大直径球头-骨水泥型人工髋关节置换治疗帕金森患者股骨颈骨折12例

目的：探讨采用大直径球头-骨水泥型人工髋关节置换的方法,治疗老年帕金森患者股骨颈骨折的临床疗效。方法：回顾性病例分析2007年1月至2010年10月收治的帕金森患者合并股骨颈骨折12例,男3例,女9例,年龄65岁至87岁,平均年龄76.17岁。假体类型：人工全髋关节假体2例,人工双极股骨头10例。置换后3个月随访,进行围置换期并发症、影像学、髋关节功能评分（Harris评分）等方法评价手术效果。结果：所有患者均安全度过围置换期,置换术后3周出现脱位1例,无深部感染及深静脉血栓形成,无围手术期死亡病例;骨盆平片上出现髋臼侧透亮线1例,无骨溶解、松动及股骨柄下沉;Harris评分：90分至100分3例,80分至89分5例,70分至79分3例,〈70分1例。结论：大直径球头-骨水泥型人工髋关节置换治疗老年帕金森患者股骨颈骨折可有效改善关节功能,减少并发症,降低脱位率,提高患者生活质量。     

髋关节表面置换后股骨侧应力分布的有限元分析

目的通过有限元分析探讨髋关节表面置换后股骨侧的生物力学意义.方法采用有限元构建分析软件ANSYS workbench v10．0,通过对髋关节表面置换后股骨侧的结构进行拆分,分别将3部分构建后生成体积建立髋关节表面置换后股骨侧三维有限元模型,利用MSC patran2007计算软件,采用四面体10节点自由划分网格,共38147节点,187547单元,其中假体模型57446单元、水泥壳模型28265单元、股骨部分101836单元,分析髋关节表面置换后股骨侧的应力分布情况：结果所构建的三维有限元模型,逼真反映髋关节表面置换后股骨侧的真实几何形态及其生物力学。结论有限元模型的构建,可以为髋关节表面置换术的生物力学行为以及假体优化设计提供精确模型.     

Automated segmentation of acetabulum and femoral head from 3-d CT images

This paper describes several new methods and software for automatic segmentation of the pelvis and the femur, based on clinically obtained multislice computed tomography (CT) data. The hip joint is composed of the acetabulum, cavity of the pelvic bone, and the femoral head. In vivo CT data sets of 60 actual patients were used in the study. The 120 (60 /spl times/ 2) hip joints in the data sets were divided into four groups according to several key features for segmentation. Conventional techniques for classification of bony tissues were first employed to distinguish the pelvis and the femur from other CT tissue images in the hip joint. Automatic techniques were developed to extract the boundary between the acetabulum and the femoral head. An automatic method was built up to manage the segmentation task according to image intensity of bone tissues, size, center, shape of the femoral heads, and other characters. The processing scheme consisted of the following five steps: 1) preprocessing, including resampling 3-D CT data by a modified Sine interpolation to create isotropic volume and to avoid Gibbs ringing, and smoothing the resulting images by a 3-D Gaussian filter; 2) detecting bone tissues from CT images by conventional techniques including histogram-based thresholding and binary morphological operations; 3) estimating initial boundary of the femoral head and the joint space between the acetabulum and the femoral head by a new approach utilizing the constraints of the greater trochanter and the shapes of the femoral head; 4) enhancing the joint space by a Hessian filter; and 5) refining the rough boundary obtained in step 3) by a moving disk technique and the filtered images obtained in step 4). The above method was implemented in a Microsoft Windows software package and the resulting software is freely available on the Internet. The feasibility of this method was tested on the data sets of 60 clinical cases (5000 CT images).     

基于形状相似性和曲线化简的统计形状模型建立

针对活动形状模型(ASM)中统计模型建立存在的标记点的自动选取和点的对应两大问题,提出了一个完整的解决方案:首先通过矩阵的相似变换对齐训练集中各样本,然后根据样本特征,选择基准样本,再利用曲线化简方法在基准样本上自动提取特征点,最后利用训练样本间形状的相似性,由基准样本上的特征点向其它样本投影得到所有样本卜的标记点,实现了标记点的自动选取.同时保证了样本间标记点的一一对应.为了验证该方法的精确性和有效性.分别建立股骨和髋臼骨的点分布模型,实验结果表明,模型形状变化表现力强、计算效率高.分别与传统的手工标记法和优化法比较,在具有相同形状表现力的情况下,本文方法建模效率更高,时间开销更小.     

图像插值方法对互信息局部极值的影响分析

多模态图像配准中常使用互信息作为配准度量,互信息中的联合概率密度函数一般是利用图像灰度对的统计值来代替的,而图像插值可能产生新的灰度对,造成互信息出现局部极值。该文利用一维信号从理论上分析了线性和最近邻两种插值方法对互信息的影响。理论分析表明,线性插值造成互信息局部极值的可能性较小,而最近邻插值会使互信息出现周期性局部极值。试验结果证实了该文的结论。分析结果对基于互信息的多模态图像配准具有理论参考价值。     

Volume manipulations for simulating bone and joint surgery.

