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1.
Epidemiology ; 30 Suppl 1: S115-S121, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31181014

RESUMO

BACKGROUND: Several studies have investigated the acute effects of high ambient temperature or extreme weather on preterm birth and stillbirth. However, little was known about whether there are any particular stages during which high ambient temperature or heat wave exposure is most harmful to fetal growth. The aim of this study was to examine the effects of heat wave exposure in different gestational months on the risk of preterm birth and stillbirth. METHODS: Based on all singleton birth records between 2000 and 2010 and the corresponding environmental data in Brisbane, Australia, we explored relationships between heat wave exposure in different months of pregnancy and preterm birth or stillbirth. Six heat wave definitions were used in this study. After controlling for confounding factors, hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using extended Cox proportional hazards regression models with time-dependent covariates. RESULTS: For most heat wave definitions, the adjusted HRs of preterm birth varied by different gestational months and ranged from 1.08 (HR = 1.08; 95% CI = 1.00, 1.18) to 1.53 (HR = 1.53; 95% CI = 1.41, 1.68). Heat wave exposure in early pregnancy was more likely to increase the risk of stillbirth compared with heat wave exposure in late pregnancy. CONCLUSIONS: Overall, we found relationships between preterm birth and heat wave exposure in all months of pregnancy based on most heat wave definitions. We did not find a specifically high period of susceptibility during pregnancy for preterm birth associated with heat wave exposure. However, earlier gestational months might be key exposure windows for heat-wave-affected stillbirth.

2.
Environ Sci Process Impacts ; 21(1): 163-173, 2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30632581

RESUMO

BACKGROUND: Eczema and dermatitis are a group of common skin conditions with multiple risk factors. Evidence of the effects of air pollutants on eczema and dermatitis remains limited. This study aimed to investigate the effects of short-term exposure to air pollution on eczema and dermatitis in Beijing. METHODS: A time-stratified case-crossover design was used to assess the associations between short-term changes in air pollution and the hospital outpatient visits for eczema and dermatitis in Beijing. RESULTS: A total of 157 595 outpatient visits for eczema and dermatitis were recorded from April 1, 2012 to April 30, 2014. All pollutants showed significant positive associations with the number of outpatient visits for eczema and dermatitis on lag 0 (the current day). Per IQR increase in PM2.5, PM10, NO2 and SO2 was associated with 3.81% (95% CI: 2.92-4.7%), 3.18% (95% CI: 2.39-3.97%), 5.43% (95% CI: 4.43-6.43%) and 5.57% (95% CI: 4.55-6.58%) increases in outpatient visits for eczema and dermatitis on lag 0. Associations of air pollutants with eczema and dermatitis outpatient visits varied with the seasons and were stronger among older people and females. Also, an association of consecutive days' high concentration pollution with increased outpatient visits was observed. CONCLUSIONS: Exposure to air pollution increases the exacerbation of eczema and dermatitis and stronger positive associations between air pollutants and outpatient visits for eczema and dermatitis were found among the aged, females and when high concentration air pollution occurs continuously.


Assuntos
Poluição do Ar/análise , Dermatite/epidemiologia , Eczema/epidemiologia , Adulto , Poluentes Atmosféricos/análise , Pequim/epidemiologia , Monitoramento Ambiental , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pacientes Ambulatoriais , Estações do Ano
3.
Sci China Life Sci ; 2019 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-30671885

RESUMO

Chronic obstructive pulmonary disease (COPD), lung cancer (LC) and tuberculosis (TB) are common chronic lung diseases that generate a large disease burden and significant health care resource use in China. The aim of this study was to quantify spatial patterns and effects of air pollution and meteorological factors on hospitalization of COPD, LC and TB in Beijing. Daily counts of hospitalization for 2010 were obtained from the Beijing Urban Employees Basic Medical Insurance (UEBMI) system. Bayesian hierarchical Poisson regression models were applied to identify spatial patterns of hospitalization for COPD, LC and TB at the district level and explore associations with inhalable particulate matter (aerodynamic diameter <10 µm, PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), mean temperature and relative humidity. There were 18,882, 14,295 and 2,940 counts of hospitalizations for COPD, LC and TB respectively, in Beijing in 2010. Clusters of high relative risk were in different locations for the three diseases. The effect of relative humidity on COPD hospitalization was most significant with a relative risk (RR) of 1.070 (95%CI: 1.054, 1.086) per one percent increase. For lung cancer hospitalization, exposure to ambient SO2 was associated with a RR of 1.034 (95%CI: 1.011, 1.058) per µg m-3 increase. For tuberculosis, the effect of mean temperature was significant with a RR of 1.107 (95%CI: 1.038, 1.180) per °C increase. Risk factors and spatial patterns were different for hospitalization of non-infectious and infectious chronic lung disease in Beijing. Even over a short time period (one year), associations were apparent with air pollution and meteorological factors.

