides new insight into the possible roles of SpoIIIAB protein within the secretion-like apparatus essential to bacterial sporulation.

Dose assesment with fast Monte Carlo codes in interventional radiology.

This study presents the performance of two fast Monte Carlo codes, PENELOPE/penEasyIR and MCGPU-IR in order to assess operator doses in interventional radiology. In particular, it aims to validate the calculations when workers are protected with shielding located between the patient and the operator. The experiments are performed in a calibration laboratory and measurements are gathered using Thermo EPD and Mirion DMC personal active dosemeters. Calculation efficiency of the fast Monte Carlo codes is approximately four orders of magnitude greater than for a standard Monte Carlo code. Satisfactory agreement between measurements and calculations is shown.

Mapping threats to power line corridors for Connecticut rights-of-way management.

Trees are a major threat to power line security across forested regions of the world. We developed a decision support system for identifying locations in Connecticut, USA where trees have grown tall enough to make contact with transmission lines during storms. We used the Random Forest algorithm, danger tree presence/absence data, and 25 raster environmental datasets to develop (1) an understanding of the abiotic environmental settings that host danger trees and (2) a spatially explicit map of danger tree distributions across Connecticut power line corridors. Danger trees were prevalent in locations (1) with an infrequent history of storms; (2) forested and residential land uses; and (3) low to middle elevations. Products from this research can be transferred to adaptive right-of-way management because they present managers with key information on where danger trees are likely to occur, and the methods presented herein have great potential for future application to other regions managers seek to identify high priority areas for danger tree removal.

PERSONAL DOSIMETRY USING MONTE-CARLO SIMULATIONS FOR OCCUPATIONAL DOSE MONITORING IN INTERVENTIONAL RADIOLOGY: THE RESULTS OF A PROOF OF CONCEPT IN A CLINICAL SETTING.

Exposure levels to staff in interventional radiology (IR) may be significant and appropriate assessment of radiation doses is needed. Issues regarding measurements using physical dosemeters in the clinical environment still exist. The objective of this work was to explore the prerequisites for assessing staff radiation dose, based on simulations only. Personal dose equivalent, Hp(10), was assessed using simulations based on Monte Carlo methods. The position of the operator was defined using a 3D motion tracking system. X-ray system exposure parameters were extracted from the x-ray equipment. The methodology was investigated and the simulations compared to measurements during IR procedures. The results indicate that the differences between simulated and measured staff radiation doses, in terms of the personal dose equivalent quantity Hp(10), are in the order of 30-70 %. The results are promising but some issues remain to be solved, e.g. an automated tracking of movable parts such as the ceiling-mounted protection shield.

Fast Monte Carlo codes for occupational dosimetry in interventional radiology.

PURPOSE: Interventional radiology techniques cause radiation exposure both to patient and personnel. The radiation dose to the operator is usually measured with dosimeters located at specific points above or below the lead aprons. The aim of this study is to develop and validate two fast Monte Carlo (MC) codes for radiation transport in order to improve the assessment of individual doses in interventional radiology. The proposed methodology reduces the number of required dosemeters and provides immediate dose results. METHODS: Two fast MC simulation codes, PENELOPE/penEasyIR and MCGPU-IR, have been developed. Both codes have been validated by comparing fast MC calculations with the multipurpose PENELOPE MC code and with measurements during a realistic interventional procedure. RESULTS: The new codes were tested with a computation time of about 120 s to estimate operator doses while a standard simulation needs several days to obtain similar uncertainties. When compared with the standard calculation in simple set-ups, MCGPU-IR tends to underestimate doses (up to 5%), while PENELOPE/penEasyIR overestimates them (up to 18%). When comparing both fast MC codes with experimental values in realistic set-ups, differences are within 25%. These differences are within accepted uncertainties in individual monitoring. CONCLUSION: The study highlights the fact that computational dosimetry based on the use of fast MC codes can provide good estimates of the personal dose equivalent and overcome some of the limitations of occupational monitoring in interventional radiology. Notably, MCGPU-IR calculates both organ doses and effective dose, providing a better estimate of radiation risk.

Decision support for mitigating the risk of tree induced transmission line failure in utility rights-of-way.

