Retrospective Estimation Research Articles

A Retrospective One-Year Estimation of the Volume and Nature of Surgical and Anaesthetic Services Delivered to the Populations of the Fako Division of the South-West Region of Cameroon: An Urgent Call for Action.

Surgery-related conditions account for the majority of admissions in primary referral hospitals in Sub-Saharan Africa. The role of surgery in the reduction of global disease burden is well recognized, but there is a great qualitative and quantitative disparity in the delivery of surgical and anaesthetic services between countries. This study aims at estimating the nature and volume of surgery delivered in an entire administrative division of Cameroon. In this retrospective survey conducted during the year 2013, we used a standard tool to analyse the infrastructure and human resources involved in the delivery of surgical and anaesthetic services in the Fako division in the south-west region of Cameroon. We also estimated the nature and volume of surgical services as a rate per catchment population. Public, private and mission hospital contributed equally to the delivery of surgical services in the Fako. For every 100,000 people, there were <5 operative rooms. A total of 2460 surgical interventions were performed by 2.2 surgeons, 1.1 gynaecologists and 0.3 anaesthetists. These surgical interventions consisted mostly of minor and emergency procedures. Neurosurgery, paediatric, thoracic and endocrine surgery were almost non-existent. The volume of surgery delivered in the Fako is far below the minimum rates required to meet up with the most basic requirements of the populations. It is likely that most of these surgical needs are left unattended. A community-based assessment of unmet surgical needs is necessary to accurately estimate the magnitude of the problem and guide surgical capacity improvements.

Retrospective Parameter Estimation and Forecast of Respiratory Syncytial Virus in the United States.

Recent studies have shown that systems combining mathematical modeling and Bayesian inference methods can be used to generate real-time forecasts of future infectious disease incidence. Here we develop such a system to study and forecast respiratory syncytial virus (RSV). RSV is the most common cause of acute lower respiratory infection and bronchiolitis. Advanced warning of the epidemic timing and volume of RSV patient surges has the potential to reduce well-documented delays of treatment in emergency departments. We use a susceptible-infectious-recovered (SIR) model in conjunction with an ensemble adjustment Kalman filter (EAKF) and ten years of regional U.S. specimen data provided by the Centers for Disease Control and Prevention. The data and EAKF are used to optimize the SIR model and i) estimate critical epidemiological parameters over the course of each outbreak and ii) generate retrospective forecasts. The basic reproductive number, R0, is estimated at 3.0 (standard deviation 0.6) across all seasons and locations. The peak magnitude of RSV outbreaks is forecast with nearly 70% accuracy (i.e. nearly 70% of forecasts within 25% of the actual peak), four weeks before the predicted peak. This work represents a first step in the development of a real-time RSV prediction system.

Measuring populations to improve vaccination coverage.

In low-income settings, vaccination campaigns supplement routine immunization but often fail to achieve coverage goals due to uncertainty about target population size and distribution. Accurate, updated estimates of target populations are rare but critical; short-term fluctuations can greatly impact population size and susceptibility. We use satellite imagery to quantify population fluctuations and the coverage achieved by a measles outbreak response vaccination campaign in urban Niger and compare campaign estimates to measurements from a post-campaign survey. Vaccine coverage was overestimated because the campaign underestimated resident numbers and seasonal migration further increased the target population. We combine satellite-derived measurements of fluctuations in population distribution with high-resolution measles case reports to develop a dynamic model that illustrates the potential improvement in vaccination campaign coverage if planners account for predictable population fluctuations. Satellite imagery can improve retrospective estimates of vaccination campaign impact and future campaign planning by synchronizing interventions with predictable population fluxes.

Electoral Reciprocity in Programmatic Redistribution: Experimental Evidence

We analyzed two conditional cash transfers experiments that preceded Honduran presidential elections in 2001 and 2013. In the first, smaller transfers had no effects on voter turnout or incumbent vote share. In the second, larger transfers increased turnout and incumbent share in similar magnitudes, consistent with the mobilization of the incumbent party base rather than vote switching. Moreover, we found that turnout and incumbent share increased when cumulative payments were similar, but larger payments were made closer to the elections. As in prior lab experiments, individuals seem to overweight “peak” and “end” payments in their retrospective estimation of net benefits. We further argue that a model of intrinsically-reciprocal voters is most consistent with the findings.

Accuracy and bias in retrospective symptom reporting.

