Comparison of the results of 4 users of a contemporary CADCAM system

The objective of this study was to investigate the variation of measurements recorded when four different users of the Tracer CAD system trace a model of known dimensions and volume. This complements a previous study by the same authors Mc Garry and Mc Hugh, (2005) where the accuracy and consistency of a single user was measured. Landmarks were added to indicate proximal, distal, anterior, medial and lateral regions of a specially manufactured cylindrical nylon 6.6 model. Four circumferential lines were added at regular intervals along the length of the cylinder with a view to calculating diameters and volumes relative to these landmarks. The model was measured using a comparator with guaranteed accuracy to one hundredth of a millimetre, and was traced using the Tracer CAD system by four different users. The difference in mean volume between measured results and Tracer CAD scans of differing users ranged to -3%. Individual trace volumes varied by up to -7.85%. In all volumes measured, eleven out of twelve maximum volume percentage differences measured greater than 2 %, and of these, seven results showed maximum volume percentage difference to measure greater than 4%

Criteria for software modularization

A central issue in programming practice involves determining the appropriate size and information content of a software module. This study attempted to determine the effectiveness of two widely used criteria for software modularization, strength and size, in reducing fault rate and development cost. Data from 453 FORTRAN modules developed by professional programmers were analyzed. The results indicated that module strength is a good criterion with respect to fault rate, whereas arbitrary module size limitations inhibit programmer productivity. This analysis is a first step toward defining empirically based standards for software modularization

Does responsibility affect the public valuation of health care interventions? A relative valuation approach to health care safety

This article is available open access through the publisher’s website at the link below. Copyright © 2012, International Society for Pharmacoeconomics and Outcomes Research (ISPOR).Objective - Health services often spend more on safety interventions than seems cost-effective. This study investigates whether the public value safety-related health care improvements more highly than the same improvements in contexts where the health care system is not responsible. Method - An online survey was conducted to elicit the relative importance placed on preventing harms caused by 1) health care (hospital-acquired infections, drug administration errors, injuries to health care staff), 2) individuals (personal lifestyle choices, sports-related injuries), and 3) nature (genetic disorders). Direct valuations were obtained from members of the public by using a person trade-off or “matching” method. Participants were asked to choose between two preventative interventions of equal cost and equal health benefit per person for the same number of people, but differing in causation. If participants indicated a preference, their strength of preference was measured by using person trade-off. Results - Responses were obtained from 1030 people, reflecting the sociodemographic mix of the UK population. Participants valued interventions preventing hospital-acquired infections (1.31) more highly than genetic disorders (1.0), although drug errors were valued similarly to genetic disorders (1.07), and interventions to prevent injury to health care staff were given less weight than genetic disorders (0.71). Less weight was also given to interventions related to lifestyle (0.65) and sports injuries (0.41). Conclusion - Our results suggest that people do not attach a simple fixed premium to “safety-related” interventions but that preferences depend more subtly on context. The use of the results of such public preference surveys to directly inform policy would therefore be premature.Brunel University

EP-1287: Software module for the characterization of geometric distortion in MRI-SIM using a large field of view phantom

The principal component regression (PCR) is often used to forecast macroeconomic variables when there are many predictors. In this letter, we argue that it makes sense to pre-whiten the predictors before including these in a PCR. With simulation experiments, we show that without such pre-whitening, spurious principal components can appear and that these can become spuriously significant in a PCR. With an illustration to annual inflation rates for five African countries, we show that non-spurious principal components can be genuinely relevant in empirical forecasting models

A spatiotemporal theory for MRI T2 relaxation time and apparent diffusion coefficient in the brain during acute ischaemia:Application and validation in a rat acute stroke model

The objective of this study is to present a mathematical model which can describe the spatiotemporal progression of cerebral ischaemia and predict magnetic resonance observables including the apparent diffusion coefficient (ADC) of water and transverse relaxation time T(2). This is motivated by the sensitivity of the ADC to the location of cerebral ischaemia and T(2) to its time-course, and that it has thus far proven challenging to relate observations of changes in these MR parameters to stroke timing, which is of considerable importance in making treatment choices in clinics. Our mathematical model, called the cytotoxic oedema/dissociation (CED) model, is based on the transit of water from the extra- to the intra-cellular environment (cytotoxic oedema) and concomitant degradation of supramacromolecular and macromolecular structures (such as microtubules and the cytoskeleton). It explains experimental observations of ADC and T(2), as well as identifying the rate of spread of effects of ischaemia through a tissue as a dominant system parameter. The model brings the direct extraction of the timing of ischaemic stroke from quantitative MRI closer to reality, as well as providing insight on ischaemia pathology by imaging in general. We anticipate that this may improve patient access to thrombolytic treatment as a future application

Interpersonal dynamics in baseline rallies in tennis

In tennis, the relative positioning of players on court constrains their opportunities to perform successful actions. In this study we proposed and validated an empirical function that captures the spatial-temporal relationship between tennis players during competitive performance. This parameter, termed goal-directed displacement index (GDD Index), is defined over time by the product of both players' distances to the central line of the court and to the centre of the net. Results showed that the GDD index successfully described tennis players' patterns of interaction, as well as identified breaks in patterns of play during competitive performance, due to changes in relative positioning on court. Our analysis revealed two different patterns of interpersonal interactions, cross and down-the-line rallies, and two ways for a break to emerge in game dynamics, parallel variation (transition from a cross court rally to a down-the-line rally) and angle opening (lateral displacement). Data suggest that the elaboration of specific individual profiles of performance for different players, using the GDD index, could improve performance analysis in tennis

Stroke onset time estimation from multispectral quantitative magnetic resonance imaging in a rat model of focal permanent cerebral ischaemia

Background Quantitative T2 relaxation magnetic resonance imaging allows estimation of stroke onset time. Aims We aimed to examine the accuracy of quantitative T1 and quantitative T2 relaxation times alone and in combination to provide estimates of stroke onset time in a rat model of permanent focal cerebral ischemia and map the spatial distribution of elevated quantitative T1 and quantitative T2 to assess tissue status. Methods Permanent middle cerebral artery occlusion was induced in Wistar rats. Animals were scanned at 9.4T for quantitative T1, quantitative T2, and Trace of Diffusion Tensor (Dav) up to 4 h post-middle cerebral artery occlusion. Time courses of differentials of quantitative T1 and quantitative T2 in ischemic and non-ischemic contralateral brain tissue (ΔT1, ΔT2) and volumes of tissue with elevated T1 and T2 relaxation times ( f1, f2) were determined. TTC staining was used to highlight permanent ischemic damage. Results ΔT1, ΔT2, f1, f2, and the volume of tissue with both elevated quantitative T1 and quantitative T2 (VOverlap) increased with time post-middle cerebral artery occlusion allowing stroke onset time to be estimated. VOverlap provided the most accurate estimate with an uncertainty of ±25 min. At all times-points regions with elevated relaxation times were smaller than areas with Dav defined ischemia. Conclusions Stroke onset time can be determined by quantitative T1 and quantitative T2 relaxation times and tissue volumes. Combining quantitative T1 and quantitative T2 provides the most accurate estimate and potentially identifies irreversibly damaged brain tissue. </jats:sec