人体参数化运动学模型建立方法的研究

目的 通过广义坐标变换,构建人体参数化运动学模型,应用于人体的相对运动和绝对运动分析.方法 通过对人体环节的划分和人体系统的机械化处理建立人体的多刚体模型,根据人体运动的特点,采用其次矩阵和广义坐标变换建立人体参数化运动学模型.结果 通过运动分析和矩阵变换建立了通用的人体参数化运动学模型.结论 通过坐标变换原理,使用齐次矩阵描述人体各个环节的相对运动方程和绝对运动方程,从而给出人体模型在特定运动条件的运动特征,并用以进行人体的步行/跑步运动分析.     

卧姿人体垂直振动模型

目的：建立卧姿人体头部、胸部和腹部垂直振动模型。方法：被试者12名，年龄24-56岁，采用频率2-35Hz的白噪声激励，根据卧姿被试者头、胸、腹部的加速度阻抗特性曲线，得到卧姿人体头部垂直振动模型，拟合出腹部和胸部的垂直振动模型。结果：头部可认为是刚体，腹部和胸部模型为三自由度。结论：卧姿人体垂直振动机械阻抗可线性表示且具有确定性，对卧姿人体头部、胸部和腹部分别建立垂直振动模型，便于计算与评价卧姿人体承受全身振动的舒适性。     

面向航天虚拟操作分析的航天员人体建模与姿态仿真技术

目的建立支持虚拟操作分析的航天员三维人体模型。方法研究了层次化、关节化和参数化人体建模方法;通过CATIA软件建立人体骨骼层、皮肤层和服饰层静态模型,并将其导入到JACK环境当中进行关联处理,赋予人体关节运动特性。结果生成了可根据百分位和各体段参数进行调整的航天员模型,并实现了姿态仿真。结论建立的航天员人体模型具有几何外观特性和基本动力学特性,结合JACK软件环境,可以实现航天操作的可视性、可达性、疲劳度等分析。     

模型在冲击性过载研究中的作用

在弹射救生过程中的冲击过载,可引起人体不同程度的损伤,甚至死亡,这一问题的研究有重要意义。由于直接用人体进行这类实验带有一定的危险性,因此必须寻找其他研究途径。本文综合介绍了国外和我们研究工作中所采用的模型方法,其中有数学模型、电子模型和机械模型。数学模型中包括了集总参数、分布参数、连续参数、有限元、人体大运动、头部运动等模型,阐述了这些模型的基本内容和它们所起的作用,还讨论了建模中存在的问题。     

飞行员头部特征分析及头型分类方法研究

目的通过构建飞行员头部三维模型及分类计算,研究一种新的头部特征分析及头型分类方法。方法利用光栅投影图像测量技术构建飞行员头部三维模型,通过数值拟合方法分析获得飞行员的头部特征外形参数,按照统计学原理根据头高、头宽、头长尺寸对飞行员的头型进行了科学的分类。结果 1)建立了飞行员头部三维模型;2)男性飞行员的头型主要分类结果:长圆型(LC)59.6%、长中型(M)24.40%、特长圆型(SLC)9.84%;3)选定长圆型、长中型、特长圆型这三类头型尺寸。结论本研究采用的外形参数分析方法和头型分类方法可以用在今后大规模飞行员头部特征测量分析以及改进头盔设计的工作。     

女大学生人体体积测量与回归方程初探

目的:测量女大学生人体体积,并在此基础上建立回归方程。方法:对18~22岁女大学生的体重、身高和身体体积进行测量。依据测量结果,建立以体重、身高为自变量,身体体积为因变量的回归方程。结果表明,5种回归方程可作为计算人体体积的计算模型。根据回归方程计算的女大学生人体体积值与其身体形态、机能和素质等体质指标的相关系数有显著性差异(P<0.001)。     

飞行员头部几何参数变化及其工效学意义分析

目的：探讨飞行员头部参数及头型随年代发展等因素的变化程度与趋势。方法：对８０名飞行员进行头水平围等１０项头部参数的测量与分析,并与７０年代的数据进行比较。结果：与７０年代相比,１０项参数值中的８项有非常显著性差异（Ｐ＜０．０１）;头型为圆颅型这一总体特征未改变,但趋于更圆,且各种头型的分布略有变化;全国不同地区之间以及飞行学员与飞行教员之间,１０项头部参数均无显著性差异（Ｐ＞０．０５）。结论：进行头部防护装具设计时,应充分考虑飞行员的头部参数较７０年代已有变化且头型总体特征未变但趋于更圆这一情况;不同地区的飞行员以及飞学员与飞行教员的头部防护装具型号无需加以区别;应开展飞行员头部参数模型的建立工作;统一严格控制招飞条件对提高飞行防护装具的适体性有重要意义。     

