AIM:To investigate the effect of 0.01%low-concentration atropine(LA)on quantitative contrast sensitivity function(qCSF)in children with myopia.METHODS:This paired case-control study included 90 eyes of 58 children who...AIM:To investigate the effect of 0.01%low-concentration atropine(LA)on quantitative contrast sensitivity function(qCSF)in children with myopia.METHODS:This paired case-control study included 90 eyes of 58 children who were sex-,age-,and refractionmatched and equally divided into two groups:the 0.01%LA group had undergone 6mo use of daily 0.01%atropine and control group was naïve to LA.Routine ophthalmic examinations and qCSF test without refractive correction were performed.Two groups were compared in monocular and binocular qCSF parameters,including the area under logCSF,CSF acuity,and contrast sensitivity(CS)at 1.0-18.0 cycle per degree(cpd).RESULTS:In the monocular comparison,the CSF acuity of the LA group was significantly higher than that of the control group(7.58±5.51 vs 6.37±4.22 cpd,P<0.05).The subgroup analysis showed that in the 6-9y group,CSF acuity was significantly higher in the LA group than the control group(8.76±6.19 vs 6.54±4.25 cpd,P<0.05),and in the Female group,low refraction sphere group,and high refraction cylinder group,the CS at high spatial frequencies(12.0 and 18.0 cpd)were significantly higher in the LA group than in the control group(all P<0.05).In the binocular test,CSF acuity and CS at 12.0 cpd were significantly higher in the LA group than in the control group(10.95±7.00 vs 8.65±5.12 cpd;0.17±0.33 vs 0.06±0.16,respectively;both P<0.05).CONCLUSION:Use of LA may result in improved CS in children with early onset myopia.展开更多
Summary: To study reliability and reliable indices of quantitative assessment of right ventricular systolic function by time-intensity curve (TIC) with right ventricular contrast, 5 % sonicated human albumin was injec...Summary: To study reliability and reliable indices of quantitative assessment of right ventricular systolic function by time-intensity curve (TIC) with right ventricular contrast, 5 % sonicated human albumin was injected intravenously at a does of 0.08 ml/kg into 10 dogs at baseline status and cardiac insufficiency. Apical four-chamber view was observed for washin and washout of contrast agent from right ventricle. The parameters of TIC were obtained by curve fitting. The differences of parameters were analyzed in different states of cardiac functions. Among the parameters derived from TIC, the time constant (k) was decreased significantly with decline of cardiac function (P<0.001). But half-time of decent of peak intensity (HT) and mean-transit-time (MTT) of washout were increased significantly (P<0.001). The k was strongly related to cardiac output of right ventricle (CO) and ejection fraction (EF) of left ventricle and fractional shortening (FS) of left ventricle. Right ventricular systolic function could be assessed reliably by the parameters derived from TIC with right ventricular contrast echocardiography. The k, HT and MTT are reliable indices for quantitative assessment of right ventricular systolic function.展开更多
The clinically applied value of myocardial perfusion and systolic function in patients with coronary artery disease after coronary artery bypass surgery using real-time myocardial contrast echocardiography （RT-MCE） ...The clinically applied value of myocardial perfusion and systolic function in patients with coronary artery disease after coronary artery bypass surgery using real-time myocardial contrast echocardiography （RT-MCE） combined with two-dimensional strain echocardiography was assessed. Twenty patients underwent intravenous RT-MCE by intravenous injections of SonoVue before and after coronary artery bypass surgery. Two-dimensional images were recorded from the left ventricular four-chamber view, two-chamber view and the apical view before, and two weeks and three months after coronary artery bypass surgery, and the peak systolic longitudinal strain was measured. The results showed that myocardial perfusion was significantly increased after coronary artery bypass surgery in about 71.6% segments. In the group that myocardial perfusion was improved, the peak systolic longitu- dinal strain three months after bypass surgery was significantly higher than that before operation [（-15.78±5.91）% vs （-10.45±8.31）%, P〈0.05]. However, the parameters did not change in the group without myocardial perfusion improvement [（-10.33±6.53）% vs （-9.41±6.09）%, P〉0.05]. It was concluded that whether or not the improvement of myocardial perfusion can mirror the recovery trend of regional systolic function, two-dimensional strain echocardiography can observe dynamic change of regional systolic function. The combination of myocardial perfusion with two-dimensional strain echocardiography can more accurately assess the curative effectiveness of coronary artery bypass surgery.展开更多
