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1831 results in Biomedical engineering

Page 21 of 92

  • 9 - Structuring a Cell by Cytoskeletal Filaments

  • from Part II - Design and operation of complex functions
  • Michael Sheetz, Columbia University, New York, Hanry Yu, National University of Singapore
  • Book:
    The Cell as a Machine
    Published online:
    06 August 2018
    Print publication:
    11 January 2018, pp 190-218

  • Summary

    Despite a lack of exoskeleton, isolated animal cells normally exhibit stable, nonspherical shapes with excess membrane area. To maintain cell shape, the plasma membrane conforms to a cytoskeleton located inside the cell, but the membrane surface area to cell volume ratio determines how extensively the membrane can conform. In a few cases, such as endothelial cells in capillary tubes, the cytoskeleton alone can support the cell shape. In most cases, however, the cytoskeleton is dynamic, and defines the cell shape in concert with the cell volume, and the effect of contracting against external contacts, or adhesions. Modulation of these adhesions, whether they are between adjacent cells, or cells and matrices, provide the stimuli to initiate cytoskeleton dynamics. These dynamics, which include filament assembly and disassembly, typically determine any changes in the shape of the cell. Actin filaments are often assembled from adhesion sites or sites of membrane extension, both of which lie primarily at the cell periphery. They are then pulled inward and disassemble in a process known as ‘actin treadmilling.’ Actin filaments are contracted by myosin and this creates tension in the cytoskeleton and is responsible for tissue organization and the cohesive property of cells. Paradoxically, the rapid loss of contractile force increases filament dynamics, and cytoskeleton assembly. Cohesion of cells over longer periods is stabilized by intermediate filaments. These appear to be the safety net that prevents acute fracture of cells in epithelia under tension. Microtubules, on the other hand, help stabilize and define cell polarity and structure. Microtubules originate from the microtubule-organizing center (MTOC) and provide directional pathways on which motors will transport membranous organelles and other cellular components. During mitosis, the dynamic microtubules of the mitotic spindle play critical roles in the transport of chromosomes to the daughter cells. Thus, the cytoskeleton is a dynamic, mechanically active component of the cell that is responsible for shaping the cell and its environment as well as for organizing the intracellular organelles.

    The cytoskeleton is comprised of three long filament systems; specifically, microtubules, actin filaments, and intermediate filaments. These filaments are crosslinked by motor proteins or multivalent binding proteins, which serve to stabilize the cytoskeleton, and provide it with dynamic qualities including the ability to disassemble, reassemble, and contract. As evidenced by photobleaching recovery experiments, filament subunit exchange occurs on the timescale of minutes for actin and microtubules.

  • 2 - Complex Functions of Robust Machines with Emergent Properties

  • from Part I - Principles of complex functions in robust machines
  • Michael Sheetz, Columbia University, New York, Hanry Yu, National University of Singapore
  • Book:
    The Cell as a Machine
    Published online:
    06 August 2018
    Print publication:
    11 January 2018, pp 25-49

  • Summary

    Cellular functions have evolved over time to better enable organisms to survive major environmental challenges (see Chapter 1). Improvements to basic functions or new functions that more successfully supported survival were preserved and shared between organisms, either by infections or by interbreeding. Because the environment is constantly changing, the complex functions have evolved to be robust so that they will work under many different conditions and the design principles of robust devices (see text box below) can be used to understand them. A complex function involves multiple functional modules coordinated to perform a complex task. In this chapter, we will describe a general approach to understanding the features of complex functions and how the functional modules that underlie complex functions may be linked to yield the desired emergent properties across different scales. An emergent property is the outcome of many steps and many modules in a complex function. We suggest that models of complex functions violating the principles of robust devices are likely to be wrong. Furthermore, we will describe why it is important to quantitatively measure the performance of complex biological functions (outputs) under different circumstances (inputs) to better test models of different complex functions.

    Principles of Robust Machines with Standard Functions

    We propose that cells are highly engineered, robust machines. They are also very small machines where all actions are dominated by diffusion. The stochastic nature of diffusion processes can account for some of the observed biological variability. However, biological systems have devised mechanisms to use diffusion to drive muscle movements and to direct the shaping of the organism. Evolutionary refinements of the basic mechanisms of biological systems enable them to reproducibly create organisms of diverse shapes using the information encoded in the DNA. Thus, fruit flies with the same DNA will look the same as well as identical twins. In the case of the twins the development took many years and yet they often do look identical. Thus, the robustness of the biological systems extends to making reliable decisions using inherently noisy stochastic processes. Because it seems that the cells that form the basis of biological systems are robust machines, the complex functions that they utilize should follow the design principles of robust devices (Figure 2.1, from Thomas et al., 2004).