运用一种外在有限元人头部模型分析头部撞击部

研究头部在直接撞击伤情况下的动力学响应和损伤机制。方法：把机械参数与头部直接撞击伤的机制联系起来，建立一个三维综合的有限元的人头部模型。用一种外在的综合有限元技术进行分析。模型反应同测得的撞击力，头部加速度和颅内压资料进行了比较。     

特殊作业条件下头部过载对人体的影响

目的获取特殊作业条件下的人体头部过载试验数据,研究人体对短时高强度过载冲击的响应特性及其对人体的影响。方法对现有试验设施进行改装,针对特殊作业条件下人体头部过载进行试验方案设计,采集获取乘体过载、人体头部过载等试验数据。通过试验数据分析了人体头部对过载冲击的响应特性,并从人体头部过载耐受性、头部损伤评估、头部共振等方面分析对人体的影响。结果在试验过程中,人体头部过载和乘体过载在趋势上具有良好一致性,但是峰值均高于乘体,二者差值随乘体运动速度增大而增大。结论人体头部对短时高强度过载的反应较剧烈,对人体安全性和舒适性造成了严重的威胁,但不会产生共振,不会对人体造成负面影响。虽然人体头部过载峰值和作用时间未超出人体耐受极限,但在不断累积情况下,可能会影响乘员健康。     

液冷服散热原理模型及其分析

目的 建立舱外航天液冷服散热的原理模型,提出其在工程设计中应遵循的基本原则。并以该原理模型为基础找到液冷服设计参数与散热量和散热效率的模化关系。方法 根据工程实际,对舱外航天液冷服散热过程进行分析。结果 液冷服各参数（管长、管径、流率和进口液温）对散热量和散热效率的影响是相互制约,相互作用的,因此各参数的合理取值是设计液冷服的关键。结论 该分析和研究对今后舱外航天液冷服的设计研制具有一定的指导意义     

Application of the keyhole technique to T1rho relaxation mapping

PURPOSE: To demonstrate the feasibility of using the keyhole technique to minimize error in a least squares regression estimation of T(1rho) from magnetic resonance (MR) image data. MATERIALS AND METHODS: The keyhole method of partial k-space acquisition was simulated using data from a virtual phantom and MR images of ex vivo bovine and in vivo human cartilage. T(1rho) maps were reconstructed from partial k-space (keyhole) image data using linear regression, and error was measured with relation to T(1rho) maps created from the full k-space images. An error model was created based on statistical theory and fitted to the error measurements. RESULTS: T(1rho) maps created from keyhole images of a human knee produced levels of error on the order of 1% while reducing standard image acquisition time approximately by half. The resultant errors were strongly correlated with expectations derived from statistical theory. CONCLUSION: The error model can be used to analytically optimize the keyhole method in order to minimize the overall error in the estimation of the relaxation parameter of interest. The keyhole method can be generalized to significantly expedite all forms of relaxation mapping.     

BI-RADS影像特征的预测模型在乳腺不可触及钙化病变中的价值

目的 探讨乳腺不可触及钙化病变患者的临床及BI-RADS-X线影像特征,建立Logistic多变量预测模型评估乳腺病变良恶性的概率,以提高乳腺不可触及钙化病变诊断准确率.方法 回顾性分析133例(147个病灶)乳腺不可触及钙化病变,先根据个人经验对病变的X线影像资料进行分析并做出BI-RADS评估分类,与病理对照绘制受试者工作特征(ROC)曲线.之后再对病变X线影像及临床特征进行单因素及多因素分析,筛选与良恶性相关的影响因素,建立Logistic模型并选取合适截点,绘制ROC曲线.最后比较术前BI-RADS分类与Logistic模型对乳腺病变诊断准确性的差别.结果 术前BI-RADS分类判断病变良恶性得到曲线下面积(AUC)为0.867 9.患者临床特征(年龄、位置、病变所在象限)及BI-RADS-X影像特征(分布方式、形态特征、病变部位腺体密度)单因素分析结果显示上述特征差异均有统计学差异;Logistic回归多因素分析示年龄、象限及形态特征差异有统计学意义,建立方程判断病变良恶性得到Logistic模型的AUC为0.906 3.结论 Logistic模型对乳腺病变诊断的准确性高于术前BI-RADS分类,对乳腺病变的正确诊断具有一定的参考价值.     

