PATIENT CARE IN RADIOGRAPHY.pdf

PATIENT CARE in RADIOGRAPHY W I T H AN I N TRODUCTION T O ME DIC AL IMAGING TENT H EDITION Ruth Ann Ehrlich, RT(R) Radiology Faculty (Retired) University of Western States Portland, Or...

PATIENT CARE in RADIOGRAPHY W I T H AN I N TRODUCTION T O ME DIC AL IMAGING TENT H EDITION Ruth Ann Ehrlich, RT(R) Radiology Faculty (Retired) University of Western States Portland, Oregon Dawn M. Coakes, BS, RT(R)(CT) Instructor and Clinical Coordinator, Radiography Program Portland Community College Portland, Oregon Elsevier 3251 Riverport Lane St. Louis, Missouri 63043 PATIENT CARE IN RADIOGRAPHY: WITH AN INTRODUCTION TO MEDICAL IMAGING, TENTH EDITION ISBN: 978-0-323-65440-1 Copyright © 2021 by Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. 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In using such infor- mation or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. With respect to any drug or pharmaceutical products identified, readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administra- tion, and contraindications. It is the responsibility of practitioners, relying on their own experience and knowledge of their patients, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors as- sume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Previous editions copyrighted 2017, 2013, 2009, 2004, 1999, 1993, 1989, 1985, and 1981 Library of Congress Control Number: 2019955979 Senior Content Strategist: Jamie Blum Senior Content Development Manager: Luke Held Publishing Services Manager: Shereen Jameel Senior Project Manager: Umarani Natarajan Senior Designer: Renee Duenow Printed in Canada Last digit is the print number: 9 8 7 6 5 4 3 2 1  REVIEWERS Gina L. Arnold, MPH, RT(R)(M) Carol R. Kocher, MS, RT(R) (M) Adjunct Faculty Program Director Radiography Program Olney Central College Northampton Community College Olney, Illinois Bethlehem, Pennsylvania Barbara Peacock, BS, RT(R)(CT) Michael B. Farah Radiography Clinical Coordinator Program Director Radiography Radiography Program Cumberland County College Lawrence Memorial/Regis College Vineland, New Jersey Medford, Massachusetts Stacy Wilfong, MAT, RT(R) Susan L. Grimm, BSRS, RT(R) Radiology Program Director Associate Professor, Radiography Allied Health–Radiology Richland Community College Mineral Area College Decatur, Illinois Park Hills, Missouri Ly N. Hunyh, MD Ingrid S. Wright Physician, PeaceHealth–Southwest Medical Center Director of Radiologic Technology Vancouver, Washington St. Johns River State College–St. Augustine Campus St. Augustine, Florida Tamara E. Janak, MTD, RT(R) (M) Instructor and Clinical Coordinator Radiologic Technology Program College of Southern Idaho Twin Falls, Idaho iii P R E FA C E During the past 35 years, Patient Care in Radiography has (ASRT) curriculum for radiography that falls within expanded to meet the changing needs of students and the general scope of the text and to provide both con- technologists in radiography and other medical imaging tent and learning tools that will aid in implementing modalities. It is a resource that provides an introduction to the ASRT curriculum guidelines. these professions and an orientation to the hospital envi- Content has been updated to reflect current informa- ronment. First and foremost, however, it is a fundamental tion and infection control guidelines from the CDC text on patient care, designed and written to help radiog- and to be consistent with Occupational Safety and raphers meet patient needs. The reader learns to care for Health Administration (OSHA) recommendations. the patient effectively while functioning as a responsible This information will help to ensure the well-being and valuable member of the health care team from the of radiographers by raising practice standards in the patient introduction, through routine procedures, and the workplace and by minimizing risks of exposure to final recording of events in the medical record. blood-borne pathogens. Although the primary goal is centered on patient Chapter 2 has new information about digital radiog- care, concern for those who provide that care is also an raphy, which has replaced film-screen technology. essential focus in this text. Discussions of significant Chapter 21 has new information on surgical laparo- aspects of self-care and professional development are scopic cholecystectomy. included in the following chapters: Chapter 5 has two new tables with information on Chapters 3, 5, 7, and 10 incorporate important self- crimes and torts that help to clarify this content for care concepts. students. Chapter 4 contains discussions on health care deliv- Chapter 9 has new information on enteric contact ery, the health care team and career. precautions. Chapter 5 describes professional attitudes, patient The Answer Key (now printed in the text) helps stu- rights, legal considerations, and medical records. dents evaluate learning. Chapter 6 includes communication strategies for many situations, including dealing with patients of all ages, patients’ families and coworkers, plus trans- KEY FEATURES cultural encounters and those who have communica- The reading level is comfortable for the student radiog- tion impairments. rapher without being overly simplistic. Again, we have Chapter 9 provides Standard Precautions and addi- done our best to retain the features that readers have tional guidelines for infection control as recom- appreciated in previous editions: mended by the Occupational Safety and Health Content outlines