探讨符合线路SPECT/CT的日常质量控制与质量保证

目的:分析带符合线路双探头SPECT/CT系统的日常质量控制与质量保证措施。方法:定期检测仪器能峰、能量分辨率和探头固有均匀性等日常质量控制和校正,以及CT日常质量控制,制定硬件保养方法及规程。结果:常规的日常硬件保养,减少了仪器故障发生率,仪器能峰、能量分辨率保持稳定,探头固有均匀性需要定期校正,校正前后1号探头均匀性(%)分别为2.71±0.28、2.37±0.11,2号探头均匀性(%)分别为2.68±0.12、2.38±0.19,差异有统计学意义(P<0.05)。结论:定期对仪器的质量控制与保养,可保证仪器性能稳定,提高设备使用效率。     

应用SPECT质控结果的统计分析评估设备

综合我科6年来APEX HELIX双探头SPECT的质控结果．对该系统的固有均匀性和固有能量分辨率两个质控指标进行统计分析．评估系统性能。统计分析结果表明．系统的两个探头校正后的两种质控指标较校正前都有显著性改善．提示系统校正性能良好：同时．通过系统质控校正后的均匀性和能峰．两个探头之间无显著性差异，提示系统双探头匹配良好。系统在一个较长时期内．工作性能稳定、设备运行良好．满足临床使用要求。     

西门子ZLC3700型E—CT探头系统校正问题研究

Ｅ—ＣＴ主要由探头系统、控制台以及计算机系统三部分组成,其中探头系统包括探头部分和信号处理部分。信号处理部分由１２块印刷电路板组成,根据其主要功能,用３个字母组成的助记符来区分它们。１２块电路板插在一块母板上,从左到右有光电倍增管、前置放大器、阀门放大器、电阻网络,还有温度传感电阻等等。如：ＳＤＤ板进行信号的求和以及二重微分放大,ＩＣＤ板进行积分与控制,ＣＤＤ板进行强度校正,ＡＩＡ板是高度分析器及自动稳定电路,ＯＤＡ板是定位与显示等等。探头性能的校正对Ｅ—ＣＴ的正常使用有着重要的意义,有些故障及…     

SPECT/CT新机安装调试及质控保养

目的通过对核医学仪器SPECT/CT的新机安装调试及日常质控保养过程的回顾,探讨其过程中的注意事项和方法经验,以利于新仪器进行顺利装机并快速地投入使用。方法 (1)安装前期规划和准备;(2)新仪器安装过程;(3)主要性能参数的检测校准;(4)技术培训和实际操作过程中的注意事项及细节。结果新仪器在两周内顺利完成安装调试及技术培训,各项主要性能参数指标合格并达到较理想状态。其中探头1、探头2的固有均匀性积分值CFOV为1.56%和1.78%,UFOV为1.85%和1.87%;探头1、探头2固有均匀性微分值CFOV为1.25%和1.43%,UFOV为1.25%和1.44%,探测器的均匀性非常理想,CT检测各项参数正常。结论在准备充分的情况下,可以在较短时间内完成新仪器装机调试并投入正常试运行,亦能快速地掌握新仪器的使用和质控保养方法。     

对SPECT均匀性的测试与校正

对ＳＰＥＣＴ均匀性的测试与校正北京友谊医院周铭娟在单光子发射型计算机断层（简称ＳＰＥＣＴ）的质量控制中，均匀性是一项十分重要的技术指标，它直接影响到临床图像的诊断质量。ＳＰＥＣＴ的均匀性是指一均匀泛源（ＦＬＯＯＤＳＯＵＲＣＥ）照射到探头（探头不装准直...     

GE NC100小C臂高压系统故障维修及调试

叙述了 GE NC100小 C臂高压系统的故障现象、检查分析、维修方法和对系统的调试校正.     

SPECT的质量控制

ＰＥＣＴ的质量控制部分为仪器本身的质量控制和图像采集与处理过程中的质量控制。１日常的质量控制主要有均匀性校正对于运动探头架作全身扫描的ＳＰＥＣＴ，有些还要做轨道扫描校正。质量控制优劣将直接影响图像采集的质量。随着电子元件的老化，机械结构变形，扫描轨道...     

