Analysis of systematic and random error in MR volumetric flow measurements

The spatial aspects of error in 2D MR cine phase-velocity mapping are considered in order to define acquisition strategies which will minimize error in measuring volumetric flow. Error was separated into two categories: systematic and random. Potential sources of systematic error examined were intravoxel phase dispersion (IVPD), partial volume effects, misalignment of flow axis and flow-encoding gradients, and improper choice of vessel voxels for flux calculations. Random error was addressed using analysis of propagation of variance. Analytical expressions for sources of error were derived; and computer models were used to test the analytical models. Flow phantom studies examining error in MR volumetric flow measurements were performed and compared with error predicted by the analytical models. Expected error in several clinical situations of interest was then derived to find appropriate acquisition strategies. Spatial resolution, signal to noise ratio, velocity sensitivity and the ratio of the modulus of moving isochromats to that of static isochromats were found to be the most important parameters in controlling error and were found to cause competing effects with respect to systematic and random error.     

低压舱5000m高度上健康青年人心功能的观察

为探讨急性高空缺氧时心血管系统的变化规律，应用ＣＦ－Ⅱ型心血管功能检诊仪对８名男性青年进行低压舱５０００ｍ心功能观察。结果发现：脉率、心输出量、心脏指数、心肌耗氧量均为５０００ｍ高度上前１０ｍｉｎ呈增加趋势，１０ｍｉｎ时达最高。冠脉缺血阈值与上述指标相反，１０ｍｉｎ时为最低。     

Accuracy and precision study in vitro for peripheral quantitative computed tomography

We evaluated the accuracy and precision of a peripheral quantitative computed tomography (pQCT) scanner, the Stratec XCT-960, using 12 human cadaveric forearms. The accuracy was determined by comparing the total bone mineral content (BMC) with the ash weight (AW). We scanned and ashed three consecutive slices (thickness 2.5 mm) at the standard position (s-position) and at 2.5 mm both proximal and distal to the s-position. The correlation coefficient between the AW and total BMC using slices at the s-position wasr=0.87 with an accuracy error (random component) of 15.5%. The correlation coefficient using all slices wasr=0.90 with an accuracy error of 14.3%. The correlation coefficient improved tor=0.95 with an accuracy error of 9.7% after averaging the results of all three slices for each forearm. The short-term precision error expressed as the coefficient of variation (CV) of bone mineral density (BMD) and BMC was determined by measuring the forearms five times either with repositioning or without repositioning. The CVs with repositioning were 2.77 and 1.15 for total BMD and BMC, 1.85 for trabecular BMD; without repositioning they were 0.29, 0.58 and 0.69 respectively. To further evaluate the influence of positioning, additional scans were performed at 1, 2 and 5 mm proximal, and 1 and 2 mm distal to the s-position. BMD and BMC were greatly influenced by the scan location; for example, the percentage differences in trabecular BMD 1 mm distal and proximal relative to the s-position were 2.5%±5.1% and 0.18%±6.3%, respectively. The Stratec XCT-960 appears to be a moderately accurate and highly precise scanner with potential usefulness for evaluating BMC and BMD of ultradistal radius.     

The effect of sleeved arms on oscillometric blood pressure measurement

The authors measured the blood pressures of 36 subjects who had bare and sleeved arms to determine the effect of wearing sleeves on automatic oscillometric blood pressure measurements. They found no statistically significant effect of sleeves on the measurement of either systolic or diastolic blood pressure (p>0.15). However, based on confidence intervals of possible sleeve effects, the authors recommend repeating blood pressure measurements on bared arms when the sleeved-arm oscillometric measurements are at least 86 mm Hg diastolic or 135 mm Hg systolic. Presented in part at the annual meeting of the Society of General Internal Medicine, Seattle, Washington, May 1–3, 1991.     

