基于二次样条小波的P波检测方法

为了能够准确地检测P波,本文应用二次样条小波变换的方法,在特定的分解尺度上,寻找QRS波前搜索窗内的极值对信息,再在极值对之间寻找极值点即为P波的顶点,最后根据P波的顶点位置,在其左右利用局部变换的方法实现对起止点的最终定位。二次样条小波变化的方法,能够很好地避开漂移、高频等噪声的干扰。利用CSE标准数据库定量的衡量P波检测的准确度,平均偏差为-0.7ms,标准偏差为7.7ms,大大提高了P波定位的准确性,为心电图自动分析的准确性提供了保障。     

Spline‐based accelerated failure time model

The accelerated failure time (AFT) model has been suggested as an alternative to the Cox proportional hazards model. However, a parametric AFT model requires the specification of an appropriate distribution for the event time, which is often difficult to identify in real‐life studies and may limit applications. A semiparametric AFT model was developed by Komárek et al based on smoothed error distribution that does not require such specification. In this article, we develop a spline‐based AFT model that also does not require specification of the parametric family of event time distribution. The baseline hazard function is modeled by regression B‐splines, allowing for the estimation of a variety of smooth and flexible shapes. In comprehensive simulations, we validate the performance of our approach and compare with the results from parametric AFT models and the approach of Komárek. Both the proposed spline‐based AFT model and the approach of Komárek provided unbiased estimates of covariate effects and survival curves for a variety of scenarios in which the event time followed different distributions, including both simple and complex cases. Spline‐based estimates of the baseline hazard showed also a satisfactory numerical stability. As expected, the baseline hazard and survival probabilities estimated by the misspecified parametric AFT models deviated from the truth. We illustrated the application of the proposed model in a study of colon cancer.     

Quantification of the neurochemical profile using simulated macromolecule resonances at 3 T

The broad resonances underlying the entire ¹H NMR spectrum of the brain, ascribed to macromolecules, can influence metabolite quantification. At the intermediate field strength of 3 T, distinct approaches for the determination of the macromolecule signal, previously used at either 1.5 or 7 T and higher, may become equivalent. The aim of this study was to evaluate, at 3 T for healthy subjects using LCModel, the impact on the metabolite quantification of two different macromolecule approaches: (i) experimentally measured macromolecules; and (ii) mathematically estimated macromolecules. Although small, but significant, differences in metabolite quantification (up to 23% for glutamate) were noted for some metabolites, 10 metabolites were quantified reproducibly with both approaches with a Cramer–Rao lower bound below 20%, and the neurochemical profiles were therefore similar. We conclude that the mathematical approximation can provide sufficiently accurate and reproducible estimation of the macromolecule contribution to the ¹H spectrum at 3 T. Copyright © 2013 John Wiley & Sons, Ltd.     

面向家庭健康监护的血压监护模块设计

目的:血压是反映人体循环系统机能的重要生理参数,血压的监测在临床和医疗保健中有着重要的地位。本文根据示波法测量人体血压的原理,研制出了一种面向家庭健康监护的血压监护系统。方法:系统采用s3c2440作为数据采集,传输及气动电路的控制核心,算法部分采用三次样条插值法来获取脉搏波包络线,最终通过幅度系数法求得舒张压和收缩压。结果:通过该系统对人体进行测试,并和柯氏音法进行了对比,得到了比较满意的结果。结论:实验结果显示本系统稳定,可靠,误差率小,可适用于家庭健康监护。     

