不同水模体直径和不同重建层厚对CT图像噪声的影响

目的 研究不同水模体直径和重建层厚等因素对CT图像噪声的影响，探讨CT质量控制检测中水模体合理的直径范围，为完善我国CT质量控制检测规范提供数据支持。方法 采用GE公司的Revolution型CT机，在两档剂量水平，即CTDI_W分别为30.20 mGy（120 kV、200 mAs）和49.82 mGy（120 kV、330 mAs）、图像重建层厚为5 mm和10 mm的条件下，分别对直径为16、18、20、22、24 cm的圆柱型均质水模体轴向扫描一圈，测量其CT值（水）和噪声等指标。比较不同水模体直径、不同层厚和不同剂量等条件下噪声测量值的差异。结果 噪声测量值随水模体直径增大而增大，随剂量增大而减小，在大小两档剂量水平下水模体直径分别为24、22 cm时的噪声值已超过现有检测标准；噪声随重建层厚的增大而减小。结论 噪声的测量结果与剂量、水模体直径、重建层厚等因素有关，在进行CT质量控制噪声项目的检测时，需规定所选择的剂量水平和层厚大小，并规定所选择水模体的直径大小。本研究结果提示CTDI_W在接近50 mGy的条件下，18~22 cm可能是比较合理的水模体直径范围。     

低kV-CT扫描在肺结节检查中的应用研究

目的探讨70 kV管电压扫描在体质量指数(BMI)≤22 kg/m~2患者肺结节检查中的应用价值。方法选取经常规CT扫描(120 kV)确诊的肺结节患者62例,1周后行70 kV扫描,所得图像分别行1 mm、2 mm重建,并按结节直径≤5mm、6~10 mm和10 mm分组,记录各组结节数目、边缘、内部特征、周围改变情况、射线剂量指数(CTDI)、计量长度乘积(DLP)、有效辐射剂量(ED)。结果 70 kV组与120 kV组扫描,层厚2 mm时,直径5 mm结节检出数目及结节边缘、内部特征以及周围改变情况比较,差异无统计学意义(P0.05);70 kV组同120 kV组相比,CTDI、DLP及ED分别降低了约65%、71%、71%,差异有统计学意义(P0.05)。结论对于BMI≤22 kg/m~2患者,70 kV管电压扫描条件下,2 mm层厚对于直径5 mm肺结节能做出准确评价,同时辐射剂量明显降低。     

螺旋CT最佳图像密度分辨力时扫描参数的研究

目的分析不同扫描参数对图像质量及密度分辨力的影响,研究螺旋CT在最佳密度分辨力时的扫描参数。结果改变扫描参数,图像质量及图像密度分辨力均有改变,并呈现一定规律的变化。对于10mm层厚、400mm重建显示视野,使用512×512重建矩阵,平滑重建算法时,最佳密度分辨力时的扫描参数为375mAs@100kV、300mAs@120kV3、00mAs@140kV。结论不同群体的肝脏病人平扫的临床最佳扫描参数:对于10mm层厚、400mm重建显示视野,使用512×512重建矩阵,平滑重建算法时,375mAs@100kV适合于偏瘦体型(体重55公斤以下)的成人患者,300mAs@120kV适合中型身材(体重55公斤-70公斤)的成人患者,300mAs@140kV适合偏胖体型(体重70公斤以上)的成人患者。     

多层螺旋CT盆腔扫描重建图像质量与X射线剂量的关系

目的分析扫描参数的设置与图像质量和吸收剂量之间的关系,选择适合于二维和三维重建较高图像质量和较低吸收剂量的扫描方式。方法使用GE L ightspeed U ltra 16层螺旋CT机,对人体盆腔模型进行扫描。扫描条件:120 kV,管电流分别为250 mA或200 mA,螺距分别为1.375或0.985,层厚分别为5 mm或7.5 mm。评价二维和三维图像质量,在辐射剂量观测栏,观测剂量长度乘积(DLP)的变化。选择其中图像质量较好和DLP相对较低的4种扫描方式对患者进行扫描。结果DLP随管电流的增加、螺距的减小而增大,而二维和三维图像质量也随mA的增加、螺距的减小而提高。二维图像选择250 mA、1.375螺距、7.5 mm层厚,图像噪声低,影像细节能清晰显示,且DLP相对较低;三维图像选择200 mA、0.938螺距、7.5 mm层厚,能够满足诊断需要。结论遵循医疗照射的正当性和防护最优化原则,科学地设置管电流、层厚、螺距等扫描参数,一方面能够保证二维和三维图像质量,另一方面又能减少DLP值,减少X射线辐射对盆腔生殖器官的损伤。     