Introduction to Biomedical Instrumentation
  • The Technology of Patient Care
  • 2nd edition
  • Barbara L. Christe
  • Published online:
    06 August 2018
    Print publication:
    07 December 2017
  • This fully updated second edition provides readers with all they need to understand the use of medical technology in patient care. Incorporating the most recent changes in healthcare, regulations, Standards, and technology, coverage is expanded to include new chapters on device testing, with a particular emphasis on safety inspections, and the interface of medical technology with the electronic medical record. A wide variety of medical instrumentation is discussed, focusing on device types and classifications, and including individual manufacturers as examples. It is designed for readers with a fundamental understanding of anatomy, physiology and medical terminology, as well as electronic concepts such as voltage, current, resistance, impedance, analog and digital signals, and sensors. Additional documents and solutions to end-of-chapter questions accompany the book online, providing biomedical engineering technicians with the resources and tools they need to become knowledgeable and effective members of the patient care team.

  • Preface to Second Edition

  • Barbara L. Christe, Indiana University–Purdue University, Indianapolis
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    06 August 2018
    Print publication:
    07 December 2017, pp vi-viii

  • Summary

    This book is designed to introduce the reader to the fundamental information necessary for work in the clinical setting, supporting the technology used in patient care. Beginning technicians/ technologists can use this book to develop a working vocabulary and fundamental knowledge of the Healthcare Technology Management (HTM) profession. Content includes a wide variety of medical technology, with an emphasis on device types and classifications; individual manufacturers are utilized as examples.

    This work is intended for the reader with a fundamental understanding of anatomy, physiology, and medical terminology appropriate for their role in the healthcare field, and assumes the reader's understanding of electronic concepts, including voltage, current, resistance, impedance, analog and digital signals, and sensors. The material covered in this book will assist the reader in the development of his or her role as a knowledgeable and effective member of the patient care team. The second edition features revisions to all of the content to reflect changes in healthcare, regulations, standards, and technology. A new chapter addresses device testing, with emphasis on safety inspections. A second new chapter explores the interface of medical technology with the electronic medical record.

    A vital connection exists between technology and the care of patients. In many cases, healthcare workers depend on technology to administer care or treatment or to make a diagnosis. This book helps readers understand how technology is tightly woven into patient care. The role of technical support for the medical team is, therefore, essential in the delivery of effective medical care.

    The section of each chapter entitled “For Further Exploration” encourages readers to use the Internet to obtain in- depth information about a related topic. The questions are designed to push the reader to integrate concepts and ideas using external sources. Answers to the questions are not specifically available within the chapters. Research exercises encourage one of the most important professional skills – the ability to investigate topics that are not well understood. In the clinical setting, it is virtually impossible to be an expert about all technology and aspects of patient care. The ability to effectively search for information is vital.

  • 8 - Cardiac Assist Devices

  • Barbara L. Christe, Indiana University–Purdue University, Indianapolis
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    06 August 2018
    Print publication:
    07 December 2017, pp 96-109

  • Summary

    Introduction

    Technology is used to support heart function in numerous ways. Perhaps the most common and well- known device is the defi- brillator. In addition, the amazing life- saving powers of artificial hearts and implantable devices regularly capture the attention of the public and news media.

    ACLS (advanced cardiac life support) is a detailed protocol to provide life- saving cardiac care. HTM professionals may be involved in the selection of technology and technical protocols used in a crisis. In addition, technicians may help establish training programs and awareness of the medical devices involved in emergency response.

    Defibrillators

    A defibrillator is familiar to most only from life- saving moments on television medical shows, but is often used in real life as first responders seek to help those with medical emergencies. It is a fairly simple device that delivers a large amount of energy across a patient's chest when the heart is not beating properly: that is, when the pacemaker of the heart, the sinoatrial (SA) node is not properly generating a periodic waveform. When the heart is not beating with a pattern, all cells are contracting at different times, this is known as fibrillation. Defibrillators, or defibs (as they are often called) in use today send about 3,000 volts (V) – up to 20 amperes (A) – across a patient's chest. (Note: The amount of voltage and current vary tremendously based on the patient's size and therapeutic settings.) This large amount of energy causes all cells in the heart to depolarize at once. This action may allow the SA node to resume function and generate a normal electrical pattern. Sometimes the SA node can recover and resume electrical control of the heart, but sometimes it cannot. The shape of the energy waveform delivered by a defibrillator has evolved with experience. The Lown waveform was the therapeutic waveform standard until recently. It looks like a damped sine wave.

