Impact of random and scattered coincidences from outside of field of view on positron emission tomography/computed tomography imaging with different reconstruction protocols

Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction protocols.Imaging was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:1.The NEMA phantom(phantom I)was scanned separately in a one-bed position.To simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different techniques.The image quality parameters were evaluated by both phantoms.Variations in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)values.Random and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere sizes.Amongst reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.

Obstruction Theory and Coincidences in Positive Codimension

Let f, g ： X→Y be two maps between closed manifolds with dim X ≥ dim Y = n ≥ 3. We study the primary obstruction on（f, g） to deforming f and g to be coincidence free on the n-th skeleton of X. We give examples for which obstructions to deforming f and g to be coincidence free are detected by on （f, g）.

Atrial fibrillation and dementia: not just a coincidence

Atrial fibrillation(AF)is the most common form of cardiac arrhythmia,affecting 3 to 6 million people in the US,with an increased incidence in women and elderly,with its prevalence estimated to increase from 5.1 million in 2000 to 15.9 million in 2050 in the US population.[1]Age,hypertension,heart failure,myocardial infarction(MI),genetic factors,and associated systemic inflammatory states are well-established risk factors for the development of AF.[2–6]Lifestyle factors including alcohol consumption,smoking,obesity,sedentary lifestyle,and vigorous physical activity have also been implicated to contribute to the development of AF.[2,7–9]Studies suggest that AF drives up medical expenditure.[10]The European Society of Cardiology,based on the duration,responsiveness to treatment,and therapeutic attitude of the patient and physician,classifies AF into 4 types;when AF occurs and terminates by itself or by intervention within 7 days of onset,it is called paroxysmal AF;if sustained for more than a week,with or without intervention.

Hypothyroidism and non-alcoholic fatty liver disease:A coincidence or a causal relationship?

Non-alcoholic fatty liver disease(NAFLD)is a global problem.It may be caused by metabolic and hormonal disorders,including hypothyroidism.However,non-thyroid causes of NAFLD in people with hypothyroidism,including improper eating behavior and low physical activity,should be acknowledged.This study aimed to present the current literature on whether the development of NAFLD is related to hypothyroidism or a typical consequence of an unhealthy lifestyle in people with hypothyroidism.The results of previous studies do not allow for an unequivocal determination of the pathogenetic relationship between hypothyroidism and NAFLD.Important non-thyroid-initiating factors include providing too many calories in relation to requirements,consuming excessive amounts of monosaccharides and saturated fats,being overweight,and maintaining low physical activity levels.The recommended nutritional model for both hypothyroidism and NAFLD may be the Mediterranean diet,which is rich in fruits and vegetables,polyunsaturated fatty acids,and vitamin E.

从语义学角度看英汉医学词汇的理解与翻译

符号学理论认为语言符号存在三种对应关系——语义关系、语用关系和语形关系。语义关系指的是符号与它所指称的外在事物之间的关系，实质上就是指称关系；语用关系指的是符号与符号使用者之间的关系；语形关系指的是符号与符号之间的关系。对应于这三种关系存在着三类意义...

四阶非线性方程周期解的存在性

在本文中,我们证明了下列方程:{x^(4)(t)-n^4x(t)+g(t、x(t)、x′(t))=p(t) x(0)=x(2π),x′(0)=x′(2π),x″(0)=x″(2π),x^(3)(0)=x^(3)(2π)至少存在一个非零解,n为自然数。

集值Coincidence度及其应用

基于集值映象的Ｃｏｉｎｃｉｄｅｎｃｅ度理论，研究了一类算子包含问题的可解性，得到了锥拉压不动点定理的一个推广形式。

集值Coincidence度及其应用

对于组合算子包含问题,在L是零指标的Fredholm算子的条件下,本文基于集值映射的广义度,建立了集值Coincidence拓扑度,并将所得结果应用于集值映射不动点的存在性,推广了已有的结果。

A super-high resolution frequency standard measuring approach based on phase coincidence characteristics between signals

A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of the two compared signals. It utilizes the regular phase shift characteristics between the signals. The resolution of the measurement approach can reach 10^-13/s at 5 MHz, and the self-calibration resolution can achieve 10^-14/s in the comparison between 10 MHz and 100 MHz, or even can reach 10^-15/s in the comparison between 10 MHz and 190 MHz. This method implies significant progress in the development of the high precision frequency standard comparison technology.