Self-reported bodily symptoms are of primary importance in healthcare and in health-related research. Typically, they are assessed in clinical interviews or by means of traditional questionnaire formats that require the respondent to provide retrospective symptom estimates rated along intuitive frequency and/or intensity standards and aggregated across varying or unspecified time windows. Retrospective symptom assessments are often biased when compared to (averaged) momentary assessments of symptoms. A variety of factors and conditions have been identified to influence the amount of bias in symptom reporting. Recent research has focused on the underlying mechanisms for the discrepancy between memory and experience. It is suggested that different types of questions and formats assess different types of information, and each may be relevant for different purposes. Knowledge of these underlying mechanisms also provides a relevant framework to better understand individual differences in symptom reporting, including somatoform and somatic symptom disorder. Accuracy of self-reported bodily symptoms is important for the clinician and the researcher. Understanding the mechanisms underlying bias may provide an interesting window to understand how symptom episodes are processed, encoded, and consolidated in memory and may also provide clues to modify symptom experiences.

Voter Response to Peak and End Transfers: Evidence From a Conditional Cash Transfer Experiment

We analyzed two conditional cash transfers experiments that preceded Honduran presidential elections in 2001 and 2013. In the first, smaller transfers had no effects on voter turnout or incumbent vote share. In the second, larger transfers increased turnout and incumbent share in similar magnitudes, consistent with the mobilization of the incumbent party base rather than vote switching. Moreover, we found that turnout and incumbent share increased when cumulative payments were similar, but larger payments were made closer to the elections. As in prior lab experiments, individuals seem to overweight “peak” and “end” payments in their retrospective estimation of net benefits. We further argue that a model of intrinsically-reciprocal voters is most consistent with the findings.Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

Relationships between steroid hormones in hair and social behaviour in ring-tailed lemurs (Lemur catta).

Relationships between the hypothalamic-pituitary adrenal and hypothalamic-pituitary gonadal axes and social behaviour in primates are complex. By using hair to quantify steroid hormones, one can obtain retrospective estimates of long-term free hormone levels from a single sample. In this study, hair was used to quantify long-term levels of cortisol, testosterone, and estradiol among members of a colony of ring-tailed lemurs (Lemur catta) to explore associations between intra- and intersexual levels of these hormones and social behaviour between the breeding and birthing seasons. Positive trends between hair cortisol and rates of receiving aggression approached significance for males and females after controlling for age. While there was no relationship between sex steroid concentrations and intrasexual social interactions, high rates of aggression in females over the study period coincided with females exhibiting the same average concentrations of testosterone as males. We, therefore, conclude that being the recipient of aggression might be more stressful than being aggressive in ring-tailed lemurs, and that testosterone potentially mediates female dominance in this species. We suggest that further investigation of hair hormones and behaviour in additional primate species could provide a useful comparative framework to guide interpretation of these novel findings.

Long-term Exposure to Air Pollution from Power Plants and Mortality in a Cohort of People Living in an Industrial Area of Southern Italy

Introduction The area around Brindisi (Apulia region) is characterized by three thermoelectric power plants established in different time periods (1961, 1969, and 1991), two of which remain active. These plants vary in terms of combustible material (oil and coal) and pollution control technology. The study aimed to evaluate the effects of emissions from the power plants on mortality in a cohort of people living in the area, taking into account the effect of socioeconomic position (SEP) and other contextual variables. Methods A cohort of residents from 2000 to 2013 were enrolled from Municipal Registers and followed until 2013. Individual data were linked with the regional mortality register. Census data from 2001 at census block level were used to assess an area-based SEP index. Exposure to power plants emissions in 1998 (PM10 as tracer) at each residential address was estimated using Lagrangian dispersion models. Cox mortality Hazard Ratios were calculated including a linear term for industrial PM10 exposure (95th-5th percentiles difference), age, gender, calendar period, and SEP (HRs, 95%CI). Results A total of 223,934 people were enrolled (48% male, 40% low SEP). The annual average population exposure levels [mean (SD, 50th percentile, 95th-5th percentile)] of industrial PM10 were 0.30 µg/m3 (0.25, 0.33, 0.62). For increases of PM10 equal to the difference between 95th-5th percentile, we found increasing risks for cancer mortality (HR 1.08, 95%CI 1.04-1.13), pancreatic (HR 1.11, 95%CI 1.01-1.23) and bladder cancers (HR 1.16, 95%CI 1.04-1.30), respiratory disease (HR 1.12, 95%CI 1.03-1.22), and acute coronary events (HR 1.11, 95%CI 1.00-1.23). Conclusions Industrial pollution from power plants was associated with cohort mortality of the people resident in the area. The effect estimates are large although there are uncertainties in the retrospective estimation of the absolute concentrations of industrial pollutants.