脑磁共振扩散张量成像最佳扫描参数的优选

目的探讨脑磁共振扩散张量成像(DTI)的最佳扫描参数。方法对30例成年健康志愿者行脑DTI扫描,比较不同扫描参数[扩散敏感方向数(NDGD)、扩散敏感系数(b)值和层厚/层间距]对图像质量的影响。随机分为三组:NDGD组改变NDGD(6、15、25个),b值为1000 s/mm2,层厚/层间距为5/0 mm;b值组改变b值(500、1000、3000 s/mm2),15个NDGD,层厚/层间距为5/0 mm;层厚/层间距组改变层厚/层间距(8/2、5/0、3/0 mm),15个NDGD,b值为1000 s/mm2。由两名高年资放射科医师采用双盲法对图像质量进行评分并进行统计学分析。结果 25个NDGD时图像质量评分最高[(2.83±0.38)分],与15个NDGD[(2.67±0.51)分]和6个NDGD[(2.17±0.43)分]时比较,差异具有统计学意义(P<0.05)。b值为1000 s/mm2时图像质量评分最高[(2.67±0.49)分],与b值为500 s/mm2[(2.50±0.56)分]时比较,差异无统计学意义(P>0.05),与b值为3000 s/mm2[(2.06±0.55)分]时比较,差异有统计学意义(P<0.05)。层厚/层间距为8/2 mm和5/0 mm时图像质量评分较高,差异无统计学意义[(2.67±0.54)分vs(2.61±0.42)分,P>0.05],与3/0 mm[(1.94±0.35)分]时比较,差异有统计学意义(P<0.05)。结论 25个NDGD,b值为1000 s/mm2,层厚/层间距为5/0 mm时所获得的图像信噪比较高,脑灰、白质对比度较佳,有利于脑白质的细微结构研究,是脑DTI最佳扫描参数。     

TECHNICARE 2060CT机扫描架部分故障检修

故障现象扫描时，选5mm和2mm薄层参数都能正常工作。当选10mm层厚扫描时，按下“ScanStart”键，开始扫描键里的灯一直闪动不停，控制台监视器提示：“Collimatoractiondonotstable，waitfor2.5minute”，2．5分钟后还不能稳定，从而夭折扫描，重新开机后，有时可扫一、二层。故障分析与检修由于5mm和2mm薄层扫描正常，仅10mm层厚扫描时不正常，而监视器提示准直器在2．5分钟后不稳定，分析是10mm层厚准直器控制有故障，而此电路在扫描架T1板中。从开机时有一、二层正常分析，估计有接触不良故障，拔下T1板，清洗该板上接点后，重新开机，…     

PHILIPS大孔径CT模拟机层敏感度曲线的测试研究

对Phihps AcQSim CT模拟机,采用头部螺旋扫描模式和CT质控体模,分别以螺距(pitch)=0.5、0.8、1.0、1.3、2.0,扫描层厚2mm(标称值)进行扫描和重建,测试和评价螺旋CT模拟机的层敏感度曲线(SSP)及半高宽(FWHM)。对于标称层厚2mm,不同pitch时测试得到的FWHM(有效层厚)均大于标称层厚。测试的SSP形状近似呈高斯分布形状。pitch的变化对SSP、有效层厚有一定影响。本研究结果有助于临床应用中优化CT扫描方案,从而为实现"三精"放射治疗提供技术支持。     

