现代光力学技术在生物医学工程中的应用

介绍了现代光力学检测技术中的数字散斑相关法、影栅云纹法、光弹性方法、云纹干涉法和电子散斑干涉法的原理;综述了近几年国内外利用上述诸方法在生物医学工程领域的应用及进展,从而为生物工程研究提供较好的研究手段和实验方法,促进生物医学工程研究内容的深入探索。     

光相干层析成像中的散斑

由于光相干层析成像中测量的干涉信号空间频带有限,会产生散斑。在高散斑生物组织图像中,散斑具有双重身份,即作为噪声源和作为组织微结构的信号载体。本的前半部分对光相支析成像中的散斑的产生原因、统计特性以及分类作了综述。通过采样束的相位和振幅扰动可以定义信号载体散斑和信号降低散斑。本的后半部分讨论了减少散斑的４种方法,偏振合成法、空间合成法、频率合成法和数字信号处理方法,并且通过举例对每一种方法的有     

光相干层析成像中的散斑

由于光相干层析成像中测量的干涉信号空间频带有限 ,因此会产生散斑。在高散射的生物组织图像中 ,散斑具有双重身份 ,即作为噪声源和作为组织微结构的信号载体。本文的前半部分对于光相干层析成像中散斑的产生原因、统计特性以及分类作了综述。通过采样束的相位和振幅扰动可以定义信号载体散斑和信号降低散斑。本文的后半部分讨论了减少散斑的 4种方法 :偏振合成法、空间合成法、频率合成法和数字信号处理方法 ,并且通过举例对每一种方法的有效性作了简单的分析。最后 ,文章提出了需进一步研究的问题     

数字散斑法测量股骨干骨折内固定下的位移****◆

背景：既往研究多采用传感器来研究钢板内固定治疗股骨干骨折的生物力学特点,存在直接接触、精度低等缺点,将数字散斑技术应用到骨折生物力学领域中,能更精确地分析螺钉断裂的力学过程。 目的：利用数字散斑法测量成人股骨加压钢板内固定后骨折端在不同拉力条件下地位移。 方法：取6 根成人股骨标本,制造肱骨中段骨折模型,骨折标本两端各使用5枚螺钉固定,进而使用电子万能机在200 N和300 N负荷下进行拉力实验,数字散斑法测量10种状态下骨折断端近侧螺钉的位移。结果与结论：300 N拉力下的位移明显大于200 N拉力(P < 0.01),除螺钉1和10,2和9,3和8,4和7,5和6外,其余组两两比较差异有显著性意义(P < 0.05),提示螺钉位移随拉力增加而增大,且骨折线附近螺钉的位移随拉力改变较大。     

云纹干涉法测量不同载荷条件下金属-瓷标本的位移

背景：云纹干涉法是现代光力学测试技术,是实验力学范畴。另外,金瓷修复体以其较好的生物相容性,色泽美观,坚固而广泛应用于临床,将云纹干涉技术应用口腔领域得到医学工程中所需位移量,体现学科交叉,较好的实现学科互补。 目的：详细介绍了云纹干涉法原理以及试件栅的复制,针对临床经常发现口腔中瓷剥落等破坏行为,应用云纹干涉法来研究金瓷复合材料受力后的位移量。 方法：采用云纹干涉技术测试金瓷试件在不同载荷下的水平和竖直位移情况,该方法灵敏度高,操作简便,适用于面内位移测量,位移量以条纹形式显示。 结果和结论：该方法能够获得到口腔材料代表面内位移的干涉图,得到不同载荷作用下试件变形量。云纹干涉法能够被用来测试金瓷修复体的位移,操作简便,结果以干涉条纹显示。     

数字散斑法加载200~400 N测量股骨干骨折髓内钉置入内固定下的形变

背景：髓内钉置入内固定治疗长骨骨折易发生螺钉断裂致骨畸形。将光学测量技术应用到生物医学领域中,能更精确的分析螺钉断裂的特点。 目的：以数字散斑法测量股骨髓内钉交锁螺钉的形变。 方法：取4根成人无名尸体防腐股骨标本,制作股骨中1/2交锁髓内钉内固定模型。4枚锁钉从上到下标记为1,2,3,4。每具标本按A~D组顺序进行测试,A组：安装交锁髓内钉模拟骨折愈合;B组：在A组基础上股骨中段横形锯断2次,即中点锯断1次,中点下5 cm处行第2次锯断,模拟较复杂型骨折;C组：在B组的基础上上端去除1枚锁钉;D组：在C组基础上下端去除1枚锁钉。在200,300,400 N拉力下,以数字散斑相关软件测量各组第4锁钉的形变。 结果与结论：在300 N拉力下,B组与C组锁钉形变差异有显著性意义(P < 0.05)。提示在载荷递增到300 N的过程中,在股骨干骨折愈合过程中远端靠近骨折线之锁钉将产生较大的应变,此钉极易发生疲劳性断裂。     