accompany each chapter. Administration (OSHA) and the Centers for Disease Smaller chapters segregate material and facilitate Control and Prevention (CDC). readability. Applying these principles is critical to your well-­ Callout boxes are used to indicate key items for learn- being and your ability to provide good care to others. ing, and warning boxes alert students to issues of safety. Step-by-step procedures are shown in photo NEW TO THIS EDITION essays, and patient care is integrated with proce- As in previous editions, the tenth edition of Patient Care dural skills. in Radiography contains updated and new information Additional pedagogical elements, such as learning designed to keep student and practicing radiographers objectives, key terms, illustrations, tables, boxes, current on important topics in this rapidly changing field: comprehensive summaries, review questions, and Every effort has been made to address the content of critical thinking exercises, have been retained and the American Society of Radiologic Technologists improved. iv  PREFACE v These features can be incorporated into classroom EVOLVE: ONLINE RESOURCES objectives and activities and will also enhance the effec- tiveness of individual study. The instructor resources for Patient Care in Radiography The chapters of this text were designed to be used are available online on Evolve and consist of: consecutively; each section builds on the preceding A test bank offering more than 450 questions information. A basic glossary is included for quick ref- An image collection with all the images from the text erence, but please note that it is not intended to replace PowerPoint slides the more detailed definitions and discussions in a good The student Evolve site includes an image collection, medical dictionary. as well as check-off forms for students to use for docu- We hope that this book proves to be a valuable mentation of clinical objectives related to patient care. resource to you as you care for patients in the challeng- For more information, visit http://evolve.elsevier.com/ ing field of medical imaging. Ehrlich/radiography/ or contact an Elsevier sales repre- sentative. AC K N OW L E D G M E N T S Suggestions by students, instructors, colleagues, and addition, they have been an excellent and most welcome reviewers have contributed greatly to this edition and resource when questions arose about hospital policies are acknowledged with our thanks. In addition to their and procedures. suggestions, many students in the Portland Community We have been privileged to benefit from the photo- College Radiologic Technology program assisted by graphic expertise of Jeff Watson; his technical ability serving as models for photography. Many thanks also is top notch, and it is applied with a sharp eye, a deep to models Leslie Danford, Gregg Norman, Kay Coakes, understanding of clinical practice, and a delightful sense Noah Coakes, Charlie Coakes, Sara Breithaupt, and Ron of humor. Kizziar, MD. As always, it has been a pleasure to work with the We are especially grateful to Dr. Ly Huynh, a radiolo- professionals at Elsevier: Jamie Blum, Senior Content gist with Radiology Specialists of the Northwest, for his Strategist; Luke Held, Senior Content Development consultation in reviewing several chapters. His exper- Manager; Umarani Natarajan, Senior Project Manager; tise, insight, and suggestions have helped beyond mea- and the fine staff at Elsevier. Our sincere gratitude to all sure. Thank you to Providence Portland Medical Center of you! and the medical imaging staff for allowing us access to their facility when we created color illustrations. In Ruth Ann Ehrlich and Dawn M. Coakes vi  CONTENTS PART 1 Introduction to Radiography Contrast Media and Special Radiographic 19  Techniques, 351   1  Introduction to Radiography, 1 Bedside Radiography: Special Conditions and 20    2  Image Quality Factors, 21 Environments, 373   3  Radiation Effects and Radiation Safety, 34 Radiography in Surgery, 393 21    4  The Health Care Delivery System, 48 Special Imaging Modalities, 401 22  Professional Roles and Behaviors, 65   5  Answer Key, 432 Bibliography, 436 PART 2 Patient Care Appendix A Informed Consent Form, 438   6  Professional Attitudes and Communications, 90 Appendix B  Accepted Abbreviations and Descriptive   7  Safety, 120 Terms Used in Charting, 439   8  Patient Transfer, 133 Appendix C Incident Report Form, 443 Infection Control Concepts, 147   9  Appendix D Abbreviated List of Useful Clinical Phrases Preventing Disease Transmission, 160 10  in Spanish, 445 Surgical Asepsis, 187 11  Appendix E  Radiology Department Infection Control Response to Patients’ Personal and Physical 12  ­Procedures, 447 Needs, 207 Appendix F Infection Control Guidelines, 449 Patient Assessment, 223 13  Appendix G Urine Collection, 453 Medication Information, 248 14  Appendix H  Iodinated Contrast Media Products for Medication Administration, 263 15  ­Radiography, 454 Emergency Response, 290 16  Appendix I Catheterization Technique, 457 Glossary, 461 Index, 485 PART 3 P  atient Care in Specific Procedures and Environments Dealing With Acute Situations, 305 17  Preparation and Examination of the 18  Gastrointestinal Tract, 326 vii This page intentionally left blank        PART 1 Introduction to Radiography 1 Introduction to Radiography OBJECTIVES At the conclusion of this chapter, the student will be able L ist five different types of electromagnetic wave to: radiation and identify those that are ionizing. Name the