Translocation pathways for inhaled asbestos fibers

We discuss the translocation of inhaled asbestos fibers based on pulmonary and pleuro-pulmonary interstitial fluid dynamics. Fibers can pass the alveolar barrier and reach the lung interstitium via the paracellular route down a mass water flow due to combined osmotic (active Na+ absorption) and hydraulic (interstitial pressure is subatmospheric) pressure gradient. Fibers can be dragged from the lung interstitium by pulmonary lymph flow (primary translocation) wherefrom they can reach the blood stream and subsequently distribute to the whole body (secondary translocation). Primary translocation across the visceral pleura and towards pulmonary capillaries may also occur if the asbestos-induced lung inflammation increases pulmonary interstitial pressure so as to reverse the trans-mesothelial and trans-endothelial pressure gradients. Secondary translocation to the pleural space may occur via the physiological route of pleural fluid formation across the parietal pleura; fibers accumulation in parietal pleura stomata (black spots) reflects the role of parietal lymphatics in draining pleural fluid. Asbestos fibers are found in all organs of subjects either occupationally exposed or not exposed to asbestos. Fibers concentration correlates with specific conditions of interstitial fluid dynamics, in line with the notion that in all organs microvascular filtration occurs from capillaries to the extravascular spaces. Concentration is high in the kidney (reflecting high perfusion pressure and flow) and in the liver (reflecting high microvascular permeability) while it is relatively low in the brain (due to low permeability of blood-brain barrier). Ultrafine fibers (length < 5 μm, diameter < 0.25 μm) can travel larger distances due to low steric hindrance (in mesothelioma about 90% of fibers are ultrafine). Fibers translocation is a slow process developing over decades of life: it is aided by high biopersistence, by inflammation-induced increase in permeability, by low steric hindrance and by fibers motion pattern at low Reynolds numbers; it is hindered by fibrosis that increases interstitial flow resistances

An automatic deep learning approach for coronary artery calcium segmentation

Coronary artery calcium (CAC) is a significant marker of atherosclerosis and cardiovascular events. In this work we present a system for the automatic quantification of calcium score in ECG-triggered non-contrast enhanced cardiac computed tomography (CT) images. The proposed system uses a supervised deep learning algorithm, i.e. convolutional neural network (CNN) for the segmentation and classification of candidate lesions as coronary or not, previously extracted in the region of the heart using a cardiac atlas. We trained our network with 45 CT volumes; 18 volumes were used to validate the model and 56 to test it. Individual lesions were detected with a sensitivity of 91.24%, a specificity of 95.37% and a positive predicted value (PPV) of 90.5%; comparing calcium score obtained by the system and calcium score manually evaluated by an expert operator, a Pearson coefficient of 0.983 was obtained. A high agreement (Cohen's k = 0.879) between manual and automatic risk prediction was also observed. These results demonstrated that convolutional neural networks can be effectively applied for the automatic segmentation and classification of coronary calcifications