    The biphasic waveform is the standard of care in defibrillators today. It has both a positive and negative component and produces much better results for patients more quickly. Because it better simulates the electrical conduction pattern through the heart, biphasic waveforms are able to deliver results with less energy. The waveform is approximated in Figure 8.1.

  • 4 - Device Testing

  • Barbara L. Christe, Indiana University–Purdue University, Indianapolis
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    06 August 2018
    Print publication:
    07 December 2017, pp 45-54

  • Summary

    Introduction

    As part of the healthcare team, technicians must ensure medical technology is safe and available when needed by clinicians. In the healthcare workplace, work is done to ensure a device is operating properly. This is in contrast to corrective actions designed to remedy problems as a result of a device malfunction. The kind of work described in this chapter is focused on reducing equipment failures and discovering hidden problems before they could impact patient care or device performance.

    Clinical sites and administrators generally define the scope of medical equipment managed by HTM technicians. As discussed in Chapter 2, medical technology is often grouped into three broad categories: therapeutic, monitoring, or diagnostic. Variation among hospitals is common based on historical support or individual skill sets, although devices that are disposable or singleuse and most implantable devices are beyond the responsibility of the HTM technician.

    Before any work begins on any medical device, technicians should be sure to utilize appropriate personal safety measures as discussed in Chapter 5.

    Device Inspection

    When a new device is delivered to an institution, removal from the packing materials, initial assembly, and incoming inspection is performed. The complexity and time required to complete these steps varies greatly depending on the device. As mentioned in Chapter 1, incoming inspections are an essential part of the HTM technician's workload, with efforts focused on the assurance that a new device will function properly when put into service within the healthcare setting.

    Preventative maintenance, another important workplace responsibility, evaluates the performance of an existing device to ensure proper operation. These activities are typically scheduled utilizing a predetermined timeline (such as once per year). The goal of these actions is to identify undetected problems before they impact patient care, reducing equipment downtime and reducing overall hospital costs.

    Simple visual inspections look for signs of deterioration, damage, or missing hardware. The stressful clinical environment may result in unintended equipment mishandling that can cause broken plastic parts, missing doors or knobs, frayed power cords, or gashes. Power cord damage, especially at the junction with the device, can be both common and potentially hazardous. Experience in healthcare settings will offer technicians the opportunity to see a wide variety of device damage (some surprising and inexplicable), and to develop a special sense to predict and find device deterioration.

  • 16 - Intravenous Pumps and Other Pumps

  • Barbara L. Christe, Indiana University–Purdue University, Indianapolis
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    06 August 2018
    Print publication:
    07 December 2017, pp 199-205

  • Summary

    Introduction

    The use of technology to push fluids into the circulatory system of a patient has evolved and expanded over time. In the past, glass bottles of fluids utilized gravity to promote fluid flow to “drip” fluids into a patient. As technology expanded into healthcare, the bottles were replaced with plastic bags and gravity was no longer medically adequate. Electromechanical pumps are more reliable and provide constant monitoring of fluid delivery. In addition, the flexibility of some pumps has improved medication dosing and caloric delivery. Healthcare has come to depend on the use of technology to deliver fluids and medications to patients.

    Infusion Pumps

    One of the most common pieces of equipment in the hospital, the infusion pump (also called intravenous pump, IVAC, and IV pump) delivers medication, blood, or fluid into the patient over a specific period of time at a particular rate. The name used may reflect brand names from the past, including IVAC. Many patients will be connected to several pumps delivering fluids to the patient through a vein (hence, the term “intravenous”). The pump ensures an accurate rate and, therefore, an exact dose. In addition, should there be a problem with the fluid delivery, an occlusion (blockage of the tubing) perhaps, or the complete fluid amount has been delivered, an alarm will sound to alert staff. The electronic monitoring allows delivery of IV fluids with minimum human intervention.

    Bags, filled with fluids of many kinds, are hung on poles, connected through tubing to the pump, and then through the pump to the veins of the patient. Settings on the device include delivery/ flow rate as well as alarms to indicate blockages or empty fluid bags.

    There are different techniques employed to pump in the fluid. One of the most common is a peristaltic pump. Rollers (in most cases) squeeze the tubing to push in the fluid. Traditional tubing from the fluid- filled bag to the patient is used.

    Another method requires some additional disposable cassettes that hold the liquid for a piston to push the liquid. This requires that the infusion tubing be specifically chosen to work with the type of pump the hospital owns.