A Study of Reverse Causation: Examining the Associations of Perfluorooctanoic Acid Serum Levels with Two Outcomes.

Background:Impaired kidney function and earlier menopause were associated with perfluorooctanoic acid (PFOA) serum levels in previous cross-sectional studies. Reverse causation, whereby health outcomes increase serum PFOA, may underlie these associations.Objective:We compared measured (subject to reverse causation) versus modeled (unaffected by reverse causation) serum PFOA in association with these outcomes to examine the possible role of reverse causation in these associations.Methods:In cross-sectional analyses, we analyzed PFOA in relation to self-reported menopause among women (n = 9,192) 30–65 years old and in relation to kidney function among adults > 20 years old (n = 29,499) in a highly exposed Mid-Ohio Valley cohort. Estimated glomerular filtration rate (eGFR, a marker of kidney function) and serum PFOA concentration were measured in blood samples collected during 2005–2006. Retrospective year-specific serum PFOA estimates were modeled independently of measured PFOA based on residential history and plant emissions. Using measured and modeled PFOA in 2005 or 2006 (predictor variables), cross-sectional associations were assessed for eGFR and menopause (yes/no). We also analyzed measured PFOA (dependent variable) in relation to the number of years since menopause.Results:Menopause and eGFR were significantly associated with measured (trend tests: p = 0.013, p = 0.0005, respectively) but not with modeled serum PFOA (p = 0.50, p = 0.76, respectively). Measured PFOA levels increased for the first 7 years after menopause (trend test, p < 0.0001), providing further evidence that the observed association between measured PFOA and menopause is subject to reverse causation for this outcome.Conclusion:Our results support the conjecture that in previous studies, earlier menopause and reduced kidney function are the causes rather than the results of increased measured serum PFOA. These results suggest caution in using biomarkers in cross-sectional studies.Citation:Dhingra R, Winquist A, Darrow LA, Klein M, Steenland K. 2017. A study of reverse causation: examining the associations of perfluorooctanoic acid serum levels with two outcomes. Environ Health Perspect 125:416–421; http://dx.doi.org/10.1289/EHP273

Why are they late? Timing abilities and executive control among students with learning disabilities

While a deficient ability to perform daily tasks on time has been reported among students with learning disabilities (LD), the underlying mechanism behind their ‘being late' is still unclear. This study aimed to evaluate the organization in time, time estimation abilities, actual performance time pertaining to specific daily activities, as well as the executive functions of students with LD in comparison to those of controls, and to assess the relationships between these domains among each group. The participants were 27 students with LD, aged 20–30, and 32 gender and age-matched controls who completed the Time Organization and Participation Scale (TOPS) and the Behavioral Rating Inventory of Executive Function-Adult version (BRIEF-A). In addition, their ability to estimate the time needed to complete the task of preparing a cup of coffee as well as their actual performance time were evaluated. The results indicated that in comparison to controls, students with LD showed significantly inferior organization in time (TOPS) and executive function abilities (BRIEF-A). Furthermore, their time estimation abilities were significantly inferior and they required significantly more time to prepare a cup of coffee. Regression analysis identified the variables that predicted organization in time and task performance time among each group. The significance of the results for both theoretical and clinical implications are discussed.What this paper adds?This study examines the underlying mechanism of the phenomena of being late among students with LD. Following a recent call for using ecologically valid assessments, the functional daily ability of students with LD to prepare a cup of coffee and to organize time were investigated. Furthermore, their time estimation and executive control abilities were examined as a possible underlying mechanism for their lateness. Although previous studies have indicated executive control deficits among students with LD, to our knowledge, this is the first analysis of the relationships between their executive control and time estimation deficits and their influence upon their daily function and organization in time abilities. Our findings demonstrate that students with LD need more time in order to execute simple daily activities, such as preparing a cup of coffee. Deficient working memory, retrospective time estimation ability and inhibition predicted their performance time and organization in time abilities. Therefore, this paper sheds light on the mechanism behind daily performance in time among students with LD and emphasizes the need for future development of focused intervention programs to meet their unique needs.