4.
J Xray Sci Technol ; 2018 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-30400125

RESUMO

BACKGROUND: Some patients cannot be imaged with cone-beam CT for image-guided radiation therapy because their size, pose, or fixation devices cause collisions with the machine. OBJECTIVE: To investigate imaging trajectories that avoid such collisions by using virtual isocenter and variable magnification during acquisition while yielding comparable image quality. METHODS: The machine components most likely to collide are the gantry and kV detector. A virtual isocenter trajectory continuously moves the patient during gantry rotation to maintain an increased separation between the two. With dynamic magnification, the kV detector is dynamically moved to increase clearance for an angular range around the potential collision point while acquiring sufficient data to maintain the field-of-view. Both strategies were used independently and jointly with the resultant image quality evaluated against the standard circular acquisition. RESULTS: Collision avoiding trajectories show comparable contrast and resolution to standard techniques. For an anthropomorphic phantom, the RMSE is <7×10- 4, multi-scale structural similarity index is >0.97, and visual image fidelity is >0.96 for all trajectories when compared to a standard circular scan. CONCLUSIONS: The proposed trajectories avoid machine-patient collisions while providing comparable image quality to the current standard thereby enabling CBCT imaging for patients that could not otherwise be scanned.

5.
Sens Imaging ; 192018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30319317

RESUMO

C-arm cone-beam computed tomography (CBCT) has been used increasingly as an imaging tool for yielding 3D anatomical information about the subjects in surgical and interventional procedures. In the clinical applications, the limited field-of-view (FOV) of C-arm CBCT can lead to significant data truncation, resulting in image artifacts that can obscure low contrast tumor embedded within soft-tissue background, thus limiting the utility of C-arm CBCT. The truncation issue can become serious as most of the surgical and interventional procedures would involve devices and tubes that are placed outside the FOV of C-arm CBCT and thus can engender angularly-varying-data truncation. Existing methods may not be adequately applicable to dealing with the angularly-varying truncation. In this work, we seek to reduce truncation artifacts by tailoring optimization-based reconstruction directly from truncated data, without performing pre-reconstruction data compensation, collected from physical phantoms and human subjects. The reconstruction problem is formulated as a constrained optimization program in which a data-derivative-ℓ2-norm fidelity is included for effectively suppressing image artifacts caused by the angularly-varying-data truncation, and the generic Chambolle-Pock algorithm is tailored to solve the optimization program. The results of the study suggest that an appropriately designed optimization-based reconstruction can be exploited for yielding images with reduced artifacts caused by angularly-varying-data truncation.

6.
Med Phys ; 2018 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-30370544

RESUMO

PURPOSE: We study the problem of spectrum estimation from transmission data of a known phantom. The goal is to reconstruct an x-ray spectrum that can accurately model the x-ray trans-mission curves and reects a realistic shape of the typical energy spectra of the CT system. METHODS: Spectrum estimation is posed as an optimization problem with x-ray spectrum as un-known variables, and a Kullback-Leibler (KL) divergence constraint is employed to incorporate prior knowledge of the spectrum and enhance numerical stability of the estimation process. The formulated constrained optimization problem is convex and can be solved efficiently by use of the exponentiated-gradient (EG) algorithm. We demonstrate the effectiveness of the proposed approach on the simulated and experimental data. The comparison to the expectation-maximization (EM) method is also discussed. RESULTS: In simulations, the proposed algorithm is seen to yield x-ray spectra that closely match the ground truth and represent the attenuation process of x-ray photons in materials, both included and not included in the estimation process. In experiments, the calculated transmission curve is in good agreement with the measured transmission curve, and the estimated spectra exhibits physi-cally realistic looking shapes. The results further show the comparable performance between the proposed optimization-based approach and EM. CONCLUSIONS: Our formulation of a constrained optimization provides an interpretable and exible framework for spectrum estimation. Moreover, a KL-divergence constraint can include a prior spec-trum and appears to capture important features of x-ray spectrum, allowing accurate and robust estimation of x-ray spectrum in CT imaging. This article is protected by copyright. All rights reserved.