西门子SPECT(E.CAM)仪"U-FLY"均匀性校正应用

通过对siemens“U-fkt”技术的分析与实践，评价其对仪器系统的作用。运行系统配置的基本测试程序，分别采用^99mTc和^57Co标准源．依指令顺序操作，对探头的非均匀性可进行有效校正，取得了满意结果。由于均匀性指标是影响临床图像质量最重要的一个因素，建议每日采集图像前进行该项测试。     

同位素仪器工作条件的调试与选择

同位素仪器用于临床检查之前,必须对其工作条件(如光电倍增管工作电压、准直器的探测区域、窗宽和放大倍数)进行调试和选择,才能使用。另一方面,同位素仪器经过一段时间使用或进行维修后,其电路参数会发生变化,这也需要对其工作条件重新进行调试和选择。这是保证同位素仪器处于正常工作状态的重要环节。本文介绍扫描仪、肾图仪、甲测仪和井型探测仪等同位素仪器工作条件的调试和选择。同位素仪器一般由探头、放大器、脉冲高度分析     

医用直线加速器机房定位激光灯的安装与调试

为了保证放射治疗精度和放射治疗体位准确,定位激光灯是放射治疗过程中通过体外标记来帮助治疗摆位并校正人体体位的一种必不可少的装置。本文主要是介绍医用直线加速器机房定位激光灯的安装与调试。     

Social class differences in coronary heart disease in middle-aged British men: implications for prevention

BACKGROUND: Though social class differences in coronary heart disease (CHD) are well recognized, few studies have assessed the effect of imprecision in social class assessment on the relationship or the overall contribution of social class to attributable CHD risk. METHODS: Prospective observational study of the relationship between occupational social class (assessed at baseline and after 20 years), major CHD (coronary death and non-fatal myocardial infarction) and all-cause mortality rates over 20 years among 5628 middle-aged British men with no previous evidence of CHD. RESULTS: The age-adjusted hazard of major CHD for manual men relative to non-manual men was 1.41 (95% CI: 1.21, 1.64) before correction and 1.50 (95% CI: 1.25, 1.79) after correction for imprecision of social class measurement. The imprecision-corrected estimate was attenuated to 1.28 (95% CI: 1.06, 1.54) after adjustment for the adult coronary risk factors (blood cholesterol, blood pressure, body mass index, cigarette smoking, alcohol, physical activity, and lung function) and to 1.20 (95% CI: 0.99, 1.45) following further adjustment for height. The population attributable risk fraction of major CHD for social class (manual versus non-manual) was 22% after correction for imprecision in social class, which was reduced to 14% after adjustment for the adult coronary risk factors, and 10% after further adjustment for height. Similar results were obtained for all-cause mortality. CONCLUSIONS: Even taking account of measurement imprecision, the contribution of social class to overall CHD risk is modest. Population-wide strategies to reduce major CHD risk factors are likely to have greater potential benefits for CHD prevention than strategies designed specifically to reduce social inequalities in CHD.     

Contribution of toxicokinetic modeling to the adjustment of exposure limits to unusual work schedules

This study compared two toxicokinetic approaches for determining correction factors to be applied to occupational exposure limits (ELs) for unusual exposure scenarios: a classic one-compartment toxicokinetic approach and the physiologically based toxicokinetic (PBTK) approach. The approaches were applied to three typical unusual exposure scenarios: four consecutive 10-hour workdays followed by 3 days of recovery; three consecutive 12-hour workdays followed by 4 days of recovery; and a 4/3 work schedule. Results indicate that use of an adjustment method for ELs based on contaminant toxicokinetics generates less protective correction factors (i.e., a smaller adjustment) than those obtained using the U.S. Occupational Safety and Health Administration approach, which is based on Haber's law. Among all scenarios tested, the highest adjustment required, resulting from the use of a toxicokinetic approach (PBTK or one-compartment), was for the 4/3 work schedule and for a contaminant with a half-life equal to 18 hours. In that case the ELs would need to be reduced by 26%. Based on previous work, the authors believe an adjustment based on a toxicokinetic approach is more realistic from a toxicological standpoint. Given the value of a substance's half-life, the use of the graphs of Hickey and Reist (developed from a one-compartment toxicokinetic model) is a rapid and reliable means of establishing the correction factor. However, this approach is limited to simple and repetitive scenarios. For more complex exposure scenarios, such as that corresponding to a 4/3 work schedule, a one-compartment model also can be developed for each of the needs. Finally, the use of PBTK models allows greater flexibility for adjusting ELs for novel work schedules.     

