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1869 results in Biomedical engineering

Page 36 of 94

  • 5 - Biotribology

  • from Part II - Engineering theory applied to orthopaedics
  • Sheraz S. Malik, Shahbaz S. Malik
  • Book:
    Orthopaedic Biomechanics Made Easy
    Published online:
    05 June 2015
    Print publication:
    28 May 2015, pp 80-94

  • Summary

    Introduction to biotribology

    A force may change the shape and/or state of motion of an object. The deforming effects of force considered so far have been related to the interactions between force and the entire object and mechanisms that result in the failure of the whole structure. This chapter looks into the deforming effects of force on the surface of an object, which in turn are linked with motion parameters of the object. Therefore, in this chapter, deformation and motion of an object are considered together.

    Tribology is the study of the interactions between two solid surfaces in relative motion. It deals with friction, wear and lubrication aspects of the interface formed between the solid surfaces. A force acting at the interface produces friction when the surfaces slide over each other. Excessive friction wastes energy and leads to wear of the surfaces. A lubricant acts to reduce friction and wear by creating a slippery film between the surfaces. The thickness of the lubricant film formed between the surfaces determines the effectiveness of the lubrication.

    Different interfaces require a different balance of friction, wear and lubrication. High friction is required between foot and ground for walking and in brakes, whereas low friction is desirable between the components of a car engine. Similarly, wear facilitates brushing teeth and is useful when writing with a pencil, but can also be harmful and lead to the breakdown of mechanical components such as gears. The principles of tribology are used to optimise the performance of interacting surfaces in mechanical systems.

  • 13 - Biomolecular Engineering I: Biotechnology

  • from PART 3 - BIOMEDICAL ENGINEERING
  • W. Mark Saltzman, Yale University, Connecticut
  • Book:
    Biomedical Engineering
    Published online:
    28 May 2018
    Print publication:
    21 May 2015, pp 544-587

  • Summary

    Prelude

    The early chapters of this book introduce some of the chemicals that are important in human biology. In fact, it is possible to think of the human body as an elaborate bag of chemicals. In the subspecialty called biomolecular engineering (or bio-technology), biomedical engineers examine the changes in chemical components within a biological system and develop methods for modifying these chemicals or their interactions. The concept of introducing chemicals to induce a change in a biological system is familiar; for example, we all have some experience with taking purified chemicals such as acetaminophen or ibuprofen as drugs to relieve pain. But new biological tools now make it possible to consider more complex chemical interventions such as gene therapy (in which a new deoxyribonucleic acid [DNA] sequence is introduced to allow expression of a new genetic activity).

    The concept of the human body as a bag of chemicals is convenient and comforting. Chemicals can be produced; chemicals can be added or replaced; chemicals are (sometimes) inexpensive. In fact, several decades ago, it was widely reported that the chemicals in the human body were worth about $1. Other investigators estimate the value at closer to $6 million (particularly if the chemicals are purchased from scientific suppliers). Regardless of the dollar value, we often imagine that our bodies can be supplemented, mended, and improved through the addition of chemicals. But the body contains large numbers of many different kinds of chemicals, and as in many complex systems, unexpected patterns can emerge from the sum of the parts. Although the body is composed of chemicals, we don't understand the identity of all of the chemicals in the system, the forces that hold these chemicals together, or the network of interactions that mold the chemicals into an organism. Yet we often attempt to heal with chemicals. This is the challenge of drug delivery (Figure 13.1).

    Biomolecular engineering includes drug delivery, but also many similar areas of inquiry in which chemical engineering principles are applied to biomedical engineering (BME) problems.