7.
Environ Res ; 167: 614-621, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30172194

RESUMO

OBJECTIVE: Extreme temperature is an important risk factor for cardiovascular diseases, and the elderly are particularly vulnerable to temperature variation. Global warming and the increasingly aging population are two major global challenges for human health; thus, an urgent need exists to project the temperature-related cardiovascular disease burden regarding both of the aforementioned factors. We aimed to the project temperature-related burden of cardiovascular diseases using years of life lost (YLL) in the elderly in a Chinese city with typical subtropical climate. METHODS: A retrospective time-series study was first conducted to estimate cardiovascular disease burden associated with temperature in the elderly from 2008 to 2015 in Ningbo, China. Then, future projections considering demographic change and adaptation under 19 global-scale climate models (GCMs) and 3 different Representative Concentration Pathways (RCPs) scenarios for the 2050s and 2070s were estimated. RESULTS: The exposure-response curve for temperature on YLL from cardiovascular diseases was U-shaped, with increased YLL for both higher- and lower- than optimal temperature. The projected annual increase in heat-related YLL was outweighed by the decrease in cold-related YLL. However, monthly analysis demonstrated that temperature-related YLL will increase significantly in August. Additionally, heat-related YLL is projected to increase 3.1-11.5 times for the 2050s and 2070s relative to baseline, when considering demographic changes, even with 30% adaptation taken into consideration. CONCLUSIONS: Although annual YLL from cardiovascular diseases in the elderly associated with temperature will decrease in the future, heat-related YLL will increase tremendously, which indicates that more adaptation strategies and greenhouse emission control measures should be undertaken to reduce the future heat-related burden of cardiovascular diseases in the elderly.

8.
Environ Pollut ; 242(Pt B): 1266-1273, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30121480

RESUMO

OBJECTIVE: Ambient ozone is one of the most important air pollutants with respect to its impacts on human health and its increasing concentrations globally. However, studies which explored the burden of ozone pollution on chronic obstructive pulmonary disease (COPD) and estimated the relevant economic loss were rare. OBJECTIVE: We explored the relationships between ambient ozone exposure and years of life lost (YLL) from COPD mortality and estimated the relevant economic loss in Ningbo, in the Yangtze River Delta of China, 2011-2015. METHODS: A time-series study was conducted to explore the effects of ozone on YLL from COPD. Seasonal stratified analyses were performed, and the effect modification of demographic factors was estimated. In addition, the related economic loss was calculated using the method of the value per statistical life year (VSLY). RESULTS: Averaged daily mean maximum 8-h average ozone concentration was 40.90 ppb in Ningbo, China, 2011-2015. The effect of short term ambient ozone exposure on COPD YLL was more pronounced in the cool season than in the warm season, with 10 ppb increment of ozone corresponding to 7.09(95%CI: 3.41, 10.78) years increase in the cool season and 0.31 (95%CI: -2.15, 2.77) years change in the warm season. The effect was higher in the elderly than the young. Economic loss due to excess COPD YLL related to ozone exposure accounted for 7.30% of the total economic loss due to COPD YLL in Ningbo during the study period. CONCLUSIONS: Our findings highlight that ozone exposure was related to tremendous disease burden of COPD in Ningbo, China. The effects were more pronounced in the cool season, and the elderly were more susceptible populations.