用投影散斑立体摄影法测量人体关节的三维运动

本文采用白光散斑法，由两个摄像机同时记录人体关节运动过程中的数字图像，通过数字相关测出各标志点的平面位移．然后用立体摄影法求解各测点在运动过程中的三维坐标，得到各标志点的三维运动．针对刚体大位移的特点，提出了被测区域的侧转和自转指标，实现对人体关节一般空间运动的定量分析，为医学手术的评价提供实验测量基础。     

微循环流速测量技术的发展与临床应用简况

微循环速流测量技术在基础医学研究和临床实践中正发挥着日益重要的作用。本文着重介绍微循环流速测量技术的国内外进展，包括显微电视系统法、激光多普勒和微光散斑技术，在掌握祥实资料的基础上，对这些微循环流速测量技术在临床实践中的应用发展情况也作了清晰简要的介绍。     

牙列完整和牙列缺损时牙槽骨承力的变形分析

目的从生物力学角度观察牙列完整和牙列缺损时相应牙槽骨承力后的形变规律。方法选用新鲜人尸成人完整颅颌骨为测试标本,牙列完整,咬合关系良好,邻接紧密。标本经处理后,制备「6缺失模型,模拟口颌系统在生理咬合状态下的典型载荷,进行垂直均匀加载和集中点加载试验,重量为:预载5kg,负载1kg、2kg、3kg、4kg、5kg。采用电子散斑干涉技术(ESPI)分别进行牙列完整和牙列缺损时牙槽骨受载的变形测试。结果无论在何种载荷条件下,牙列完整时相应牙槽骨的离面位移较牙列缺损时小,牙槽骨的条纹稀疏,曲线平缓。牙列缺损时牙槽骨的条纹密集,在缺牙区有中断。均匀加载和点加载条件下,牙列完整与牙列缺损相比较,牙列完整时牙槽骨的散斑干涉条纹均匀平缓,其离面位移相对较小。结论牙齿缺失后,缺牙区邻近牙相应牙槽骨的变形明显增加,为临床修复牙列缺损提供了力学依据。     

数字散斑法测量加载100 N与400 N肱骨干骨折钢板固定下的位移

背景：将光学测量技术数字散斑相关方法应用到生物医学领域中,能更精确地分析螺钉断裂的特点。 目的：以数字散斑法测量肱骨钢板螺钉的位移。 方法：取4根肱骨制造肱骨中段骨折模型。将骨折标本进行复位,用8孔钢板固定,骨折线两端各使用4枚螺钉固定。分别在100及400 N拉力下,将模型设计成骨折前后的5种状态,即状态a是未骨折加压钢板坚强内固定组(模拟骨折愈合,未锯断);状态b是骨折后近端去1枚螺钉;状态c是在状态b的基础上远端去1枚螺钉;状态d是在状态c的基础上近端去1枚螺钉;状态e是在状态d的基础上远端去1枚螺钉。分别测量骨折线两端两枚螺钉的位移,通过相关软件计算位移。 结果与结论：在100 N及400 N拉力下,骨折线旁对称分布的两枚螺钉随着其他螺钉的减少,所产生的位移差异存在显著性意义(P < 0.01);骨折线旁成对称分布的两枚螺钉所承受的应力差异无显著性意义(P > 0.05)。提示骨折线两端的2枚螺钉是承受较多应力的部位(应力集中),易于发生断裂,应选用比现有螺钉的直径增大1.0~2.5 mm的螺钉,增加骨折线旁的固定螺钉稳定性以避免断钉等后遗症。     

Structure–function relations of primate lower incisors: a study of the deformation of Macaca mulatta dentition using electronic speckle pattern interferometry (ESPI)