discoverer of x-rays, state the place and List six characteristics of x-radiation. date of the discovery, and describe the discovery. Define wavelength, frequency, and velocity with Name four other pioneers in the development of respect to a sine wave and state which of these radiography and describe their contributions. factors is a constant. Summarize the history and development of Describe the differences between primary radiation, radiography education. scatter radiation, and remnant radiation. List four essentials for the production of x-rays. Correctly identify the essential devices found in a Draw a diagram of a simple x-ray tube and label the typical radiographic room and state the purpose of parts. each. Briefly describe the process by which x-rays are Demonstrate the vertical, horizontal, and angulation produced in the tube. motions of an x-ray tube. CHAPTER OUTLINE History, 2 X-Ray Tube Support, 10 Discovery of X-Rays, 2 Collimator, 11 X-Ray Pioneers, 3 Radiographic Table, 12 Early Radiographers, 4 Grids and Buckys, 12 Radiography Education, 4 Upright Image Receptor Units, 15 Overview of Radiographic Procedure, 4 Transformer, 15 X-Ray Production, 5 Control Console, 15 Electromagnetic Energy, 6 Fluoroscopy, 17 Characteristics of Radiation, 7 Fluoroscopic Equipment, 17 The Primary X-Ray Beam, 8 Radiographer’s Duties in Fluoroscopic Scatter Radiation, 8 Examinations, 18 Radiographic Equipment, 9 Summary, 18 The X-Ray Tube, 9 X-Ray Tube Housing, 9 1 2 PART 1 Introduction to Radiography KEY TERMS amplitude grid cap anode image intensifier attenuation image receptor (IR) bucky latent image cathode photon collimator photostimulable p hosphor detent quantum (pl. quanta) electromagnetic energy remnant radiation electron stream scatter radiation filament sine wave fluoresce space charge fluoroscope target focal spot Trendelenburg position frequency wavelength grid    The study of radiography includes many topics, and environment require some guidance for comprehen- each topic is best understood when a host of others have sion. A good way to introduce you to radiography might already been mastered. Obviously, something has to be to guide you through a medical imaging department, come first. As you progress in your radiography educa- exploring and pointing things out. Think of this chap- tion, you will discover that learning occurs somewhat ter as the textbook version of such a tour. But before we like the peeling of an onion—one layer at a time will be enter the modern world of radiology, let’s take a moment revealed. You will visit topics again and again, each time to see how it all began more than a century ago. building a broader understanding based on your previ- ous learning and experience. The subject matter in this HISTORY section is treated on an introductory level to provide a starting place for your radiography education. All these Discovery of X-Rays topics will be presented in depth at a later time in your In the 1870s and 1880s, research involving electric- program; some are the subjects of entire courses in the ity was the cutting edge of physical science, and many radiography curriculum. Eventually, this information physicists were experimenting with a device called a will be woven together to provide a sound basis for clin- Crookes tube (Fig. 1.1), a cathode ray tube that was the ical practice and decision making. Have patience and forerunner of the fluorescent lamp and the neon sign. confidence in yourself as you take the first steps in your Although Crookes tubes also produced x-rays, no one new profession. detected them. Some radiography programs combine the topics of Then, on November 8, 1895, Wilhelm Conrad Roent- patient care with an introduction to medical imaging, gen, a German physicist (Fig. 1.2), was working with a and instructors find that the five chapters of Part I pro- Crookes tube at the University of Würzburg. In his dark- vide a suitable beginning. The curriculum designs of ened laboratory, he enclosed the tube with black pho- other schools may include this introductory material tographic paper so that no light could escape. Across under a different course heading. Regardless of whether the room, a plate coated with barium platinocyanide the content of this chapter is a part of your current crystals (a fluorescent material) began to glow. Roent- course, it may serve as a useful resource. gen noted that the plate fluoresced in relation to its dis- Entering a hospital radiology department as a student tance from the tube, becoming brighter when the plate for the first time can be both exciting and bewildering. was moved closer. He placed various materials, such as The equipment, language, and activities unique to this wood, aluminum, and his hand, between the plate and  CHAPTER 1 Introduction to Radiography 3 Fig. 1.1 Pear-shaped Hittorf–Crookes tube used in Roentgen’s initial experiments. (Courtesy of Eastman Kodak, Rochester, New York.) Fig. 1.2 Photograph of W.C. Roentgen, the discoverer of the tube, noting variations in the effect on the plate. He x-rays, taken in 1906. (Courtesy Wellcome Library, London.) spent the next few weeks investigating this mysterious energy that he called “x ray,” x being the symbol for the unknown. By the end of the year, Roentgen had identi- fied nearly all the properties of x-rays known today. He was awarded the first Nobel Prize in Physics in 1901 in recognition of his discovery. In November of 1895, Wilhelm Conrad Roentgen discovered x-rays while working with a Crookes tube in