  • 3 - Wireless Intracranial Pressure Systems for the Assessment of Traumatic Brain Injury

  • Edited by Isar Mostafanezhad, University of Hawaii, Manoa, Olga Boric-Lubecke, University of Hawaii, Manoa, Jenshan Lin, University of Florida
  • Book:
    Medical and Biological Microwave Sensors and Systems
    Published online:
    14 December 2017
    Print publication:
    07 December 2017, pp 89-123

  • Summary

    A significant reason for death and long-term disability due to head injuries and pathologic conditions is an elevation in the intracranial pressure (ICP) due to vascular compromise and secondary sequelae causing edema. ICP measurements before and after injury in a completely closed-head environment have a significant research value, particularly in the acute postinjury period. With current technology, a tethered fiberoptic probe penetrates the brain and therefore can only remain implanted for relatively short time periods. Use of the probe also can cause complications such as infection and hemorrhage and prohibit immediate (at the time of injury) and long-term measurements of ICP. A small, fully embedded, wireless ICP device may simplify clinical management and research protocols by offering a means for semi-invasive and long-term ICP measurement following brain injury. In this chapter, a new digital wireless ICP (DICP) device is described. The dynamic ICP measurement performances of both the analog ICP (AICP) devices (described in Chapter 2) and the DICP devices are evaluated in a specific traumatic brain injury (TBI) (swine) model of closed-head rotational injury.

    Introduction

    In Chapter 2, a prototype of an AICP device operating in the industrial-scientific-medical (ISM) band at 2.4 GHz was described that successfully simplified the surgical procedure by reducing the infection rate, the risk of hemorrhage, and the degree of tissue injury.

    The AICP device was implanted in a canine model only for a static test, and hypo- and hyperventilation were used to affect variations in ICP. Dynamic ICP variations as a result of TBI in a completely closed-head environment are of paramount importance for understanding the development of a prolonged postconcussion syndrome and facilitating institution of the correct treatment at different stages, particularly in the acute postinjury period. Currently, in experimental (animal) models of TBI, a tethered fiberoptic probe (if inserted before the injury) has to be removed before an injury is induced in order to avoid significant focal damage at the point of probe insertion. Moreover, reinsertion of the probe is possible only after the animal's vital signs have stabilized. However, the act of breaching the cranium after the injury affects the fidelity of the ICP measurements. In addition, proposed noninvasive ICP (NICP) solutions, such as the pulsatility index method based on the use of trancranial Doppler, argued by Figaji et al. [1], have been shown to be insufficient for accurate ICP estimation.

  • 7 - Noise- and Interference-Reduction Methods for Microwave Doppler Radar Vital Signs Monitors

  • Edited by Isar Mostafanezhad, University of Hawaii, Manoa, Olga Boric-Lubecke, University of Hawaii, Manoa, Jenshan Lin, University of Florida
  • Book:
    Medical and Biological Microwave Sensors and Systems
    Published online:
    14 December 2017
    Print publication:
    07 December 2017, pp 202-227

  • Summary

    Introduction

    Doppler radar has recently been extensively used in noncontact cardiopulmonary monitoring [1–3]. A continuous wave (CW) microwave signal is transmitted toward a human subject. Physical motion caused by the respiration and heartbeat of the human subject phase modulates the transmitted signal and reflects it back to the transmit antenna, where it is received and phase demodulated to yield the heart and respiration rates of the subject. Physical motion of the human chest during respiration and heart motion are measured to be about 0.2 to 2 and 8 to 20 mm, respectively [4]. Thus the system has to be very sensitive to phase changes, which are caused by path-length variations. For a stationary transmitter and subject, this path length only varies with a subject's heartbeat and respiration. A nonstationary transceiver antenna or a fidgeting subject will produce additional path variations causing interference in radar signal (Figure 7.1).

    There are cases where the transmit/receive antenna cannot be assumed to be physically stationary. For example, if the transceiver is a handheld unit used in search and rescue operations or to sense through walls in military applications, “hand shake” of the operator will introduce path-length variations that phase modulate the received signal in addition to that of the target's cardiopulmonary motion. Also, if the antenna is placed on a platform subject to some vibration, the vibration can cause antenna motion, creating an interference with the radar signal. Monitoring a driver in a vehicle is an example of such an application. Thus the final demodulated signal will include components resulting from operator's unwanted hand shake to the extent that life signs monitoring will become impossible due to excessive interference. The fidgeting of the subject, which can be the result of coughing, sneezing, itching, and similar activities, is another source of this type of interference.

    While most sources of unwanted interference motion are random, they can still be categorized to a certain extent by their frequency spectrum and amplitude. For example, a 2003 Ford Taurus with a V6 engine being driven on a flat freeway at a speed of 65 mph creates about 3 to 9 mm of shake at a low frequency of 1.2 Hz [5].

