962-61 Late Redistribution T1-201/Stress Tc-99m Sestamibi Separate Acquisition Dual Isotope Myocardial Perfusion SPECT: A Feasibility Study

Rest TI201(TI)/stress Tc-sestamibi dual isotope SPECT (DIMPS) is an efficient myocardial perfusion protocol. Patients with rest defects, however, frequently require late TI redistribution imaging the next day. Thus, we recently implemented a modified DIMPS (M-DIMPS), with 3.5 mCi TI injected at rest the night before stress testing. On the day of stress testing, 12–18 hr redistribution TI (late TI) SPECT was performed prior to stress sestamibi study. To assess image quality of late TI, we prospectively studied 107 patients who underwent M-DIMPS. For purposes of comparison between conventional DIMPS and M-DIMPS, a subset (group A, n=41) also had rest TI(25sec/stop, 60 stops) the night before M-DIMPS. Late TI used 30sec/stop. Prereconstruction processing used a 20 Butterworth filter (cut-off: 0.5/order 10 for rest TI, 0.35/order 10 for late TI). Comparisons were made for cardiac counts (counts/pixel) and quantitative heart to background ratio (H/B ratio). Image quality was assessed visually using a 5 point score (0=unacceptable, 4=excellent), based on the evaluation of image uniformity, defect clarity, left ventricular border definition and the apparent H/B ratio, Comparisons between rest TI and late TI in 41 group A patients yielded quantitative H/B ratio of 1.63±0.39 and 1.49±0,31 (p=0.002), and total myocardial counts of 41.4±18.1 and 29.3±11.6 (p<0.001), respectively. Image quality agreement between rest TI and late TI was 90%, with 31 concordant good to excellent and 6 concordant fair studies. Analysis of the 107 late TI studies by patient weight revealed:<150 Ibs (n = 31)150–200 Ibs (n = 60)>200 Ibs (n = 16)pcardiac counts30.4±9.628.9±13.828.9±7.5nsH/B ratio1.49±0.241.46±0.321.42±0.25nsquality = 3 or 490%90%63%<0.05**> 200lbs vs. the other two weight categoriesConclusionAlthough quantitatively different, late TI has acceptable count statistics and comparable visual image quality to rest TI, establishing the feasibility of late TI/stress Tc-sestamibi dual isotope SPECT in non-obese (<200 Ibs) patients. The protocol allows for final reporting on the same day as stress testing, potentially decreasing the length of hospitalization

Effective risk stratification using exercise myocardial perfusion SPECT in women: Gender-related differences in prognostic nuclear testing

AbstractObjectives. This study was designed to evaluate the incremental prognostic value over clinical and exercise variables of rest thallium-201/exercise technetium-99m sestamibi single-photon emission computed tomography (SPECT) in women compared with men and to determine whether this test can be used to effectively risk stratify patients of both genders.Background. To minimize the previously described gender-related bias in the evaluation of coronary artery disease in women, there is a need to identify a noninvasive testing strategy that is able to accurately and effectively risk stratify women.Methods. We identified 4,136 consecutive patients (2,742 men, 1,394 women) who underwent dual-isotope SPECT. The incremental value of nuclear testing was determined using both a stepwise Cox proportional hazards model and Kaplan-Meier survival analysis. Receiver operating characteristic curve analysis was performed to determine test discrimination for high risk patients in men and women.Results. The patient population was followed up for 20 ± 5 months for events (cardiac death or nonfatal myocardial infarction). During this time, 63 myocardial infarctions and 32 cardiac deaths occurred in the men, and 31 myocardial infarctions and 14 cardiac deaths occurred in the women. Nuclear testing significantly stratified both men and women irrespective of their rest electrocardiogram. Cox proportional hazards analysis revealed that nuclear testing added incremental prognostic value in both men and women after inclusion of the most predictive clinical and exercise variables (overall chi-square 89 in men vs. 120 in women, p < 0.005). Kaplan-Meier survival analysis demonstrated that nuclear testing further stratified men and women with both intermediate to high and low prescan likelihoods of coronary artery disease (p < 0.005 for all). Receiver operating characteristic curve analysis demonstrated superior discrimination for the nuclear scan results in identifying high risk women than men (area under the curve: 0.84 ± 0.03 vs. 0.71 ± 0.03 in men, p < 0.0005). The odds ratio comparing event rates in patients with abnormal versus those with normal scan results was greater in women than in men, suggesting superior stratification using nuclear testing in women.Conclusions. Dual-isotope myocardial perfusion imaging yields incremental prognostic value in both men and women. This modality identifies low risk women and men equally well but relatively high risk women more accurately than relatively high risk men and, thus, is able to stratify women more effectively than men