Background:For years,studies using several animal models have highlighted the predominant role of the primary visual area in visual information processing.Its six cortical layers have morphological,hodological and phy...Background:For years,studies using several animal models have highlighted the predominant role of the primary visual area in visual information processing.Its six cortical layers have morphological,hodological and physiological differences,although their roles regarding the integration of visual contrast and the messages sent by the layers to other brain regions have been poorly explored.Given that cortical layers have distinct properties,this study aims to understand these differences and how they are affected by a changing visual contrast.Methods:A linear multi-channel electrode was placed in the primary visual cortex(V1)of the anesthetized mouse to record neuronal activity across the different cortical layers.The laminar position of the electrode was verified in real time by measuring the current source density(CSD)and the multi-unit activity(MUA),and confirmed post-mortem by histological analysis.Drifting gratings varying in contrast enabled the measurement of the firing rate of neurons throughout layers.We fitted this data to the Naka-Rushton equations,which generated the contrast response function(CRF)of neurons.Results:The analysis revealed that the baseline activity as well as the rate of change of neural discharges(the slope of the CRF)had a positive correlation across the cortical layers.In addition,we found a trend between the cortical position and the contrast evoking the semi-saturation of the activity.A significant difference in the maximum discharge rate was also found between layers II/III and IV,as well as between layers II/III and V.Conclusions:Since layers II/III and V process visual contrast differently,our results suggest that higher cortical visual areas,as well subcortical regions,receive different information regarding a change in visual contrast.Thus,a contrast may be processed differently throughout the different areas of the visual cortex.展开更多
Background:All neurons of the visual system exhibit response to differences in luminance.This neural response to visual contrast,also known as the contrast response function(CRF),follows a characteristic sigmoid shape...Background:All neurons of the visual system exhibit response to differences in luminance.This neural response to visual contrast,also known as the contrast response function(CRF),follows a characteristic sigmoid shape that can be fitted with the Naka-Rushton equation.Four parameters define the CRF,and they are often used in different visual research disciplines,since they describe selective variations of neural responses.As novel technologies have grown,the capacity to record thousands of neurons simultaneously brings new challenges:processing and robustly analyzing larger amounts of data to maximize the outcomes of our experimental measurements.Nevertheless,current guidelines to fit neural activity based on the Naka-Rushton equation have been poorly discussed in depth.In this study,we explore several methods of boundary-setting and least-square curve-fitting for the CRF in order to avoid the pitfalls of blind curve-fitting.Furthermore,we intend to provide recommendations for experimenters to better prepare a solid quantification of CRF parameters that also minimize the time of the data acquisition.For this purpose,we have created a simplified theoretical model of spike-response dynamics,in which the firing rate of neurons is generated by a Poisson process.The spike trains generated by the theoretical model depending on visual contrast intensities were then fitted with the Naka-Rushton equation.This allowed us to identify combinations of parameters that were more important to adjust before performing experiments,to optimize the precision and efficiency of curve fitting(e.g.,boundaries of CRF parameters,number of trials,number of contrast tested,metric of contrast used and the effect of including multi-unit spikes into a single CRF,among others).Several goodness-of-fit methods were also examined in order to achieve ideal fits.With this approach,it is possible to anticipate the minimal requirements to gather and analyze data in a more efficient way in order to build stronger functional models.Methods:Spike-trains were randomly generated following a Poisson distribution in order to draw both an underlying theoretical curve and an empirical one.Random noise was added to the fit to simulate empirical conditions.The correlation function was recreated on the simulated data and re-fit using the Naka-Rushton equation.The two curves were compared:the idea being to determine the most advantageous boundaries and conditions for the curve-fit to be optimal.Statistical analysis was performed on the data to determine those conditions for experiments.Experiments were then conducted to acquire data from mice and cats to verify the model.Results:Results were obtained successfully and a model was proposed to assess the goodness of the fit of the contrast response function.Various parametres and their influence of the model were tested.Other similar models were proposed and their performance was assessed and compared to the previous ones.The fit was optimized to give semi-strict guidelines for scientists to follow in order to maximize their efficiency while obtaining the contrast tuning of a neuron.Conclusions:The aim of the study was to assess the optimal testing parametres of the neuronal response to visual gratings with various luminance,also called the CRF.As technology gets more powerful and potent,one must make choices when experimenting.With a strong model,robust boundaries,and strong experimental conditioning,the best fit to a function can lead to more efficient analysis and stronger cognitive models.展开更多