Translocation pathways for inhaled asbestos fibers

We discuss the translocation of inhaled asbestos fibers based on pulmonary and pleuro-pulmonary interstitial fluid dynamics. Fibers can pass the alveolar barrier and reach the lung interstitium via the paracellular route down a mass water flow due to combined osmotic (active Na+ absorption) and hydraulic (interstitial pressure is subatmospheric) pressure gradient. Fibers can be dragged from the lung interstitium by pulmonary lymph flow (primary translocation) wherefrom they can reach the blood stream and subsequently distribute to the whole body (secondary translocation). Primary translocation across the visceral pleura and towards pulmonary capillaries may also occur if the asbestos-induced lung inflammation increases pulmonary interstitial pressure so as to reverse the trans-mesothelial and trans-endothelial pressure gradients. Secondary translocation to the pleural space may occur via the physiological route of pleural fluid formation across the parietal pleura; fibers accumulation in parietal pleura stomata (black spots) reflects the role of parietal lymphatics in draining pleural fluid. Asbestos fibers are found in all organs of subjects either occupationally exposed or not exposed to asbestos. Fibers concentration correlates with specific conditions of interstitial fluid dynamics, in line with the notion that in all organs microvascular filtration occurs from capillaries to the extravascular spaces. Concentration is high in the kidney (reflecting high perfusion pressure and flow) and in the liver (reflecting high microvascular permeability) while it is relatively low in the brain (due to low permeability of blood-brain barrier). Ultrafine fibers (length < 5 μm, diameter < 0.25 μm) can travel larger distances due to low steric hindrance (in mesothelioma about 90% of fibers are ultrafine). Fibers translocation is a slow process developing over decades of life: it is aided by high biopersistence, by inflammation-induced increase in permeability, by low steric hindrance and by fibers motion pattern at low Reynolds numbers; it is hindered by fibrosis that increases interstitial flow resistances

Il metodo deposimetrico per la misura della dispersione di fibre di asbesto dalle coperture in cemento amianto : revisione e perfezionamento

Background: The present article is a follow-up of previous research, in which a sedimentation method was proposed to measure the dispersion of fibre bundles (primary pollution) from asbestos-cement roofs.Objectives: The aim of this study was to improve and standardize a screening method to evaluate asbestos bundle release from asbestos-containing materials. Methods: An appropriate instrument (deposimetro) was used to passively sample asbestos on microscope slides by direct sedimentation. The microscopic analysis of samples was improved by the dispersion staining method, combined with the calculation of weight concentrations of asbestos per surface and time unit. The sampling efficiency was improved by introducing a new adhesive treatment of the microscope slides (85% stearyl alcohol, 15% octyldodecan) and a size cut-off restricting the counting method only to fibre bundles with diameters larger than 2 \u3bcm. Results: The optimal sampling time was defined as 25-30 days without rain, extending the sampling time established in the previous investigation, and the optimal instrument position was defined at distances of 50 cm (vertical) and 0 cm (horizontal) from the roof edge. The effect of wind direction and velocity on asbestos release was also assessed, showing that wind gusts with a velocity of more than 10 m/s are mostly associated with dispersion peaks. Conclusions: A simple algorithm was proposed on the basis of field data (n=32) and 5 hazard classes were defined as a function of weight concentrations and asbestos type. The passive sampler is low in cost and is intended for use in large-scale surveys to identify removal priorities

Patient Perceptions and Knowledge of Ionizing Radiation from Medical Imaging

Importance: Although imaging has become a standard tool of modern medicine, its widespread use has been paralleled by an increasing cumulative radiation dose to patients despite technological advancements and campaigns calling for better awareness and minimization of unnecessary exposures. Objective: To assess patients' knowledge about medical radiation and related risks. Design, Setting, and Participants: A survey study of hospitals in Italy was conducted; all patients in waiting rooms for medical imaging procedures before undergoing imaging examinations at 16 teaching and nonteaching hospitals were approached to take the survey. The survey was performed from June 1, 2019, to May 31, 2020. Main Outcomes and Measures: Survey respondents' basic knowledge of ionizing radiation levels and health risks, earlier imaging tests performed, and information and communication about radiation protection issues. Results: Among 3039 patients invited to participate, the response rate was 94.3% (n = 2866). Participants included 1531 women (53.4%); mean (SD) age was 44.9 (17.3) years. Of the 2866 participants, 1529 (53.3%) were aware of the existence of natural sources of ionizing radiation. Mammography (1101 [38.4%]) and magnetic resonance imaging (1231 [43.0%]) were categorized as radiation-based imaging modalities. More than half of the 2866 patients (1579 [55.1%]; P =.03) did not know that chest computed tomography delivers a larger dose of radiation than chest radiography, and only 1499 (52.3%) knew that radiation can be emitted after nuclear medicine examinations (P =.004). A total of 667 patients (23.3%) believed that radiation risks were unrelated to age, 1273 (44.4%) deemed their knowledge about radiation risks inadequate, and 2305 (80.4%) preferred to be informed about radiation risks by medical staff. A better knowledge of radiation issues was associated with receiving information from health care professionals (odds ratio [OR], 1.71; 95% CI, 1.43-2.03; P &lt;.001) and having a higher educational level (intermediate vs low: OR, 1.48; 95% CI, 1.17-1.88; P &lt;.001; high vs low: OR, 2.68; 95% CI, 2.09-3.43; P &lt;.001). Conclusions and Relevance: The results of this survey suggest that patients undergoing medical imaging procedures have overall limited knowledge about medical radiation. Intervention to achieve better patient awareness of radiation risks related to medical exposures may be beneficial