New technique for right heart catheterization using a mullins' sheath

A new technique for right heart catheterization using a Muilins' sheath is described. This device allows a Swan-Ganz catheter to reach pulmonary artery position easily and permits simultaneous pressure recordings in right heart chambers, thus avoiding a double venous puncture and two catheters. This new technique, its indications, and our experience in 29 patients are described. It is most useful in patients with severe pulmonary hypertension and in those conditions in which accurate right heart pressure measurements are needed.     

Additive scoring of reported symptoms: Validity and item bias problems in morbidity scales

The objective of this study was to validate a symptom scalebased on additive scoring of self-reported symptom data foruse in multivariate analyses in a cross-sectional interviewsurvey investigation of an urban sample of persons over 65 yearsof age. The majority of the sample members reported 1 to 3 symptomepisodes, but over one-third of the sample reported 4 or moreepisodes and 50 persons (9% of the sample) reported 7 or moresymptoms. A 20 item symptom scale was validated with Kern responsetheory methods based on the binary Rasdi model, a 1 parameterlogistic model, plus procedures developed for checking the model.The Rasdi logistic test result of Z=52.9 and p=0.000 providedstrong evidence against the hypothesis that the items representeda unldimensional symptom scale. A series of negatively correlatedKerns suggested the presence of 2 or more dimensions in thedata. Subsequently, 2 different morbidity variables satisfyingminimum requirements for scaling data were identified. Kernsfalling on both scales were found to be gender biased, meaningthat the scales could only be used validly in gender-specificanalyses. The findings illustrate multidimensionality and itembias hidden in additive symptom scales, problems that couldseriously distort the findings of multivariate analyses usingsuch scales.     

A Spectrophotometric Modification of the Winkler Method for Measurement of Dissolved Oxygen

Pharmaceutical Research -     

A literary approach to managerial discourse after the NHS reforms

The 1990 NHS and Community Care Act can be seen as the culmination of the importation into the UK National Health Service of ‘business’ language. This has entailed struggles between the values of new general managers and the traditional professions and unprecedented attention to issues of ‘measurement’. A recent study of NHS Trusts involved three yearly rounds of interviews with managers and the administration of questionnaires to the nursing workforce in the same areas. Although the main intentions of the research lay in gauging the job satisfaction of the workforce and describing the managers', approaches to organisational strategy, the way that each group used language soon emerged as an area of interest and as a pointer to the foundational values and epistemologies of each group. An approach to the texts of interviews and questionnaire responses was informed partly by an analysis of discourse, elaborated by Foucault and others and partly by deconstraction, an approach usually associated with literary texts. The approach to analysis is based on the realisation that language is structured in a way that reflects existing power relations and that attention to metaphor and other rhetorical devices can give insight into these discourses. After briefly introducing the policy context and a particular approach to literary texts, this paper offers analysis of how managers talked about measurement and financial constraints.     

The objective clinical assessment of the quality of the anterior segment by means of the Oqual

The Oqual is a simple new device attachable to the (Haag-Streit or Topcon) slit-lamp. It provides objective numerical assessments of the optical quality of the anterior segment. In the present study, patients attending Outpatients Clinics at Moorfields Eye Hospital were divided into those who suffered from lenticular symptoms and those who did not. Their monocular visual acuity was measured routinely by means of a Snellen chart, and thereafter their eyes were examined with the Oqual. Results are given for the correlation between the two measures overall (R² = 47.35%), and for inter-observer performance (r = 0.8878). Earlier conclusions on the effects of smoking habits are supported.     

自操作式视力测定仪

本仪器在标准视力表面每一视标的下方安装发光二极管,通过发光管的发光来指定某一视标准提供受检者判别,采用数字电路实现受检者视标判别信息的鉴别,视标换行及同行视标的随机选取。受检者通过键盘输入自己对于视标开口方向的判别即可实现自操作式视力测定。所测定的视力由数码管显示。经试用,与人工视力检查对照其结果高度相关。