Platform-independent models for age prediction using DNA methylation data

Age prediction has been in the spotlight recently because it can provide an important information about the contributors of biological evidence left at crime scenes. Specifically, many researchers have actively suggested age-prediction models using DNA methylation at several CpG sites and tested the candidates using platforms such as the HumanMethylation 450 array and pyrosequencing. With DNA methylation data obtained from each platform, age prediction models were constructed using diverse statistical methods typically with multivariate linear regression. However, because each developed model is based on single-platform data, the prediction accuracy is reduced when applying DNA methylation data obtained from other platforms. In this study, bisulfite sequencing data for 95 saliva samples were generated using massively parallel sequencing (MPS) and compared with methylation SNaPshot data from the same 95 individuals. The predicted age obtained by applying MPS data to an age-prediction model built for methylation SNaPshot data differed greatly from the chronological age due to platform differences. Therefore, novel variables were introduced to indicate the platform type, and construct platform-independent age predictive models using a neural network and multivariate linear regression. The final neural network model had a mean absolute deviation (MAD) of 3.19 years between the predicted and chronological age, and the mean absolute percentage error (MAPE) was 8.89% in the test set. Similarly, the linear regression model showed 3.69 years of MAD and 10.44% of MAPE in the same test set. The platform-independent age-prediction model was made extensible to an increasing number of platforms by introducing platform variables, and the idea of platform variables can be applied to age prediction models for other body fluids.     

Direct integral linear least square regression method for kinetic evaluation of hepatobiliary scintigraphy: theory, basic analysis and comparison with non-linear least square regression method

In hepatobiliary scintigraphy, kinetic model analysis, which provides kinetic parameters like hepatic extraction or excretion rate, have been done for quantitative evaluation of liver function. In this analysis, unknown model parameters are usually determined using nonlinear least square regression method (NLS method) where iterative calculation and initial estimate for unknown parameters are required. As a simple alternative to NLS method, direct integral linear least square regression method (DILS method), which can determine model parameters by a simple calculation without initial estimate, is proposed, and tested the applicability to analysis of hepatobiliary scintigraphy. In order to see whether DILS method could determine model parameters as good as NLS method, or to determine appropriate weight for DILS method, simulated theoretical data based on prefixed parameters were fitted to 1 compartment model using both DILS method with various weightings and NLS method. The obtained parameter values were then compared with prefixed values which were used for data generation. The effect of various weights on the error of parameter estimate was examined, and inverse of time was found to be the best weight to make the error minimum. When used this weight, DILS method could give close parameter values to those obtained by NLS method and both parameter values were very close to prefixed values. With appropriate weighting, the DILS method could provide reliable parameter estimate which is relatively insensitive to the data noise. In conclusion, the DILS method could be used as a simple alternative to NLS method, providing reliable parameter estimate.     

基于分割后断层成像数据的人体头部有限元模型构建方法

目的 基于分割后的断层成像数据构建人体头部的有限元模型.方法 采用四步剖分法得到初始网格并用最长边繁衍路径(longest edge propagation path)与棱边收缩(edge collapse)的方法进行网格的细分与优化.在通过该方法得到的三层球与真实头模型上分别进行脑电正问题的仿真计算.结果 结果显示在此模型基础上进行有限元计算的合理性与可靠性.结论 采用该方法生成的人体头部有限元模型可包含多层组织,并能应用于基于有限元方法的生物力学、生物电磁学领域的各种科学计算.     

11～16岁肥胖青少年体力活动耗氧量推算方法实验研究

目的:采用多水平线性模型分析方法建立适用于肥胖青少年的耗氧量推算方程,为测量体力活动能量消耗提供简便有效的方法。方法:以60名11~16岁年龄段的肥胖青少年为研究对象,随机分为公式组(40名)和回代验证组(20名),男女各半。公式组在坡度为0的跑台上以2km/h、3km/h、4km/h、5km/h、6km/h、7km/h、8km/h的速度运动,每级负荷持续2.5分钟后继续增加,以心率达到80%HRmax为运动终止标准。采用气体代谢系统连续测量运动过程中耗氧量和心率,建立耗氧量多元线性回归方程,并进行回代验证。结果:所建回归方程R2男生为0.795,女生为0.75;耗氧量与负荷心率、瘦体重(LBM)具有线性关系(P<0.001);自变量系数及常数项均有极显著意义,得回归方程为男:耗氧量(ml/min)=20.098×负荷心率(bmp)+25.160×瘦体重(kg)-2935.835;女:耗氧量(ml/min)=19.863×负荷心率(bmp)+26.551×瘦体重(kg)-2675.676。回代验证组耗氧量预测值与实测值的平均相对误差男生为6.84%～8.72%,女生为6.53%～8.23%。结论:以负荷心率和瘦体重为自变量建立耗氧量的多元回归方程,可应用于肥胖青少年体力活动耗氧量的推算。     