Teeth adopt a variety of different morphologies, each of which is presumably optimized for performing specific functions during feeding. It is generally agreed that the enamel cap is a crucial element in controlling the mechanical behavior of mammalian teeth under load. Incisors are particularly interesting in terms of structure–function relations, as their role in feeding is that of the ‘first bite’. However, little is known how incisor cap morphology is related to tooth deformation. In the present paper we examine the mechanical behavior of mandibular central incisors in the cercopithecine primate Macaca mulatta under loads similar to those encountered during ingestion. We map three‐dimensional displacements on the labial surface of the crown as it is compressed, using electronic speckle pattern interferometry (ESPI), an optical metrology method. In addition, micro‐computed tomography is used to obtain data regarding the morphology of the enamel cap, which in the M. mulatta lower incisors exhibits missing or very little enamel on the lingual face. The results showed that although compressed along a longitudinal axis, deformation in the incisors mostly occurred in the lingual direction and orthogonal to the direction of the applied load. Both isolated, embedded teeth and teeth in the mandible showed considerable lingual deformation. Incisor deformation in the mandible was generally greater, reflecting the additional freedom of movement enabled by the supporting structures. We show that the association with adjacent teeth in the arch is significant for the behavior of the tooth under load. Finally, loading two teeth simultaneously in the mandible showed that they work as one functional unit. We suggest that these results demonstrate the importance of enamel cap morphology in directing deformation behavior; an ability stemming from the stiffness of the enamel cap overlying the more pliable dentin.     

Holographic interferometry

Since its inception three decades ago, holographic interferometry has proven to be a powerful nondestructive testing technique for the measurement of displacement and its derivatives. It is a whole-field, noncontact method which requires the use of a hologram to record three-dimensional information about the surface of an object. After a stress is applied to the object, its new surface geometry is compared with the previously recorded state. Changes of the surface of the object, which are manifest as a series of interference fringes superimposed on the image of the object, can be observed statically or in real time to reveal the displacement. Current state-of-the-art techniques such as heterodyne and digital phase shifting interferometry, which have extended the resolution of holographic interferometry far beyond fringe counting, are reviewed. Particular emphasis is placed upon applications in biomedical engineering and medicine, although potentially applicable techniques from other disciplines are examined. The paper is broken into two main parts. In the first part, the scope and potential limitations of this branch of metrology are presented. In the second part, a review of applications in biomedical engineering is presented. The references cited in the first section are the seminal papers in the field. The applications section, which relies upon the results of the first section, presents a critical review of the literature by analyzing the results of a few representative studies.     

Computer aided speckle interferometry: a technique for measuring deformation of the surface of the heart

An investigation of the inhomogeneous and anisotropic properties of myocardium necessitates a whole field measurement technique with high spatial resolution. Computer aided speckle interferometry (CASI) may be applied to measuring deformation on the epicardial surface of the heart. Silicone carbide particles (approximately 40 m in diameter) were sprinkled randomly onto the epicardial surface of isolated rabbit hearts. When illuminated with white light, speckles may be observed with a charge coupled device (CCD) camera. A balloon was placed in the left ventricle to control the intracavitary load on the arrested heart. To compare CASI to the gold standard technique of sonomicrometry, two ultrasonic transducers were implanted into the wall of the myocardium. Three hearts were exposed to various loading conditions, and at each condition speckle images were recorded. CASI was used to determine the distribution of displacement vectors (both direction and magnitude) in the region imaged by the CCD camera. Strain along the axis of the implanted transducers was determined with CASI and compared to that obtained with sonomicrometry. Strain determined from CASI and sonomicrometry produced equivalent results. Unlike sonomicrometry, whereby the displacement between two points with a relatively large gauge length is obtained, CASI is able to determine displacement vectors for hundreds of points within the same region. In conclusion, CASI produced equivalent results to those obtained from sonomicrometry (although not with the same temporal resolution), but it is a whole field deformation mapping technique that has a spatial resolution three orders of magnitude higher than that of sonomicrometry. © 2001 Biomedical Engineering Society. PAC01: 8763Lk, 8719Hh, 8719Rr     

Validity and sensitivity of a human cranial finite element model: implications for comparative studies of biting performance

