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1831 results in Biomedical engineering

Page 80 of 92

  • 13 - Medical applications of imaging

  • from Part IV - Medical applications and ongoing developments
  • Geoff Dougherty
  • Book:
    Digital Image Processing for Medical Applications
    Published online:
    12 September 2018
    Print publication:
    09 April 2009, pp 381-394

  • Summary

    Overview

    Imaging science visualizes an object and quantitatively characterizes its structure and/or function. Biomedical imaging applies imaging science to the presentation of and interaction with multi-modality biomedical images with a view to using them productively to examine and diagnose disease in human patients. This chapter discusses a number of specific applications in medicine that illustrate many of the concepts introduced in this book. The examples have been chosen to demonstrate a wide range of algorithms and approaches; none represent complete solutions, but are rather examples of continuing research.

    Learning objectives

    After reading this chapter you will be able to:

  • • appreciate the complexity and problems associated with imaging tasks;

  • • recognize broad schemes for approaching image analysis;

  • • analyze the component parts in an imaging problem;

  • • select potential strategies for analyzing images from a variety of applications.

    • Computer-aided diagnosis in mammography

    Mammography (Section 3.2.3) is the single most important technique in the investigation of breast cancer, the most common malignancy in women. It can detect disease at an early stage when therapy or surgery is most effective. However the interpretation of screening mammograms is a repetitive task involving subtle signs, and suffers from a high rate of false negatives (10–30% of women with breast cancer are falsely told that they are free of the disease on the basis of their mammograms (Martin, Moskowitz and Milbrath, 1979)), and false positives (only 10–20% of masses referred for surgical biopsy are actually malignant (Kopans, 1992)). Computer-aided diagnosis (CAD) aims to increase the predictive value of the technique by pre-reading mammograms to indicate the locations of suspicious abnormalities, and analyze their characteristics, as an aid to the radiologist.

  • 4 - Medical images obtained with non-ionizing radiation

  • from Part I - Introduction to image processing
  • Geoff Dougherty
  • Book:
    Digital Image Processing for Medical Applications
    Published online:
    12 September 2018
    Print publication:
    09 April 2009, pp 90-120

  • Summary

    Overview

    Diagnostic medical ultrasound uses high-frequency sound and a simple pulse–echo technique. When an ultrasound beam is swept across a volume of interest, a crosssectional image can be formed from a mapping of echo intensities. Current medical ultrasound imaging systems are based on envelope detection, and therefore only display intensity information. Despite this shortcoming, ultrasound imaging has become an important and widely accepted modality for non-invasive imaging of the human body because of its ability to produce real-time images, its low cost and its low risk to the patient. Magnetic resonance imaging (MRI) uses the phenomenon of nuclear magnetic resonance (NMR): unpaired nucleons, such as protons, orientate themselves in a magnetic field, and radiofrequency pulses can be used to change the balance of the orientations. When the system returns to equilibrium it produces signals that can be used to produce an image, which is characterized by its high contrast for soft tissues. MRI images map function, as well as structure. Digital images from any imaging modality can be compared or combined, after image registration, using a networking system.

    Learning objectives

    After reading this chapter you will be able to:

  • • explain the basis of imaging using non-ionizing radiation, specifically ultrasound and radiofrequency (RF) radiation with a strong magnetic field;

  • • outline the physical factors involved in these imaging modalities;

  • • describe the factors which determine the speed of ultrasound waves in a material;

  • • explain the purpose of time gain compensation and describe how it is implemented;

  • • summarize the steps involved in the reconstruction of B-mode ultrasound images;

  • • identify the factors that affect image quality and artifacts in ultrasound imaging;

  • • describe the phenomenon of nuclear magnetic resonance (NMR);

  • • explain how MRI images can be constructed from NMR spectra;

  • • describe the use of magnetic field gradients to add spatial information to MRI images;

  • • summarize the changes that occur to the spins using the spin echo pulse sequence;

  • • identify the factors that affect image quality and artifacts in MRI imaging;

  • • describe how functional information can be obtained from MRI imaging;

  • • summarize the advantages of a picture, archiving and communications system (PACS);

  • • outline the factors involved in the co-registration of images from different modalities.

  • 8 - Image restoration

  • from Part II - Fundamental concepts of image processing
  • Geoff Dougherty
  • Book:
    Digital Image Processing for Medical Applications
    Published online:
    12 September 2018
    Print publication:
    09 April 2009, pp 246-270

  • Summary

    Overview

    An image is never an exact representation of the object under observation; it is always corrupted by degradations during acquisition and within the imaging system itself. These include noise, blurring and distortion. Image restoration removes or reduces these degradations. The point spread function (PSF) or the modulation transfer function (MTF) provides a complete, quantitative description of an imaging system and directly characterizes the image degradation within the system and can be used to restore the fine detail in images. The problem is more complicated if the image is also degraded by significant amounts of noise. Restoration techniques attempt to model the degradation and apply the inverse process to recover the original image. They are most effective when the point spread function or modulation transfer function is known and the nature of the blurring and noise are well understood. Geometric distortions can be reversed using inverse bilinear equations and gray-level interpolation.