  • 11 - Bioinstrumentation

  • from PART 3 - BIOMEDICAL ENGINEERING
  • W. Mark Saltzman, Yale University, Connecticut
  • Book:
    Biomedical Engineering
    Published online:
    28 May 2018
    Print publication:
    21 May 2015, pp 448-496

  • Summary

    Prelude

    Modern health care has benefited enormously from the work of biomedical engineers to create instruments that are used in clinical monitoring and laboratory analysis. Hospital operating rooms, emergency rooms, and doctors' offices each contain an array of instruments used to measure and record a patient's vital signs such as temperature, blood pressure, pulse, and oxygen saturation (Figure 11.1). Many of the most popular instruments enable noninvasive monitoring of vital signs of patient health: The stethoscope allows doctors to listen reliably to the beating heart, the sphygmomanometer allows them to estimate pressure within vessels deep in the body (Figure 11.2), and the ophthalmoscope allows them to see structures on the retina. It is impossible to estimate the number of lives that have been lengthened or improved by these devices.

    The medical device industry—the constellation of large and small companies that design, manufacture, and sell medical devices and instruments—is one of the largest and most rapidly growing sectors of the U.S. economy. Medical device companies employ biomedical engineers to invent, design, build, and test devices for use in medicine. Biomedical engineers also provide technical training to physicians on the use of such devices. Some biomedical engineers work in hospitals overseeing maintenance of medical instruments and adapting instruments to serve patients and doctors: These individuals are often called clinical engineers. In research laboratories, biomedical engineers and other scientists routinely use instruments to take measurements (Figure 11.3). For example, researchers use instruments called spectrophotometers to measure light absorption within liquid samples to quantify the rates of enzymatic reactions or to measure the composition or viability of cells. Microscopes are used to view cells in preparations such as blood smears, which are routinely used to diagnose blood diseases.

    The next generation of medical devices and laboratory instruments will provide patients, physicians, and researchers with more information, more rapidly than the instruments of today.

  • 12 - Bioimaging

  • from PART 3 - BIOMEDICAL ENGINEERING
  • W. Mark Saltzman, Yale University, Connecticut
  • Book:
    Biomedical Engineering
    Published online:
    28 May 2018
    Print publication:
    21 May 2015, pp 497-543

  • Summary

    Prelude

    Biomedical imaging has revolutionized medicine and biology by allowing us to see inside the body and to visualize biological structures and function at microscopic levels. Images are representations of measurable properties that vary with spatial position (and often time). Images can provide exquisitely detailed information about biological structures; the most powerful imaging modalities provide functional information as well, allowing the recording of molecular and cellular processes, or physical properties (such as elasticity or temperature). Methods to visualize and quantify these properties are now available at the macroscopic (i.e., of a size visible to the human eye) and microscopic level. This information can be used clinically for diagnosis and monitoring of treatment as well as scientifically for understanding normal and abnormal structure and physiology.

    Technology has brought about remarkable changes in imaging (Figure 12.1). Gene expression can now be imaged using positron emission tomography (PET) imaging—an image creation method that depends on injection of special radioisotopes—coupled with methods from genetics. The brain can be imaged in real time during cognitive tasks with functional MRI (fMRI), generating information can be used to guide neurosurgery. The mechanical action of the heart can be mapped using high-frequency sound waves (ultrasound imaging); these maps identify areas of injury after a heart attack. Images are essential tools in medicine because they provide a spatial map, enabling physicians to localize the biological phenomena being examined in space as well as time.

    The many different imaging modalities—or types of imaging methods—fill different scientific and/or clinical niches. Every modality has limitations: A particular method may be low in quality, slow in acquiring images, expensive, or not suitable for all patients. The set of advantages for a particular technology (e.g., high quality, faster, cheaper, or dynamic) will make it suitable in the right situations. Different modalities operate over different time or length scales and—because of the physics that underlie their operation—can measure different structures or functions (Table 12.1).

    Virtually all imaging modalities are now digital; the images are acquired by a computer and are made up of individual picture elements, or pixels. Digital images can be readily processed to improve their quality, make measurements, and extract features of interest.