Assuntos
Poluentes Atmosféricos/toxicidade , Poluição do Ar/análise , Exposição Ambiental/análise , Ozônio/toxicidade , Doença Pulmonar Obstrutiva Crônica/induzido quimicamente , Doença Pulmonar Obstrutiva Crônica/mortalidade , Idoso , Poluentes Atmosféricos/análise , China , Feminino , Humanos , Masculino , Ozônio/análise , Rios , Estações do Ano
9.
Lancet Planet Health ; 2(7): e313-e323, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30074894

RESUMO

BACKGROUND: To mitigate the serious levels of air pollution in China, the State Council of China issued the Air Pollution Prevention and Control Action Plan (APPCAP) in 2013. This policy is a milestone in air quality control in China. We aimed to evaluate the effects of the APPCAP on long-term air quality management and the related health impacts in China. METHODS: We did an analysis of national air quality monitoring and mortality data to estimate the health impact of the APPCAP from 2013 to 2017 in 74 key cities in China. Changes in mortality and in years of life lost (YLL), an indicator that considers life expectancy at death, were calculated to assess the health impact of air quality management during the 5-year period. FINDINGS: Between 2013 and 2017, annual average concentrations of PM2·5 decreased by 33·3% (95% CI 16·3-50·3), PM10 by 27·8% (8·0-47·5), sulphur dioxide by 54·1% (28·2-80·0), and carbon monoxide by 28·2% (3·1-53·3) in the 74 key cities. However, no significant change was seen in annual average concentrations of nitrogen dioxide (9·7% reduction; 95% CI -23·0 to 42·4) or ozone (20·4% increase; -30·1 to 71·0). In 2017, as a result of substantial improvements in air quality, there were 47 240 (95% CI 25 870-69 990) fewer deaths and 710 020 (420 230-1 025 460) fewer YLL in the 74 key cities in China than in 2013. INTERPRETATION: Substantial reductions in mortality and YLL related to control of ambient air pollution were achieved from 2013 to 2017 in China, indicating appreciable effectiveness of China's APPCAP. However, emissions control efforts for ozone and nitrogen dioxide should be strengthened in the future. FUNDING: National Natural Science Foundation of China and the National Key Research and Development Program of China.

10.
J Magn Reson ; 294: 24-34, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30005191

RESUMO

Electron paramagnetic resonance imaging (EPRI) can yield information about the 3-dimensional (3D) spatial distribution of the unpaired-electron-spin density from which the spatial distribution of oxygen concentration within tumor tissue, referred to as the oxygen image or electron paramagnetic resonance (EPR) image in this work, can be derived. Existing algorithms for reconstruction of EPR images often require data collected at a large number of densely sampled projection views, resulting in a prolonged data-acquisition time and consequently numerous practical challenges especially to in vivo animal EPRI. Therefore, a strong interest exists in shortening data-acquisition time through reducing the number of data samples collected in EPRI, and one approach is to acquire data at a reduced number of sparsely distributed projection views from which existing algorithms may reconstruct images with prominent artifacts. In this work, we investigate and develop an optimization-based technique for image reconstruction from data collected at sparsely sampled projection views for reducing scanning time in EPRI. Specifically, we design a convex optimization program in which the EPR image of interest is formulated as a solution and then tailor the Chambolle-Pock (CP) primal-dual algorithm to reconstruct the image by solving the convex optimization program. Using computer-simulated EPRI data from numerical phantoms and real EPRI data collected from physical phantoms, we perform studies on the verification and characterization of the optimization-based technique for EPR image reconstruction. Results of the studies suggest that the technique may yield accurate EPR images from data collected at sparsely distributed projection views, thus potentially enabling fast EPRI with reduced acquisition time.