    Learning objectives

    After reading this chapter you will be able to:

  • • identify the main sources of image noise and discuss their characteristics;

  • • choose appropriate general strategies for minimizing the effects of noise;

  • • discuss the advantages of adaptive filtering;

  • • model image degradation comprising blur and additive noise;

  • • employ suitable values to Wiener filter a noisy, blurred image;

  • • compare the performance of inverse filtering with Wiener filtering;

  • • explain how distortion can be removed from images.

    • Image degradation

    Images can be degraded by a number of different mechanisms, including noise, blurring and distortion. Noise is present because any imaging device must use a finite exposure (or integration) time, which introduces stochastic noise from the random arrival of photons. Optical imperfections and instrumentation noise (for example, thermal noise in CCD devices) result in more noise. Sampling causes noise due to aliasing of high-frequency signal components, and digitization produces quantization errors. Further noise can be introduced by communication errors and compression. Blurring is present in any imaging system which uses electromagnetic radiation (for example, visible light and x-rays).

  • Preface

  • Barbara Christe, Purdue University, Indiana
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    05 June 2012
    Print publication:
    06 April 2009, pp vii-viii

  • Summary

    This book serves readers who would like to explore medical equipment that is used in the clinical setting. It offers an overview of the fundamental information necessary for work in the field. The material is designed to provide a working vocabulary and elementary knowledge of the medical equipment involved in the treatment of patients. Readers are encouraged to become knowledgeable and effective members of the patient care team, building on the information in this book as a foundation for further study.

    Readers should have a fundamental understanding of anatomy, physiology, and medical terminology appropriate for their role in the health care field. Readers are assumed to have a fundamental knowledge of basic electronics concepts including voltage, current, resistance, impedance, analog and digital signals, and sensors. Readers without this background may have to explore terms and concepts referenced in the text.

    There is a vital connection between technology and the care of patients. In many cases, health care 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 topic. Questions are designed to push the reader to integrate concepts using external sources. Answers are not specifically available within the chapters.

  • 8 - Respiration and respiratory therapy

  • Barbara Christe, Purdue University, Indiana
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    05 June 2012
    Print publication:
    06 April 2009, pp 113-126

  • Summary

    LEARNING OBJECTIVES

    1. 1 list and describe the components of inspired and expired air

    2. 2 list and describe the important lung volumes

    3. 3 describe a spirometer

    4. 4 describe impedance plethysmography

    5. 5 describe apnea

    6. 6 describe capnography

    7. 7 list and describe the functions and settings of a ventilator

    8. 8 describe and characterize high-frequency ventilation

    9. 9 describe the method of connection between patients and the ventilator

    10. 10 describe nebulizer, oxygen tent, and humidifier

    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 internal respiration, but it is not essential to this chapter. Here are some important facts related to respiration:

    1. Make-up of air: 79% nitrogen, 20.96% oxygen, and 0.04% carbon dioxide

    2. Make-up of expired air: 79% nitrogen (unaffected by respiration), 17% oxygen, and 4% carbon dioxide (human's waste product)

    It is important to know that the exchange of gas in the lungs occurs in the alveoli.

    Respiration measurements

    Volumes of gases that fill the lungs during different moments in respiration are important to BMETs since many machines try to fill those volumes. Amounts vary by the age, height, gender, and physical condition of a patient.

    Tidal volume: Breathing volume is about 500 milliliters (mL) for an average adult male. This is the main value of importance. Figure 8.1 shows a sine wave that illustrates the action of breathing in and out.

  • 6 - Cardiac assist devices

  • Barbara Christe, Purdue University, Indiana
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    05 June 2012
    Print publication:
    06 April 2009, pp 87-102

  • Summary

    LEARNING OBJECTIVES

    1. 1 describe defibrillator waveforms and characteristics

    2. 2 define the term AED and describe why it is useful

    3. 3 describe cardioversion

    4. 4 describe assistive technologies such as LVAD, pacemaker, implantable defibrillator, heart-lung bypass, ECMO, cardiac catheter, and IABP

    Introduction

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

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

    Defibrillators

    A defibrillator, which is often used in life-saving moments on television medical shows, is a fairly simple device that delivers a large amount of energy across a patient's chest when the heart is not beating properly. When the heart is not beating with a pattern, all cells are contracting at different times; this is known as fibrillation. 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.