KKM TYPE THEOREMS AND COINCIDENCE THEOREMS ON L-CONVEX SPACES

Some KKM theorems and coincidence theorems involving admissible set-valued mappings and the set-valued mappings with compactly local intersection property are proved in L-convex: spaces. As applications, some new fixed point theorems are obtained in L-convex spaces. These theorems improve and generalize many important known results in recent literature.

EXISTENCE OF POSITIVE SOLUTION FOR A TWO-PATCHES COMPETITION SYSTEM WITH DIFFUSION AND TIME DELAY AND FUNCTIONAL RESPONSE

By using the continuation theorem of coincidence theory, the existence of a positive periodic solution for a two patches competition system with diffusion and time delay and functional responsex [FK(W1*3/4。*2/3]′ 1 (t)=x 1(t)a 1(t)-b 1(t)x 1(t)-c 1(t)y(t)1+m(t)x 1(t)+D 1(t)[x 2(t)-x 1(t)], x [FK(W1*3/4。*2/3]′ 2 (t)=x 2(t)a 2(t)-b 2(t)x 2(t)-c 2(t)∫ 0 -τ k(s)x 2(t+s) d s+D 2(t)[x 1(t)-x 2(t)], y′(t)=y(t)a 3(t)-b 3(t)y(t)-c 3(t)x 1(t)1+m(t)x 1(t)is established, where a i(t),b i(t),c i(t)(i=1,2,3),m(t) and D i(t)(i=1,2) are all positive periodic continuous functions with period w >0, τ is a nonnegative constant and k(s) is a continuous nonnegative function on [- τ ,0].

Intrinsic background radiation of LaBr3(Ce)detector via coincidence measurements and simulations

The LaBr3(Ce)detector has attracted much attention in recent years because of its superior characteristics compared with other scintillating materials in terms of resolution and efficiency.However,it has a relatively high intrinsic background radiation because of the naturally occurring radioisotopes in lanthanum,actinium,and their daughter nuclei.This limits its applications in low-counting rate experiments.In this study,we identified the radioactive isotopes in theφ3"x 3"Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system.Moreover,we carried out a Geant4 simulation of the experimental spectra to evaluate the activities of the main internal radiation components.The total activity of the background radiation of B380 is determined to be 1.523(34)Bq/cm^3.The main sources include 138La at 1.428(34)Bq/cm^3,207Tl at 0.0135(13)Bq/cm^3,211Bi at 0.0136(15)Bq/cm^3,215Po at 0.0135(3)Bq/cm^3,219Rn at 0.0125(12)Bq/cm^3,223Fr at 0.0019(11)Bq/cm^3,223Ra at 0.0127(10)Bq/cm^3,227Th at 0.0158(22)Bq/cm^3,and 227Ac at 0.0135(13)Bq/cm^3.Of these,the activities of 207Tl,211Po,215Po,223Fr,and 227Ac are deduced for the first time from the secular equilibrium established in the decay chain of 227Ac.

New Unique Common Fixed Point Results for Four Mappings with Ф-Contractive Type in 2-Metric Spaces

In this paper, some new unique common fixed points for four mappings satisfying Ф-contractive conditions on non-complete 2-metric spaces are obtained, in which the mappings do not satisfy continuity and commutation. The main results generalize and improve many well-known and corresponding conclusions in the literatures.