Reconstruction of implanted marker trajectories from cone-beam CT projection images using interdimensional correlation modeling.

Cone-beam CT (CBCT) is a widely used imaging modality for image-guided radiotherapy. Most vendors provide CBCT systems that are mounted on a linac gantry. Thus, CBCT can be used to estimate the actual 3-dimensional (3D) position of moving respiratory targets in the thoracic/abdominal region using 2D projection images. The authors have developed a method for estimating the 3D trajectory of respiratory-induced target motion from CBCT projection images using interdimensional correlation modeling. Because the superior-inferior (SI) motion of a target can be easily analyzed on projection images of a gantry-mounted CBCT system, the authors investigated the interdimensional correlation of the SI motion with left-right and anterior-posterior (AP) movements while the gantry is rotating. A simple linear model and a state-augmented model were implemented and applied to the interdimensional correlation analysis, and their performance was compared. The parameters of the interdimensional correlation models were determined by least-square estimation of the 2D error between the actual and estimated projected target position. The method was validated using 160 3D tumor trajectories from 46 thoracic/abdominal cancer patients obtained during CyberKnife treatment. The authors' simulations assumed two application scenarios: (1) retrospective estimation for the purpose of moving tumor setup used just after volumetric matching with CBCT; and (2) on-the-fly estimation for the purpose of real-time target position estimation during gating or tracking delivery, either for full-rotation volumetric-modulated arc therapy (VMAT) in 60 s or a stationary six-field intensity-modulated radiation therapy (IMRT) with a beam delivery time of 20 s. For the retrospective CBCT simulations, the mean 3D root-mean-square error (RMSE) for all 4893 trajectory segments was 0.41 mm (simple linear model) and 0.35 mm (state-augmented model). In the on-the-fly simulations, prior projections over more than 60° appear to be necessary for reliable estimations. The mean 3D RMSE during beam delivery after the simple linear model had established with a prior 90° projection data was 0.42 mm for VMAT and 0.45 mm for IMRT. The proposed method does not require any internal/external correlation or statistical modeling to estimate the target trajectory and can be used for both retrospective image-guided radiotherapy with CBCT projection images and real-time target position monitoring for respiratory gating or tracking.

LONG-TERM BIODOSIMETRY REDUX.

This paper revisits and reiterates the needs, purposes and requirements of biodosimetric assays for long-term dose and health risk assessments. While the most crucial need for biodosimetric assays is to guide medical response for radiation accidents, the value of such techniques for improving our understanding of radiation health risk by supporting epidemiological (long-term health risk) studies is significant. As new cohorts of exposed persons are identified and new health risk studies are undertaken with the hopes that studying the exposed will result in a deeper understanding of radiation risk, the value of reliable dose reconstruction is underscored. The ultimate application of biodosimetry in long-term health risk studies would be to completely replace model-based dose reconstruction-a complex suite of methods for retrospectively estimating dose that is commonly fraught with large uncertainties due to the absence of important exposure-related information, as well as imperfect models. While biodosimetry could potentially supplant model-based doses, there are numerous limitations of presently available techniques that constrain their widespread application in health risk research, including limited ability to assess doses received far in the past, high cost, great inter-individual variability, invasiveness, higher than preferred detection limits and the inability to assess internal dose (for the most part). These limitations prevent the extensive application of biodosimetry to large cohorts and should be considered a challenge to researchers to develop new and more flexible techniques that meet the demands of long-term health risk research. Events in recent years, e.g. the Fukushima reactor accident and the increased threat of nuclear terrorism, underscore that any event that results in significant radiation exposures of a group of people will also produce a much larger population, exposed at lower levels, but that likewise needs (or demands) an exposure assessment. Hence, the needs for retrospective dose estimation are likely to be greater in the future. The value of biodosimetry can be considerably enhanced with the development of new or improved methods, particularly with suitability for application at long periods of time after exposure.

