1,027 research outputs found
Quality assurance of radiodiagnostic equipment -Overview of literature since 2004
Het Britse handboek voor de kwaliteitsborging (Quality Assurance) van CT-scanners en andere rontgentoestellen, kan met enkele aanpassingen ook in Nederland gebruikt worden. Dit blijkt uit een literatuurstudie van het RIVM naar de kwaliteitsborging van deze apparaten. Beelden van CT-scanners en andere rontgentoestellen moeten goed genoeg zijn om een juiste diagnose te kunnen stellen. Ze worden gemaakt met rontgenstraling en die is schadelijk voor de gezondheid. De beelden worden echter vaak beter als er meer straling wordt gebruikt. Om goede beelden te krijgen met een zo laag mogelijke stralingsdosis is er veel aandacht nodig voor het optimaal laten functioneren van de apparatuur. Het geheel van maatregelen die hieraan bijdragen wordt kwaliteitsborging genoemd. Er is in Nederland geen algemeen handboek voor de kwaliteitsborging van CT-scanners en andere rontgenapparaten. Uit het onderzoek van het RIVM blijkt dat het Britse handboek, aangevuld met enkele andere documenten, vrij eenvoudig naar de Nederlandse praktijk vertaald kan worden. Wel is er nog een enkele toevoeging nodig en moeten grenswaarden worden aangepast aan de Nederlandse regelgeving.The British handbook on quality assurance of CT and other x-ray equipment may, with some adaptations, also be used in the Netherlands. This is the main conclusion of a literature study by RIVM on quality assurance of such equipment. Images from CT scanners and other x-ray equipment must have sufficient quality to enable a correct diagnosis. They are obtained using x-rays, which have adverse health effects. However, in diagnostic imaging, higher x-ray doses often lead to better image quality. To obtain good images while keeping the radiation dose as low as reasonably achievable, much attention is needed for the optimal performance of the equipment. Quality assurance is the complex of all measures needed to achieve this. A general handbook on quality assurance of CT and other x-ray equipment adapted to the Dutch practice does not exist. The literature study by RIVM shows that it should be relatively straightforward to adapt, with some additions, the British handbook to the Dutch practice and legislation.Inspectie voor de Gezondheidszor
Curvature-Induced Instabilities of Shells
Induced by proteins within the cell membrane or by differential growth,
heating, or swelling, spontaneous curvatures can drastically affect the
morphology of thin bodies and induce mechanical instabilities. Yet, the
interaction of spontaneous curvature and geometric frustration in curved shells
remains still poorly understood. Via a combination of precision experiments on
elastomeric spherical bilayer shells, simulations, and theory, we show a
spontaneous curvature-induced rotational symmetry-breaking as well as a
snapping instability reminiscent of the Venus fly trap closure mechanism. The
instabilities and their dependence on geometry are rationalized by reducing the
spontaneous curvature to an effective mechanical load. This formulation reveals
a combined pressurelike bulk term and a torquelike boundary term, allowing
scaling predictions for the instabilities in excellent agreement with
experiments and simulations. Moreover, the effective pressure analogy suggests
a curvature-induced buckling in closed shells. We determine the critical
buckling curvature via a linear stability analysis that accounts for the
combination of residual membrane and bending stresses. The prominent role of
geometry in our findings suggests the applicability of the results over a wide
range of scales.Comment: 12 pages, 9 figures (including Supporting Information
Quality assurance for the optimization of patient dose in interventional radiology
Drie maatregelen kunnen de dosis straling optimaliseren die patienten ontvangen tijdens radiologische interventies. Ten eerste moderne apparatuur gebruiken die speciaal geschikt is voor interventies. Ten tweede extra aandacht schenken aan stralingsbescherming tijdens opleidingen op het gebied van de interventieradiologie. En tot slot complicaties van straling opnemen in het complicatieregister van de sectie Interventieradiologie van de Nederlandse Vereniging voor Radiologie. Dit blijkt uit onderzoek dat het RIVM in opdracht van de Inspectie voor de Gezondheidszorg heeft uitgevoerd naar de kwaliteitsborging van de interventieradiologie in Nederland. De opdracht is ingegeven door de relatief hoge stralingsdosis waaraan patienten kunnen worden blootgesteld tijdens radiologische interventies. Bij interventieradiologie worden medische behandelingen uitgevoerd via een kleine opening in de huid, terwijl die ingreep in beeld wordt gebracht met behulp van rontgen, CT, MRI of echografie. Bij gebruik van rontgen of CT kan de stralingsdosis leiden tot nadelige effecten voor de gezondheid, zoals roodheid, verbranding van de huid, (tijdelijke) ontharing of op de lange termijn kanker.Three measures may optimize the radiation dose