Radiographic quality control devices

In this study, we evaluate eight radiographic quality control (QC) devices, which noninvasively measure the output from a variety of diagnostic x-ray production systems. When used as part of a quality assurance (QA) program, radiographic QC devices help ensure that x-ray equipment is working within acceptable limits. This in turn helps ensure that high-quality images are achieved with appropriate radiation doses and that resources are used efficiently (for example, by minimizing the number of repeat exposures required). Our testing focused on the physical performance, ease of use, and service and maintenance characteristics that affect the use of these devices for periodic, routine measurements of x-ray system parameters. We found that all the evaluated models satisfactorily measure all the parameters normally needed for a QA program. However, we did identify a number of differences among the models--particularly in the range of exposure levels that can be effectively measured and the ease of use. Three models perform well for a variety of applications and are very easy to use; we rate them Preferred. Three additional models have minor limitations but otherwise perform well; we rate them Acceptable. We recommend against purchasing two models because, although each performs acceptably for most applications, neither model can measure low levels of radiation. This Evaluation covers devices designed to measure the output of x-ray tubes noninvasively. These devices, called radiographic quality control (QC) devices, or QC meters, are typically used by medical physicists, x-ray engineers, biomedical engineers, and suitably trained radiographic technologists to make QC measurements. We focus on the use of these devices as part of an overall quality assurance (QA) program. We have not evaluated their use for other applications, such as acceptance testing. To be included in this study, a device must be able to measure the exposure- and kVp-related characteristics of most x-ray systems. At minimum, it must be able to make routine QC measurements of general radiographic, fluoroscopic, and most mammographic equipment. We prefer that it also be usable with dental x-ray systems, more advanced mammography systems (see the supplementary article on page 103), and computed tomography (CT) systems. The device may be a single unit, or it may be a kit consisting of multiple components that, when combined, can perform all the relevant measurements. The evaluated devices are designed to assess only x-ray production systems, not x-ray detection systems such as image intensifiers and film. Those types of systems are typically assessed using test phantoms and other tools that produce test images, which can be quantitatively measured and compared against standards.     

Cost evaluation of control measures for indoor radon progeny

Based on assumed conditions within a typical U.S. home, annualized costs for reducing indoor airborne radon progeny concentrations have been calculated for a variety of methods of control. These analyses were limited to methods for control in existing homes. Control through modified construction techniques was not evaluated. Methods assessed included increased air circulation, increased ventilation, particle removal using electrostatic precipitation and unipolar ion generation, and the application of sealants to room surfaces. Although surface sealants proved to be reasonably cost-effective per person- sievert dose reduction, such sealants are prone to cracking and the durability of their effectiveness is questionable. Use of ceiling fans for increased air circulation and particle deposition appears to be least cost-effective, but this method may be attractive in some cases for reasons of comfort. The use of unipolar ion generators appears to be the best approach from the standpoint of cost effectiveness. These devices are also easy to install and are esthetically readily acceptable.     

Capture efficiency of portable high-efficiency air filtration devices used during building construction activities

The portable high-efficiency air filtration (PHEAF) device is used to control particulate matter (PM) generated from construction-type activities occurring within the built environment. Examples of activities where PHEAF devices are mobilized include building renovation, asbestos abatement, remediation of microbial contamination, and lead-based paint projects. Designed for use on short-term, temporary projects the PHEAF device captures airborne PM using a high-efficiency particulate air (HEPA) filter. This study sought to evaluate the capture efficiency of the PHEAF device in a field setting. An aerosol generator and photometer were used to measure particle penetration through 85 PHEAF devices. Average overall capture efficiency ranged from 41.78% to ≥99.97% with more than 88% of the tests failing to achieve 99.97% capture efficiency. Approximately 73% of the PHEAF device sample population failed to demonstrate HEPA performance criteria during any test round. A higher occurrence of PM concentrations measured around the perimeter of the filter suggested the presence of bypass leakage. While PHEAF devices were effective in capturing a significant quantity of aerosol test agent, these findings suggest that routine testing of the PHEAF device should be conducted to validate performance.     

A leak quantification method using sulfur hexafluoride as tracer gas

Filter holders and continuous air monitors are used extensively in the nuclear industry. It is important to minimize leakage in these devices, and, in recognition of this consideration, a limit on leakage for sampling systems is specified in; however, the protocol given in the standard is really germane to measurement of significant leakage, e.g., several percent of the sampling flow rate. In the present study, we developed a technique for quantifying leakage and used that approach to measure the sealing integrity of a continuous air monitor and two kinds of filter holders. The methodology involves use of sulfur hexafluoride as a tracer gas with the device being tested operated under dynamic flow conditions. The leak rates in these devices were determined in the pressure range from 2.49 kPa (10 inches H2O) vacuum to 2.49 kPa (10 inches H2O) pressure at a flow rate of 56.6 L min-1 (2 cfm). For the two filter holders, the leak rates were less than 0.007% of the nominal flow rate. The leak rate in the continuous air monitors was less than 0.2% of the nominal flow rate. These values are well within the limit prescribed in the ANSI standard, which is 5% of the nominal flow rate. We suggest that the limit listed in the ANSI standard should be reconsidered as lower values can be achieved, and the methodology presented herein can be used to quantify lower leakage values in sample collectors and analyzers.     