放疗定位扫描条件对CT值的影响

目的 探讨放疗定位时不同扫描条件对CT值的影响程度。方法 对CIRS 062型电子密度体模在不同扫描条件下分别进行CT扫描并测定其CT值,评价和分析管电流、管电压、层厚、螺距、图像重建算法、扫描床面高度、扫描序列的改变对CT值的影响程度。结果 管电流、层厚、螺距的改变对CT值的影响基本可以忽略(<1%)。管电压、图像重建算法的改变对高密度组织如密质骨的影响较为显著,对低密度组织的影响则不明显。扫描床面高度及扫描序列的改变对不同密度组织的CT值均有不同程度的影响。结论 CT扫描参数和定位条件的差异可能会使某一组织重建影像的CT值发生改变,值得临床参考。     

女性胸部多层CT扫描X射线辐射对乳腺损伤的研究

目的探讨女性胸部CT扫描时,X射线辐射对乳腺的损伤。方法38例女性患者,使用GE LightspeedUltra16层CT机,电压120kV,电流分别选择150mA、200mA、250mA,螺距0.938或1.375。计算每例胸部扫描层数和乳腺所占的层数;从扫描程序设置栏,记录胸部剂量长度积(DLP),并依此计算出乳腺DLP。分析mA、层厚、螺距对患者吸收剂量的影响。结果38例中,胸部平扫层数19~33层,乳腺扫描层数7~16层,乳腺扫描层数和DLP占胸部扫描层数和DLP的27.59%~66.66%。扫描相同范围内,选择不同毫安和螺距对DLP影响较大。结论中等体型女性选择150mA,1.375螺距,7.5mm层厚,能够充分保证图像质量,且DLP相对较低,同时充分利用该机软件功能进行不同方式的重建,图像质量也良好。科学地选择螺距、扫描层数、层厚、mA等参数,能够达到减少患者乳腺接受X射线剂量的目的。     

基于MAGNETOM Skyra型磁共振（MRI）设备影像质量测试和分析

目的 探讨检测磁共振影像质量指标的过程,建立磁共振设备影像质量指标的基线值,为完善国家相关标准提供一定的依据。方法 依据国内外现行标准的测试条件,借助SMR 170磁共振影像质量控制模体对新安装的MAGNETOM Skyra型磁共振的信噪比、影像均匀性、层厚、层厚非均匀性、空间分辨力、几何畸变率、低对比度分辨力、共振频率、纵横比等指标进行测试,得到对应的各项指标的基线值,并结合相关材料,探讨影响磁共振影像质量检测的情况。结果 采集图像使用自旋回波序列（SE）、头部线圈、脉冲回波时间为20 ms、脉冲恢复时间为250 ms、视野（FOV）为250 mm×250 mm、采集2次的设置条件,预设层厚分别为5 mm、8 mm和10 mm：测量层厚和非均匀性分别为5.2 mm/1.3%、8.3 mm/2.0%和10.4 mm/3.2%;信噪比和图像均匀性在矩阵为256 mm×256 mm时的结果分别是103.2/98.3%、105.6/96.0%和110.2/96.4%,信噪比在矩阵为512 mm×512 mm时的测量结果分别是102.6、104.8和106.2;空间分辨力在矩阵为256 mm×256 mm时均为1 mm,矩阵为512 mm×512 mm时为0.556 mm、0.556 mm和0.5 mm;低对比度分辨力均为可分辨直径4 mm、孔深0.5 mm的圆孔。几何畸变率在孔径间距为20 mm、40 mm、80 mm和100 mm处的测量结果分别为20.0 mm、40.3 mm、80.5 mm和100.8 mm。结论 应用SMR 170模体检测该型磁共振影像指标的参数设置和建立的基线值可为后续状态检测提供一定的依据;完善MRI影像质量检测指标,研发配套MRI影像质量测试模体,更新相关标准是今后MRI质量控制工作中的重点。     

Calcium intake in the elderly: validation of a dietary questionnaire

Epidemiological studies of calcium and osteoporosis have been hampered by the lack of a suitable tool for assessing calcium intake. This report describes a new frequency and amount questionnaire for measuring present and past calcium intake in the elderly. The validity of the questionnaire was tested against two commonly used standards of dietary assessment, five-day duplicate diets and seven-day weighed dietary inventories. The resulting correlation coefficients were, respectively, r = 0.76 and r = 0.69, while that for repeatability was r = 0.84. Furthermore, the questionnaire categorized subjects into thirds of the distribution of intake with almost no gross misclassification. It is suggested that the present findings may be extended to the majority of normal, healthy elderly subjects, implying wide application for the questionnaire in the assessment of calcium intake in the elderly.     