Finite element analysis (FEA) is a modelling technique increasingly used in anatomical studies investigating skeletal form and function. In the case of the cranium this approach has been applied to both living and fossil taxa to (for example) investigate how form relates to function or infer diet or behaviour. However, FE models of complex musculoskeletal structures always rely on simplified representations because it is impossible completely to image and represent every detail of skeletal morphology, variations in material properties and the complexities of loading at all spatial and temporal scales. The effects of necessary simplifications merit investigation. To this end, this study focuses on one aspect, model geometry, which is particularly pertinent to fossil material where taphonomic processes often destroy the finer details of anatomy or in models built from clinical CTs where the resolution is limited and anatomical details are lost. We manipulated the details of a finite element (FE) model of an adult human male cranium and examined the impact on model performance. First, using digital speckle interferometry, we directly measured strains from the infraorbital region and frontal process of the maxilla of the physical cranium under simplified loading conditions, simulating incisor biting. These measured strains were then compared with predicted values from FE models with simplified geometries that included modifications to model resolution, and how cancellous bone and the thin bones of the circum‐nasal and maxillary regions were represented. Distributions of regions of relatively high and low principal strains and principal strain vector magnitudes and directions, predicted by the most detailed FE model, are generally similar to those achieved in vitro. Representing cancellous bone as solid cortical bone lowers strain magnitudes substantially but the mode of deformation of the FE model is relatively constant. In contrast, omitting thin plates of bone in the circum‐nasal region affects both mode and magnitude of deformation. Our findings provide a useful frame of reference with regard to the effects of simplifications on the performance of FE models of the cranium and call for caution in the interpretation and comparison of FEA results.     

基于血管内超声图像时空相关性的血流斑点去噪方法

血管内超声成像的优越成像方式使得它越来越广泛地被应用到冠心病的诊断和介入治疗中。但随着超声频率的提高，血流分子回波信号（即血流斑点噪声）也显著增强，这会降低管腔和管壁的对比度，加大医生辨别、测量管腔和斑块几何参数及物理参数的难度。我们提出了一种新颖的去噪方法，它利用血管内超声图像在时间、空间上的相关信息，即组织在时间、空间上的变化比血流小这一事实。实验结果表明该方法能显著地去除斑点噪声，增强管腔和管壁的对比度，更好地帮助医生区别血管壁和周围组织。     

Biomedical engineering education in Canada, 1996

This paper updates the information contained in a previously published paper, ?Bioengineering Education in Canada, 1988,? which appeared in the Journal of Clinical Engineering (Volume 13, No. 5). It describes the current biomedical engineering and biomedical engineering technology programs available in Canada, but does not attempt to evaluate them. There are no undergraduate degree programs specifically in biomedical engineering, although three universities have created options in biomedical engineering in undergraduate programs. Also, the clinical engineering program at the University of British Columbia has been discontinued.     

Holographic interferometry: A critique of the technique and its potential for biomedical measurements

Double-exposure holographic interferometry is a contactless whole-field method. Dimensional changes are visualized as a series of interference fringes overlaid on the holographic image of the femur, where each fringe represents 0.316 μm (half the wavelength of the laser light) of motion. Interferograms for intact femora and for femora with identical geometry prostheses were produced. We have shown that the femur bends as a beam under axial load. The position of maximum deflection is a function of the properties of the composite structure. Under a known load the amount of deflection can be calculated and the effect of the prosthesis's modulus can be ascertained. In addition to bending, rotational effects can be perceived. Although data interpretation is complex and holographic production is costly and time-consuming, the technique holds promise for biomechanical applications as well as other biomedical disciplines.     

Strain and mechanical behavior measurements of soft tissues with digital speckle method

Soft tissues of the body are composite, typically being made up of collagen and elastin fibers with high water contents. The strain measurement in soft tissues has proven to be a difficult task. The digital speckle method, combined with the image processing technique, has many advantages such as full field, noncontact, and real time. We focus on the use of an improved digital speckle correlation method (DSCM) and time-sequence electric speckle pattern interferometry (TSESPI) to noninvasively obtain continual strain measurements on cartilage and vessel tissues. Monoaxial tensile experiments are well designed and performed under constant temperature and the necessary humidity with smart sensors. Mechanical behaviors such as the tensile modulus and Poisson ratio of specimens are extracted based on the deformation information. A comparison of the advantages and the disadvantages of these techniques as well as some problems concerning strain measurements in soft tissues are also discussed.