Evaluating and mapping of spatial air ion quality patterns in a residential garden using a geostatistic method

Negative air ions (NAI) produce biochemical reactions that increase the levels of the mood chemical serotonin in the environment. Moreover, they benefit both the psychological well being and the human body's physiological condition. The aim of this research was to estimate and measure the spatial distributions of negative and positive air ions in a residential garden in central Taiwan. Negative and positive air ions were measured at thirty monitoring locations in the study garden from July 2009 to June 2010. Moreover, Kriging was applied to estimate the spatial distribution of negative and positive air ions, as well as the air ion index in the study area. The measurement results showed that the numbers of NAI and PAI differed greatly during the four seasons, the highest and the lowest negative and positive air ion concentrations were found in the summer and winter, respectively. Moreover, temperature was positively affected negative air ions concentration. No matter what temperature is, the ranges of variogram in NAI/PAI were similar during four seasons. It indicated that spatial patterns of NAI/PAI were independent of the seasons and depended on garden elements and configuration, thus the NAP/PAI was a good estimate of the air quality regarding air ions. Kriging maps depicted that the highest negative and positive air ion concentration was next to the waterfall, whereas the lowest air ions areas were next to the exits of the garden. The results reveal that waterscapes are a source of negative and positive air ions, and that plants and green space are a minor source of negative air ions in the study garden. Moreover, temperature and humidity are positively and negatively affected negative air ions concentration, respectively. The proposed monitoring and mapping approach provides a way to effectively assess the patterns of negative and positive air ions in future landscape design projects.     

Electrets to measure ion concentration in air

Positive and negative ions are produced in air, mainly due to radon and terrestrial/cosmic radiation sources. Measuring ion concentration in air indirectly provides a measure of these sources. Electrets (electrically charged pieces of Teflon), when exposed in the environment, collect ions of opposite sign leading to a measurable decrease in charge, depending upon the exposure time and ion concentration. This work describes a method of correlating electret discharge rate to the ion concentration as measured by a calibrated ion density meter. Once calibrated, electrets can then be used to measure ion concentration of either sign. The ion concentration in ambient air was measured to be about 200 ions mL(-1), measured over several hours. Both positive and negative ion concentrations were similar. In a typical room, negative ion concentration was about 3,500 ions mL(-1), and, surprisingly, there were no positive ions at all in that room. Being an integrating passive device, the method provides the unique possibility of measuring low or high concentrations of positive or negative ions over extended periods, which is difficult to do with other ion concentration measuring instruments.     

Mathematical model of the air sterilization process

The mathematical model of the air sterilization process is proposed. The model describes nonstationary temperature fields for a sterilizing agent and objects under sterilization in devices of the chamber type. It is useful in studying the effects of control factors on the sterilization process, in calculating optimum charges for air sterilizers, and in developing automated systems to handle the operating process of the air sterilization.     

医院供气设备无线监控系统的设计

本文介绍了医院供气设备的无线监控系统设计。该系统通过无线方式捕获各个供气设备的当前状态,及时发现故障并通知职守人员。该系统中主要有3个供气设备,分别是:正压空气,正压氧气和负压吸引。系统将三个设备的输出压力通过A/D转换转变为数字信号,通过无线收发器实时的监测设备运转情况。该系统很容易扩展为监测更多设备的通用型数据采集系统,为医院设备维护实现自动化提供了一种解决方案。     

A method to assess the proportion of treatment effect explained by a surrogate endpoint.

Randomized clinical trials are the standard for evaluating new drugs, devices and procedures. Traditional clinical trials entail not only considerable expense, but require considerable time to complete. The use of surrogate endpoints constitutes an effort to control cost and completion time for clinical trials. We propose a method to quantify the proportion of treatment effect explained by a surrogate endpoint based on a general model setting which includes the commonly used linear, logistic and Cox regression models. The interpretation of this quantitative measure is facilitated by graphical displays. To reduce the variability associated with the estimate, a meta-analytic approach is proposed based on random effects models. An example using real clinical trial data is given to illustrate the proposed procedures.     