The human drama of genetics: 'hard' and 'soft' media representations of inherited breast cancer

This paper examines media coverage of 'breast cancer genetics', and explores its implications for public understanding. We present a content analysis of coverage in British newspapers and look at a variety of popular forms, including women's magazines, television soap opera and radio drama. Genetic/inherited risk receives a great deal of coverage across a wide range of media formats and outlets. Much of this attention has focused on individuals from 'high risk families' and dilemmas around prophylactic mastectomies. Through examining media coverage, combined with interviews with media personnel and their sources, we show why this story proved so attractive to the media and highlight the different production values which influence coverage. Finally, we introduce preliminary findings from focus group discussions to demonstrate how such 'human interest' framing has engaged audience attention and influenced public understandings. The paper concludes by highlighting the implications for analysing, predicting, and engaging with, media representations of science.     

Worker education in the primary prevention of occupational dermatoses

This paper reports the evaluation of a skin care education programmeconducted on a fine chemicals manufacturing site where over1,000 employees are located. Approximately 60% are involvedin chemical manufacture. Over a 12 month period production staffreceived training in prevention of occupational dermatoses linkedto a site-wide poster initiative. The incidence of new casesof occupational dermatoses fell from 0.055 (70 cases in 1,277employees) to 0.021 (27 cases in 1,277 employees) before andafter the intervention respectively (p<0.0001). After otherfactors such as chemicals handled, observer bias and changesin reporting related to socioeconomic climate were taken intoaccount it is concluded that this study demonstrates the importanceof worker education as a tool for primary prevention of disease.Training materials such as video and poster presentations maybe effectively used in the chemical manufacturing industry asan adjunct to prevention and control of exposure to substanceshazardous to the skin. Such methods may also be used in otherindustries where there are significant risks of dermatoses.     

Regional Variation in Travel-related Illness acquired in Africa,March 1997–May 2011

To understand geographic variation in travel-related illness acquired in distinct African regions, we used the GeoSentinel Surveillance Network database to analyze records for 16,893 ill travelers returning from Africa over a 14-year period. Travelers to northern Africa most commonly reported gastrointestinal illnesses and dog bites. Febrile illnesses were more common in travelers returning from sub-Saharan countries. Eleven travelers died, 9 of malaria; these deaths occurred mainly among male business travelers to sub-Saharan Africa. The profile of illness varied substantially by region: malaria predominated in travelers returning from Central and Western Africa; schistosomiasis, strongyloidiasis, and dengue from Eastern and Western Africa; and loaisis from Central Africa. There were few reports of vaccine-preventable infections, HIV infection, and tuberculosis. Geographic profiling of illness acquired during travel to Africa guides targeted pretravel advice, expedites diagnosis in ill returning travelers, and may influence destination choices in tourism.     

Self-reported health problems among Swedish miners one year after unemployment

Unemployment is considered to be a public health concern sincedeterioration in the health of the unemployed is often anticipated.However, for some groups, such as miners, unemployment mightimprove health due to a cessation of potentially harmful occupationalexposures. This study evaluates the health of 79 miners in oneSwedish iron-ore mine, and 226 age-matched controls from thegeneral population, during one year after the closure of themine. The participants received a questionnaire regarding medicalhistory and subjective symptoms at the beginning of the studyperiod, and after one year. Statistically significant negativeeffects on self-reported health attributable to unemploymentwere not found, although neuropsychiatric symptoms were morecommon among the unemployed miners. The miners reported a statisticallysignificant improvement in grip force (p=0.031). They had asignificantly higher prevalence of symptoms associated withmining related exposures when compared with the population controls;pain in the upper extremities [relative risk (RR)=2.27, 95%confidence interval (Cl)=1.44–3.59), back pain (RR=1.84;Cl=1.237–2.75), vasospastic disease of the fingers (RR=2.05;Cl=1.18–3.57) and obstructive respiratory symptoms (attacksof dyspnea and wheezing: RR=3.67; Cl=1.167–11.6).     