Estimation in medical imaging without a gold standard

RATIONALE AND OBJECTIVES: In medical imaging, physicians often estimate a parameter of interest (eg, cardiac ejection fraction) for a patient to assist in establishing a diagnosis. Many different estimation methods may exist, but rarely can one be considered a gold standard. Therefore, evaluation and comparison of different estimation methods are difficult. The purpose of this study was to examine a method of evaluating different estimation methods without use of a gold standard. MATERIALS AND METHODS: This method is equivalent to fitting regression lines without the x axis. To use this method, multiple estimates of the clinical parameter of interest for each patient of a given population were needed. The authors assumed the statistical distribution for the true values of the clinical parameter of interest was a member of a given family of parameterized distributions. Furthermore, they assumed a statistical model relating the clinical parameter to the estimates of its value. Using these assumptions and observed data, they estimated the model parameters and the parameters characterizing the distribution of the clinical parameter. RESULTS: The authors applied the method to simulated cardiac ejection fraction data with varying numbers of patients, numbers of modalities, and levels of noise. They also tested the method on both linear and nonlinear models and characterized the performance of this method compared to that of conventional regression analysis by using x-axis information. Results indicate that the method follows trends similar to that of conventional regression analysis as patients and noise vary, although conventional regression analysis outperforms the method presented because it uses the gold standard which the authors assume is unavailable. CONCLUSION: The method accurately estimates model parameters. These estimates can be used to rank the systems for a given estimation task.     

Head rotation during vertical impact predicted using initial head angle and anthropometry

INTRODUCTION: Dynamic inertial loading to the head and neck complex, similar to what is experienced during the rocket boost phase of pilot ejection, results in diverse kinematic responses when observed in live human volunteers. The purpose of this study was to develop a predictive model of head rotation during the compressive phase of pilot ejection. METHODS: Post hoc analyses were conducted on data from two previous experimental studies. This analysis included observing 138 tests involving 27 human volunteers (both men and women) where the various kinematic responses were categorized into five modes based on the location of primary rotation and the direction of head rotation. Several statistical methods (logistic regression, linear regression, and Fisher's Exact test) were employed to evaluate the influence of independent variables, body anthropometry, and initial head angle on dependent variables head acceleration and direction of head rotation. RESULTS: Statistical results of this data indicated that initial head position and body anthropometry are significant factors with respect to head response during the compressive phase of an ejection. Two statistical tools were developed; one to assist in predicting the location of primary head rotation, and the other to predict the direction of head rotation. DISCUSSION: By using the two statistical tools together, a simplified method was developed for predicting the modes of head response to vertical impact based on initial position and anthropometry. The results of this study show the importance of initial position prior to an ejection and may assist in identifying individuals at greater risk of injury during an ejection.     

Computer simulation for postmortem cooling processes in the outer ear

INTRODUCTION: A simulation using a computer model was undertaken to investigate postmortem cooling patterns in the outer ear. METHODS: Cooling patterns were analyzed using a 3-dimensional head model built from brain CT images of a volunteer. The simulation was verified with a case subject under constant environmental conditions to obtain an appropriate heat transmission coefficient. RESULTS: The cooling pattern of the head model agreed with that of the case subject when the heat transmission coefficient was 6W/m(2) degrees C, and it could be approximated to a single exponential curve. DISCUSSION: This is the first simulative study to show the postmortem cooling pattern of the head of an adult human. Our head model will prove useful to predict the cooling patterns of not only the outer ear but also of the entirety of the head.     

SAR and B1 field distributions in a heterogeneous human head model within a birdcage coil

Calculations of radiofrequency magnetic (B₁) field and specific energy absorption rate (SAR) distributions in a sphere of tissue and a multi-tissue human head model in a 12-element birdcage coil are presented. The coil model is driven in linear and quadrature modes at 63, 175, 200, and 300 MHz. Plots of B, field magnitude and SAR distributions, average SAR, maximum local SAR, and measures of B₁ field homogeneity and signal-to-noise ratio are given. SAR levels for arbitrary pulse sequences can be estimated from the calculated data. Maximum local SAR levels are lower at lower frequencies, in quadrature rather than in linear coils, and in linear fields oriented posterior-to-anterior rather than left-to-right in the head. It should be possible to perform many experiments in the head at frequencies up to 300 MHz without exceeding standard limits for local or average SAR levels.