    The problem of undesired instrument shake is similar in still image and video cameras, where it causes motion blur in the captured image.

  • 5 - Wearable Radar Tag Systems for Physiological Sensing/Monitoring

  • Edited by Isar Mostafanezhad, University of Hawaii, Manoa, Olga Boric-Lubecke, University of Hawaii, Manoa, Jenshan Lin, University of Florida
  • Book:
    Medical and Biological Microwave Sensors and Systems
    Published online:
    14 December 2017
    Print publication:
    07 December 2017, pp 154-171

  • Summary

    Introduction

    One limitation with Doppler radar is that for vital sign monitoring, any torso movement by the subject will affect the measurements. Other limitations include interference from moving objects or people in the vicinity and an inability to detect multiple targets. These issues arise due to the fact that a continuous-wave (CW) radar motion-detecting system is not inherently selective and will detect any motion in its field of view. Various solutions have been proposed for this, such as the use of multiple antennas with blind source separation (BSS) techniques to identify multiple respiration signatures [2,36] and use of two and four radars to cancel body sway [12,38]. BSS techniques are very effective in identifying multiple motion signatures but cannot associate those signatures with a particular source, leading to ambiguity in the interpretation of results. A good solution still does not exist for identification of a subject from the environmental clutter and making the Doppler radar system selective.

    Bringing selectivity to the radar implies introducing ways to ensure that the motion signals obtained correspond to the desired source. By rejecting clutter motion and detecting the physiologic motion of a subject, we are implementing the first stage of selectivity. The only way to resolve targets without placing any circuit on them is by spatial resolution and range. Spatial resolution can be brought to the radar through coherent detection using pulse Doppler radar. This principle is used in synthetic aperture radars (SARs) and inverse synthetic aperture radars (ISARs) [33]. In order to achieve good resolution, we would have to use millimeter-wave signals and associated circuitry and would still have ambiguities in the range. Spatial resolution can also be obtained through multiple-input, multiple-output (MIMO) systems and BSS techniques, but the sources of motion would still remain ambiguous. Range can also be calculated using frequency-modulated continuous-wave (FMCW) radars, but then Doppler processing would become more challenging. The resolution provided by FMCW radar is also limited by the bandwidth of frequencies used.

    Introducing modulation at the source of motion may allow more flexible solutions compatible with the current Doppler radar system. The way to achieve selectivity would be to have some form of modulated backscatter from the subject and no modulated backscatter from other objects, similar to radiofrequency identification (RFID) systems. Although RFID technology is mature and easily available, it is difficult to apply to motion-sensing applications.

  • 10 - Respiration and Respiratory Therapy

  • Barbara L. Christe, Indiana University–Purdue University, Indianapolis
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    06 August 2018
    Print publication:
    07 December 2017, pp 119-132

  • Summary

    Introduction

    The focus of this chapter is external human respiration. Moving air in and out of the lungs is external respiration and the focus of technological interventions. The exchange of gases in the alveoli is part of external respiration (although it occurs within the lungs) and reflects the effectiveness of breathing – note that internal respiration does not mean “inside the lungs,” it refers to the gas exchange at the cellular level within the tissues. Patients need to move air in and out of the lungs and exchange gases in the alveoli, a substructure of the lungs. Oxygen is taken in by the body and carbon dioxide is expelled. Air is made up of 79% nitrogen, 20.96% oxygen, and 0.04% carbon dioxide. However, the air that is expired out of the lungs contains differing percentages. Expired air still contains 79% nitrogen (unaffected by respiration), but notice that the concentration of oxygen is decreased to 17%, and the concentration of carbon dioxide is substantially increased to 4%.

    Respiration Effectiveness

    One important patient characteristic that is monitored is the effectiveness of respiration – a patient may be breathing (air moving in and out), but it is more important to know whether this activity is resulting in appropriate oxygenation of the body. One method to examine breathing effectiveness is to evaluate the properties of a patient blood sample. Chemical analysis of blood (often performed at the bedside or in the unit), especially the measurement of pH (i.e. the acidity of the blood), can help clinicians determine a patient's respiratory status. See Chapter 15 for more information regarding blood testing.

    Pulse oximetry, as discussed in Chapter 7, is also used to simply and non- invasively characterize the effectiveness of respiration. The percentage of hemoglobin molecules that carry oxygen can be displayed by a simple device and will increase or decrease as the body is able to absorb and circulate oxygen.