11.
Environ Pollut ; 242(Pt A): 492-499, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30005261

RESUMO

Severe and persistent haze accompanied by high concentrations of fine particulate matter (PM2.5) has become a great public health concern in urban China. However, research on the health effects of PM2.5 in China has been hindered by the lack of high-quality exposure estimates. In this study, we assessed the excess mortality associated with both short- and long-term exposure to ambient PM2.5 simultaneously using satellite-derived exposure data at a high spatiotemporal resolution. Adult registries of non-accidental, respiratory and cardiovascular deaths in urban Beijing in 2013 were collected. Exposure levels were estimated from daily satellite-based PM2.5 concentrations at 1 km spatial resolution from 2004 to 2013. Mixed Poisson regression models were fitted to estimate the cause-specific mortality in association with PM2.5 exposures. With the mutual adjustment of short- and long-term exposure of PM2.5, the percent increases associated with every 10 µg/m3 increase in short-term PM2.5 exposure were 0.09% (95% CI: -0.14%, 0.33%; lag 01), 1.02% (95% CI: 0.08%, 1.97%; lag 04) and 0.09% (95% CI: -0.23%, 0.42%; lag 01) for non-accidental, respiratory and cardiovascular mortality, respectively; those attributable to every 10 µg/m3 increase in long-term PM2.5 exposure (9-year moving average) were 16.78% (95% CI: 10.58%, 23.33%), 44.14% (95% CI: 20.73%, 72.10%) and 3.72% (95% CI: -3.75%, 11.77%), respectively. Both associations of short- and long-term exposure with the cause-specific mortality decreased after they were mutually adjusted. Associations between short-term exposure to satellite-based PM2.5 and cause-specific mortality were larger than those estimated using fixed measurements. Satellite-based PM2.5 predictions help to improve the spatiotemporal resolution of exposure assessments and the mutual adjustment model provide better estimation of PM2.5 associated health effects. Effects attributable to long-term exposure of PM2.5 were larger than those of short-term exposure, which should be more concerned for public health.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Exposição Ambiental/estatística & dados numéricos , Mortalidade/tendências , Material Particulado/análise , Imagens de Satélites , Adulto , Pequim/epidemiologia , China , Humanos , Saúde Pública
12.
BMC Infect Dis ; 18(1): 158, 2018 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-29614964

RESUMO

BACKGROUND: Hand-foot-mouth disease (HFMD) is a common infectious disease in China and occurs mostly in infants and children. Beijing is a densely populated megacity, in which HFMD has been increasing in the last decade. The aim of this study was to quantify spatio-temporal characteristics of HFMD and the relationship between meteorological factors and HFMD incidence in Beijing, China. METHODS: Daily counts of HFMD cases from January 2010 to December 2012 were obtained from the Beijing Center for Disease Prevention and Control (CDC). Seasonal trend decomposition with Loess smoothing was used to explore seasonal patterns and temporal trends of HFMD. Bayesian spatiotemporal Poisson regression models were used to quantify spatiotemporal patterns of HFMD incidence and associations with meteorological factors. RESULTS: There were 114,777 HFMD cases reported to Beijing CDC from 1 January 2010 to 31 December 2012 and the raw incidence was 568.6 per 100,000 people. May to July was the peak period of HFMD incidence each year. Low-incidence townships were clustered in central, northeast and southwest regions of Beijing. Mean temperature, relative humidity, wind velocity and sunshine hours were all positively associated with HFMD. The effect of wind velocity was significant with a RR of 3.30 (95%CI: 2.37, 4.60) per meter per second increase, as was sunshine hours with a RR of 1.20 (95%CI: 1.02, 1.40) per 1 hour increase. CONCLUSIONS: The distribution of HFMD in Beijing was spatiotemporally heterogeneous, and was associated with meteorological factors. Meteorological monitoring could be incorporated into prediction and surveillance of HFMD in Beijing.


Assuntos
Doença de Mão, Pé e Boca/diagnóstico , Análise Espaço-Temporal , Adolescente , Teorema de Bayes , Criança , Pré-Escolar , China/epidemiologia , Feminino , Doença de Mão, Pé e Boca/epidemiologia , Doença de Mão, Pé e Boca/etiologia , Humanos , Umidade , Incidência , Lactente , Recém-Nascido , Masculino , Risco , Estações do Ano , Temperatura Ambiente , Vento
13.
Sci Total Environ ; 630: 943-950, 2018 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-29499549

RESUMO

It is widely accepted that temperatures is associated with cardiovascular mortality, however, few studies have explored the effects of temperature on years of life lost (YLL) from cardiovascular mortality in China under future global warming scenarios. Therefore, there is an urgent need to obtain projections of YLL from cardiovascular diseases. Here we applied nineteen global-scale climate models (GCMs) and three Representative Concentration Pathway emission scenarios (RCPs) in the 2050s and 2070s for temperature-related YLL projection in Tianjin, China. We found the relationships between daily maximum temperatures with YLL from cardiovascular mortality were basically U-shaped. We observed increasing net annual YLL across a range of multiple models under different climate scenarios, suggesting that increasing heat-related YLL from cardiovascular mortality could offset decreasing cold-related YLL from cardiovascular mortality. The largest temperature-related YLL from cardiovascular mortality were observed under the RCP8.5 scenario and increased more rapidly in the 2070s versus the 2050s. Monthly analyses of percent changes in YLL from cardiovascular mortality showed that the largest percent increases occurred from May to September. If warm adaptation occurs, only the adverse effects under RCP2.6 could be fully offset in both 2050 and 2070. Our exploration provided further evidence for the potential health impacts of global warming and highlighted that government should develop environmental policies for future health risks.