Liver cancer is the common malignant tumor in China and current treatment is based on surgery. However, liver function of many liver cancer patients is impaired before surgery, so there’s a high possibility of occurr...Liver cancer is the common malignant tumor in China and current treatment is based on surgery. However, liver function of many liver cancer patients is impaired before surgery, so there’s a high possibility of occurrence of liver failure after the tumor resection. Therefore, it’s necessary to accurately evaluate liver function before surgery. Currently, clinical methods are mostly limited to assess the function of overall liver. But the application of hepatocyte-specific contrast agent—gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) makes it possible to assess the function of local liver segment accurately. This paper reviewed the progress of using Gd-EOB-DTPA dynamic contrast enhanced magnetic resonance imaging (MRI) to assess liver function preoperatively, such as parameters selection for liver function assessment, clinical factors affecting Gd-EOB-DTPA enhanced MRI and so on.展开更多
AIM: To evaluate the sources of variation influencing the microvascularization parameters measured by dynamic contrast-enhanced ultrasonography (DCE-US). METHODS: Firstly, we evaluated, in vitro , the impact of the ma...AIM: To evaluate the sources of variation influencing the microvascularization parameters measured by dynamic contrast-enhanced ultrasonography (DCE-US). METHODS: Firstly, we evaluated, in vitro , the impact of the manual repositioning of the ultrasound probe and the variations in flow rates. Experiments were conducted using a custom-made phantom setup simulating a tumor and its associated arterial input. Secondly, we evaluated, in vivo , the impact of multiple contrast agent injections and of examination day, as well as the influence of the size of region of interest (ROI) associated with the arterial input function (AIF). Experiments were conducted on xenografted B16F10 female nude mice. For all of the experiments, an ultrasound scanner along with a linear transducer was used to perform pulse inversion imaging based on linear raw data throughout the experiments. Semi-quantitative and quantitative analyses were performed using two signal-processing methods. RESULTS:In vitro , no microvascularization parameters, whether semi-quantitative or quantitative, were significantly correlated (P values from 0.059 to 0.860) with the repositioning of the probe. In addition, all semiquantitative microvascularization parameters were correlated with the flow variation while only one quantitative parameter, the tumor blood flow, exhibited P value lower than 0.05 (P = 0.004). In vivo , multiple contrast agent injections had no significant impact (P values from 0.060 to 0.885) on microvascularization parameters. In addition, it was demonstrated that semi-quantitative microvascularization parameters were correlated with the tumor growth while among the quantitative parameters, only the tissue blood flow exhibited P value lower than 0.05 (P = 0.015). Based on these results, it was demonstrated that the ROI size of the AIF had significant influence on microvascularization parameters: in the context of larger arterial ROI (from 1.17 ± 0.6 mm 3 to 3.65 ± 0.3 mm 3 ), tumor blood flow and tumor blood volume were correlated with the tumor growth, exhibiting P values lower than 0.001. CONCLUSION: AIF selection is an essential aspect of the deconvolution process to validate the quantitative DCE-US method.展开更多
Contrastive linguistics is a branch of linguistics which mainly involves contrast or comparison,and it can leave us some useful insights into our problems,especially for translation work.This paper discusses similarit...Contrastive linguistics is a branch of linguistics which mainly involves contrast or comparison,and it can leave us some useful insights into our problems,especially for translation work.This paper discusses similarities and differences between English attributes and Chinese attributes from the perspective of the location,the composition,and the function,for the purpose of presenting a sound version for the original text.展开更多
Objective:To investigate the correlation of abdominal aorta CT value,renal artery CT value and renal cortex thickness with renal cortex CT value on contrast enhanced 64-slice CT images.Methods:96patients(50 men and 46...Objective:To investigate the correlation of abdominal aorta CT value,renal artery CT value and renal cortex thickness with renal cortex CT value on contrast enhanced 64-slice CT images.Methods:96patients(50 men and 46women;16~74years)with normal kidney function,which was confirmed by kidney function test were enrolled in this study,including bilateral kidneys of 92cases and unilateral kidney of 4cases(total of 188kidneys;92left,96right).After intravenous(IV)injection of contrast agent the kidneys of the selected patients were scanned by MDCT.The scans were performed in arterial,venous and 3min delayed phases.All statistical analyses were performed by using IBM SPSS 20.0.Graphs were generated using Graph Pad Prism 5software.Quantitative data were presented as mean±standard deviation,while qualitative data were presented as frequency(%).P<0.05was considered to be statistically significant.Results:The mean renal cortex thickness was(5.19±0.81)mm in all kidneys.In the arterial phase,a statistically significant positive correlation between renal cortex CT values and abdominal aortic CT values was showed(r=0.584;P<0.001).A statistically significant positive correlation between renal cortex CT values and renal cortex thickness was demonstrated(r=0.533,P<0.0001).Likewise,there was a positive correlation between renal cortex CT value and renal artery CT values(r=0.43,P<0.001).Conclusion:It is a promising approach to assess the individual kidney function by measuring abdominal aorta CT value,renal artery CT value,renal cortex CT value and renal cortex thickness using contrast MDCT.展开更多