that patients receive during interventional radiology procedures. The first is by using modern equipment that is appropriate for interventional radiology procedures, while the second involves paying extra attention to radiation protection in courses in the field of interventional radiology. A final measure is to incorporate radiation-related complications into the complication register of the Interventional Radiology section of the Dutch Association for Radiology. This was found in an investigation of quality assurance in interventional radiology in the Netherlands that was assigned to RIVM by the Dutch Health Inspectorate. The investigation was motivated by the relatively high radiation dose that patients undergoing an interventional radiology procedure may be exposed to. In interventional radiology, medical treatment is applied through a small opening in the skin, while the procedure is monitored using medical imaging such as X-ray, CT, MRI or ultrasound. In the case of X-ray or CT, the radiation dose may cause adverse health effects such as erythema, burnt skin, (temporary) epilation or, in the long term, cancer.Inspectie voor de Gezondheidszor
Flying is the safest way to travel
Independent investigations of aviation accidents and incidents have been broadly accepted within the aviation sector throughout its history as a valuable tool to enhance safety. Such investigations enable the sector to learn by establishing the sequence of events that provides a satisfactory explanation of the accident leads to the drafting of recommendations to prevent reoccurrences. In addition, these investigations, which are publicly disseminated, encourage public confidence in the sector. Other transport sectors, including road, rail and water, have been slower in coming to enjoy the same acceptance of independent investigations; here, there is considerable variation amongst nations, and—with the exception of the International Civil Aviation Organization agreement—almost no international consistency. This article examines why aviation has had a different tradition in this regard. Reasons are found in parallel growth of aviation technology and the philosophy of investigative bodies, the inherently international aspect of commercial aviation, and the role of public and political pressure following major accidents. The safety investigative orientation of the aviation sector is gradually expanding to other transport sections and beyond that to other sectors such as fixed site production plants, health care, and management of natural disasters. With the newly installed Safety Investigation Board, the Netherlands has arguably placed itself at the head of this league table
Vectorcardiographic changes during extended space flight
To assess the effects of space flight on cardiac electrical properties, vectorcardiograms were taken on the 9 Skylab astronauts during the flights of 28, 59, and 84 days. The Frank lead system was used and observations were made at rest; during 25%, 50% and 75% of maximum exercise; during a short pulse of exercise (150 watts, 2 minutes); and after exercise. Data from 131 in-flight tests were analyzed by computer and compared to preflight and postflight values. Statistically significant increase in QRS vector magnitude (six of nine crewmen); T vector magnitude (five of nine crewmen); and resting PR interval duration (six of nine crewmen) occurred. During exercise the PR interval did not differ from preflight. Exercise heart rates inflight were the same as preflight, but increased in the immediate postflight period. With the exception of the arrhythmias, no deleterious vectorcardiographic changes were observed during the Skylab missions
Incorporating climate change effects into the European power system adequacy assessment using a post-processing method
The demand-supply balance of electricity systems is fundamentally linked to
climate conditions. In light of this, the present study aims to model the
effect of climate change on the European electricity system, specifically on
its long-term reliability. A resource adequate power system -- a system where
electricity supply covers demand -- is sensitive to generation capacity, demand
patterns, and the network structure and capacity. Climate change is foreseen to
affect each of these components.
In this analysis, we focused on two drivers of power system adequacy: the
impact of temperature variations on electricity demand, and of water inflows
changes on hydro generation. Using a post-processing approach, based on results
found in the literature, the inputs of a large-scale electricity market model
covering the European region were modified. The results show that climate
change may decrease total LOLE (Loss of Load Expectation) hours in Europe by
more than 50%, as demand will largely decrease because of a higher temperatures
during winter. We found that the climate change impact on demand tends to
decrease LOLE values, while the climate change effects on hydrological
conditions tend to increase LOLE values.