    Capnography is the measurement of carbon dioxide concentrations in expired air. This technique evaluates the changes in carbon dioxide values over time. Expired air is sampled or passed through sensors that can electronically detect the concentration of carbon dioxide. Sensors that utilize infrared (IR) light and light detectors are typically placed within the tubing that connects patients with respiratory devices.

  • 8 - Biomedical Applications of UWB Technology

  • Edited by Isar Mostafanezhad, University of Hawaii, Manoa, Olga Boric-Lubecke, University of Hawaii, Manoa, Jenshan Lin, University of Florida
  • Book:
    Medical and Biological Microwave Sensors and Systems
    Published online:
    14 December 2017
    Print publication:
    07 December 2017, pp 228-264

  • Summary

    Introduction

    Interest in ultra-wideband (UWB) technology has increased significantly since the Federal Communications Commission's (FCC's) inquiry in 1998 and approval of its use in 2002. The FCC opened up two bands, the 3.1- to 10.6- and 22- to 29-GHz frequency bands. UWB has been used for both communication and radar applications. The fundamental purpose of this chapter is to open up new areas of application for UWB technologies applied to medicine. This includes pushing the achievable limits in terms of high-accuracy indoor three-dimensional (3D) localization using UWB technology and to use this technology in a real-time location system that tracks multiple tags simultaneously with high 3D accuracy in the millimeter range. The application of this technology goes beyond localization to other areas such as breast cancer detection, human gait analysis, and vital signs monitoring, and the list goes on.

    Historically, Time Domain Corporation has pioneered real-time precise location of people and assets. Time Domain is the first company to unleash its full potential [1]. Their pulse-on system enables real-time localization in the most difficult environments – where GPS fails and where ad hoc or moving frames of reference are required. Multispectral Solutions, Inc., also used UWB for multiuser networking applications – more specifically, an ad hoc wireless UWB communications network for tactical voice and high-speed communications, a long-range UWB system for over-the-water and non-line-of-sight voice, data, and video communications, and a wireless UWB communications network for support of both tactical and strategic (long-haul) communications [2].

    In this chapter, we will focus on three areas: (1) indoor positioning, (2) human gait analysis and vital signs detection, and (3) early breast cancer detection.

    Overview of UWB Technology for Indoor Positioning Systems

    It is important to recognize that the use of UWB technology in a high-performance localization system requiring millimeter 3D accuracy has not been well researched, and far fewer systems have been developed compared with its use in cheaper but more widespread systems with lower accuracy requirements on the order of 10- to 15-cm 3D accuracy.

    These localization systems based on using UWB narrow pulses are typically comprised of a transmitter and numerous receivers. The transmitter (the tag) has a narrow-pulse generator (in the picosecond range) controlled by a clock, a power amplifier, and a wide-band omnidirectional antenna.

  • 15 - Clinical Laboratory Equipment

  • Barbara L. Christe, Indiana University–Purdue University, Indianapolis
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    06 August 2018
    Print publication:
    07 December 2017, pp 189-198

  • Summary

    Introduction

    The clinical laboratory is vital to a hospital's ability to treat patients. Bodily fluids from patients are analyzed for their chemical makeup as well as evidence of disease. Many therapeutic and treatment decisions are made based on the results of this important analysis. Almost all testing is automated and most devices perform many tasks. As a very equipment- intensive department, technical support is vital. The high level of complex equipment does require some hospitals to obtain service contracts for the support of clinical laboratory equipment.

    Common fluids from patients analyzed include blood, urine, and cerebrospinal fluid. A tremendous number of categories and tests are performed. This chapter focuses on the principles that form the foundation for the complex equipment. Most devices utilize multiple reagents, bar codes, robotics, and computers to perform the sample preparation and multiple tests. In addition to automated fluid analysis, many laboratory tests evaluate tissue and fluid samples for evidence of abnormalities. Many of these tests are not automated and require the expertise of a pathologist or clinical laboratory technician.

    The naming conventions associated with this part of healthcare have varied over time. Originally termed medical technology, a shift was made to more clearly identify the profession. Previously, clinical staff who managed sample analysis techniques were known as “med techs,” causing confusion with medical assistants, phlebotomists, and HTM technicians. Now laboratory staff are often called clinical laboratory scientists. Newer labels for the department include medical laboratory, clinical laboratory, and clinical technology.

    Clinical laboratories have their own specific regulations, and organizations that offer guidelines and best practices. These include the American Association of Blood Banks (AABB), College of American Pathologists, and Clinical Laboratory Improvement Amendments (CLIA). CLIA observance is a federal requirement.