Heterogeneity in Preferences towards Complexity

We analyze lottery-choice data in a way that separately estimates the effects of risk aversion and complexity aversion. Complexity is represented by the number of different outcomes in the lottery. A finite mixture random effects model is estimated which assumes that a proportion of the population are complexity-neutral. We find that around 33% of the population are complexity-neutral, around 50% complexity-averse, and the remaining 17% are complexity-loving. Subjects who do react to complexity appear to have a bias towards complexity aversion at the start of the experiment, but complexity aversion reduces with experience, to the extent that the average subject is (almost) complexity-neutral by the end of the experiment. Complexity aversion is found to increase with age and to be higher for non-UK students than for UK students. We also find some evidence that, when evaluating complex lotteries, subjects perceive probabilities in accordance with Prospective Reference Theory

Assessing the importance of car meanings and attitudes in consumer evaluations of electric vehicles

This paper reports findings from a research study which assesses the importance of attitudinal constructs related to general car attitudes and the meanings attached to car ownership over evaluations of electric vehicles (EVs). The data are assessed using principal component analysis to evaluate the structure of the underlying attitudinal constructs. The identified constructs are then entered into a hierarchical regression analysis which uses either positive or negative evaluations of the instrumental capabilities of EVs as the dependent variable. Results show that attitudinal constructs offer additional predictive power over socioeconomic characteristics and that the symbolic and emotive meanings of car ownership are as, if not more, effective in explaining the assessment of EV instrumental capability as compared to issues of cost and environmental concern. Additionally, the more important an individual considers their car to be in their everyday life, the more negative their evaluations are of EVs whilst individuals who claim to be knowledgeable about cars in general and EVs in particular have a lower propensity for negative EV attitudes. However, positive and negative EV attitudes are related to different attitudinal constructs suggesting that it is possible for someone to hold both negative and positive assessments at the same time

New appraisal values of travel time saving and reliability in Great Britain

© 2017, The Author(s). This paper provides an overview of the study ‘Provision of market research for value of time savings and reliability’ undertaken by the Arup/ITS Leeds/Accent consortium for the UK Department for Transport (DfT). The paper summarises recommendations for revised national average values of in-vehicle travel time savings, reliability and time-related quality (e.g. crowding and congestion), which were developed using willingness-to-pay (WTP) methods, for a range of modes, and covering both business and non-work travel purposes. The paper examines variation in these values by characteristics of the traveller and trip, and offers insights into the uncertainties around the values, especially through the calculation of confidence intervals. With regards to non-work, our recommendations entail an increase of around 50% in values for commute, but a reduction of around 25% for other non-work—relative to previous DfT ‘WebTAG’ guidance. With regards to business, our recommendations are based on WTP, and thus represent a methodological shift away from the cost saving approach (CSA) traditionally used in WebTAG. These WTP-based business values show marked variation by distance; for trips of less than 20miles, values are around 75% lower than previous WebTAG values; for trips of around 100miles, WTP-based values are comparable to previous WebTAG; and for longer trips still, WTP-based values exceed those previously in WebTAG

Inference of Consumer Consideration Sets

When consumers face a large number of alternatives, they tend to simplify the decision problem by reducing the number of available alternatives to a subset of relevant alternatives, i.e. a consideration set. Since consideration sets are typically unobserved, most studies in the demand literature have to assume a consideration model. If these consideration models are misspecified, the demand estimates can be biased. In this paper, we develop an approach to formally test any two competing models of consideration against one another in order to determine which model fits the data best. Our test follows the intuition of a menu approach and uses supplemental data on marginal cost-shifters to construct overidentifying restrictions. We show an application to German retailing of coffee and milk. We find that consideration sets are fundamentally different for coffee and milk, and relate our findings to differences in demand and supply conditions of the two product categories

The Internalization of Externalities in the Production of Electricity: Willingness to Pay for the Attributes of a Policy for Renewable Energy

This paper investigates the willingness to pay of a sample of residents of Bath, England, for a hypothetical program that promotes the production of renewable energy. Using choice experiments, we assess the preferences of respondents for a policy for the promotion of renewable energy that (i) contributes to the internalization of the external costs caused by fossil fuel technologies; (ii) affects the security of energy supply; (iii) has an impact on the employment in the energy sector; (iv) and leads to an increase in the electricity bill. Responses to the choice questions show that our respondents are in favour of a policy for renewable energy and that they attach a high value to a policy that brings private and public benefits in terms of climate change and energy security benefits. Our results therefore suggest that consumers are willing to pay a higher price for electricity in order to internalize the external costs in terms of energy security, climate change and air pollution caused by the production of electricity