The study is built on a limited amount of open-source data and can flexibly
incorporate various sets of assumptions. Outcomes also show the current
difficulties to reliably model the effects of climate change on power system
adequacy. Overall, our presented method displays the relevance of climate
change effects in electricity network studies
Iodine-131 in Household waste - a pilot study
Werknemers in de thuis- en verpleegzorg en vuilnisophalers komen soms zonder dat te weten in aanraking met de radioactieve stof jodium-131. Toch is het niet aannemelijk dat zij aan een te hoge stralingsdosis blootstaan. Voorwaarde is, dat ze de normale hygienische voorschriften naleven. Dit blijkt uit verkennend onderzoek van het RIVM. Aanleiding is een tiental stralingsmeldingen bij een afvalverbrandingsinstallatie voor huishoudelijk afval in Dordrecht tussen april 2008 en april 2009. De straling was afkomstig van jodium-131 in incontinentiemateriaal en ander afval van patienten die met deze radioactieve stof zijn behandeld wegens een schildklierafwijking. Voor het onderzoek zijn vijf ziekenhuizen bezocht en zijn gegevens van de VROM-Inspectie gebruikt. Op basis hiervan heeft het RIVM scenario's opgesteld waarmee dosisschattingen voor werknemers zijn gemaakt. Deze schattingen zijn gebaseerd op de veronderstelling dat de hoeveelheid jodium-131 in incontinentiemateriaal niet groter is dan tot nu toe in het huishoudelijk afval is waargenomen. Er zijn twee mogelijke verklaringen voor de aanwezigheid van jodium-131 in het incontinentiemateriaal. Incontinente patienten mogen in Nederland niet poliklinisch met jodium-131 worden behandeld, maar in de praktijk gebeurt dat toch. De eerste 24 uur na de behandeling bevat de urine van deze patienten relatief veel van deze radioactieve stof. Een tweede verklaring zou kunnen zijn dat patienten die met een hoge dosering zijn behandeld, in sommige ziekenhuizen vaker vervroegd worden ontslagen. In Duitsland is poliklinische behandeling met jodium-131 niet toegestaan. Gezien de beperkte risico's lijkt een dergelijk totaalverbod in Nederland niet te rechtvaardigen. Om de risico's voor derden laag te houden, zou men bij incontinente patienten terughoudend moeten zijn met poliklinische behandeling en vervroegd ontslag.Workers in homecare and nursing homes are occasionally exposed to the radioactive drug iodine-131. Still, it is unlikely that dose limits are exceeded, provided that sanitary procedures are followed. This is shown in a pilot study by RIVM carried out after a number of radiation alerts at the household waste incinerator in Dordrecht between April 2008 and April 2009. The radiation originated from iodine-131 in diapers and similar waste from patients that had been treated for thyroid disorders. For this pilot study, five hospitals have been visited, and data were obtained from the environmental inspectorate. Based on this, scenarios were drawn up and dose estimates were made for workers. Two explanations are given for the unexpected presence of iodine-131 in household waste. First iodine-131 therapy is not allowed for outpatients if they are incontinent, but it is still done. Second, early release of patients treated with high doses may occur more often in some hospitals. In Germany, iodine therapy of outpatients is not allowed at all. In view of the limited risks, such a total ban seems unjustifiable in the Netherlands. To keep the risks for others to a minimum, hospitals should exercise restraint on sending incontinent patients home early.VRO
Incunabula in communities of canonesses regular and tertiaries related to the Devotio moderna: toward an ‘inclusive’ approach of Late medieval book ownership in the Low Countries
This contribution discusses the hitherto overlooked ownership of the earliest printed books (incunabula) by Netherlandish female religious communities of tertiaries and canonesses regular connected to the religious reform movement of the Devotio moderna. Studies of book ownership and book collections in these communities have tended to focus on manuscripts. From the last decades of the fifteenth century onwards, however, these religious women increasingly came in contact with printed books, even though the involvement of the Devotio moderna with the printing press was limited. The discussion focuses on the channels via which tertiaries and canonesses acquired books produced by commercially operating printers, the ways in which incunabula affected what these (semi-)religious women read, as well as the ratio between printed books in Latin and the vernacular, and their function(s) within these communities. Thus the essay intends to sketch a preliminary image of the role of incunabula in female convents, and advocates a more inclusive approach of female religious book ownership.NWO275-30-036Medieval and Early Modern Studie
Detection of Critical Events in Renewable Energy Production Time Series
The introduction of more renewable energy sources into the energy system
increases the variability and weather dependence of electricity generation.
Power system simulations are used to assess the adequacy and reliability of the
electricity grid over decades, but often become computational intractable for
such long simulation periods with high technical detail. To alleviate this
computational burden, we investigate the use of outlier detection algorithms to
find periods of extreme renewable energy generation which enables detailed
modelling of the performance of power systems under these circumstances.
Specifically, we apply the Maximum Divergent Intervals (MDI) algorithm to power
generation time series that have been derived from ERA5 historical climate
reanalysis covering the period from 1950 through 2019. By applying the MDI
algorithm on these time series, we identified intervals of extreme low and high
energy production. To determine the outlierness of an interval different
divergence measures can be used. Where the cross-entropy measure results in
shorter and strongly peaking outliers, the unbiased Kullback-Leibler divergence
tends to detect longer and more persistent intervals. These intervals are
regarded as potential risks for the electricity grid by domain experts,
showcasing the capability of the MDI algorithm to detect critical events in
these time series. For the historical period analysed, we found no trend in
outlier intensity, or shift and lengthening of the outliers that could be
attributed to climate change. By applying MDI on climate model output, power
system modellers can investigate the adequacy and possible changes of risk for
the current and future electricity grid under a wider range of scenarios
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