放疗模拟定位机在PICC导管异位中的应用

目的：探讨放疗模拟定位机在PICC导管异位中的应用价值。方法：将56例患者异位入颈外静脉、右心房、锁骨下静脉、腋静脉及头臂静脉的导管,在放疗模拟定位机下进行机下调管。正位后应用计算机的可视功能确定导管头端是否位于上腔静脉．记录正位后导管头端的位置及成功率。结果：56例导管异位患者中,除2例血管畸形者,正位成功率为85．2％。结论：放疗模拟定位机是一种实用、直观、简便、科学的用于PICC导管异位后正位的机器,值得临床推广。     

Using pseudo-data to correct for publication bias in meta-analysis

In many ways, adjustment for publication bias in meta-analysis parallels adjustment for ascertainment bias in genetic studies. We investigate a previously published simulation-based method for dealing with complex ascertainment bias and show that it can be modified for use in meta-analysis when publication bias is suspected. The method involves simulating sets of pseudo-data under the assumed model using guesses for the unknown parameters. The pseudo-data are subjected to the same selection criteria as are believed to have operated on the original data. A conditional likelihood is then used to estimate the adjusted values of the unknown parameters. This method is used to re-analyse a published meta-analysis of the effect of the MTHFR gene on homocysteine levels. Simulation studies show that the pseudo-data method is unbiased; they give an indication of the number of pseudo-data values required and suggest that a two-stage adjustment produces less variable estimates. This method can be thought of as an example of the selection model approach to publication bias correction. As the selection mechanism must be assumed, it is important to investigate the sensitivity of any conclusions to this assumption.     

Validation of a food frequency questionnaire by direct measurement of habitual ad libitum food intake

Food frequency questionnaires are commonly used to assess habitual food intake. Although food frequency questionnaires are known to produce measurement error, the amount of error and effectiveness of correction methods are poorly understood. Twelve men from the Baltimore, MD/Washington, DC, area consumed an ad libitum diet for 16 weeks during the spring of 2001. At the end of the study period, subjects reported their food intakes with a food frequency questionnaire (Block 98). During weeks 8 and 16, subjects were dosed with doubly labeled water and maintained physical activity logs. Absolute and relative macronutrient intakes were poorly predicted by the food frequency questionnaire. The application of a single, group mean energy adjustment (using doubly labeled water or physical activity) reduced the variance of carbohydrate intake and increased the variance of fat and protein intakes, but none significantly (p>0.05). Subject-specific energy adjustments reduced the variance for carbohydrate and protein intakes (p<0.05). Including a body weight adjustment reduced the variance in fat intake (p<0.05) when doubly labeled water was used to first correct energy intake. The application of correction methods based on energy expenditure and body weight can be used to reduce measurement error, improving the ability of the food frequency questionnaire to measure food intake.     

Genetic background comparison using distance‐based regression,with applications in population stratification evaluation and adjustment

Population stratification (PS) can lead to an inflated rate of false‐positive findings in genome‐wide association studies (GWAS). The commonly used approach of adjustment for a fixed number of principal components (PCs) could have a deleterious impact on power when selected PCs are equally distributed in cases and controls, or the adjustment of certain covariates, such as self‐identified ethnicity or recruitment center, already included in the association analyses, correctly maps to major axes of genetic heterogeneity. We propose a computationally efficient procedure, PC‐Finder, to identify a minimal set of PCs while permitting an effective correction for PS. A general pseudo F statistic, derived from a non‐parametric multivariate regression model, can be used to assess whether PS exists or has been adequately corrected by a set of selected PCs. Empirical data from two GWAS conducted as part of the Cancer Genetic Markers of Susceptibility (CGEMS) project demonstrate the application of the procedure. Furthermore, simulation studies show the power advantage of the proposed procedure in GWAS over currently used PS correction strategies, particularly when the PCs with substantial genetic variation are distributed similarly in cases and controls and therefore do not induce PS. Genet. Epidemiol. 33:432–441, 2009. © 2009 Wiley‐Liss, Inc.     

