Scatter coincident events are the important factor that affects the quality of positron emission tomography (PET) images. In this paper, according to the characters of projection data, a scatter correction method which uses maximum likelihood expectation maximization (MLEM) algorithm based on poisson model is proposed. We compared the sinograms and reconstructed images corrected by MLEM algorithm and deconvolution method respectively. The results indicate that the algorithm proposed in this paper increases the contrast of images while correcting scatter. It is better than the traditional method.
Algorithms ; Image Processing, Computer-Assisted ; methods ; Nonlinear Dynamics ; Poisson Distribution ; Positron-Emission Tomography ; methods ; Scattering, Radiation

Bursting is an important firing mode of neurons. To propose a stochastic model of bursting spike train, the interspike interval (ISI) characteristics of single-spiking train and bursting spike train were analyzed and compared. In contrast with the exponential distribution of ISI in single-spiking train, normal distribution is supposed to be the ISI model of bursting spike train. Simulated neural spike trains were produced to investigate the spectrum features of the ISI model. The results showed that: (1) bursting spike train with normally distributed ISI held a low-pass spectrum while the spectrum of single-spiking train was flat; (2) the coefficient of variation of ISI in bursting train decided the bandwidth of its low-pass spectrum. Then neural activities from anesthetized rodent were used to check the validity of the model. 10 simultaneously recorded bursting spike trains and 10 single-spiking trains were selected during anesthesia and after pure-oxygen-washout period respectively. The spectrograms of these neural spike trains were analyzed and the results were matched with our mathematical model. It is believed that the bursting spike train model established in this paper will help to theoretically study the statistical characters of neural spike train and to add mathematical foundation in neural coding schemes.
Action Potentials ; physiology ; Animals ; Computer Simulation ; Electroencephalography ; Humans ; Male ; Models, Neurological ; Models, Theoretical ; Neurons ; physiology ; Periodicity ; Poisson Distribution ; Rats ; Rats, Wistar ; Spectrum Analysis ; Stochastic Processes

Based on a nonlinear neuron model, the Poisson noise is used to imitate the noisy environments of neurons, and, further, the phenomenon of coherence resonance (CR) of a nonlinear neuron model subject to a voltage-gated channel noise and a random point trains synaptic noise is investigated. Based on the fractional noise theory and Euler schemes, the evolution of the membrane potential and the coefficient of variation (CV) of the interval-spike-interval of the neuron firing have been obtained. It is shown that, in the absence of external periodic signal, such CV can be decreased at a certain intensity of neurotransmitter arrivals trains lambda and a proper strength of the voltage-gated channel noise D, so that the coherence of the system is maximal and the phenomenon of CR can take place.
Action Potentials ; physiology ; Cerebral Cortex ; cytology ; physiology ; Computer Simulation ; Humans ; Models, Neurological ; Neurons ; cytology ; physiology ; Poisson Distribution ; Stochastic Processes ; Synapses ; physiology

OBJECTIVETo investigate the effect of air pollution on stroke mortality in Tianjin, China, and to provide basis for stroke control and prevention.

METHODSTotal data of mortality surveillance were collected by Tianjin Centers for Disease Control and Prevention. Meteorological data and atmospheric pollution data were from Tianjin Meteorological Bureau and Tianjin Environmental Monitoring Center, respectively. Generalized additive Poisson regression model was used in time-series analysis on the relationship between air pollution and stroke mortality in Tianjin. Single-pollutant analysis and multi-pollutant analysis were performed after adjustment for confounding factors such as meteorological factors, long-term trend of death, "days of the week" effect and population.

RESULTSThe crude death rates of stroke in Tianjin were from 136.67 in 2001 to 160.01/100000 in 2009, with an escalating trend (P = 0.000), while the standardized mortality ratios of stroke in Tianjin were from 138.36 to 99.14/100000, with a declining trend (P = 0.000). An increase of 10 µg/m³ in daily average concentrations of atmospheric SO₂, NO₂ and PM₁₀ led to 1.0105 (95%CI: 1.0060 ∼ 1.0153), 1.0197 (95%CI: 1.0149 ∼ 1.0246) and 1.0064 (95%CI: 1.0052 ∼ 1.0077), respectively, in relative risks of stroke mortality. SO₂ effect peaked after 1-day exposure, while NO₂ and PM₁₀ effects did within 1 day.

CONCLUSIONAir pollution in Tianjin may increase the risk of stroke mortality in the population and induce acute onset of stroke. It is necessary to carry out air pollution control and allocate health resources rationally to reduce the hazard of stroke mortality.