Assuntos
Doenças Cardiovasculares/epidemiologia , Expectativa de Vida , Temperatura Ambiente , China/epidemiologia , Temperatura Baixa , Exposição Ambiental , Política Ambiental , Previsões , Temperatura Alta , Humanos
14.
Stroke ; 49(4): 828-834, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29523649

RESUMO

BACKGROUND AND PURPOSE: Global warming has attracted worldwide attention. Numerous studies have indicated that stroke is associated with temperature; however, few studies are available on the projections of the burden of stroke attributable to future climate change. We aimed to investigate the future trends of stroke years of life lost (YLL) associated with global warming. METHODS: We collected death records to examine YLL in Tianjin, China, from 2006 to 2011. We fitted a standard time-series Poisson regression model after controlling for trends, day of the week, relative humidity, and air pollution. We estimated temperature-YLL associations with a distributed lag nonlinear model. These models were then applied to the local climate projections to estimate temperature-related YLL in the 2050s and 2070s. We projected temperature-related YLL from stroke in Tianjin under 19 global-scale climate models and 3 different greenhouse gas emission scenarios. RESULTS: The results showed a slight decrease in YLL with percent decreases of 0.85%, 0.97%, and 1.02% in the 2050s and 0.94%, 1.02%, and 0.91% in the 2070s for the 3 scenarios, respectively. The increases in heat-related annual YLL and the decreases in cold-related YLL under the high emission scenario were the strongest. The monthly analysis showed that the most significant increase occurred in the summer months, particularly in August, with percent changes >150% in the 2050s and up to 300% in the 2070s. CONCLUSIONS: Future changes in climate are likely to lead to an increase in heat-related YLL, and this increase will not be offset by adaptation under both medium emission and high emission scenarios. Health protections from hot weather will become increasingly necessary, and measures to reduce cold effects will also remain important.

15.
IEEE Trans Biomed Eng ; 65(4): 936-946, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29570054

RESUMO

OBJECTIVE: We investigate an optimization-based approach to image reconstruction from list-mode data in digital time-of-flight (TOF) positron emission tomography (PET) imaging. METHOD: In the study, the image to be reconstructed is designed as a solution to a convex, non-smooth optimization program, and a primal-dual algorithm is developed for image reconstruction by solving the optimization program. The algorithm is first applied to list-mode TOF-PET data of a typical count level from physical phantoms and a human subject. Subsequently, we explore the algorithm's potential for image reconstruction in low-dose and/or fast TOF-PET imaging of practical interest by applying the algorithm to list-mode TOF-PET data of different, low-count levels from the same physical phantoms and human subject. RESULTS: Visual inspection and quantitative-metric analysis reveal that the optimization reconstruction approach investigated can yield images with enhanced spatial and contrast resolution, suppressed image noise, and increased axial volume coverage over the reference images obtained with a standard clinical reconstruction algorithm especially for low-dose TOF-PET data. SIGNIFICANCE: The optimization-based reconstruction approach can be exploited for yielding insights into potential quality upper bound of reconstructed images in, and design of scanning protocols of, TOF-PET imaging of practical significance.