血尿酸与糖尿病前期和新检出2型糖尿病的关系

目的 探讨成年人血尿酸与糖尿病前期、新检出2型糖尿病之间的相关性。方法 基于上海市“高峰计划”松江人群队列基线调查数据,根据基线FPG、糖化血红蛋白将符合条件的研究对象分为血糖正常组、糖尿病前期组、新检出2型糖尿病组,采用非条件logistic回归模型探索血尿酸水平对糖尿病前期和新检出2型糖尿病的影响,采用限制性立方样条（RCS）函数来探索血尿酸水平与新检出2型糖尿病、糖尿病前期之间的非线性剂量反应关系。结果 纳入研究对象30 375名,年龄（55.36±11.52）岁,女性占60.2%（18 299名）。基线调查发现糖尿病前期患病率为38.6%（11 739名）,新检出2型糖尿病检出率为6.6%（1 992名）。logistic回归分析结果显示,在女性中,血尿酸浓度每增加10 μmol/L,患糖尿病前期、2型糖尿病的风险分别增加2.4%（OR=1.024,95%CI：1.018~1.030）、1.5%（OR=1.015,95%CI：1.005~1.025）;在男性中,血尿酸浓度每增加10 μmol/L,患糖尿病前期、2型糖尿病的风险分别减少0.8%（OR=0.992,95%CI：0.987~0.998）和5.0%（OR=0.950,95%CI：0.939~0.960）;RCS函数显示,女性血尿酸水平与新检出2型糖尿病关联呈非线性剂量反应关系（P=0.017）,但与糖尿病前期不呈非线性剂量反应关系（P=0.670）,男性血尿酸水平与糖尿病前期、新检出2型糖尿病均呈非线性剂量反应关系（新检出2型糖尿病P < 0.001;糖尿病前期P=0.040）。结论 在女性中,随着血尿酸水平升高成年女性糖尿病前期、新检出2型糖尿病患病风险增加,在男性中,随着血尿酸水平升高成年男性新检出2型糖尿病患病风险降低,男性血尿酸水平与糖尿病前期关联无统计学意义。     

A semiparametric probit model for case 2 interval‐censored failure time data

Interval‐censored data occur naturally in many fields and the main feature is that the failure time of interest is not observed exactly, but is known to fall within some interval. In this paper, we propose a semiparametric probit model for analyzing case 2 interval‐censored data as an alternative to the existing semiparametric models in the literature. Specifically, we propose to approximate the unknown nonparametric nondecreasing function in the probit model with a linear combination of monotone splines, leading to only a finite number of parameters to estimate. Both the maximum likelihood and the Bayesian estimation methods are proposed. For each method, regression parameters and the baseline survival function are estimated jointly. The proposed methods make no assumptions about the observation process and can be applicable to any interval‐censored data with easy implementation. The methods are evaluated by simulation studies and are illustrated by two real‐life interval‐censored data applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Establishment of BMD reference plots and determination of peak BMD at multiple skeletal regions in mainland Chinese women and the diagnosis of osteoporosis

Osteoporosis is a major public health problem, particularly in women. Bone mineral density (BMD) reference plot is a basic, and the peak BMD (PBMD) an important, parameter in the diagnosis of osteoporosis. In order to establish reference plots of BMD at multiple skeletal sites in Chinese women and improve the diagnostic accuracy for osteoporosis, we measured BMDs at several skeletal regions in 3,378 Chinese women, aged 5–96 years, using a dual-energy X-ray absorptiometry fan-beam bone densitometer. After determining that the cubic regression model best fit all skeletal regions, we utilized the curve-fitting to establish BMD reference plots and utilized the curve-fitting equation to calculate the highest BMDs at all skeletal regions using three different methods of calculation—actual PBMD (method A), PBMD of each 5-year age group (method B), and a cross-section of age (method C). When the three methods were compared, we found significant differences among them at the majority of skeletal regions studied. When we utilized these three methods to determine the prevalence of osteoporosis in 2,120 women aged 40 years and older, except for the Wards triangle, we observed significant differences among them at all skeletal regions. In the present study, we established new BMD reference plots at multiple skeletal regions for women of mainland China. Our findings also indicate that curve-fitting equations can be employed to calculate actual PBMDs specific to individual regions, and that the use of different methods to calculate PBMD may have a significant impact on both PBMD and the diagnosis of osteoporosis. Therefore, we suggest that a standardized method be established to calculate site-specific PBMDs based on the peak values of best-fit reference curves in appropriate age groups.     