Characteristics of pesticide pyrotechnic smoke devices

Pesticide smoke generating products are widely used by amateurs and professionals but there is little published information available about their burn and deposition characteristics to enable the risks associated with using these devices to be assessed. This paper investigates their burn characteristics, deposition patterns, pesticide air concentrations and potential exposure to operators. Thirteen firings were carried out in different spaces with different ventilation conditions. Three types of devices were investigated: dicloran, permethrin and red dye. Pesticide air concentrations increased after firing, reaching a maximum determined by the room volume in approximately 10 min and decreasing exponentially as a result of ventilation and deposition. Ejected pesticide was present in the aerosol phase but there were only occasional traces of vapour. Settlement of pesticide was affected by surface orientation, height, sampling material and the pesticide-to-space volume ratio. The manufacturer's recommended treatment period for dicloran of 4 h followed by half an hour of ventilation may be insufficient to reduce pesticide to safe levels for re-entry under very calm conditions.     

Formaldehyde: a comparative evaluation of four monitoring methods

The performances of four formaldehyde monitoring devices were compared in a series of laboratory and field experiments. The devices evaluated included the DuPont C-60 formaldehyde badge, the SKC impregnated charcoal tube, an impinger/polarographic method and the MDA Lion formaldemeter. The major evaluation parameters included: concentration range, effects of humidity, sample storage, air velocity, accuracy, precision, interferences from methanol, styrene, 1,3-butadiene, sulfur dioxide and dimethylamine. Based on favorable performances in the laboratory and field, each device was useful for monitoring formaldehyde in the industrial work environment; however, these devices were not evaluated for residential exposure assessment. The impinger/polarographic method had a sensitivity of 0.06 ppm, based on a 20-liter air sample volume, and accurately determined the short-term excursion limit (STEL). It was useful for area monitoring but was not very practical for time-weighted average (TWA) personal monitoring measurements. The DuPont badge had a sensitivity of 2.8 ppm-hr and accurately and simply determined TWA exposures. It was not sensitive enough to measure STEL exposures, however, and positive interferences resulted if 1,3-butadiene was present. The SKC impregnated charcoal tube measured both TWA and STEL concentrations and had a sensitivity of 0.06 ppm based on a 25-liter air sample volume. Lightweight and simple to use, the MDA Lion formaldemeter had a sensitivity of 0.2 ppm. It had the advantage of giving an instantaneous reading in the field; however, it must be used with caution because it responded to many interferences. The method of choice depended on the type of sampling required, field conditions encountered during sampling and an understanding of the limitations of each monitoring device.     

Are smokers'' self-reports of inhalation a useful measure of smoke exposure.

The relation between self-assessed and objective measures of inhalation was studied in 75 smokers who assigned themselves to one of four inhalation categories, and also estimated inhalation using a rating scale. The analysis of presmoking carbon monoxide concentration in expired air, and of the rise in carbon monoxide concentration over smoking, provided an objective measure of inhalation. These was a weak but significant correlation between self-rated inhalation and rise in carbon monoxide, but no correlation with the longer-term exposure measured by presmoking levels of carbon monoxide. Differences in exposure to carbon monoxide according to self-assessed inhalation category were non-significant. It is concluded that neither subjective measure of inhalation contributes usefully to the estimation of smoke exposure among smokers who inhale.     

A review of assigned protection factors of various types and classes of respiratory protective equipment with reference to their measured breathing resistances

The British Standards Institution 'Guide to implementing an effective respiratory protective device programme' (BS 4275) lists assigned protection factors (APFs) for various types of respiratory protective equipment (RPE). The APFs were allocated either on the basis of available workplace studies data which met set criteria or on the basis of professional judgement that there is equivalence between its operation and that of a device for which an APF is derived from workplace data. However, in many cases no workplace study information exists to support this professional judgement. As an interim measure, pending information based on workplace measurements, the breathing resistance of a range of tight-fitting RPE from negative pressure filtering devices through to self-contained positive pressure breathing apparatus was measured at various breathing rates. The relative inhalation resistances were then compared on the assumption that similar breathing resistance performance is likely to give similar inward leakage on a facepiece and hence similar protection if all other factors, such as fit, etc., are equal. This work indicates that for most devices the allocation of APFs by analogy to other devices seems to be acceptable. However, there appears to be no justification for the allocation of an APF value of 100 to continuous flow compressed air line breathing apparatus. It is recommended that it should be lowered to 40 until there is valid workplace study data to support the current APF of 100. The work provides an informative insight into the relative performance of devices.     