Maladie d’Alzheimer et appropriation de la durée d’action

In the course of Alzheimer disease (AD), different authors have reported disturbances of the perception of time. Incapacity to be on top of the time dimension in daily life is a major handicap as witnessed by caregivers of these patients. Very basic stimuli of very short duration and out of context have been used in research on temporality so far. The objective of the research presented here is to determine, whether in the course of AD, the capacity of time representation and time perception for daily activities is affected or not. In AD, we have noticed that the semantic memory for temporal knowledge is significantly altered while the estimation of duration based upon a script is preserved. To approach the representation of perception of time duration for daily activities in AD patients, we applied a combined methodology. A temporal semantic knowledge scale, a time duration estimation test about 12 defined daily activities as well as patient's interviews about temporality in daily life, registered and transcribed verbatim are used. We studied 6 patients with mild to moderately severe AD with comparable sociocultural characteristics and stage of the disease. We analysed the interviews and studied for each activity, verbal outputs relating to themes of temporality such as chronological reference points and time duration estimations as compared to information relating to the activity itself, the location in which the activity took place. The answers are classified according to their pertinence and whether they have been spontaneous or sollicited. We confirm that temporality is significantly altered in the course of mild to moderate AD. Analysis of the patients’ responses to questions exploring above-mentioned aspects of temporality revealed that time duration estimation was more altered than memory of chronological reference points. The approach presented here widens the comprehension of the different alterations as well as the understanding of some underlying processes involved in the perception of time. A reduction of attentional resources allocated to time can explain the observed alterations as proposed by the model of internal clock and attentional gate. We hypothesize that units of time representation have episodic, semantic and procedural components; moreover, our results support the notion that a link exists between retrospective time duration estimation and autonoetic travel as described by Tulving. The results of this research are in favor of the hypothesis that two ways may exist to manage temporality, as proposed by Chambon, one, controlled, conscious and intentional and a second, automated one which would rely on non-intentional and unconscious processes. Analysing the cognitive processes involved in our approach of temporality in AD allows to hypothesize an intersection between episodic, semantic memory and scripts knowledge included in procedural memory. Our results suggest the possibility of an interaction between episodic and semantic memory; this could explain our observation that memory of chronological reference points is relatively less affected in AD. Analysis of the cognitive processes involved in the representation of elapsing time as perceived by Alzheimer patients may potentially explain some of the difficulties these patients face in their daily life. Based upon these findings, a simple scheme of exploration could be introduced in medical practice, reducing the need for more sophisticated and time consuming diagnostic exploration. This deepened understanding may lead to improvements of care with potentially significant impact on daily life of patients and their caregivers.

Seasonal Influenza Infections and Cardiovascular Disease Mortality.

Cardiovascular deaths and influenza epidemics peak during winter in temperate regions. To quantify the temporal association between population increases in seasonal influenza infections and mortality due to cardiovascular causes and to test if influenza incidence indicators are predictive of cardiovascular mortality during the influenza season. Time-series analysis of vital statistics records and emergency department visits in New York City, among cardiovascular deaths that occurred during influenza seasons between January 1, 2006, and December 31, 2012. The 2009 novel influenza A(H1N1) pandemic period was excluded from temporal analyses. Emergency department visits for influenza-like illness, grouped by age (≥0 years and ≥65 years) and scaled by laboratory surveillance data for viral types and subtypes, in the previous 28 days. Mortality due to cardiovascular disease, ischemic heart disease, and myocardial infarction. Among adults 65 years and older, who accounted for 83.0% (73 363 deaths) of nonpandemic cardiovascular mortality during influenza seasons, seasonal average influenza incidence was correlated year to year with excess cardiovascular mortality (Pearson correlation coefficients ≥0.75, P ≤ .05 for 4 different influenza indicators). In daily time-series analyses using 4 different influenza metrics, interquartile range increases in influenza incidence during the previous 21 days were associated with an increase between 2.3% (95% CI, 0.7%-3.9%) and 6.3% (95% CI, 3.7%-8.9%) for cardiovascular disease mortality and between 2.4% (95% CI, 1.1%-3.6%) and 6.9% (95% CI, 4.0%-9.9%) for ischemic heart disease mortality among adults 65 years and older. The associations were most acute and strongest for myocardial infarction mortality, with each interquartile range increase in influenza incidence during the previous 14 days associated with mortality increases between 5.8% (95% CI, 2.5%-9.1%) and 13.1% (95% CI, 5.3%-20.9%). Out-of-sample prediction of cardiovascular mortality among adults 65 years and older during the 2009-2010 influenza season yielded average estimates with 94.0% accuracy using 4 different influenza metrics. Emergency department visits for influenza-like illness were associated with and predictive of cardiovascular disease mortality. Retrospective estimation of influenza-attributable cardiovascular mortality burden combined with accurate and reliable influenza forecasts could predict the timing and burden of seasonal increases in cardiovascular mortality.