Air Pollutants ; analysis ; Air Pollution ; analysis ; China ; epidemiology ; Environmental Monitoring ; Humans ; Models, Theoretical ; Particulate Matter ; analysis ; Poisson Distribution ; Stroke ; epidemiology ; mortality ; Survival Rate ; Time Factors

A dichotomous (2-category) outcome variable is often encountered in biomedical research, and Multiple Logistic Regression is often deployed for the analysis of such data. As Logistic Regression estimates the Odds Ratio (OR) as an effect measure, it is only suitable for case-control studies. For cross-sectional and time-to-event studies, the Prevalence Ratio and Cumulative Incidence Ratio can be estimated and easily interpreted. The logistic regression will produce the OR which is difficult to interpret in these studies. In this report, we reviewed 3 alternative multivariate statistical models to replace Logistic Regression for the analysis of data from cross-sectional and time-to-event studies, viz, Modified Cox Proportional Hazard Regression Model, Log-Binomial Regression Model and Poisson Regression Model incorporating the Robust Sandwich Variance. Although none of the models is without flaws, we conclude the last model is the most viable. A numeric example is given to compare the statistical results obtained from all 4 models.
Cross-Sectional Studies ; Humans ; Incidence ; Models, Statistical ; Multivariate Analysis ; Odds Ratio ; Outcome Assessment (Health Care) ; methods ; Poisson Distribution ; Prevalence ; Proportional Hazards Models ; Risk ; Risk Assessment

OBJECTIVES: Over the past several years, the incidence of hepatitis A infection has been increasing rapidly in the young-adult population in Korea. We examined the effects of area-level socioeconomic status and environmental hygiene on the incidence of hepatitis A. METHODS: This study is based on the registered national population of Korea and the national health insurance data from 2004 to 2008. A total of 73 459 individuals were confirmed to have had hepatitis A. The standardized incidences of hepatitis A in 232 districts adjusted for sex and age of people were calculated for each year, and the rate ratios of the incidence rates were estimated according to area-level socioeconomic status and environmental hygiene using multiple Poisson regression models. RESULTS: The incidence rates of hepatitis A infection were 15.6 (per 100 000) in 2004, 19.0 (per 100 000) in 2005, 27.2 (per 100 000) in 2006, 25.1 (per 100 000) in 2007, and 61.7 (per 100 000) in 2008. The analysis of the area-level effects showed that residential areas of the less deprived than other regions, areas with higher levels of education, and heavily populated areas were significantly associated with increased risk. CONCLUSIONS: There is a very strong possibility that both area-level socioeconomic status and environmental hygiene play a role in increasing the risk of hepatitis A infection in Korea. Therefore, to reduce hepatitis A infection, we need a nationwide strategy that considers these area-level characteristics.
Adolescent ; Adult ; Child ; Child, Preschool ; Female ; Hepatitis A/*epidemiology/etiology ; Humans ; Incidence ; Infant ; Infant, Newborn ; Male ; Middle Aged ; *National Health Programs ; Poisson Distribution ; Republic of Korea/epidemiology ; Risk Factors ; Social Class ; Young Adult

OBJECTIVES: Most of the studies on the effect of heat stress on preterm birth (PTB) are conducted in temperate climates. Evidence on this effect in hot and arid countries with low and middle income is limited. This paper describes the short-term effect of exposure to the hot and cold environment on a daily number of PTB in Iran. METHODS: The daily number of PTB was obtained from all hospitals of the city. Meteorological and air pollution data from 2011 to 2017 were obtained from a metrological station in the city. A semi-parametric generalized additive model following a quasi-Poisson distribution with the distributed lag non-linear model was selected as a modeling framework for time-series analysis to simultaneously model the short-term and lagged effect of heat stress on PTB in the Sabzevar city. RESULTS: The minimum and maximum daily temperature were - 11.2 and 45.4 °C respectively. The highest risk estimate at extreme cold temperature was found for apparent temperature (relative risk (RR) 1.83; 95% CI 1.61: 2.09). This pattern was seen for both models. For extreme hot temperatures, the model with mean temperature showed the highest risk increase for both the main model and air pollution adjusted model (RR 1.36; 95% CI 1.25: 1.49). The lowest risk estimate in extremely cold conditions was found in the model with mean temperature. However, for extremely hot temperature conditions, the lowest risk estimate was found for both maximum and apparent temperature. CONCLUSION Obstetricians working in semi-arid areas should be aware of the influence of environmental extreme temperature on the incidence of PTB.
Air Pollutants ; analysis ; Climate ; Cold Temperature ; adverse effects ; Environmental Exposure ; adverse effects ; Environmental Monitoring ; methods ; Female ; Hospital Records ; Hot Temperature ; adverse effects ; Humans ; Infant, Newborn ; Iran ; epidemiology ; Poisson Distribution ; Pregnancy ; Premature Birth ; etiology ; Risk Factors