农村改厕中参与式健康教育的探讨

动员群众改厕和培养其正确使用卫生厕所的行为习惯是改厕健康教育的基本职能 ,本文在对此进行分析的基础上 ,探讨了几种参与式健康教育方法     

工作场所空气中氟化氢的离子色谱测定法

目的建立工作场所空气中氟化氢的离子色谱测定方法。方法根据《工作场所有害物质监测的采样规范》(GBZ159-2004)进行采样,3.6 mmol/L的Na2CO3溶液作淋洗液和采样吸收液,使用SI-524E色谱柱和SI-90G保护柱进行离子色谱法(电导检测器)测定。结果在0.05~2.0 mg/L的范围内呈线性关系,相关系数r=0.9998;检出限为0.005 mg/L;样品加标回收率为98%~103%,精密度为1.2%。该方法能简便、快捷有效地测定空气中的氟化氢浓度。结论该方法采样简单、操作快捷、准确度精密度好,适合于工作场所空气中大批量氟化氢样品的测定。     

CT检查中的过度使用研究

目的，证实并定量分析大型医用设备利用中的过度使用情况，为制定医疗保险政策和CT配置规划提供参考。方法：使用前瞻性的Expert Panel方法对利用CT的患者进行适宜性评价，得到过度使用的水平，使用Logistic和Probit模型对影响过度使用的因素进行分析。结果：研究证实在利用CT的患者中有一定比例的利用是不必要的，占总量的16．3％，计量分析结果表明，影响过度使用的主要原因是医疗机构和医疗保险因素。前瞻性的同行专家评的结果显示，在CT利用中有一部分可以使用其他普通的检查来替代而不影响诊断质量。结论：诱导需求和道德损害存在于大型医用设备的利用中，必须采取措施减少不必要的检查，防止卫生资源的浪费。     

Passive, integrated measurement of indoor radon using activated carbon

Activated carbon canisters were tested to determine their adsorption and retention characteristics for radon. Our tests conducted indoors under typical conditions of temperature and relative humidity indicate that simple, inexpensive and maintenance-free passive devices containing 150-200 g of activated carbon can measure radon conveniently and adequately. The amount of radon absorbed in the collector is determined by counting the gamma rays from the decay products of radon. The lower limit of detection for radon is 0.2 pCi/l. for an exposure of 72 hr. Greater sensitivity can be obtained with larger counting systems and devices containing carbon with more surface area. Tests in a residential building and in a test chamber indicate that the measured radon in the canister is proportional to the mean concentration of radon during the period of exposure when correction for relative humidity is made. For practical situations encountered indoors, the device yields results accurate to within +/- 20%. Results from field measurements indicate that the use of the device is feasible.     

New technologies in the use of exhaled breath analysis for biological monitoring

Breath analysis is an attractive non-invasive procedure for screening workers exposed to solvents. It has been used in numerous laboratory based studies and for field research. Despite the obvious advantages in routine biological monitoring it has failed to become widely accepted as a tool in occupational hygiene. Recent advances in breath sampling and analysis are such that it is likely to become more widely used in the future. In this paper, the past 5 years have been reviewed to try to assess what developments might now contribute to the increased use of breath analysis in biological monitoring; in particular, the development of a selected ion flow tube mass spectrometer for real time direct analysis of trace gases in breath and the more immediately available and less expensive indirect methods involving collection devices with adsorbent tubes is important. The introduction of guidance values for biological monitoring with clear advice on sampling times and the recognition of the importance of quality assurance programmes will help improve confidence in the technique.

 

     

Validation of the sterilization procedure of medical and hospital devices according to different packaging types

Safety in the processing of medical and hospital devices in healthcare organizations is an important measure of nosocomial infection control. This investigation aimed at establishing the period during which it is safe to use medical and hospital articles processed through sterilization by saturated steam under pressure using different types of packaging at a private hospital. The methodological procedure consisted of four phases: preparation of articles, evaluation of autoclave functioning, sterilization cycle and microbiological tests. Results showed bacterial growth on articles packed in surgical grade paper with and without film on the 21st day, in crepe paper on the 90th day and absence of growth when raw cotton packaging was used. In face of the results, a 21-day period was established for the use of articles after sterilization by saturated steam under pressure regardless of the type of packaging utilized, considering that storage conditions were also evaluated.     

An evaluation of the effectiveness of a recirculating laboratory hood

Ductless, benchtop hoods have become a popular tool for use in the control of toxic substances in the laboratory. Low price and ease of installation are major factors contributing to their increased utilization. Little objective performance data exist for these devices. One such hood was evaluated for efficacy as an engineering control in typical laboratory applications. Face velocity, flow profile, ability to retain vapors, sorptive capacity of the filter media and overall worker protection were evaluated. The manufacturer's report of an average face velocity of 30.6 cm/s (60 fpm) proved to be accurate; however, this value was found to be substandard when compared with the hood and room design criteria which must be met for this rate to provide adequate control. The hood was designed in a manner which prevented smooth flow through the hood and increased observed turbulence and rolling. The sorptive capacity of the carbon filter proved to be comparable to that reported for organic vapor respirator cartridges. Design deficiencies are discussed to improve protection offered to the worker in an as-used situation. Further work is needed to provide a quantitative measure of the protection offered by these hoods.