    Blood Analysis

    Many tests are performed on blood. A common test is blood cell count. The automation of this test was vital to improvement in analysis speed. W. H. Coulter created an automated method of particle counting using electrical impedance. As the blood cells pass between electrodes, the impedance increases in pulses. These pulses can be counted to determine the amount of cells (particles) in a sample. Since red blood cells and platelets have different sizes, the pulses vary in size. This allows for very specific results.

  • 14 - Imaging

  • Barbara L. Christe, Indiana University–Purdue University, Indianapolis
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    06 August 2018
    Print publication:
    07 December 2017, pp 175-188

  • Summary

    Introduction

    The technology involved in imaging the inside of the human body is tremendously complex and amazingly broad. There are a vast array of unique devices, but this chapter will deal with general categories of imaging modalities based on the technique or source of image.

    Common Imaging Modalities

    Ultrasound: this imaging technique uses sound waves to image anatomy and physiology function. Ultrasound can also be used to detect blood flow, anatomic movement (heart valves, for example), and, most commonly, anatomical structures. It is frequently chosen as an imaging modality because it does not use radiation and carries less risk to the patient. Ultrasound imaging uses highfrequency sound waves (1– 20 MHz) which are projected into the body. The waves hit an object, bounce back, and are detected with a piezoelectric crystal sensor (as discussed in Chapters 6 and 9). The distance from the transmitter probe and the anatomical structure can be calculated, and this data is used to produce an image. Computers can manipulate the transducer data to present three- dimensional or moving images.

    Transducer probes, which contain both the transmitter and the sensor, come in many shapes and sizes. Some are designed to enter body cavities such as the esophagus or the vagina for better imaging quality. Most commonly, probes are placed on top of the skin and transmit high- frequency waves into the soft tissues. Ultrasound waves are generally blocked by air and bone. This can be a problem since air is contained in the lungs and there are bones surrounding some organs like the brain and heart. However, creative approaches to bypass bones (between the ribs, for example) are utilized to image most organs. In addition, a gel is often used to help block any air between the probe and the skin. This ensures effective transmission of the waves and an unobstructed image. An example of a probe used for a trans- thoracic (cardiac) ultrasound is shown in Figure 14.1.

    Because of the inherent safety of this type of imaging, women often undergo ultrasound imaging to evaluate the progress of pregnancy. Many abnormalities can be detected early and, in some cases, perinatal treatment can take place. Another common application of ultrasound is echocardiography. The anatomy and function of the heart can be examined.

  • 1 - Implantable Wireless Medical Devices for Gastroesophageal Applications

  • Edited by Isar Mostafanezhad, University of Hawaii, Manoa, Olga Boric-Lubecke, University of Hawaii, Manoa, Jenshan Lin, University of Florida
  • Book:
    Medical and Biological Microwave Sensors and Systems
    Published online:
    14 December 2017
    Print publication:
    07 December 2017, pp 1-39

  • Summary

    Introduction

    Advances in low-power-consumption radiofrequency integrated circuits (RFICs), multifunctional integrated circuits, high-sensitivity sensing electrodes, biocompatible materials, and packaging techniques have made implants with wireless communication functionality and/or wireless charging capability more feasible and practical. However, wireless communication or wireless powering has not been widely used in implants. There are several challenges. The implant applications are typically disease oriented and implementation focused. The designs of implants have to address specific needs in the disease diagnosis or treatment modalities, which are strongly related to both electronic and mechanical parameters. The sensing modalities or therapy methods determine the electrical specifications, while the biological environments often present serious design constrains. The implementation has to suit clinical settings for safe, cost-effective, and relatively easy implantation procedures and, most important, the needs and comfort of patients in daily life.

    It is obvious that integration of wireless communication functionality in implants can provide critical and increased capabilities in applications. The outbound communication brings sensor signals and device conditions to the reader outside the body. The sensors can monitor physiologic signals, such as blood pressure, intracranial pressure, core temperature, electrical signals of tissue or motility of organs, and biochemical conditions such as pH and certain protein or factor concentrations, of patients in vivo and in real time. In addition, the wireless communication can periodically report device conditions such as battery level, electrical resistance of electrodes, and current/voltage delivered to tissues. The inbound communication can be used for device reconfiguration, dosage setting, and condition probing. Bidirectional communication will be ideal for remote access of the implants, adding capabilities for real-time feedback as an integrated system between body and computer. The wireless closed-loop system also can provide real-time patient condition alerts, patient self-diagnosis using smart phones, and autonomous treatment-efficacy studies over a population of patients.