SU‐F‐J‐80: Deformable Image Registration for Residual Organ Motion Estimation in Respiratory Gated Treatments with Scanned Carbon Ion Beams

Purpose:At the Centro Nazionale di Adroterapia Oncologica (CNAO, Pavia, Italy) C‐ions respiratory gated treatments of patients with abdominal tumours started in 2014. In these cases, the therapeutic dose is delivered around end‐exhale. We propose the use of a respiratory motion model to evaluate residual tumour motion. Such a model requires motion fields obtained from deformable image registration (DIR) between 4DCT phases, estimating anatomical motion through interpolation. The aim of this work is to identify the optimal DIR technique to be integrated in the modeling pipeline.Methods:We used 4DCT datasets from 4 patients to test 4 DIR algorithms: Bspline, demons, log‐domain and symmetric log domain diffeomorphic demons. We evaluate DIR performance in terms of registration accuracy (RMSE between registered images) and anatomical consistency of the motion field (Jacobian) when registering end‐inhale to end‐exhale. We subsequently employed the model to estimate the tumour trajectory within the ideal gating window.Results:Within the liver contour, the RMSE is in the range 31–46 HU for the best performing algorithm (Bspline) and 43–145 HU for the worst one (demons). The Jacobians featured zero negative voxels (which indicate singularities in the motion field) for the Bspline fields in 3 of 4 patients, whereas diffeomorphic demons fields showed a non‐null number of negative voxels in every case. GTV motion in the gating window measured less than 7 mm for every patient, displaying a predominant superior‐inferior (SI) component.Conclusion:The Bspline algorithm allows for acceptable DIR results in the abdominal region, exhibiting the property of anatomical consistency of the computed field. Computed trajectories are in agreement with clinical expectations (small and prevalent SI displacements), since patients lie wearing semi‐rigid immobilizing masks. In future, the model could be used for retrospective estimation of organ motion during treatment, as guided by the breathing surrogate signal.

Spatio‐temporal modelling of auk abundance after the Erika oil spill and implications for conservation

Summary Species distribution models are widely used in applied ecology and conservation. While accounting for spatial dependences is now the rule, temporal dependences have rarely been dealt with explicitly. In this study, we analyse wintering auk distribution in the Bay of Biscay and English Channel and estimate changes in abundance within and between years while accounting for space–time dependencies. We then propose a retrospective estimate of the impact of the Erika oil spill that occurred in December 1999. Two series of extensive aerial surveys, repeated at intervals of 1–2 months, were carried out at a 10‐year interval off the French Atlantic coast (2001–2002 and 2011–2012). Spatially and temporally explicit Bayesian models were fitted to these data to provide spatio‐temporal predictions of auk abundance. These were then used to compare abundances within the area affected by the Erika oil spill two and twelve years after the catastrophe. The results showed that 1·55 million auks wintered in the study area in 2011–2012. The main wintering area was the English Channel (more than one million auks) but the Bay of Biscay also became an important area in the middle of winter (470 000 auks) owing to a strong southward shift in auk distribution. Two years after the catastrophe (2001–2002), the area affected by the Erika oil spill hosted a small proportion of auks of the Bay of Biscay – about 80 000 individuals. This number increased by more than three times 10 years later and reached 270 000 individuals, whereas no significant change was detected elsewhere. We suggest that it could result from a recovery after the extra‐mortality induced by the Erika oil spill. Policy implications. This study identified major auk wintering areas, with abundances much higher than previously realized. Oil spills have occurred regularly in these areas, with major delayed impacts on auk breeding populations. The worst case scenario would be if a major oil spill occurred in the English Channel in February, when abundance reaches one million auks. Although such a disaster has not so far occurred, stricter policies on the transport of hydrocarbons should be implemented to prevent such a possibility.