Bone and joint surgery is widely used in orthopedic, oral, and maxillofacial, and dental and plasty departments to correct bone and joint pathology such as bone and joint tumors and fractures, and skeletal morphological deformities. This article presents a voxel structure to represent topologically and geometrically correct surfaces and algorithms to accurately compute intersections of tool swept surfaces with bones based on this voxel structure. This article then presents various volume manipulation algorithms to operate on virtual bones, bone grafts, and prostheses for bone and joint surgery simulations. A complicated knee arthroplasty illustrates the practicality and versatility of the proposed method.     

A haptic-enabled multimodal interface for the planning of hip arthroplasty

Multimodal environments help fuse a diverse range of sensory modalities, which is particularly important when integrating the complex data involved in surgical preoperative planning. The authors apply a multimodal interface for preoperative planning of hip arthroplasty with a user interface that integrates immersive stereo displays and haptic modalities. This article overviews this multimodal application framework and discusses the benefits of incorporating the haptic modality in this area.     

Vibration arthrometry in the patients with failed total knee replacement

This is a preliminary research on the vibration arthrometry of artificial knee joint in vivo. Analyzing the vibration signals measured from the accelerometer on patella, there are two speed protocols in knee kinematics: 1) 2 degrees/s, the signal is called "physiological patellofemoral crepitus (PPC)", and 2) 67 degrees/s, the signal is called "vibration signal in rapid knee motion". The study has collected 14 patients who had revision total knee arthroplasty due to prosthetic wear or malalignment represent the failed total knee replacement (FTKR), and 12 patients who had just undergone the primary total knee arthroplasty in the past two to six months and have currently no knee pain represent the normal total knee replacement (NTKR). FTKR is clinically divided into three categories: metal wear, polyethylene wear of the patellar component, and no wear but with prosthesis malalignment. In PPC, the value of root mean square (rms) is used as a parameter; in vibration signals in rapid knee motion, autoregressive modeling is used for adaptive segmentation and extracting the dominant pole of each signal segment to calculate the spectral power ratios in f < 100 Hz and f > 500 Hz. It was found that in the case of metal wear, the rms value of PPC signal is far greater than a knee joint with polyethylene wear and without wear, i.e., PPC signal appears only in metal wear. As for vibration signals in rapid knee motion, prominent time-domain vibration signals could be found in the FTKR patients with either polyethylene or metal wear of the patellar component. We also found that for normal knee joint, the spectral power ratio of dominant poles has nearly 80% distribution in f < 100 Hz, is between 50% and 70% for knee with polyethylene wear and below 30% for metal wear, whereas in f > 500 Hz, spectral power ratio of dominant poles has over 30% distribution in metal wear but only nonsignificant distribution in polyethylene wear, no wear, and normal knee. The results show that vibration signals in rapid knee motion can be used for effectively detecting polyethylene wear of the patellar component in the early stage, while PPC signals can only be used to detect prosthetic metal wear in the late stage.     

A reassessment of satellite communications in the 20 and 30 GHz bands

Notwithstanding the additional spectrum allocations of the 1979 World Administrative Radio Conference (WARC '79) and the ever-increasing sophistication of spacecraft antennas which allow more intensive spectrum reuse, saturation of the 6/4 and 14/11 GHz bands is foreseeable by the late-1990s. The next available frequency bands at 30/20 GHz were allocated at WARC '71, when knowledge of propagation phenomena and their effect on satellite communications systems performance was fragmentary. During the past 8 years, numerous experimental programmes have led to the acquisition of more precise information about hydrometeor-induced propagation disturbances. Analysis of the data reveals that even with corrective means such as diversity and coding, service reliability of satellite communications systems with up-links at 30 GHz and down-links at 20 GHz could not reach 99.99 per cent as currently available at the lower frequencies and could be 98.0 per cent, or lower, in certain parts of the world. Since the conventionally proposed use of the 30/20 GHz bands does not lead to optimal solutions, alternative approaches are needed. An approach which would involve a revision of the spectrum allocations at 30/20 GHz is proposed. Placing both up- and down-links around 20 GHz and redistributing the spectrum available at 20 GHz would prevent the intrinsic imbalance of the up- and down-links with consequent higher reliability, reduced earth-station transmitter power, reduced construction and operational costs, and simplification of the spacecraft transponders and antenna design. The use of frequencies around 30 GHz could be postponed until the 20 GHz bands became saturated. When the 30 GHz bands would eventually be used, there would be no imbalance of up- and down-links.     