THE COLLOCATION METHODS FOR SINGULAR INTEGRAL EQUATIONS WITH CAUCHY KERNELS

This paper applies the singular integral operators, singular quadrature operators and discretization matrices associated with singular integral equations with Cauchy kernels, which are established in [1], to give a unified framework for various collocation methods of numerical solutions of singular integral equations with Cauchy kernels. Under the framework, the coincidence of the direct quadrature method and the indirect quadrature method is very simple and obvious.

Existence of two periodic solutions of a ratio-dependent Holling-Taner model with infinite delay and prey harvest

This paper considers a class of ratio-dependent Holling-Taner model with infinite delay and prey harvest, which is of periodic coefficients. By means of the coincidence degree theory, a set of sufficient conditions for the existence of at least two positive periodic solutions of this model is established.

Periodic Solution for Diffusive Predator-Prey System with Functional Response

In this paper, a three species diffusive predator-prey model with functional response is studied, where all parameters are time dependent. By using the continuation theorem of coincidence degree theory, the existence of a positive periodic solution for this system is established.

在精神分裂症和听觉的幻觉的多模式的 morphometry 和功能的磁性的回声成像

AIM:To validate a multimodal[structural and functional magnetic resonance(MR)]approach as coincidence brain clusters are hypothesized to correlate with clinical severity of auditory hallucinations.METHODS:Twenty-two patients meeting Diagnostic and Statistical Manual of Mental Disorders(fourth edition,DSM-Ⅳ)criteria for schizophrenia and experiencing persistent hallucinations together with 28 healthy controls were evaluated with structural and functional MR imaging with an auditory paradigm designed to replicate those emotions related to the patients’hallucinatory experiences.Coincidence maps were obtained by combining structural maps of gray matter reduction with emotional functional increased activation.Abnormal areas were correlated with the brief psychiatric rating scale(BPRS)and the psychotic symptom rating scale(PSYRATS)scales.RESULTS:The coincidence analysis showed areas with coexistence gray matter reductions and emotional activation in bilateral middle temporal and superior temporal gyri.Significant negative correlations between BPRS and PSYRATS scales were observed.BPRS scores were negatively correlated in the middle temporal gyrus(right)(t=6.86,P=0.001),while negative PSYRATS correlation affected regions in both the superior temporal gyrus(left)(t=7.85,P=0.001)and middle temporal gyrus(left)(t=4.97,P=0.002).CONCLUSION:Our data identify left superior and middle temporal gyri as relevant areas for the understanding of auditory hallucinations in schizophrenia.The use of multimodal approaches,sharing structural and functional information,may demonstrate areas specifically linked to the severity of auditory hallucinations.

EXISTENCE OF SOLUTIONS FOR HIGHER ORDER MULTI-POINT BOUNDARY VALUE PROBLEM AT RESONANCE

Using the theory of coincidence degree, a class of higher order multi-point boundary value problem for ordinary differential equations are studied. Under the boundary conditions satisfying the resonance case, some new existence results are obtained by supposing some conditions to the nonlinear term and applying a priori estimates.

EXISTENCE OF PERIODIC SOLUTIONS OF PLANAR SYSTEMS WITH FOUR DELAYS

The sufficient condition for the existence of non constant periodic solutions of the following planar system with four delays are obtained:x [FK(W1*1。*3/4]′ 1(t)=-a 0x α 1(t)+a 1f 1(x 1(t-τ 1),x 2(t-τ 2)), x [FK(W1*1。*3/4]′ 2(t)=-b 0x α 2(t)+b 1f 2(x 1(t-τ 3),x 2(t-τ 4)).This approach is based on the continuation theorem of the coincidence degree, and the a priori estimate of periodic solutions.

Precipitation Study in Inconel 625 Alloy by Positron Annihilation Spectroscopy

Precipitation in Inconel 625 alloy has been studied by positron annihilation spectroscopy and electron microscopy. The observed dependence of annihilation characteristics on aging time is attributed to the change of the positron state due to the increase and decrease of the density and size of the 7' precipitates. Hardness measurements and lifetime measurements are in good agreement.