Mesothelioma: the aetiological role of ultrathin fibres and repercussions on prevention and medical legal evaluation

BACKGROUND: Mesothelioma has until now been considered to be a manifestation, occurring in the pleura and/or peritoneum, of the carcinogenic action of the total burden of inhaled asbestos fibres, in the same way as lung cancer. Because of the pathogenic potential of very low exposure levels, the fact that the onset of the neoplasm always occurs in the parietal pleura, and the absence of any synergism with smoking, which is typical in the case of carcinoma, it was suspected that aetiopathogenetic differences existed but the reasons for such differences still could not be explained. In the past experimental results indicated the oncogenicity of very thin fibres but mesothelioma in practice was not exclusively linked to this specific dimensional size class. OBJECTIVES: The paper proposes to take full advantage of the significant knowledge that must emerged from research carried out in recent years and use this knowledge to reconstruct the mosaic of the aetiopathogenesis of mesothelioma. Due consideration will also be given to the consequent new approach required in the field of medical-legal evaluation of cases and in the field of prevention. RESULTS: The most important knowledge that must today be taken as certain is the fact that mesothelioma is not caused, as is the case for asbestosis, by all the fibres that are inhaled but only by the ultrathin fraction of these fibres, having diameter of 0.2 microm and length of only a few microm. Only fibres of this class of size can cross the pulmonary-pleural barrier and are, therefore, the causal agent of mesothelioma and other benign pleural manifestations (plaques). Moreover the ultrathin fibres that translocate from the lung to the pleura are not distributed casually on the parietal and visceral surfaces but move over the surfaces, to concentrate around the lymphatic reabsorption stomata situated on the parietal pleura. Due to their shape, the fibres cannot easily be absorbed into the stoma via the lymphatic flow and so remain clustered for an indefinite period of time among the mesothelial cells that surround the stoma. The concentration of ultrathin fibres in punctiform areas of the parietal pleura and the extremely long biopersistence of the amphiboles now finally explain how very low exposures can cause mesothelioma in susceptible subjects and why the neoplasm always occurs on the parietal pleura. CONCLUSIONS: In medical-legal assessments of cases of mesothelioma the etiological importance of the ultrathin fraction of fibres means that any assumption of the disease being avoidable must be discarded, at least up to the second half of the 1980s because until then this class of fibres, which today must be considered as the true causal agent of the neoplasm, was not visible under the optical microscope, nor could such fibres be measured or eliminated from the atmosphere of working environments. The filter materials available both for fixed ventilation systems and for individual protective masks were not able to block the ultrathin fibres and were therefore only efficacious for the prevention of asbestosis and probably pulmonary carcinoma. It was only with the use of highly efficient HEPA filters and "absolute" filters towards the end of the 1980s that efficacious protection against all size classes of respirable fibres became possible in industrial plants. Preventive measures in the public hygiene area must also take account of the aetiological role of ultrathin fibres by making full use of electron microscope investigations and by using "absolute" filters for domestic purposes, in ventilation systems and above all in the filter systems of the mechanical devices used in town street cleaning operations