    From the perspectives of patients, wireless communication removes the discomfort and inconvenience of tethered wires coming out of the body. Currently, the wires either go through small surgical openings in the body, such as for the extension wire from the head in deep brain stimulation, or an orifice, such as the nostril for stomach stimulation and multichannel intraluminal impedance tests or the urethra for bladder monitoring. The tethered wires connecting to the external electronic device, either a reader or a pulse generator, obviously bring some inconvenience to patients and sometimes pain, and they often limit patient mobility, hindering quality of life.

  • 2 - Patient Safety

  • Barbara L. Christe, Indiana University–Purdue University, Indianapolis
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    06 August 2018
    Print publication:
    07 December 2017, pp 20-29

  • Summary

    Introduction

    An important responsibility of the HTM profession is related to patient safety. Ensuring the safe use of technology is a vital role of the HTM technician as part of the medical care team. Understanding the human body and its interaction with technology is critical to patient safety.

    Healthcare Technology

    Many forms of technology are utilized as tools in medical care. The devices must be safe and effective. In addition, the devices must perform in a way that healthcare providers expect, consistently and reliably. Devices range from very simple (without electricity or moving parts) to highly complex (imaging devices). In general, devices fall into three categories: therapeutic, monitoring, or diagnostic.

  • Therapeutic devices generally offer support or treatment to the patient, such as ventilators that provide assisted breathing for patients who cannot breathe on their own.

  • Monitoring devices gather physiological information for clinicians to interpret and utilize for treatment decisions, such as an automated device to measure blood pressure.

  • Some devices are diagnostic, offering information about the patient, such as an X- ray machine producing internal images to identify a broken bone.

    • Medical devices can also be categorized by inherent risk. Highrisk devices are associated with the functions critical to sustaining human life (life support) and can result in serious injury or death to a patient if they malfunction. An example would be an anesthesia machine utilized during surgery. Medium- risk technology is important to patient care but a malfunction is unlikely to cause serious injury. An example of a medium- risk device would be an ultrasound machine, whose images are extremely useful but not critical to patient survival. Lastly, low- risk devices have few consequences related to malfunction other than staff or patient frustration. An infant scale would be an example of a low- risk device.

    Patient Safety and Risk

    Medical care and treatment of patients depends on a balance between benefits and risks. If safety alone is the focus, then the safest approach in healthcare would be to offer no treatment, and utilize no techniques, or technology. This would be safe but not beneficial. In contrast, interventions are integral to healthcare. The HTM profession works to minimize any risks associated with use of technology. Understanding why patients who seek medical interventions are at risk from technology is important to minimizing potential hazards.

  • 7 - The Heart

  • Barbara L. Christe, Indiana University–Purdue University, Indianapolis
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    06 August 2018
    Print publication:
    07 December 2017, pp 81-95

  • Summary

    Introduction

    The beat of the heart and the electrical signal transmitted to create the beat is one of the most familiar waveforms found in healthcare. The waveform deserves this status. The electrical activity of the heart is fairly simple to measure and tells a great deal about the health of the patient. In the very early 1900s, Willem Einthoven invented the electrocardiogram and won the Nobel Prize in medicine for this work.

    Patient Monitoring

    Monitoring a patient's heart is a very common procedure. A patient's vital signs are often tracked at regular time intervals or continuously (vital signs usually include blood pressure, related to heart function). Using technology means the patient's condition can be tracked without the need for someone standing next to the bedside continually taking measurements. In addition to tracking the condition of a patient continuously, monitoring can provide diagnostic information upon which treatment decisions are based. Vital signs such as blood pressure and respiration are discussed in their respective chapters.

    Note about assumptions for vital signs: Most patients in most hospitals are adults (they are simply sicker more often). Therefore, when a vital sign is listed and unlabeled (as to the age/ type of patient) it is assumed to belong to an adult.

    Electrical Activity of the Heart

    The heart generates electrical signals to contract (pump blood). Cells within the heart have the ability to depolarize and repolarize, and this process generates electrical energy. The electrical signal in the heart begins at the sinoatrial (SA) node, which stimulates the atria (the two upper chambers of the heart) to contract. The signal then travels to the atrioventricular (AV) node, followed by the Bundle of His, and then through the Purkinje network, which stimulates the ventricles (the two lower chambers of the heart) to contract. When the ventricles are being stimulated to contract, the atria are repolarizing.

    The electrical signal is called an electrocardiogram. The abbreviation used for this can be EKG (which comes from German Elektrokardiogramm) or ECG (you will find these letters used interchangeably). Some people prefer the term EKG since it is less likely to be confused with the term EEG when spoken. Generally, little consensus exists upon the use of the label EKG or ECG, although the EKG seems to be diminishing in clinical use over time. There may be times when the terms are used together.

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