  • 2 - Biomolecular Principles

  • from PART 1 - MOLECULAR AND CELLULAR PRINCIPLES
  • W. Mark Saltzman, Yale University, Connecticut
  • Book:
    Biomedical Engineering
    Published online:
    28 May 2018
    Print publication:
    21 May 2015, pp 37-93

  • Summary

    Prelude

    Biomedical engineers are engaged in a great diversity of activities: Chapter 1 described many of the fields in which biomedical engineers make significant contributions. This chapter, together with Chapters 3 and 4, reviews fundamental chemistry concepts that are important for understanding human physiology and biomedical engineering (BME). These chapters introduce several families of biological molecules—proteins, nucleic acids, carbohydrates, and lipids—that will be explored in more detail throughout the rest of the book.

    Why should biomedical engineers understand chemistry? Knowing how molecules interact with each other and with their environments helps biomedical engineers to manipulate these molecules to create new tools for treating disease. For example, biomedical engineers have developed methods to assemble lipid molecules into liposomes (Figure 2.1). Liposomes have already found many uses in human health—as carriers of the anticancer drug doxorubicin and as alternate vehicles for gene therapy that do not require the use of viruses. Similarly, biomedical engineers have used their skills in mathematical modeling and their understanding of molecular interactions to understand the formation of molecular complexes, such as the extracellular clumps of protein-rich materials (plaques) that form in Alzheimer's disease (Figure 2.1). A better understanding of the properties of the proteins that form plaque may someday lead to treatments for Alzheimer's disease.

    Understanding basic chemical concepts is important in almost every aspect of BME. Artificial hips and knees are made of synthetic materials, usually metals and polymers and ceramics. Early efforts to create safe and long-lasting artificial devices sometimes failed because of unwanted interactions between molecules of the artificial device and molecules of the body. Magnetic resonance imaging (MRI), one of the most powerful methods for non-invasive imaging of the internal structure of humans, is derived from a method that has been used for decades by chemists to understand the structures of molecules and their interactions with each other.

  • 16 - Biomedical Engineering and Cancer

  • from PART 3 - BIOMEDICAL ENGINEERING
  • W. Mark Saltzman, Yale University, Connecticut
  • Book:
    Biomedical Engineering
    Published online:
    28 May 2018
    Print publication:
    21 May 2015, pp 666-704

  • Summary

    Prelude

    Cancer is a common, often life-threatening, disease involving the uncontrolled growth and spread of abnormal cells. Cancer is one of the leading causes of death in the world, particularly in developed nations such as the United States. Cancer is really a group of diseases; it can arise in any organ of the body and has differing characteristics that depend on the site of the cancer, the degree of spread, and other factors. Mutations in certain genes within cells—called protooncogenes and tumor suppressor genes—are the primary cause of cancer (1).

    Sadly, almost every college student has some knowledge of cancer, gained through experience with classmates, family members, or friends. Cancer occurs in people from all countries of the world, all segments of society, and people of all ages, although it is relatively rare in childhood. Some cancers can be inherited, but most cancers are strongly linked to environmental factors such as exposure to radiation, tobacco, viruses, or chemicals. Cancer can occur many years after exposure, making it difficult to find precise links between factors and disease. However, much is now known about the risk of exposure to certain toxins and infectious agents: Cigarette smoking increases the risk of lung cancer by 23 times in males and by a similar factor in females (2) and infection with human papilloma virus (HPV) is the cause of almost all cervical cancers and many oropharyngeal (mouth and throat) cancers in men and women.

    Biomedical engineers have played important roles in the development of methods for cancer treatment, and many biomedical engineers are working on new approaches that they hope will prevent or treat cancers in the future. Cancer is a worldwide problem, with over 12 million newly diagnosed cancers each year: A 2012 meeting of leaders from groups that fund and perform cancer research in 15 different countries around the world led to a concensus that reduction in cancer mortality and improvement in cancer care requires improved methods for cancer prevention, detection, and treatment, and outlined some of the most important next steps (3).