Background:In the visual system,one of the most explored neural behaviors is the response of cells to changes in visual contrast.This neural response to visual contrast,also known as the contrast response function(CRF...Background:In the visual system,one of the most explored neural behaviors is the response of cells to changes in visual contrast.This neural response to visual contrast,also known as the contrast response function(CRF),can be fitted with the Naka-Rushton equation(NRE).Assessing the CRF of many neurons at the same time is critical to establishing functional visual properties.However,maximizing the performance of neurons to fit the NRE,while minimizing their time acquisitions is a challenge.We present a method to accurately obtain reliable NRE fits from experimental data,that ensure a reasonable time of record acquisition.Methods:We simulated CRF of cortical neurons with a toy model based on the response of Poisson spike trains to varied levels of contrasts.We first tested whether mean values or the whole set of contrast responses fit better the NRE.Then,we analyzed what were the boundaries to optimize the fit of the NRE,and after we explore the consequences of fitting the NRE with single-or multi-units.With these outcomes,we varied experimental parameters such as the number of trials,number of input contrasts and length of time acquisition to calculate the errors of fitting CRFs.Those data sets that maximize the CRF fit but minimize the time of recording were selected.The selected data set was then evaluated in visual cortical neurons of anesthetized cats from areas 17,18 and 21a.Results:First,we found that is always better to fit the NRE with mean values rather than the whole set of points.Then,we noticed that either removing or imposing loose boundaries to the CRF parameters lead to an increase in the performance of the NRE fit.Afterward,we found that single units(SU)or assume multi-unit formed of several SUs(>30)adjusted considerably better the NRE fit.Finally,the experiments showed that specific sets of patterns(number of trials,number of input contrasts and length of time acquisition)satisfied our two constraints:minimize the error of the NRE fit while maximizing the acquisition time of recording.The most characteristic pattern was the one with 6 points,15 repetitions and 1 second of duration.However,cortical areas varied in the representation of the patterns.Conclusions:Theoretical simulations of many different sets of patterns and their following experimental validation suggest strongly that a particular set of patterns can satisfy the imposed constraints.With this approach,we provided a tool that allows an optimal design of stimuli to assess the CRF of large neuronal populations and guarantees the finest fit for each unit analyzed.展开更多
The step-type contrast structure for a singular singularly perturbed problem is shown. By use of the method of boundary function, the formal asymptotic expansion is constructed. At the same time, based on sewing orbit...The step-type contrast structure for a singular singularly perturbed problem is shown. By use of the method of boundary function, the formal asymptotic expansion is constructed. At the same time, based on sewing orbit smooth, the existence of the step- type solution and the uniform validity of the asymptotic expansion are proved. Finally, an example is given to demonstrate the effectiveness of the present results.展开更多
This paper presents a preprocessing technique that can provide the improved quality of image robust to illumination changes. First, in order to enhance the image contrast, we proposed new adaptive histogram transforma...This paper presents a preprocessing technique that can provide the improved quality of image robust to illumination changes. First, in order to enhance the image contrast, we proposed new adaptive histogram transformation combining histogram equalization and histogram specification. Here, by examining the characteristic of histogram distribution shape, we determine the appropriate target distribution. Next, applying the histogram equalization with an image histogram, we have obtained the uniform distribution of pixel values, and then we have again carried out the histogram transformation using an inverse of target distribution function. Finally we have conducted various experiments that can enhance the quality of image by applying our method with various standard images. The experimental results show that the proposed method can achieve moderately good image enhancement results.展开更多
Objective: High resolution image is required for accurate measurement of cardiac function for the analysis of detailed regional function especially in a small animal. Methods: Left ventricular function of rat hearts w...Objective: High resolution image is required for accurate measurement of cardiac function for the analysis of detailed regional function especially in a small animal. Methods: Left ventricular function of rat hearts was measured using micro-computed tomography (micro-CT) with administration of contrast agent in a rat with normal heart as well as rats with mild and severe myocardial infarction (MI). Following the CT acquisition, the hearts were sectioned for pathological evaluation. Results: The volume plot per each disk of the normal heart revealed that contraction force peaked at the middle of the heart. In the heart with mild infarction, the volume plot curve clearly demonstrated that infarction was located only at the apex of the heart, whereas severe infarction was disturbed in larger area. The left ventricular ejection fraction of the normal, mild MI, and severe MI hearts were 68.6%, 40.0%, and 16.4%, respectively. In addition, volume analysis in severe MI demonstrated ventricular dilatation, although that in mild MI did not show any change in the ventricular volume. Histological results were consistent with the CT measurement. Conclusions: Micro-CT provided accurate measurement of cardiac function in rats, which is especially useful for the analysis of small animals with heterogeneous dysfunction of the heart.展开更多