On the Interaction of Lightning Upward Connecting Positive Leaders With Humans

Upward connecting leaders can be initiated from humans under the influence of lightning downward stepped leaders, thereby causing severe injuries. In order to improve the scarce knowledge about the interaction of upward connecting leaders with humans, a self-consistent model based on the physics of leader discharges is used in this paper. Furthermore, a current-generation-type return-stroke model is applied to calculate the current pulse produced during the neutralization of unsuccessful aborted upward leaders. It is estimated that an upward connecting leader can be initiated even when the victim is located several tens of meters away from the lightning channel. However, the lightning exposure to a direct strike and to an aborted leader is found to be reduced by 50% and 70%, respectively, when an individual standing straight adopts the squat position. In the case of an aborted upward leader, it is estimated that a short-duration pulse of opposite polarity in the kiloampere range would be produced by the neutralization of the leader charge. Rough estimates of the total energy dissipated in the victim's body by the current of an aborted unsuccessful upward leader range between hundred and thousand joules.      

Use of induced acceleration to quantify the (de)stabilization effect of external and internal forces on postural responses

Due to the mechanical coupling between the body segments, it is impossible to see with the naked eye the causes of body movements and understand the interaction between movements of different body parts. The goal of this paper is to investigate the use of induced acceleration analysis to reveal the causes of body movements. We derive the analytical equations to calculate induced accelerations and evaluate its potential to study human postural responses to support-surface translations. We measured the kinematic and kinetic responses of a subject to sudden forward and backward translations of a moving platform. The kinematic and kinetics served as input to the induced acceleration analyses. The induced accelerations showed explicitly that the platform acceleration and deceleration contributed to the destabilization and restabilization of standing balance, respectively. Furthermore, the joint torques, coriolis and centrifugal forces caused by swinging of the arms, contributed positively to stabilization of the Center of Mass. It is concluded that induced acceleration analyses is a valuable tool in understanding balance responses to different kinds of perturbations and may help to identify the causes of movement in different pathologies.     

Pemberton手术联合股骨近端截骨治疗先天性髋关节脱位

目的探讨儿童先天性髋关节脱位用Pemberton手术联合股骨近端截骨治疗的临床效果。方法采用Mckav的临床评价标准和WilletX线测量方法,对笔者1997年12月-2008年5月所做的190例（212个髋）Pemberton手术进行回顾性研究。手术年龄1．5-8岁（平均4．2岁）,男29例,女161例,男女比例1：5．55,左侧141例,右侧27例,双侧22例。结果其中181例获得随诊,随诊时间1～8年,平均29．6月,优183例,良33例,差8例,优良率96．4％,髋臼指数由术前30&#176;-45&#176;（平均36&#176;）减少到术后4&#176;-15&#176;,平均10&#176;。结论Pemberton手术联合股骨近端截骨疗效确定,是治疗儿童先天性髋关节脱位的理想术式之一。     

Design of a Variable Constraint Hip Mechanism for a Hybrid Neuroprosthesis to Restore Gait After Spinal Cord Injury

A variable constraint hip mechanism (VCHM) has been developed for a hybrid neuroprosthesis system (HNP) to provide postural stability and uninhibited sagittal hip rotation throughout the gait of individuals with paraplegia. This paper describes the design concepts used in the development of the VCHM. The VCHM utilizes a hydraulic system to reciprocally couple the hips or individually lock and/or free a hip to rotate in one or both sagittal directions. Bench testing results show the feasibility of utilizing a portable hydraulic system in controlling hip joint kinematics. The passive resistive torques of the VCHM against user hip rotation at hip angular velocities typical of gait does not exceed 10% of the achievable hip torque generated by functional neuromuscular stimulation of paralyzed muscle. With the state of the VCHM configured to reciprocally couple the hips, the normalized mechanical efficiency of the VCHM was determined to be 0.7. Since each hip will be independently driven by the FNS of muscle, high torque transfer efficiency between the hips is not essential for successful operation of the VCHM. Future work will focus on the development of a sensor-based feedback controller to modulate the hip constraints of the VCHM and validation of the VCHM as part of a HNP for paraplegic individuals implanted with FNS systems.     

Assessment of acceleration models used for BGA solder joint reliability studies

Solder joint reliability was one of the top priorities when evaluating the reliability of electronic packages. In general, an acceleration model would be used to predict solder joint fatigue life in the use conditions. However, the accuracy of the model was difficult to validate. As a result, the fatigue life of the solder joints could be over-designed with added cost or time, or under-estimated with a compromised reliability performance. It was an important goal for engineers to use valid and accurate life models to predict the field life of the solder joints and reduce development cost and time.Many empirical models including Norris-Landzberg model and its modifications usually considered the effects of temperature range, the cycle frequency, and the maximum temperature. No matter what the package structures were or the materials were used, engineers had been using the same model parameters for many years. Moreover, little was done to validate the models for modern packages structures and materials.In this article, a variety of package was studied and the failure data was analyzed through a reliability engineering approach. The results showed that the available model parameters were not suitable to predict the solder joint life of test samples exclusively. A new set of model parameters might be required for certain cases. Also, the acceleration factor models would depend on the solder joint materials and microstructures. The solder joint fatigue life performance was too complicated to be assumed as a fixed empirical model. One of the reasons was there were too many factors affecting the strain which the solder joints would endure.In the future study, critical factors such as materials or structures could be integrated into the current model format. Additionally, the ramp rate could be a concern especially when dealing with cases under thermal shock conditions. The methodology to develop an acceleration factor model and the demonstration of their weakness would help achieve reliable solder connections in the future.     