Estimating dose-response relationship between ethanol and risk of cancer using regression spline models

Cancers of the upper aero-digestive tract (i.e., oral cavity, pharynx, larynx and oesophagus) are largely attributable to smoking and drinking habits, but the correct estimation of the dose-response relationship between alcohol and cancer risk is challenging. Step functions are widely used to estimate risks and to evaluate trends of continuous exposure. However, results are influenced by the selection of the reference category and cutpoints. More flexible models, like spline regression and fractional polynomial models, may be an attractive alternative for avoiding strict assumptions about the dose-response relationship. Data from a large series of hospital-based case-control studies conducted in Italy and the Swiss Canton of Vaud in the last 2 decades were reassessed to compare findings from logistic regression spline models and standard step function analysis. For all examined cancers, the risk increased to the consumption of 150 grams of ethanol per day (1.5 litre/day of wine), with a possible threshold effect emerging for cancer of the pharynx and larynx (<50 grams of ethanol per day) only. For higher consumptions, the risks flattened. Our study suggests that regression spline models can be useful to estimate the pattern of risk of a continuous exposure variable, such as alcohol consumption, and provide more accurate estimates than categorical analysis when ORs within each interval, especially in the reference category, are not homogeneous.     

Morphospatial analysis of soft-tissue profile in patients with Class II Division 1 malocclusion treated using twin block appliances: geometric morphometrics

Author– Singh GD Objectives– To study soft‐tissue profile changes in patients treated with twin block appliances (TBA) for the correction of Class II division 1 malocclusion. The null hypothesis is that soft‐tissue profiles do not show any significant improvements associated with TBA treatment. Design– Longitudinal, retrospective. Setting and Sample Population– Scotland, UK, using lateral cephalographs of 46 consecutive, prepubertal children (aged 9–11 years) and 55 adolescents (aged 12–14 years) obtained from an orthodontic practice. Experimental Variable– The prepubertal children underwent ≈13 months of TBA treatment, while the adolescents underwent ≈22 months of treatment. Outcome Measures– Configurations of 13 digitized homologous landmarks of pre‐ and post‐treatment soft‐tissue facial profiles were compared using cephalometry, Euclidean distance matrix analysis (EDMA) and thin plate spline (TPS) analysis. Results– Cephalometry showed that height increases associated with the TBA were in the labiomental areas, and the most significant height decreases were seen in the lip regions. The results of EDMA also indicated significant changes (P < 0.05). The distance between the lips decreased by >5%, with increases in length in the labiomental region. The TPS analysis showed the soft‐tissues of the mandibular complex being displaced antero‐inferiorly, with anterior displacement of the landmarks of the lip region. These changes showed that the lips were brought into closer proximity with each other, permitting a functional oral seal. Moreover, the labiomental groove became less pronounced, reflecting the underlying dento‐alveolar correction. Conclusion– Demonstrable improvements in soft‐tissue facial profile may be associated with TBA treatment.     

Body surface Laplacian electrocardiogram of ventricular depolarization in normal human subjects

INTRODUCTION: The body surface Laplacian electrocardiogram (ECG) mapping provides a noninvasive means for spatiotemporal mapping of cardiac electrical events. The aim of the present study was to explore the relationship between the Laplacian ECG and the underlying cardiac activities during ventricular depolarization in healthy human subjects. METHODS AND RESULTS: A 95-channel body surface potential ECG was recorded over the anterolateral chest from 11 healthy male subjects. The surface Laplacian (SL) ECG was estimated from the recorded potentials during QRS complex by means of a novel spline SL estimator, as well as by the conventional 5-point SL estimator for comparison purpose. A simulation study was also conducted using a realistic geometry heart-torso model in an attempt to qualitatively interpret the experimental results. For all subjects, more spatial details were observed in the SL ECG maps compared with the potential ECG maps, with spline SL more robust against noise than the 5-point SL. In total, three positive activities (denoted as P1, P2, P3) and four negative activities (denoted as N1, N2, N3, N4) in the spline SL ECG maps were observed during ventricular depolarization. Initial localized P1 and N1 activities were observed in 11 and 8 subjects, respectively. Then, the initial P1 was divided into three positive activities (P1, P2, P3) in 9 subjects. After the appearance of multiple positive activities, three negative activities (N2, N3, N4) appeared in 11, 8, and 9 subjects, respectively. Similar findings were obtained in the computer simulation study. CONCLUSION: The present study demonstrates that the SL ECG provides more spatial details than the potential ECG, and multiple simultaneously active ventricular activities could be revealed in the SL ECG maps. The results suggest that the SL ECG may provide an alternative for noninvasive mapping of cardiac electrical activity.