Based on the theoretical framework of Halliday’s interpersonal function,this thesis studies the contrast between Chinese and English cosmetic advertising texts.The author chooses thirty Chinese texts and thirty Engli...Based on the theoretical framework of Halliday’s interpersonal function,this thesis studies the contrast between Chinese and English cosmetic advertising texts.The author chooses thirty Chinese texts and thirty English texts from famous top magazines as the materials of this study.These samples will be discussed in four perspectives:mood,modality,tense and person systems.There are two main purposes of the study:1)to prove the operability and feasibility in cosmetic advertising texts of Chinese and English from the aspect of interpersonal function.2)to give useful suggestions for composing Chinese and English cosmetic advertisements in the future.展开更多
基金Supported by National Key Research and Development Program of China(No.2023YFA0915000)。
文摘AIM:To investigate the effect of 0.01%low-concentration atropine(LA)on quantitative contrast sensitivity function(qCSF)in children with myopia.METHODS:This paired case-control study included 90 eyes of 58 children who were sex-,age-,and refractionmatched and equally divided into two groups:the 0.01%LA group had undergone 6mo use of daily 0.01%atropine and control group was naïve to LA.Routine ophthalmic examinations and qCSF test without refractive correction were performed.Two groups were compared in monocular and binocular qCSF parameters,including the area under logCSF,CSF acuity,and contrast sensitivity(CS)at 1.0-18.0 cycle per degree(cpd).RESULTS:In the monocular comparison,the CSF acuity of the LA group was significantly higher than that of the control group(7.58±5.51 vs 6.37±4.22 cpd,P<0.05).The subgroup analysis showed that in the 6-9y group,CSF acuity was significantly higher in the LA group than the control group(8.76±6.19 vs 6.54±4.25 cpd,P<0.05),and in the Female group,low refraction sphere group,and high refraction cylinder group,the CS at high spatial frequencies(12.0 and 18.0 cpd)were significantly higher in the LA group than in the control group(all P<0.05).In the binocular test,CSF acuity and CS at 12.0 cpd were significantly higher in the LA group than in the control group(10.95±7.00 vs 8.65±5.12 cpd;0.17±0.33 vs 0.06±0.16,respectively;both P<0.05).CONCLUSION:Use of LA may result in improved CS in children with early onset myopia.
文摘Summary: To study reliability and reliable indices of quantitative assessment of right ventricular systolic function by time-intensity curve (TIC) with right ventricular contrast, 5 % sonicated human albumin was injected intravenously at a does of 0.08 ml/kg into 10 dogs at baseline status and cardiac insufficiency. Apical four-chamber view was observed for washin and washout of contrast agent from right ventricle. The parameters of TIC were obtained by curve fitting. The differences of parameters were analyzed in different states of cardiac functions. Among the parameters derived from TIC, the time constant (k) was decreased significantly with decline of cardiac function (P<0.001). But half-time of decent of peak intensity (HT) and mean-transit-time (MTT) of washout were increased significantly (P<0.001). The k was strongly related to cardiac output of right ventricle (CO) and ejection fraction (EF) of left ventricle and fractional shortening (FS) of left ventricle. Right ventricular systolic function could be assessed reliably by the parameters derived from TIC with right ventricular contrast echocardiography. The k, HT and MTT are reliable indices for quantitative assessment of right ventricular systolic function.
文摘The clinically applied value of myocardial perfusion and systolic function in patients with coronary artery disease after coronary artery bypass surgery using real-time myocardial contrast echocardiography （RT-MCE） combined with two-dimensional strain echocardiography was assessed. Twenty patients underwent intravenous RT-MCE by intravenous injections of SonoVue before and after coronary artery bypass surgery. Two-dimensional images were recorded from the left ventricular four-chamber view, two-chamber view and the apical view before, and two weeks and three months after coronary artery bypass surgery, and the peak systolic longitudinal strain was measured. The results showed that myocardial perfusion was significantly increased after coronary artery bypass surgery in about 71.6% segments. In the group that myocardial perfusion was improved, the peak systolic longitu- dinal strain three months after bypass surgery was significantly higher than that before operation [（-15.78±5.91）% vs （-10.45±8.31）%, P〈0.05]. However, the parameters did not change in the group without myocardial perfusion improvement [（-10.33±6.53）% vs （-9.41±6.09）%, P〉0.05]. It was concluded that whether or not the improvement of myocardial perfusion can mirror the recovery trend of regional systolic function, two-dimensional strain echocardiography can observe dynamic change of regional systolic function. The combination of myocardial perfusion with two-dimensional strain echocardiography can more accurately assess the curative effectiveness of coronary artery bypass surgery.