OBJECTIVE: The association between neutrophil-to-lymphocyte ratio (NLR) with subclinical macrovascular and microvascular diseases has been less investigated. We sought to examine the association between NLR and new-onset subclinical macrovascular and microvascular abnormalities in the Chinese population. METHODS: From a community cohort, we included 6,430 adults aged ≥ 40 years without subclinical macrovascular and microvascular diseases at baseline. We measured subclinical macrovascular and microvascular abnormalities separately using the ankle-brachial index (ABI), brachial-ankle pulse wave velocity (baPWV), and albuminuria. RESULTS: During a mean follow-up of 4.3 years, 110 participants developed incident abnormal ABI, 746 participants developed incident elevated baPWV, and 503 participants developed incident albuminuria. Poisson regression analysis indicated that NLR was significantly associated with an increased risk of new-onset abnormal ABI, elevated baPWV, and albuminuria. Compared to overweight/obese participants, we found a much stronger association between NLR and subclinical vascular abnormalities in participants with normal weight. Furthermore, we found an interaction between the NLR and body mass index (BMI) on the risk of new-onset abnormal ABI ( P for interaction: 0.01). CONCLUSION NLR was associated with subclinical macrovascular and microvascular diseases in the Chinese population. Furthermore, in participants with normal weight, the association between NLR and subclinical vascular abnormalities was much stronger.
Adult ; Aged ; Ankle Brachial Index ; Body Mass Index ; China/epidemiology* ; Cohort Studies ; Female ; Humans ; Incidence ; Lymphocytes/cytology* ; Male ; Middle Aged ; Neutrophils/cytology* ; Poisson Distribution ; Prospective Studies ; Vascular Diseases/etiology*

Anemia is common in patients with advanced chronic kidney disease (CKD). Though erythropoiesis-stimulating agents (ESAs) have been strongly endorsed in guidelines, it is of particular financial interest. Recently, the reimbursement of ESAs in non-dialytic patients was started by the Korean National Health Insurance System. Thus, we investigated the impact of the reimbursement of ESAs on the anemia care in non-dialytic CKD patients. Medical records of patients with advanced CKD (estimated GFR <30 mL/min/1.73 m2) were reviewed. Use of ESAs, blood transfusion, and hemoglobin concentrations were analyzed from one year prior to reimbursement to three years following. We used multivariable modified Poisson regression to estimate the utilization prevalence ratio (PRs). A total of 1,791 medical records were analyzed. The proportion of patients receiving ESAs increased from 14.8% before reimbursement to a peak 33.6% in 1 yr after reimbursement; thereafter, ESA use decreased to 22.4% in 3 yr after reimbursement (compared with baseline; PR, 2.19 [95% CI, 1.40-3.42]). In patients with Hb <10 g/dL, the proportion of receiving ESAs increased from 32.1% before reimbursement to 66.7% in 3 yr after reimbursement (compared with baseline; PR, 2.04 [95% CI, 1.25-3.32]). Mean hemoglobin concentrations were 10.06±1.54 g/dL before reimbursement and increased to 10.78±1.51 g/dL in 3 yr after the reimbursement change (P=0.001). However, the requirement of blood transfusion was not changed over time. With the reimbursement of ESAs, the advanced CKD patients were more likely to be treated with ESAs, and the hemoglobin concentrations increased.
Adolescent ; Adult ; Aged ; Anemia/complications/*drug therapy/epidemiology ; Blood Transfusion ; Female ; Glomerular Filtration Rate ; Hematinics/*therapeutic use ; Hematocrit ; Hemoglobins/analysis ; Humans ; Male ; Middle Aged ; National Health Programs ; Poisson Distribution ; Prevalence ; Renal Insufficiency, Chronic/complications/*drug therapy/epidemiology ; Republic of Korea/epidemiology ; Retrospective Studies ; Young Adult

OBJECTIVES: To examine the sex-specific factors associated with being unaware of one's hepatitis B virus surface antigen (HBsAg) seropositivity status in a large, HBsAg-positive population of Koreans. METHODS: In total, 1197 subjects aged 19 years or older who were HBsAg-positive according to data from the 2007-2012 Korea National Health and Nutrition Examination Survey were included. Subjects were considered unaware of their HBsAg seropositivity status if they answered that they had no knowledge of being previously infected by the hepatitis B virus (HBV) or diagnosed with HBV hepatitis. Multivariate Poisson regression models with robust variance estimate were used to assess the significance of the variables using weighted frequencies. RESULTS: The majority (77.8%) of HbsAg-positive Korean adults (females, 81.9%; males, 74.6%) were unaware of their HBsAg seropositivity status. We found that sex (female: prevalence ratio [PR] 1.19), household income (low: PR, 1.15), marital status (never married: PR, 1.18), self-rated health (moderate: PR, 1.14; good: PR, 1.12), and alcohol use (at least 2-3 times/wk: PR, 1.21) were associated with being unaware. In females, age (50 to 59 years: PR, 1.29; > or =70 years: PR, 1.30), household income (low: PR, 1.37; middle-low: PR, 1.24), and marital status (never married: PR, 1.33) were associated with being unaware. In males, self-rated health (moderate: PR, 1.14; good: PR, 1.21) and alcohol use (at least 2-3 times/wk: PR, 1.21) were associated with being unaware. CONCLUSIONS: Factors related to the socioeconomic status of females and the health-related behaviors of males were found to be associated with being unaware of one's HBsAg seropositivity status.
Adult ; Aged ; Alcohol Drinking ; Asian Continental Ancestry Group ; Awareness/*physiology ; Body Mass Index ; Female ; Health Status ; Hepatitis B/*diagnosis/epidemiology/virology ; Hepatitis B Surface Antigens/*blood ; Hepatitis B virus/*metabolism ; Humans ; Income ; Male ; Middle Aged ; Nutrition Surveys ; Poisson Distribution ; Prevalence ; Republic of Korea/epidemiology ; Sex Factors ; Young Adult