Utility of the affected sib pair method to detect linkage of a sex-linked dominant disease with a sex-linked recessive trait

Use of affected sib-pairs for linkage determination of a sex-linked dominant disease with a recessive X-chromosome marker will require extremely large sample sizes, particularly when the marker is marginally polymorphic. In addition, this method should not be used without caution on data collected for a traditional LOD score analysis, without considering the parental mating types involved in the informative families. Nevertheless, ascertainment adjustment and correction for dependence of multiple pairs of affected sib-pairs in families suggests that this method provides linkage inference concordant with that of the traditional LOD score analysis.     

The performance of methods for correcting measurement error in case-control studies

BACKGROUND: It is generally agreed that adjustment for measurement error (when feasible) can substantially increase the validity of epidemiologic analyses. Although a broad variety of methods for measurement error correction has been developed, application in practice is rare. One reason may be that little is known about the robustness of these methods against violations of their restrictive assumptions. METHODS: We carried out a simulation study to assess the performance of two error correction methods (a regression calibration method and a semiparametric approach) as compared with standard analyses without measurement error correction in case-control studies with internal validation data. Performance was assessed over a wide range of model parameters including varying degrees of violations of assumptions. RESULTS: In nearly all the settings assessed, the semiparametric estimate performed better than all alternatives under investigation. The regression calibration method is sensitive to violations of the assumptions of nondifferential error and small error variance. CONCLUSIONS: The semiparametric method is a very robust method to correct for measurement error in case-control studies, but lack of functional software hinders widespread use. If the assumptions for the regression calibration method are fulfilled, application of this method, originally developed for cohort studies, in case-control studies may be a useful alternative that is easy to implement.     

综合治疗儿童单纯肥胖症

以新医学模式对35例儿童单纯肥胖症采用以家庭为基础的饮食调整,运动疗法和行为指导综合治疗。并设单纯饮食治疗组和对照组。对体重、皮脂厚度和身高进行观测,疗程3个月。结果显示:综合治疗组明显优于单纯饮食治疗组,更优于对照组。并讨论了综合治疗的可行性和治疗效果的可靠性,以及新医学模式在肥胖症治疗中的重要作用。     

Interval estimation of the common odds ratio from k(2 x 2) tables under cluster sampling.

We propose a simple correction factor for the variance of the logarithm of the common odds ratio estimated by the method of Mantel and Haenszel from a series of (2 x 2) tables when data are cluster correlated. The adjustment is applied to the variance estimators proposed by Hauck and by Robins, Breslow and Greenland for the log of the Mantel-Haenszel common odds ratio, and its performance is evaluated in a simulation study. The key features of the proposed adjustment are: (i) it has closed-form; (ii) it can accommodate covariates defined at the cluster-specific level, the site-specific level, or both; and (iii) it does not require the user to specify a particular correlation structure for the response data. The correction derives from Liang and Zeger's generalized estimating equations (GEE) technique for logistic regression modelling. Via simulation, we examine empirical versus nominal coverage probabilities for interval estimation of the common odds ratio using adjusted and unadjusted variance estimates, and we present ratios of observed to estimated variances. Results are compared to those obtained from the fully iterated GEE analysis. The characteristics of the simulation study mimic scenarios common in the periodontal research setting, with small numbers of subjects (N = 25, 50), moderate numbers of sites per cluster (m = 4, 16, 32), and modest intracluster correlation levels (rho = 0.0, 0.1, 0.2, 0.3). Results show that adjusted confidence intervals (applied to the Hauck or the Robins, Breslow, Greenland variance estimate) provide coverage probabilities close to the nominal level for the Mantel--Haenszel common odds ratio over a variety of cluster sizes and levels of correlation.