Maximization of the channel utilization in wireless heterogeneousmultiaccess networks

The key aspect of personal communication services (PCS) is wireless access through local and wide area networks where there may exist a variety of services having different rates and diverse quality-of-service (QOS) requirements. This paper addresses the problem of maximizing the channel utilization in a wireless heterogeneous network with finite population. Slotted ALOHA with packet capture is used as the multiaccess protocol in the presence of background noise and Rayleigh fading. It is known that the capture effect, while significantly increasing the network throughput, causes unfairness among users in a heterogeneous network. To take fairness into consideration, individual throughput is used as the constraint with the channel utilization being the maximization objective. The maximization problem is then studied under various conditions by controlling the transmission power and/or probability. It is shown that for a narrow-band system under equal individual throughput requirement, transmission probability control is more effective than power control, and when a joint control strategy is employed, perfect or near perfect channel utilization can be achieved in the absence or presence of Rayleigh fading     

Bayesian Segmentation of Hip and Thigh Muscles in Metal Artifact-Contaminated CT Using Convolutional Neural Network-Enhanced Normalized Metal Artifact Reduction

Journal of Signal Processing Systems - In total hip arthroplasty, analysis of postoperative medical images is important to evaluate surgical outcome. Since Computed Tomography (CT) is most...     

Hierarchical neural network for hand pose estimation

Hand pose estimation plays an important role in human–computer interaction and augmented reality. Regressing the joints coordinates is a difficult task due to the flexibility of the joint, self-occlusion and so on. In this paper, we propose a novel and simple hierarchical neural network for hand pose estimation. The hand joint coordinates are divided into six parts and each part is regressed in sequence with this hierarchical architecture. This can divide the complex task of regressing all hand joints coordinates into several sub-tasks which can make the estimation more accurate. When regress the joint coordinates of one part, the features of other parts may bring negative influence to this part due to the similarity among the fingers, so we use an interference cancellation operation in our hierarchical architecture. At the time the joint coordinates of one part are regressed, the corresponding features will be removed from the hand global feature to eliminate the interference of this part. The obtained features will be used as input for regressing the joints coordinates of the next part. The ablation study verifies the effectiveness of our hierarchical architecture. The experimental results demonstrate that our method can achieve state-of-the-art or comparable results relative to existing methods on four public hand pose datasets.     

The evaluation of cortical bone remodeling with a new ultrasonictechnique

Total hip arthroplasty causes biomechanical changes in the normal femur including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Three complementary techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. A graphics package was used to obtain section geometrical information, an ultrasonic wave propagation technique to determine elastic properties, and a new scanning acoustic microscope (SAM) to map the acoustic impedance profile of each section. The effects of the implantation of two different types of hip prostheses were investigated, an uncemented bipolar prosthesis with an Austin-Moore type stem and a cemented Charnley prosthesis. Prosthesis implantation resulted in an increase in cortical area and mediolateral diameter and a decrease in anterio-posterior diameter. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. Finally, the SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.     

基于红外热像的网架焊接空心球节点疲劳试验研究

焊接空心球网架结构被广泛使用在带悬挂吊车的工业厂房中。悬挂吊车带来的往复交变荷载会造成网架焊接节点的疲劳破坏。在焊接空心球节点的疲劳试验过程中,借助红外热像仪记录试件表面的温度,得到了试件表面的温升分布,温升高区位于钢管与焊接球的焊接连接球面焊趾处,此区域对应节点最后的疲劳破坏位置。在疲劳试验过程中,焊趾处的温升高区位置几乎不变,当疲劳裂纹穿透球壁厚时,温升高区的位置发生变化。试验表明:红外热像仪可以实时记录焊接空心球节点试件在疲劳试验过程中表面的温度,通过分析温升高区在没有可见裂纹的情况下就可预测疲劳破坏发生的位置,温升高区位置的变化对应裂纹贯穿球壁时节点试件的疲劳寿命。     

系留光电复合旋转连接器的研制

利用光电复合旋转连接器可以实现在转动状态下光电信号和电源动力的传输。介绍了系留光电复合旋转连接器各个部件的设计,并对其整体性能进行了分析。