  • 10 - Biomechanics

  • from PART 3 - BIOMEDICAL ENGINEERING
  • W. Mark Saltzman, Yale University, Connecticut
  • Book:
    Biomedical Engineering
    Published online:
    28 May 2018
    Print publication:
    21 May 2015, pp 413-447

  • Summary

    Prelude

    Humans can hold their bodies erect, vertically above the earth, because our bodies are solid objects capable of supporting our own weight. The human skeletal system is a collection of 206 bones, connected by soft tissues—cartilage, ligaments, tendons, and muscles—that together provide a mechanical support system for the human body.

    Humans are also capable of movement. Muscles—connected to the solid bone framework—contract to generate forces that result in motion. Dancers, high jumpers, and surgeons learn to control these movements precisely to accomplish tasks and transport their bodies with precision (Figure 10.1). Strength, agility, and stamina can all be enhanced by training and, as a species, our understanding of the effects of training improves each year. As a result, humans continually improve performance on certain tasks, such as Olympic events (Figure 10.2).

    This chapter describes some elements of the human body structure and mechanics. To aid in description, the chapter begins with some basic concepts about the mechanical properties of materials. These concepts will be used throughout the chapter to provide quantitative descriptions of the behavior of the biological materials that make up the human body.

    Mechanical properties of materials

    Biological materials, such as bones, muscles their cells, are mechanical objects and, therefore, are subject to forces that occur because of the world around them. The human body and its components can be studied by force and moment analysis, which is among the first concepts students in physics learn (Box 10.1). Physical forces are present throughout the body. Some forces are large: The head of the femur regularly experiences forces that are 2–3 times the weight of the whole body or 1, 800–2,700 N (for a 200-lb man). Much smaller forces have important biological effects: Muscles, which enable the macroscopic movements on body parts, typically generate forces of ~1 N. Nonmuscle cells—when attached to solid substrates (see Figure 5.5C)—can each generate forces of 100–800 nN (1).

  • 4 - Biomolecular Principles: Proteins

  • from PART 1 - MOLECULAR AND CELLULAR PRINCIPLES
  • W. Mark Saltzman, Yale University, Connecticut
  • Book:
    Biomedical Engineering
    Published online:
    28 May 2018
    Print publication:
    21 May 2015, pp 160-189

  • Summary

    Prelude

    Proteins are the workhorses of the cell (Figure 4.1): They provide structural support in the cytoskeleton, facilitate communication with other cells by acting as receptors, neutralize foreign pathogens, generate contraction forces in muscle, and most ubiquitously catalyze chemical reactions. Proteins are abundant in biological systems, such as eggs (Figure 4.2). Proteins are one of the major macronutrients in the human diet (Figure 4.3).

    Some recombinant proteins now serve as therapeutic drugs for treatment or prevention of disease. Biomedical engineers also use recombinant proteins, such as growth factors, to promote growth and differentiation of cells in engineered tissues. Some biomedical engineers have been using techniques of protein engineering to design new biomaterials for use in tissue engineering, drug-delivery systems, or other medical applications. Biomedical engineers working in the area of systems biology are developing models for the function of signaling networks in cells: these signaling networks are interconnected sets of biochemical reactions, which happen inside cells and which are controlled largely by intracellular proteins.

    This chapter describes the structure and function of proteins and also includes a brief introduction to some of the techniques used to determine protein structure, chiefly nuclear magnetic resonance (NMR) and x-ray crystallography. Researchers in the pharmaceutical industry use these protein structures in structure-guided drug design. Chemicals that interfere with protein function have long been used as drugs, but traditionally these chemical-protein interactions have been discovered empirically (or by accident). Now, chemical agents can be designed rationally, based on a detailed knowledge of the protein's structure, to interact with enzymes or receptors and enhance or inhibit their function. Because the structure of a protein determines its function, and because chemicals that interact with specific structural units within proteins can be useful as drugs, biomedical engineers and computer scientists are developing computer programs that will help predict the three-dimensional structure of a protein based on its primary amino acid sequence.

