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1831 results in Biomedical engineering

Page 18 of 92

  • Preface to the Second Edition

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp xvii-xviii

  • Summary

    Since 2009, when this book was published for the first time, we have been using it in our Biomechanics courses in the educational programme Biomedical Engineering, giving us hands-on experience with the book and the exercises. When we were investigating ideas for a second edition, we found that external reviewers were primarily asking for more examples and exercises, concurring with our own thoughts on the book. Over the years, we have assembled quite a number of examples that were often used to animate the lectures and to illustrate the theory in biomedical applications. At the same time, the number of available exercises increased considerably. Eventually, adding many of these examples and increasing the number of exercises are the most significant changes in the second edition. The major changes in the text are:

  • • Mathematical preliminaries are now concentrated in Chapter 1 and no longer spread over different chapters.

  • • At some points in the original text, explanations were terse and too concise for students. Based on our experiences over the past eight years, we have extended the text at a number of points and, most importantly, added the earlier mentioned new examples. The biggest change is in Chapter 12, including a separate section on material frame indifference of constitutive equations and a more extensive treatment of hyperelastic materials.

    • The objectives of the book did not change. It is still meant to be a basic training in mechanics, appropriate for our candidate biomedical engineers at Bachelor level, starting with the basic concepts of mechanics and ending with numerical solution procedures. This book differs from most books on biomechanics, which are usually aimed at students with already considerable knowledge in continuum mechanics and wishing to enter the field of biomechanics. Consequently, those books pay great attention to biology and physiology. In contrast, we assume that students start at a very basic level in terms of mechanics, but already have substantial physiological and biological background knowledge.

  • 2 - The Concepts of Force and Moment

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp 16-38

  • Summary

    Introduction

    We experience the effects of force in everyday life and have an intuitive notion of force. For example, we exert a force on our body when we lift or push an object, while we continuously (fortunately) feel the effect of gravitational forces, for instance while sitting, walking, etc. All parts of the human body in one way or the other are loaded by forces. Our bones provide rigidity to the body and can sustain high loads. The skin is resistant to force: simply pull on the skin to witness this. The cardiovascular system is continuously loaded dynamically owing to the pulsating blood pressure. The bladder is loaded and stretched when it fills up. The intervertebral discs serve as flexible force-transmitting media that give the spine its flexibility. Beside force, we are using levers all the time in our daily life to increase the ‘force’ that we want to apply to some object, for example by opening doors with the latch, opening a bottle with a bottle-opener. We feel the effect of a lever arm when holding a weight close to our body instead of using a stretched arm. These experiences are the result of the moment that can be exerted by a force. Understanding the impact of force and moment on the human body requires us to formalize the intuitive notion of force and moment. That is the objective of this chapter.

    Definition of a Force Vector

    Imagine pulling on a thin wire that is attached to a wall. The pulling force exerted on the point of application is a vector with a physical meaning: it has

  • • a length: the magnitude of the pulling force

  • • an orientation in space: the direction of the wire

  • • a line-of-action, which is the line through the force vector.

    • The graphical representation of a force vector, denoted by, is given in Fig. 2.1. The ‘shaft’ of the arrow indicates the orientation in space of the force vector. The point of application of the force vector is denoted by the point P.

  • About the Cover

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp xiii-xiv

  • Summary

    The cover contains images reflecting biomechanics research topics at the Eindhoven University of Technology. An important aspect of mechanics is experimental work to determine material properties and to validate models. The application field ranges from microscopic structures at the level of cells to larger organs like the heart. The core of biomechanics is constituted by models formulated in terms of partial differential equations and computer models to derive approximate solutions.

  • • Main image: Myogenic precursor cells have the ability to differentiate and fuse to form multinucleated myotubes. This differentiation process can be influenced by means of mechanical as well as biochemical stimuli. To monitor this process of early differentiation, immunohistochemical analyses are performed to provide information concerning morphology and localization of characteristic structural proteins of muscle cells. In the illustration, the sarcomeric proteins actin (red), and myosin (green) are shown. Nuclei are stained blue. Image courtesy of Mrs Marloes Langelaan.

  • • Left top: To study the effect of a mechanical load on the damage evolution of skeletal tissue, an in-vitro model system using tissue engineered muscle was developed. The image shows this muscle construct in a set-up on a confocal microscope. In the device the construct can be mechanically deformed by means of an indentor. Fluorescent identification of both necrotic and apoptotic cells can be established using different staining techniques. Image courtesy of Mrs Debby Gawlitta.

  • • Left middle: A three-dimensional finite element mesh of the human heart ventricles is shown. This mesh is used to solve the equations of motion for the beating heart. The model was used to study the effect of depolarization waves and mechanics in the paced heart. Image courtesy of Mr Roy Kerckhoffs.

  • • Left bottom: The equilibrium equations are derived from Newton's laws and describe (quasi-)static force equilibrium in a three-dimensional continuum. See Eqs. (8.33), (8.34) and (8.35) in the present book.