Vegetation management is a critical component of rights-of-way (ROW) maintenance for preventing electrical outages and safety hazards resulting from tree contact with conductors during storms. Northeast Utility's (NU) transmission lines are a critical element of the nation's power grid; NU is therefore under scrutiny from federal agencies charged with protecting the electrical transmission infrastructure of the United States. We developed a decision support system to focus right-of-way maintenance and minimize the potential for a tree fall episode that disables transmission capacity across the state of Connecticut. We used field data on tree characteristics to develop a system for identifying hazard trees (HTs) in the field using limited equipment to manage Connecticut power line ROW. Results from this study indicated that the tree height-to-diameter ratio, total tree height, and live crown ratio were the key characteristics that differentiated potential risk trees (danger trees) from trees with a high probability of tree fall (HTs). Products from this research can be transferred to adaptive right-of-way management, and the methods we used have great potential for future application to other regions of the United States and elsewhere where tree failure can disrupt electrical power.

Impact of Diflubenzuron on Bombus impatiens (Hymenoptera: Apidae) Microcolony Development.

Reliance on the honey bee as a surrogate organism for risk assessment performed on other bees is widely challenged due to differences in phenology, life history, and sensitivity to pesticides between bee species. Consequently, there is a need to develop validated methods for assessing toxicity in non-Apis bees including bumble bees. The usefulness of small-scale, queenless colonies, termed microcolonies, has not been fully investigated for hazard assessment. Using the insect growth regulator diflubenzuron as a reference toxicant, we monitored microcolony development from egg laying to drone emergence using the Eastern bumble bee Bombus impatiens (C.), a non-Apis species native to North America. Microcolonies were monitored following dietary exposure to diflubenzuron (nominal concentrations: 0.1, 1, 10, 100, and 1,000 µg/liter). Microcolony syrup and pollen consumption was significantly reduced by diflubenzuron exposure. Pupal cell production was also significantly decreased at the highest diflubenzuron concentration assessed. Ultimately, diflubenzuron inhibited drone production in a concentration-dependent manner and a 42-d 50% inhibitory concentration (IC50) was determined. None of the dietary concentrations of diflubenzuron tested affected adult worker survival, or average drone weight. These data strengthen the foundation for use of this methodology, and provide valuable information for B. impatiens; however, more work is required to better understand the utility of the bumble bee microcolony model for pesticide hazard assessment.

An XROMM Study of Food Transport and Swallowing in Channel Catfish.

Most predatory ray-finned fishes swallow their food whole, which can pose a significant challenge, given that prey items can be half as large as the predators themselves. How do fish transport captured food from the mouth to the stomach? Prior work indicates that, in general, fish use the pharyngeal jaws to manipulate food into the esophagus, where peristalsis is thought to take over. We used X-Ray Reconstruction of Moving Morphology to track prey transport in channel catfish (Ictalurus punctatus). By reconstructing the 3D motions of both the food and the catfish, we were able to track how the catfish move food through the head and into the stomach. Food enters the oral cavity at high velocities as a continuation of suction and stops in the approximate location of the branchial basket before moving in a much slower, more complex path toward the esophagus. This slow phase coincides with little motion in the head and no substantial mouth opening or hyoid depression. Once the prey is in the esophagus, however, its transport is surprisingly tightly correlated with gulping motions (hyoid depression, girdle retraction, hypaxial shortening, and mouth opening) of the head. Although the transport mechanism itself remains unknown, to our knowledge, this is the first description of synchrony between cranial expansion and esophageal transport in a fish. Our results provide direct evidence of prey transport within the esophagus and suggest that peristalsis may not be the sole mechanism of esophageal transport in catfish.

Electron microscopy of living insects.

Electron micrographs of living specimens of the various developmental stages of the insect Tribolium confusum have been obtained with a scanning electron microscope. In most cases the specimens resumed their normal activity after being examined with the electron microscope and under went metamorphosis into the next stage.

Efficacy of Muscodor albus for the Control of Phytophthora Blight of Sweet Pepper and Butternut Squash.

The efficacy of Muscodor albus, a potential soil biofumigant, to control root and stem rot by Phytophthora capsici, was examined in a greenhouse study. P. capsici-infested potting mix was treated with three rates of M. albus, mefenoxam (Ridomil Gold EC, Syngenta Crop Protection, Inc.), or nothing. Seedlings of five sweet pepper cultivars and one butternut squash cultivar were transplanted into the treated potting mix. After 7 days, the plants were rated on a scale of 0 (healthy) to 5 (dead). The experiment was conducted three times and there was a significant interaction between pepper cultivar and soil treatment. Treatment with the highest rate of M. albus resulted in a slight but significant reduction in disease severity on Alliance, Aristotle, Paladin, and Revolution pepper compared with the pathogen-only control, while no significant decreases in disease severity were observed with butternut squash or the highly susceptible pepper cv. Red Knight. Of the four less-susceptible pepper cultivars, Paladin (the most tolerant cultivar) was the only one on which M. albus, as applied in this study, reduced disease severity to commercially acceptable levels.