  • 1 - Introduction: What Is Biomedical Engineering?

  • W. Mark Saltzman, Yale University, Connecticut
  • Book:
    Biomedical Engineering
    Published online:
    28 May 2018
    Print publication:
    21 May 2015, pp 1-34

  • Summary

    Prelude

    The practice of medicine has changed dramatically since you were born. Consider a few of these changes:

  • • Vaccines are now available for chicken pox and human papilloma virus;

  • • Microarrays allow rapid patient-specific testing for mutations in genes controlling metabolism of potentially toxic drugs;

  • • Inexpensive contact lenses provide clear vision;

  • • Prosthetic legs allowed a double-amputee to run in the Olympics;

  • • Ultrasound imaging follows the progress of pregnancy with ever greater precision;

  • • Stem cells in human cord blood have been used to treat dozens of diseases in donors, or their siblings;

  • • An iPhone app driving a bionic pancreas offers better control of diabetes.

    • For your parents, the changes have been even more sweeping. Overall life expectancy—that is, the span of years that people born in a given year are expected to live—increased from 50 in 1900 to almost 80 by 2010 (Figure 1.1). You can expect to live 30 years longer than your great-grandparents; you can also expect to be healthier and more active during all the years of your life.

    How has this happened? One answer is obvious. People are living longer because they are not dying in situations that were previously fatal, such as childbirth and bacterial infections. Biomedical engineering is a major factor in this extension of life and improvement of health. Biomedical engineers have contributed to every field of medicine—from radiology to obstetrics to cancer treatment to control of diabetes. The next few paragraphs illustrate the far-reaching contributions of biomedical engineers with examples from emergency medicine.

    Loss of life in accidents and trauma is a major cause of death and disability around the world. In the United States, it is overwhelmingly the leading cause of death among people of college age, and it is ranked fifth among causes of death for all ages (1).

  • 8 - Circulation

  • from PART 2 - PHYSIOLOGICAL PRINCIPLES
  • W. Mark Saltzman, Yale University, Connecticut
  • Book:
    Biomedical Engineering
    Published online:
    28 May 2018
    Print publication:
    21 May 2015, pp 341-376

  • Summary

    Prelude

    Our bodies appear, from the outside, to be solid masses that are slow to change but, just beneath the surface, the body's fluids are in constant motion. Blood moves at high velocity throughout the body within an interconnected and highly branched network of vessels (Figure 8.1). The human circulatory system is responsible for the movement of fluid, and therefore the vital nutrients contained in the fluid, throughout the body.

    The purpose of the circulatory system is a familiar one to engineers and bakers; it provides mixing, and good mixing is an essential element of many successful enterprises. Cakes are made from flour, eggs, sugar, and milk (among other things); your birthday will be ruined (or at least a bit tarnished) if the chef does not mix these ingredients well. But why must humans be mixed? Mixing exposes cells throughout the body to oxygen and other nutrients, while simultaneously providing a pathway for removal of waste products. It is the circulatory system that enables us to grow large, so that we have inner regions that are separated from the atmospheric oxygen that all cells need for energy (Figure 8.2).

    Circulation of fluids is the function of the cardiovascular system. The human cardiovascular system is composed of three separate organs: The heart serves as a pump, the vasculature serves as the plumbing, and the blood is the circulated fluid. Failure in any of these organs can result in failure of the system, so diseases of the cardiovascular system have grave consequences.

    Biomedical engineers have made contributions to almost every area of cardiovascular health, including construction of artificial hearts and heart valves (see Chapter 15), understanding of the flow properties of blood, and mathematical modeling of the microcirculation. In fact, some of the most important work in understanding the special blood vessels that develop in tumors has been done by biomedical engineers (Figure 8.3).

Page 36 of 94