Excès de cas humains et animaux de tularémie en France au cours de l’hiver 2007–2008 : émergence ou phénomène isolé ?

Context

Tularemia is a zoonosis affecting humans and hares in France. We describe the results of surveillance in both species, in 2007 and 2008.

Methods

Human tularemia cases are mandatorily notifiable in France since 2003. In hares, surveillance relies on volunteer hunter associations in all districts of the country. Data from mandatory reports and volunteer surveillance in 2007/2008 were analyzed and compared with previous results.

Results

In 2007/2008, 144 cases were reported in humans and 117 cases in hares. This was a 100% increase compared to previous years. Human cases differed from those of previous years only by the frequency of contact with breeding animals. Human cases without any documented risk exposure were also more frequent.

Conclusion

An increase of tularemia cases occurred in 2007/2008 in both species. Complementary studies are needed to identify the species reservoir in France to understand the causes of this peak of cases.     

深圳公立医院管理体制改革制度设计

深圳公立医院管理体制改革实行政事分开、管办分开,在理事会架构下按法定机构模式组建市医管中心,落实公立医院运营管理自主权.作者从当前公立医院管理体制的弊端入手,介绍了深圳市进行公立医院管理体制改革的基本思路及改革方案设计的主要举措,深入剖析了的改革方案的特点,并对改革效果进行了预测.     

Effects of nitrogen dioxide on red blood cells of rats: Changes in components of red cell membranes during in vivo exposure to NO2

Red cell membranes, prepared from red blood cells of rats exposed to 4, 10, or 20 ppm nitrogen dioxide (NO₂) for 1 to 10 days, were examined for evidence of changes in membrane components. Appreciable changes were not found in contents of phospholipid and cholesterol during exposure to 10 ppm NO₂. By contrast, protein content altered with the time of exposure. Moreover, changes in protein composition were observed by employing sodium dodecyl sulfate — polyacrylamide gel electrophoresis. Twenty-four-hour exposure to NO₂ at the concentration above 10 ppm resulted in a marked increase in the percentage of lysophosphatidylethanolamine (LysoPE) to the total phospholipids. The prolonged exposure to 10 ppm NO₂ gave rise to a further increase in LysoPE, whereas the percentage of phosphatidylethanolamine (PE) showed a gradual decrease. A 1-day exposure to 4.0 ppm NO₂ also caused an increase in sialic acid content and decreases in those of PE and hexose. In addition to contents of these components the percentage of LysoPE increased 5 days after exposure and the elevated values were maintained up to the end of exposure period. These results demonstrate that red blood cells in circulation exhibit different membrane properties in terms of lipid and carbohydrate composition during 10 days of exposure to 4.0 ppm NO₂.     

The design of hazard risk assessment matrices for ranking occupational health risks and their application in mining and minerals processing

Two hazard risk assessment matrices for the ranking of occupational health risks are described. The qualitative matrix uses qualitative measures of probability and consequence to determine risk assessment codes for hazard-disease combinations. A walk-through survey of an underground metalliferous mine and concentrator is used to demonstrate how the qualitative matrix can be applied to determine priorities for the control of occupational health hazards. The semi-quantitative matrix uses attributable risk as a quantitative measure of probability and uses qualitative measures of consequence. A practical application of this matrix is the determination of occupational health priorities using existing epidemiological studies. Calculated attributable risks from epidemiological studies of hazard-disease combinations in mining and minerals processing are used as examples. These historic response data do not reflect the risks associated with current exposures. A method using current exposure data, known exposure-response relationships and the semi-quantitative matrix is proposed for more accurate and current risk rankings.