文摘Background:For years,studies using several animal models have highlighted the predominant role of the primary visual area in visual information processing.Its six cortical layers have morphological,hodological and physiological differences,although their roles regarding the integration of visual contrast and the messages sent by the layers to other brain regions have been poorly explored.Given that cortical layers have distinct properties,this study aims to understand these differences and how they are affected by a changing visual contrast.Methods:A linear multi-channel electrode was placed in the primary visual cortex(V1)of the anesthetized mouse to record neuronal activity across the different cortical layers.The laminar position of the electrode was verified in real time by measuring the current source density(CSD)and the multi-unit activity(MUA),and confirmed post-mortem by histological analysis.Drifting gratings varying in contrast enabled the measurement of the firing rate of neurons throughout layers.We fitted this data to the Naka-Rushton equations,which generated the contrast response function(CRF)of neurons.Results:The analysis revealed that the baseline activity as well as the rate of change of neural discharges(the slope of the CRF)had a positive correlation across the cortical layers.In addition,we found a trend between the cortical position and the contrast evoking the semi-saturation of the activity.A significant difference in the maximum discharge rate was also found between layers II/III and IV,as well as between layers II/III and V.Conclusions:Since layers II/III and V process visual contrast differently,our results suggest that higher cortical visual areas,as well subcortical regions,receive different information regarding a change in visual contrast.Thus,a contrast may be processed differently throughout the different areas of the visual cortex.
文摘Background:All neurons of the visual system exhibit response to differences in luminance.This neural response to visual contrast,also known as the contrast response function(CRF),follows a characteristic sigmoid shape that can be fitted with the Naka-Rushton equation.Four parameters define the CRF,and they are often used in different visual research disciplines,since they describe selective variations of neural responses.As novel technologies have grown,the capacity to record thousands of neurons simultaneously brings new challenges:processing and robustly analyzing larger amounts of data to maximize the outcomes of our experimental measurements.Nevertheless,current guidelines to fit neural activity based on the Naka-Rushton equation have been poorly discussed in depth.In this study,we explore several methods of boundary-setting and least-square curve-fitting for the CRF in order to avoid the pitfalls of blind curve-fitting.Furthermore,we intend to provide recommendations for experimenters to better prepare a solid quantification of CRF parameters that also minimize the time of the data acquisition.For this purpose,we have created a simplified theoretical model of spike-response dynamics,in which the firing rate of neurons is generated by a Poisson process.The spike trains generated by the theoretical model depending on visual contrast intensities were then fitted with the Naka-Rushton equation.This allowed us to identify combinations of parameters that were more important to adjust before performing experiments,to optimize the precision and efficiency of curve fitting(e.g.,boundaries of CRF parameters,number of trials,number of contrast tested,metric of contrast used and the effect of including multi-unit spikes into a single CRF,among others).Several goodness-of-fit methods were also examined in order to achieve ideal fits.With this approach,it is possible to anticipate the minimal requirements to gather and analyze data in a more efficient way in order to build stronger functional models.Methods:Spike-trains were randomly generated following a Poisson distribution in order to draw both an underlying theoretical curve and an empirical one.Random noise was added to the fit to simulate empirical conditions.The correlation function was recreated on the simulated data and re-fit using the Naka-Rushton equation.The two curves were compared:the idea being to determine the most advantageous boundaries and conditions for the curve-fit to be optimal.Statistical analysis was performed on the data to determine those conditions for experiments.Experiments were then conducted to acquire data from mice and cats to verify the model.Results:Results were obtained successfully and a model was proposed to assess the goodness of the fit of the contrast response function.Various parametres and their influence of the model were tested.Other similar models were proposed and their performance was assessed and compared to the previous ones.The fit was optimized to give semi-strict guidelines for scientists to follow in order to maximize their efficiency while obtaining the contrast tuning of a neuron.Conclusions:The aim of the study was to assess the optimal testing parametres of the neuronal response to visual gratings with various luminance,also called the CRF.As technology gets more powerful and potent,one must make choices when experimenting.With a strong model,robust boundaries,and strong experimental conditioning,the best fit to a function can lead to more efficient analysis and stronger cognitive models.