  • 5 - Fibres: Time-Dependent Behaviour

  • Cees Oomens, Technische Universiteit Eindhoven, The Netherlands, Marcel Brekelmans, Technische Universiteit Eindhoven, The Netherlands, Sandra Loerakker, Technische Universiteit Eindhoven, The Netherlands, Frank Baaijens, Technische Universiteit Eindhoven, The Netherlands
  • Book:
    Biomechanics
    Published online:
    02 February 2018
    Print publication:
    08 February 2018, pp 79-115

  • Summary

    Introduction

    In the previous chapter on fibres, the material behaviour was constantly considered to be elastic, meaning that a unique relation exists between the extensional force and the deformation of the fibre. This implies that the force versus stretch curves for the loading and unloading path are identical. There is no history dependency, and all energy that is stored into the fibre during deformation is regained during the unloading phase. This also implies that the rate of loading or unloading does not affect the force–stretch curves. However, most biological materials do not behave elastically.

    An example of a loading history and a typical response of a biological material is shown in Figs. 5.1(a) and (b). In Fig. 5.1(a), a deformation history is given that might be used in an experiment to mechanically characterize some material specimen. The specimen is rapidly stretched to a certain value, then the deformation is fixed and after a certain time restored to zero. After a short resting period, the stretch is applied again but to a higher value of the stretch. This deformation cycle is repeated several times. In this case the length change is prescribed and the associated force is measured. Figure 5.1(b) shows the result of such a measurement. When the length of the fibre is kept constant, the force decreases with time. This phenomenon is called relaxation. Conversely, if a constant load is applied, the length of the fibre will increase. This is called creep.

    When the material is subjected to cyclic loading, the force versus stretch relation in the loading process is usually somewhat different from that in the unloading process. This is called hysteresis and is demonstrated in Fig. 5.2. The difference in the response paths during loading and unloading implies that energy is dissipated, usually in the form of heat, during the process. Most biological materials show more or less the behaviour given above, which is called visco-elastic behaviour. The present chapter discusses how to describe this behaviour mathematically. Pure viscous behaviour, as can be attributed to an ideal fluid, is considered first.

Biomechanics
  • Concepts and Computation
  • 2nd edition
  • Cees Oomens, Marcel Brekelmans, Sandra Loerakker, Frank Baaijens
  • Published online:
    02 February 2018
    Print publication:
    08 February 2018
  • Thoroughly revised and updated for the second edition, this comprehensive textbook integrates basic and advanced concepts of mechanics with numerical methods and biomedical applications. Coverage is expanded to include a complete introduction to vector and tensor calculus, and new or fully updated chapters on biological materials and continuum mechanics, motion, deformation and rotation, and constitutive modelling of solids and fluids. Topics such as kinematics, equilibrium, and stresses and strains are also included, as well as the mechanical behaviour of fibres and the analysis of one-dimensional continuous elastic media. Numerical solution procedures based on the Finite Element Method are presented, with accompanying MATLAB-based software and dozens of new biomedical engineering examples and exercises allowing readers to practise and improve their skills. Solutions for instructors are also available online. This is the definitive guide for both undergraduate and graduate students taking courses in biomechanics.

  • Preface

  • Andrew G. Webb
  • Book:
    Principles of Biomedical Instrumentation
    Published online:
    11 August 2019
    Print publication:
    11 January 2018, pp xi-xv

  • Summary

    The main aim of this textbook is to provide the tools to understand the function and design of different biomedical instruments and devices, and for the reader to be able to use these tools to envision new and improved future technology and designs. Throughout the book the terms medical and biomedical are used interchangeably, and similarly with the terms device and instrument. With several thousand instruments and devices on the market it is clearly impossible to consider more than a handful in detail. Instead, this book concentrates on the following general approach.

  • (i) What is the clinically relevant measurement that needs to be made?

  • (ii) What are the pathophysiological mechanisms that give rise to the clinical condition?

  • (iii) What are the characteristics (e.g. magnitude, frequency, bandwidth) of the signal to be measured? How accurate and reproducible does the measurement have to be? What are the interfering signals that have to be suppressed?

  • (iv) What are the recommended instrumental specifications for the particular device? How does one design the device to meet these specifications?

  • (v) How does one test the biocompatibility and electrical safety of such a device, whether it is external or implanted, so that it can operate safely for a number of years?

    • Traditionally, most of these instruments and devices have been located in a hospital, and patients travel to the clinics for the measurements to be performed by trained personnel. However, this model is changing and nowadays there is an increasing role for what is termed mobile health (m-health), which involves a much greater degree of healthcare being performed by the patients themselves at home. This means that a biomedical device must operate in the patient's home environment without specialized training, as well as transmit the data wirelessly and securely to the physician. This model of continuous patient monitoring not only provides a much more complete assessment of the patient's health, but also reduces the number of visits that a patient has to make to the hospital.

    The main areas of technological development that have enabled the rapid incorporation of m-health into the healthcare infrastructure are wearable and implantable devices that can transmit data to the physician via mobile phone networks.

Page 18 of 92