Comparison of methods for H*(10) calculation from measured LaBr3(Ce) detector spectra.

The Universitat Politecnica de Catalunya (UPC) and the Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT) have evaluated methods based on stripping, conversion coefficients and Maximum Likelihood Estimation using Expectation Maximization (ML-EM) in calculating the H*(10) rates from photon pulse-height spectra acquired with a spectrometric LaBr3(Ce)(1.5″ × 1.5″) detector. There is a good agreement between results of the different H*(10) rate calculation methods using the spectra measured at the UPC secondary standard calibration laboratory in Barcelona. From the outdoor study at ESMERALDA station in Madrid, it can be concluded that the analysed methods provide results quite similar to those obtained with the reference RSS ionization chamber. In addition, the spectrometric detectors can also facilitate radionuclide identification.

Sceletium tortuosum may delay chronic disease progression via alkaloid-dependent antioxidant or anti-inflammatory action.

The link between obesity-induced systemic inflammation and decreased insulin signalling is well-known. It is also known that peripherally produced inflammatory cytokines can cross the blood-brain barrier, resulting in the release of neurotoxins that can ultimately lead to the demise of central nervous system integrity. A high-mesembrine Sceletium tortuosum extract was recently shown to possess cytoprotective and mild anti-inflammatory properties in monocytes and to target specific p450 enzymes to reduce adrenal glucocorticoid synthesis. This is significant since the aetiology of both obesity and diabetes is linked to inflammation and excess glucocorticoid production. Given the interlinked nature of glucocorticoid action and inflammation, central immunomodulatory effects of two Sceletium tortuosum extracts prepared by different extraction methods were investigated. Human astrocytes were pre-treated for 30 min, before exposure to Escherichia coli lipopolysaccharide for 23.5 h (in the presence of treatment). Cytotoxicity, mitotoxicity and cytokine responses (basally and in response to inflammatory stimulus) were assessed. In addition, total polyphenol content, antioxidant capacity and selected neural enzyme inhibition capacity were assessed for both extracts. The high-mesembrine Sceletium extract exerted cytoprotective and anti-inflammatory effects. In contrast, the high delta7-mesembrenone extract, rich in polyphenols, exhibited potent antioxidant effect, although with relatively higher risk of adverse effects with overdose. We conclude that both Sceletium tortuosum extracts may be employed as either a preventative supplement or complimentary treatment in the context of obesity and diabetes; however, current data also highlights the impact that extraction methods can have on plant product mechanism of action.

INFLUENCE OF RADON PROGENY ON DOSE RATE MEASUREMENTS STUDIED AT PTB'S RADON REFERENCE CHAMBER.

The responses of electronic dose rate meters were investigated in a large volume radon chamber at PTB in a wide range of radon activity concentrations. The measurements were conducted under controlled laboratory conditions and measured dose rate data are compared with Monte-Carlo simulations. Consequences concerning environmental monitoring are described. A further result is that the direct measurement of the dose rates produced by radon progeny in air is hardly possible in radon atmospheres with high activity concentrations, because the major contribution of measured dose rates is produced by radon progeny on the housing of the dose rate instruments. The latter effect largely depends on the ability of surfaces to absorb radon progeny. The Monte-Carlo simulations revealed quantitative results on the height of the single contributions to the total dose rate measured in the radon chamber. When environmental dose rate measurements are performed, the plate-out on detectors can be neglected.

Can't take the heat: Temperature-enhanced toxicity in the mayfly Isonychia bicolor exposed to the neonicotinoid insecticide imidacloprid.