文摘Liver cancer is the common malignant tumor in China and current treatment is based on surgery. However, liver function of many liver cancer patients is impaired before surgery, so there’s a high possibility of occurrence of liver failure after the tumor resection. Therefore, it’s necessary to accurately evaluate liver function before surgery. Currently, clinical methods are mostly limited to assess the function of overall liver. But the application of hepatocyte-specific contrast agent—gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) makes it possible to assess the function of local liver segment accurately. This paper reviewed the progress of using Gd-EOB-DTPA dynamic contrast enhanced magnetic resonance imaging (MRI) to assess liver function preoperatively, such as parameters selection for liver function assessment, clinical factors affecting Gd-EOB-DTPA enhanced MRI and so on.
文摘AIM: To evaluate the sources of variation influencing the microvascularization parameters measured by dynamic contrast-enhanced ultrasonography (DCE-US). METHODS: Firstly, we evaluated, in vitro , the impact of the manual repositioning of the ultrasound probe and the variations in flow rates. Experiments were conducted using a custom-made phantom setup simulating a tumor and its associated arterial input. Secondly, we evaluated, in vivo , the impact of multiple contrast agent injections and of examination day, as well as the influence of the size of region of interest (ROI) associated with the arterial input function (AIF). Experiments were conducted on xenografted B16F10 female nude mice. For all of the experiments, an ultrasound scanner along with a linear transducer was used to perform pulse inversion imaging based on linear raw data throughout the experiments. Semi-quantitative and quantitative analyses were performed using two signal-processing methods. RESULTS:In vitro , no microvascularization parameters, whether semi-quantitative or quantitative, were significantly correlated (P values from 0.059 to 0.860) with the repositioning of the probe. In addition, all semiquantitative microvascularization parameters were correlated with the flow variation while only one quantitative parameter, the tumor blood flow, exhibited P value lower than 0.05 (P = 0.004). In vivo , multiple contrast agent injections had no significant impact (P values from 0.060 to 0.885) on microvascularization parameters. In addition, it was demonstrated that semi-quantitative microvascularization parameters were correlated with the tumor growth while among the quantitative parameters, only the tissue blood flow exhibited P value lower than 0.05 (P = 0.015). Based on these results, it was demonstrated that the ROI size of the AIF had significant influence on microvascularization parameters: in the context of larger arterial ROI (from 1.17 ± 0.6 mm 3 to 3.65 ± 0.3 mm 3 ), tumor blood flow and tumor blood volume were correlated with the tumor growth, exhibiting P values lower than 0.001. CONCLUSION: AIF selection is an essential aspect of the deconvolution process to validate the quantitative DCE-US method.
文摘Contrastive linguistics is a branch of linguistics which mainly involves contrast or comparison,and it can leave us some useful insights into our problems,especially for translation work.This paper discusses similarities and differences between English attributes and Chinese attributes from the perspective of the location,the composition,and the function,for the purpose of presenting a sound version for the original text.
文摘Objective:To investigate the correlation of abdominal aorta CT value,renal artery CT value and renal cortex thickness with renal cortex CT value on contrast enhanced 64-slice CT images.Methods:96patients(50 men and 46women;16~74years)with normal kidney function,which was confirmed by kidney function test were enrolled in this study,including bilateral kidneys of 92cases and unilateral kidney of 4cases(total of 188kidneys;92left,96right).After intravenous(IV)injection of contrast agent the kidneys of the selected patients were scanned by MDCT.The scans were performed in arterial,venous and 3min delayed phases.All statistical analyses were performed by using IBM SPSS 20.0.Graphs were generated using Graph Pad Prism 5software.Quantitative data were presented as mean±standard deviation,while qualitative data were presented as frequency(%).P<0.05was considered to be statistically significant.Results:The mean renal cortex thickness was(5.19±0.81)mm in all kidneys.In the arterial phase,a statistically significant positive correlation between renal cortex CT values and abdominal aortic CT values was showed(r=0.584;P<0.001).A statistically significant positive correlation between renal cortex CT values and renal cortex thickness was demonstrated(r=0.533,P<0.0001).Likewise,there was a positive correlation between renal cortex CT value and renal artery CT values(r=0.43,P<0.001).Conclusion:It is a promising approach to assess the individual kidney function by measuring abdominal aorta CT value,renal artery CT value,renal cortex CT value and renal cortex thickness using contrast MDCT.