Association of retrospective time estimation and severity of cognitive impairment

ABSTRACTIntroduction. Time perception has an important role in everyday life, but is not commonly measured in clinical routine assessment of suspected cognitive impairment, given the complexity of available assessment methods. Furthermore, evidence on the pattern of retrospective time perception in neurodegenerative diseases is contradictory. Method. We asked 321 patients referred to neuropsychological assessment to retrospectively estimate the duration of the neuropsychological assessment session. We calculated the session actual duration, ratio, and accuracy of response. Patients were grouped into three categories: subjective cognitive impairment, mild cognitive impairment, and mild to moderate dementia. Results. We found an overall tendency for underestimation of time, but no significant differences between groups regarding time estimation. There were significant, but weak, associations between time estimation and severity of cognitive impairment in several domains, with slightly different patterns across groups. Conclusions. Regardless of etiology, the majority of patients underestimated time, which was weakly associated with the severity of cognitive impairment. Global retrospective estimation may be clinically informative, particularly in a minority of extreme cases.

Convolution-based estimation of organ dose in tube current modulated CT

Estimating organ dose for clinical patients requires accurate modeling of the patient anatomy and the dose field of the CT exam. The modeling of patient anatomy can be achieved using a library of representative computational phantoms (Samei et al Pediatr. Radiol. 44 460–7). The modeling of the dose field can be challenging for CT exams performed with a tube current modulation (TCM) technique. The purpose of this work was to effectively model the dose field for TCM exams using a convolution-based method. A framework was further proposed for prospective and retrospective organ dose estimation in clinical practice.The study included 60 adult patients (age range: 18–70 years, weight range: 60–180 kg). Patient-specific computational phantoms were generated based on patient CT image datasets. A previously validated Monte Carlo simulation program was used to model a clinical CT scanner (SOMATOM Definition Flash, Siemens Healthcare, Forchheim, Germany). A practical strategy was developed to achieve real-time organ dose estimation for a given clinical patient. CTDIvol-normalized organ dose coefficients () under constant tube current were estimated and modeled as a function of patient size. Each clinical patient in the library was optimally matched to another computational phantom to obtain a representation of organ location/distribution. The patient organ distribution was convolved with a dose distribution profile to generate values that quantified the regional dose field for each organ. The organ dose was estimated by multiplying with the organ dose coefficients (). To validate the accuracy of this dose estimation technique, the organ dose of the original clinical patient was estimated using Monte Carlo program with TCM profiles explicitly modeled. The discrepancy between the estimated organ dose and dose simulated using TCM Monte Carlo program was quantified. We further compared the convolution-based organ dose estimation method with two other strategies with different approaches of quantifying the irradiation field.The proposed convolution-based estimation method showed good accuracy with the organ dose simulated using the TCM Monte Carlo simulation. The average percentage error (normalized by CTDIvol) was generally within 10% across all organs and modulation profiles, except for organs located in the pelvic and shoulder regions.This study developed an improved method that accurately quantifies the irradiation field under TCM scans. The results suggested that organ dose could be estimated in real-time both prospectively (with the localizer information only) and retrospectively (with acquired CT data).

Estimating long-haul airline pilots’ at-home baseline sleep duration

ObjectiveCharacterize the baseline sleep of long-haul airline pilots. MethodsSleep of 332 pilots (median age = 51 years, range = 23-64 years) from 4 airlines was measured by actigraphy while at home and off-duty and by retrospective estimate of the total amount of nighttime sleep usually obtained at home. ResultsMean actigraphic sleep per 24 hours during baseline periods was 6.8 hours (SD = 1.0 hour), 52 minutes shorter than mean self-reported usual nighttime sleep (7.6 hours, SD = 1.1 hours). ConclusionsPilots’ self-reported sleep duration was comparable to weekend sleep of men in general population samples, but their actigraphic baseline sleep was longer than objectively monitored sleep of other samples. Long-haul pilots routinely experience sleep restriction and circadian disruption across trips, both of which are implicated in increased health risks. We recommend that they be educated about the long-term importance for health of obtaining adequate sleep on off-duty days.

Transformation and development of production-logistics enterprises in Ukrainian agrarian economy

What are the processes of transformation and economic development of production-logistics enterprises in agriculture and what conceptual ways for balancing the sphere of agribusiness with steady development of rural areas in Ukraine? Therefore the purpose of the article is the development of strategic directions of post-reform harmonization in development of enterprises in agrarian sphere and rural territorial communities. Based on SWOT-analysis the author’s methodological approach to retrospective systematic estimation of alternatives for transformation production-logistics enterprises has been applied. The research has been carried out on reformed collective agricultural enterprises, 19 agroholdings and 668 cooperatives throughout 1999–2014. Prospective ways and conceptual approaches to harmonization of budget-creating role of agribusiness and social economical role of development of rural area have been suggested.