16.
Med Phys ; 45(5): 1857-1870, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29516523

RESUMO

PURPOSE: We seek to investigate an optimization-based one-step method for image reconstruction that explicitly compensates for nonlinear spectral response (i.e., the beam-hardening effect) in dual-energy CT, to investigate the feasibility of the one-step method for enabling two dual-energy partial-angular-scan configurations, referred to as the short- and half-scan configurations, on standard CT scanners without involving additional hardware, and to investigate the potential of the short- and half-scan configurations in reducing imaging dose and scan time in a single-kVp-switch full-scan configuration in which two full rotations are made for collection of dual-energy data. METHODS: We use the one-step method to reconstruct images directly from dual-energy data through solving a nonconvex optimization program that specifies the images to be reconstructed in dual-energy CT. Dual-energy full-scan data are generated from numerical phantoms and collected from physical phantoms with the standard single-kVp-switch full-scan configuration, whereas dual-energy short- and half-scan data are extracted from the corresponding full-scan data. Besides visual inspection and profile-plot comparison, the reconstructed images are analyzed also in quantitative studies based upon tasks of linear-attenuation-coefficient and material-concentration estimation and of material differentiation. RESULTS: Following the performance of a computer-simulation study to verify that the one-step method can reconstruct numerically accurately basis and monochromatic images of numerical phantoms, we reconstruct basis and monochromatic images by using the one-step method from real data of physical phantoms collected with the full-, short-, and half-scan configurations. Subjective inspection based upon visualization and profile-plot comparison reveals that monochromatic images, which are used often in practical applications, reconstructed from the full-, short-, and half-scan data are largely visually comparable except for some differences in texture details. Moreover, quantitative studies based upon tasks of linear-attenuation-coefficient and material-concentration estimation and of material differentiation indicate that the short- and half-scan configurations yield results in close agreement with the ground-truth information and that of the full-scan configuration. CONCLUSIONS: The one-step method considered can compensate effectively for the nonlinear spectral response in full- and partial-angular-scan dual-energy CT. It can be exploited for enabling partial-angular-scan configurations on standard CT scanner without involving additional hardware. Visual inspection and quantitative studies reveal that, with the one-step method, partial-angular-scan configurations considered can perform at a level comparable to that of the full-scan configuration, thus suggesting the potential of the two partial-angular-scan configurations in reducing imaging dose and scan time in the standard single-kVp-switch full-scan CT in which two full rotations are performed. The work also yields insights into the investigation and design of other nonstandard scan configurations of potential practical significance in dual-energy CT.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador/métodos , Tomografia Computadorizada por Raios X , Imagens de Fantasmas , Razão Sinal-Ruído
17.
Environ Int ; 113: 42-49, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29421406

RESUMO

Limited studies have explored the impacts of exposure to sustained high levels of air pollution (air pollution wave) on mortality. Given that the frequency, intensity and duration of air pollution wave has been increasing in highly polluted regions recently, understanding the impacts of air pollution wave is crucial. In this study, air pollution wave was defined as 2 or more consecutive days with air pollution index (API) > 100. The impacts of air pollution wave on years of life lost (YLL) due to non-accidental, cardiovascular and respiratory deaths were evaluated by considering both consecutive days with high levels of air pollution and daily air pollution levels in Tianjin, China, from 2006 to 2011. The results showed the durational effect of consecutive days with high levels of air pollution was substantial in addition to the effect of daily air pollution. For instance, the durational effect was related to an increase in YLL of 116.6 (95% CI: 4.8, 228.5) years from non-accidental deaths when the air pollution wave was sustained for 4 days, while the corresponding daily air pollution's effect was 121.2 (95% CI: 55.2, 187.1) years. A better interpretation of the health risks of air pollution wave is crucial for air pollution control policy making and public health interventions.

18.
Skin Pharmacol Physiol ; 31(2): 107-113, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29408821

RESUMO

BACKGROUND/AIMS: There is increasing evidence that exposure to air pollutants, including particulate matter (PM2.5, PM10), nitrogen dioxide (NO2), and sulfur dioxide (SO2), might aggravate preexisting skin diseases such as eczema and urticaria. Here we investigated if a possible link exists between air pollution and acne vulgaris. We assessed the association between ambient air pollutant concentrations and the number of visits of patients for acne vulgaris to a dermatological outpatient clinic in Beijing, China, from April 1, 2012 to April 30, 2014. METHODS: In this time period, 59,325 outpatient visits were recorded because of acne vulgaris. Daily air pollution parameters for PM10, PM2.5, SO2, and NO2 were obtained from the Beijing Municipal Environmental Monitoring Center. RESULTS: Increased concentrations of ambient PM2.5, PM10, and NO2 were significantly associated with increased numbers of outpatient visits for acne vulgaris over the 2 years. These effects could be observed for NO2 in a single-pollutant model and for PM2.5, PM10, and NO2 in 2-pollutant models, which are closer to real-life exposure. Of note, these effects were specific because they were not observed for increased SO2 concentrations, which even showed negative correlations in all test models. CONCLUSION: This study provides indirect evidence for a link between acne vulgaris and air pollution.