文摘Background:In the visual system,one of the most explored neural behaviors is the response of cells to changes in visual contrast.This neural response to visual contrast,also known as the contrast response function(CRF),can be fitted with the Naka-Rushton equation(NRE).Assessing the CRF of many neurons at the same time is critical to establishing functional visual properties.However,maximizing the performance of neurons to fit the NRE,while minimizing their time acquisitions is a challenge.We present a method to accurately obtain reliable NRE fits from experimental data,that ensure a reasonable time of record acquisition.Methods:We simulated CRF of cortical neurons with a toy model based on the response of Poisson spike trains to varied levels of contrasts.We first tested whether mean values or the whole set of contrast responses fit better the NRE.Then,we analyzed what were the boundaries to optimize the fit of the NRE,and after we explore the consequences of fitting the NRE with single-or multi-units.With these outcomes,we varied experimental parameters such as the number of trials,number of input contrasts and length of time acquisition to calculate the errors of fitting CRFs.Those data sets that maximize the CRF fit but minimize the time of recording were selected.The selected data set was then evaluated in visual cortical neurons of anesthetized cats from areas 17,18 and 21a.Results:First,we found that is always better to fit the NRE with mean values rather than the whole set of points.Then,we noticed that either removing or imposing loose boundaries to the CRF parameters lead to an increase in the performance of the NRE fit.Afterward,we found that single units(SU)or assume multi-unit formed of several SUs(>30)adjusted considerably better the NRE fit.Finally,the experiments showed that specific sets of patterns(number of trials,number of input contrasts and length of time acquisition)satisfied our two constraints:minimize the error of the NRE fit while maximizing the acquisition time of recording.The most characteristic pattern was the one with 6 points,15 repetitions and 1 second of duration.However,cortical areas varied in the representation of the patterns.Conclusions:Theoretical simulations of many different sets of patterns and their following experimental validation suggest strongly that a particular set of patterns can satisfy the imposed constraints.With this approach,we provided a tool that allows an optimal design of stimuli to assess the CRF of large neuronal populations and guarantees the finest fit for each unit analyzed.
基金Project supported by the National Natural Science Foundation of China(No.11071075)the Natural Science Foundation of Shanghai(No.10ZR1409200)
文摘The step-type contrast structure for a singular singularly perturbed problem is shown. By use of the method of boundary function, the formal asymptotic expansion is constructed. At the same time, based on sewing orbit smooth, the existence of the step- type solution and the uniform validity of the asymptotic expansion are proved. Finally, an example is given to demonstrate the effectiveness of the present results.
文摘This paper presents a preprocessing technique that can provide the improved quality of image robust to illumination changes. First, in order to enhance the image contrast, we proposed new adaptive histogram transformation combining histogram equalization and histogram specification. Here, by examining the characteristic of histogram distribution shape, we determine the appropriate target distribution. Next, applying the histogram equalization with an image histogram, we have obtained the uniform distribution of pixel values, and then we have again carried out the histogram transformation using an inverse of target distribution function. Finally we have conducted various experiments that can enhance the quality of image by applying our method with various standard images. The experimental results show that the proposed method can achieve moderately good image enhancement results.
文摘Objective: High resolution image is required for accurate measurement of cardiac function for the analysis of detailed regional function especially in a small animal. Methods: Left ventricular function of rat hearts was measured using micro-computed tomography (micro-CT) with administration of contrast agent in a rat with normal heart as well as rats with mild and severe myocardial infarction (MI). Following the CT acquisition, the hearts were sectioned for pathological evaluation. Results: The volume plot per each disk of the normal heart revealed that contraction force peaked at the middle of the heart. In the heart with mild infarction, the volume plot curve clearly demonstrated that infarction was located only at the apex of the heart, whereas severe infarction was disturbed in larger area. The left ventricular ejection fraction of the normal, mild MI, and severe MI hearts were 68.6%, 40.0%, and 16.4%, respectively. In addition, volume analysis in severe MI demonstrated ventricular dilatation, although that in mild MI did not show any change in the ventricular volume. Histological results were consistent with the CT measurement. Conclusions: Micro-CT provided accurate measurement of cardiac function in rats, which is especially useful for the analysis of small animals with heterogeneous dysfunction of the heart.
文摘Based on the theoretical framework of Halliday’s interpersonal function,this thesis studies the contrast between Chinese and English cosmetic advertising texts.The author chooses thirty Chinese texts and thirty English texts from famous top magazines as the materials of this study.These samples will be discussed in four perspectives:mood,modality,tense and person systems.There are two main purposes of the study:1)to prove the operability and feasibility in cosmetic advertising texts of Chinese and English from the aspect of interpersonal function.2)to give useful suggestions for composing Chinese and English cosmetic advertisements in the future.