Neonicotinoid insecticide usage has increased globally in recent decades. Neonicotinoids, such as imidacloprid, are potent insect neurotoxicants that may pose a threat to non-target aquatic organisms, such as aquatic insects. In nature, insects typically live in thermally fluctuating conditions, which may significantly alter both contaminant exposures and affects. Here we investigate the relationship between temperature and time-to-effect for imidacloprid toxicity with the aquatic insect Isonychia bicolor, a lotic mayfly. Additionally, we examined the mechanisms driving temperature-enhanced toxicity including metabolic rate, imidacloprid uptake rate, and tissue bioconcentration. Experiments included acute toxicity tests utilizing sublethal endpoints and mortality, as well as respirometry and radiotracer assays with [(14)C] imidacloprid. Further, we conducted additional uptake experiments with a suite of aquatic invertebrates (including I. bicolor, Neocloeon triangulifer, Macaffertium modestum, Pteronarcys proteus, Acroneuria carolinensis, and Pleuroceridae sp) to confirm and contextualize our findings from initial experiments. The 96h EC50 (immobility) for I. bicolor at 15°C was 5.81µg/L which was approximately 3.2 fold lower than concentrations associated with 50% mortality. Assays examining the impact of temperature were conducted at 15, 18, 21, and 24°C and demonstrated that time-to-effect for sublethal impairment and immobility was significantly decreased with increasing temperature. Uptake experiments with [(14)C] imidacloprid revealed that initial uptake rates were significantly increased with increasing temperature for I. bicolor, as were oxygen consumption rates. Further, in the separate experiment with multiple species across temperatures 15, 20, and 25°C, we found that all the aquatic insects tested had significantly increased imidacloprid uptake with increasing temperatures, with N. triangulifer accumulating the most imidacloprid on a mass-specific basis. Our acute toxicity results highlight the importance of evaluating sublethal endpoints, as profound impairments of motor function were evident far before mortality. Further, we demonstrate that temperature is a powerful modulator of sublethal toxicity within a range of environmentally relevant temperatures, impacting both uptake rates and metabolic rates of I. bicolor. Finally, we show that temperature alters imidacloprid uptake across a range of species, highlighting the physiological variation present within aquatic invertebrate communities and the challenge associated with relying solely on surrogate species. Taken together, this research points to the need to consider the role of temperature in toxicity assessments.

Equivalence of computer codes for calculation of coincidence summing correction factors - Part II.

The aim of this study was to check for equivalence of computer codes that are capable of performing calculations of true coincidence summing (TCS) correction factors. All calculations were performed for a set of well-defined detector parameters, sample parameters and decay scheme data. The studied geometry was a point source of (133)Ba positioned directly on the detector window of a low-energy (n-type) detector. Good agreement was established between the TCS correction factors computed by the different codes.

Prognostic value of intravenous dipyridamole thallium imaging in patients with diabetes mellitus considered for renal transplantation.

Patients with diabetes and end-stage renal failure are known to have a high risk for cardiac morbidity and mortality associated with renal transplantation. The most efficient method to determine preoperative cardiac risk has not been established. To determine the effectiveness of intravenous dipyridamole thallium imaging in predicting cardiac events, 40 diabetic renal transplant candidates were studied preoperatively in a prospective trial. The study group consisted of 40 patients whose average age was 42 years (range 27 to 64); 34 (85%) were hypertensive and 21 (53%) were cigarette smokers. Cardiac history included chest pain in 6 patients and prior myocardial infarction in 3 patients. Dipyridamole thallium imaging showed reversible defects in 9 patients, fixed defects in 8 patients and normal scans in 23 patients. Dipyridamole thallium imaging was performed using 0.56 mg/kg of dipyridamole infused intravenously over 4 minutes. Cardiac events occurred only in patients with reversible thallium defects, of which there were 6. Of these 6 patients, 3 had cardiac events before transplantation and 3 had them in the early postoperative phase (within 6 weeks of surgery). Of 21 patients who underwent renal transplantation, 3 had cardiac events within 6 weeks of transplantation. The average duration of follow-up was 11 months (range 1 to 21). Thus, dipyridamole thallium imaging is an effective method of identifying renal transplant candidates likely to develop cardiac complications. Routine coronary angiography may not be necessary to screen all renal transplant candidates for coronary artery disease before surgery.

Usefulness of transesophageal echocardiography in unexplained cerebral ischemia.

Two-hundred seventy consecutive patients with "unexplained cerebral ischemia" were studied with transesophageal echocardiography to determine the value of this test in identifying potential cardiac sources of cerebral embolism. The findings of this group were compared with those of 772 consecutive patients undergoing transesophageal echocardiographic evaluation for indications other than cerebral ischemia. This study also examined this group of patients with unexplained cerebral ischemia to determine differences in relation to underlying cardiac rhythm and patient age. Intracardiac thrombus, atrial septal aneurysm, patent foramen ovale, spontaneous left atrial contrast and protruding debris in the thoracic aorta were found more often in patients with unexplained cerebral ischemia. Wall motion abnormalities of the left ventricle, as well as mild to moderate valvular lesions including mitral valve prolapse, were found to be similar in both groups. Spontaneous left atrial contrast, as well as mild to moderate valvular abnormalities, were found more often in patients with atrial fibrillation (22% of the group with unexplained cerebral ischemia). However, the presence of intracardiac thrombus was no more frequent in patients with atrial fibrillation than in those with normal sinus rhythm. Patients aged > 50 years were found to have atrial fibrillation and larger left atrial size more often than their younger cohorts, as well as a greater incidence of valvular abnormalities and left ventricular wall motion abnormalities. Mitral valve prolapse was seen more frequently in the younger cohort of patients.