Assuntos
Acne Vulgar/patologia , Poluentes Atmosféricos/efeitos adversos , Poluição do Ar/efeitos adversos , Exposição Ambiental/efeitos adversos , Adolescente , Adulto , Pequim , Feminino , Humanos , Masculino , Dióxido de Nitrogênio/efeitos adversos , Pacientes Ambulatoriais , Material Particulado/efeitos adversos , Dióxido de Enxofre/efeitos adversos , Fatores de Tempo , Adulto Jovem
19.
Environ Res ; 162: 152-159, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29306663

RESUMO

Human health faces unprecedented challenges caused by climate change. Thus, studies of the effect of temperature change on total mortality have been conducted in numerous countries. However, few of those studies focused on temperature-related mortality due to cardiovascular disease (CVD) or considered future population changes and adaptation to climate change. We present herein a projection of temperature-related mortality due to CVD under different climate change, population, and adaptation scenarios in Beijing, a megacity in China. To this end, 19 global circulation models (GCMs), 3 representative concentration pathways (RCPs), 3 socioeconomic pathways, together with generalized linear models and distributed lag non-linear models, were used to project future temperature-related CVD mortality during periods centered around the years 2050 and 2070. The number of temperature-related CVD deaths in Beijing is projected to increase by 3.5-10.2% under different RCP scenarios compared with that during the baseline period. Using the same GCM, the future daily maximum temperatures projected using the RCP2.6, RCP4.5, and RCP8.5 scenarios showed a gradually increasing trend. When population change is considered, the annual rate of increase in temperature-related CVD deaths was up to fivefold greater than that under no-population-change scenarios. The decrease in the number of cold-related deaths did not compensate for the increase in that of heat-related deaths, leading to a general increase in the number of temperature-related deaths due to CVD in Beijing. In addition, adaptation to climate change may enhance rather than ameliorate the effect of climate change, as the increase in cold-related CVD mortality greater than the decrease in heat-related CVD mortality in the adaptation scenarios will result in an increase in the total number of temperature-related CVD mortalities.

20.
Environ Sci Process Impacts ; 20(2): 395-405, 2018 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-29337319

RESUMO

BACKGROUND: the effects of interaction between temperature and inhalable particulate matter (aerodynamic diameter < 10 µm, PM10) on mortality have been examined in some previous studies, but the results were inconsistent. This study aims to explore whether the effects of PM10 on daily non-accidental, cardiovascular and respiratory mortality were modified by temperature levels in Beijing from 2006 to 2009. METHODS: we applied a bivariate response surface model and temperature-stratified model based on time-series Poisson generalized additive models (GAMs) to examine the interactive effects in single- and two-pollutant models. The modification of age and gender was examined in subgroup analyses. RESULTS: the median of temperature (15.9 °C) and visualized turning point (20 °C) were chosen as cut-offs to define the temperature strata as two levels (low and high). Results showed that the effect estimates of PM10 were stronger at the high temperature level for non-accidental, cardiovascular and respiratory mortality than at the low temperature level. When controlling the moving average lag of temperature for 14 days, the effect estimates per 10 µg m-3 increase in PM10 for non-accidental, cardiovascular and respiratory mortality increased 0.14% (95% CI: 0.05, 0.22), 0.12% (95% CI: 0.02, 0.23) and 0.14% (95% CI: -0.06, 0.34) when the temperature was low and 0.24% (95% CI: 0.12, 0.35), 0.17% (95% CI: 0.01, 0.34) and 0.45% (95% CI: 0.13, 0.78) at the high temperature level, respectively. In the two-pollutant model, the effects of PM10 were attenuated at both high and low temperatures at all lags after adjusting SO2 and NO2. The PM10 effects were stronger at the high temperature level for females and elderly people (≥65 years old). CONCLUSION: the findings suggest that daily mortality attributed to PM10 might be modified by temperature. The interaction between air pollution and global climate change has potential strategy and policy implications.


Assuntos
Poluentes Atmosféricos/análise , Mudança Climática , Mortalidade/tendências , Material Particulado/análise , Temperatura Ambiente , Adolescente , Idoso , Pequim , Feminino , Humanos , Masculino , Modelos Estatísticos , Tamanho da Partícula
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