  • 11 - The operating room

  • Barbara Christe, Purdue University, Indiana
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    05 June 2012
    Print publication:
    06 April 2009, pp 155-176

  • Summary

    LEARNING OBJECTIVES

    1. 1 list and describe the characteristics of surgical lights

    2. 2 list and describe the two functions of an anesthesiologist or CRNA (monitor patient and deliver medications)

    3. 3 list and describe the four functions of anesthesia

    4. 4 list and describe the staff in an OR

    5. 5 list and describe the items that must be worn in the OR

    6. 6 list and describe the four types of surgical procedures

    7. 7 list and describe the many surgical specialties

    8. 8 list and describe the two common methods of equipment sterilization

    9. 9 list and describe the stress related to the operating room environment

    10. 10 list and describe where patients go immediately after surgery

    11. 11 list and describe the function of the following pieces of OR equipment: depth-of-anesthesia monitors, operating microscopes, robots, smoke evacuators, patient warmers, blood and fluid warmers, operating room tables

    12. 12 list and describe laparoscopic surgery and the devices used in it

    13. 13 list and describe the functions and parts of an electrosurgical unit

    14. 14 define the term LASER and describe some common medical LASERs

    Introduction

    The operating room (OR) in a hospital is a unique environment that contains a great deal of equipment as well as many protocols and rules that impact a BMET. Many types of surgery are performed here. Operating rooms may be located in a hospital, in a free-standing surgery center, or in a doctor's office. BMETs must have a solid and accurate understanding of the operating room in order to perform their job effectively.

  • 14 - Intravenous pumps and other pumps

  • Barbara Christe, Purdue University, Indiana
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    05 June 2012
    Print publication:
    06 April 2009, pp 205-212

  • Summary

    LEARNING OBJECTIVES

    1. 1 identify and describe the function and purpose of an intravenous pump

    2. 2 identify and describe the function and purpose of a syringe pump

    3. 3 identify and describe the function and purpose of PCA devices

    4. 4 identify and describe the function and purpose of feeding pumps

    Introduction

    The use of technology to push fluids into a patient has evolved and expanded over time. Bottles of fluids used gravity flow to “drip” fluids into a patient. As technology expanded into health care, the bottles were replaced with plastic bags and gravity was no longer medically adequate. Electromechnical 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. Hospitals have 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.

  • 12 - Imaging

  • Barbara Christe, Purdue University, Indiana
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    05 June 2012
    Print publication:
    06 April 2009, pp 177-192

  • Summary

    LEARNING OBJECTIVES

    1. 1 describe ultrasound imaging

    2. 2 describe basic x-ray imaging

    3. 3 describe CT scanners and identify how they differ from basic x-ray devices

    4. 4 describe DICOM and PACS

    5. 5 describe and characterize MRI

    6. 6 describe and characterize nuclear medicine – both imaging and treatment

    7. 7 describe and characterize PET scans

    Introduction

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

    Ultrasound

    Ultrasound uses sound waves to image anatomy and anatomical 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 uses high-frequency sound waves (1–20 MHz) that are projected into the body. The waves hit an object, bounce back, and are detected with a piezoelectric crystal sensor. 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 and the vagina for better imaging quality.

  • 1 - BMET as a career

  • Barbara Christe, Purdue University, Indiana
  • Book:
    Introduction to Biomedical Instrumentation
    Published online:
    05 June 2012
    Print publication:
    06 April 2009, pp 1-18

  • Summary

    LEARNING OBJECTIVES

    1. 1 describe the role of a BMET

    2. 2 list and describe potential employers of a BMET

    3. 3 characterize field service representatives

    4. 4 list and describe the many job functions of a BMET

    5. 5 list and characterize the certification requirements

    6. 6 list and describe related professional societies and journals

    What is the name of this career?

    There are many definitions for what the letters BMET stand for – biomedical equipment technician, biomedical electronics technology, medical maintenance, biomedical engineering technologist, biomedical engineer, medical engineer, medical equipment repair technician, and many more. In general, it is the title for someone who works in the clinical setting and supports the equipment involved in patient care.

    At different hospitals, staff may have a wide variety of titles. Staff may be called the “biomeds,” “clinical engineers,” or the “equipment guys.” In some hospitals, BMETs may be responsible for everything from printers to computers to DVD players in the rooms of patients. In some hospitals, BMETs work for the maintenance departments and wear janitor's jumpsuits. Other hospitals hire a wide range of technical staff who wear lab coats, monogrammed polo shirts, or dress shirts.

    Because there is so little uniformity, it can be difficult for the career field to get the recognition it deserves. Some basic facts are true for most BMETs.

    What do BMETs do?

    Most BMETs perform several main categories of job function. In general, BMETs are responsible for the support of the technology used in health care.

Page 80 of 92