Fig. 1.3 The Coolidge “hot cathode” x-ray tube, prototype of his laboratory at the University of Würzburg in Germany. modern tubes, was introduced in 1910. Idvorsky Pupin demonstrated the radiographic use of fluorescent screens, now called intensifying screens. He X-Ray Pioneers used light emitted by fluorescent materials when acti- Early radiography often required as long as 30 minutes vated by x-rays to expose photographic plates. to create a visible image. Over the years, many advances In 1898, Thomas Edison began experiments with in this technology have reduced the time and radiation more than 1800 materials to investigate their fluorescent exposure involved in radiography. The early sources of properties. He invented the first fluoroscope and dis- electricity were not powerful enough to be efficient and covered many of the fluorescent chemicals used in radi- could not be easily adjusted until H.C. Snook, working ography over the intervening years. Edison abandoned with an alternating current generator, developed the his research when his assistant and long-time friend, interrupterless transformer. William Coolidge designed Clarence Dally, became severely burned on his arms as the hot cathode x-ray tube to work with Snook’s a result of serving as a subject for many of Edison’s x-ray improved electrical supply. The Coolidge tube (Fig. 1.3), experiments. Dally’s arms had to be amputated, and in introduced in 1910, was the prototype for the x-ray 1904 he died from his exposure. His death was the first tubes of today. recorded x-ray fatality in the United States. Roentgen used a glass plate coated with a photo- Until World War I, glass photographic plates were graphic emulsion to create the first radiograph. Soon used as a base for x-ray images. During the war, man- after Roentgen’s discovery was published, Michael ufacturers of photographic plates for radiography could 4 PART 1 Introduction to Radiography not obtain high-quality glass from suppliers in Belgium, radiation therapy technologists was separated from that and the U.S. government turned to George Eastman, for radiographers. founder of the Eastman Kodak Company, for help. East- Colleges were first involved in radiography educa- man had invented photographic film using cellulose tion because hospital-based radiography programs took nitrate, a new plastic material, as a substitute for glass. advantage of the academic offerings at local colleges. He produced the first radiographic film in 1914. Radiography students often attended college part-time Early in the 20th century, radiation injuries, such as to learn basic science subjects such as anatomy and skin burns, hair loss, and anemia, began to appear in physiology. both doctors and patients. Measures were taken to mon- After World War II, with many returning soldiers itor and reduce exposures; this process is still ongoing. wanting to attend college with the financial assistance Lead apparel, protective barriers, and exposure limita- provided by the GI Bill, junior colleges were developed tions have substantially decreased the amount of radia- to provide the first 2 years of academic education for tion received by those involved in the use of x-rays. university-bound students. In the 1960s, these institu- tions expanded and multiplied into the community col- Today, because of improved technology and safety lege system that is currently a significant part of national precautions, x-ray examinations are much safer for pa- public education in the United States. In the process of tients, and radiography is considered to be a very safe this expansion, more emphasis was placed on vocational occupation. education. Community colleges formed effective part- nerships with companies and institutions that provided on-the-job training. Following this trend, many hospi- tal-based radiography programs became affiliated with Early Radiographers community colleges to provide the necessary academic During his early experimentation with x-rays, Roentgen courses. Some 4-year colleges and universities also began produced the first anatomic radiograph—an image of to offer educational programs in radiologic technology. his wife’s hand. The first documented medical applica- As the requirements for accreditation of educational tion of x-rays in the United States was an examination programs in radiography have increased over the years performed at Dartmouth College in February 1896 of a (see Chapter 4), the organizational structure of colleges young boy’s fractured wrist. has proved to be well suited to the management of these The first radiographers were physicists familiar with programs. Today, colleges and hospitals still cooperate the operation of the Crookes tube. As equipment for to provide education in radiography. generating x-rays was installed in hospitals and physi- cians’ offices, physicians learned to take radiographs and Although many outstanding hospital-based pro- soon developed techniques to demonstrate many differ- grams exist, the majority of radiography programs are ent anatomic structures. These physicians began to train based in colleges. their assistants to develop the photographic plates and to assist with x-ray examinations. In time, many of these assistants became skilled in radiography and were called OVERVIEW OF RADIOGRAPHIC x-ray technicians. PROCEDURE Radiography Education Educational preparation provides the radiographer On-the-job training of x-ray technicians in hospitals with the necessary knowledge and skills to confidently evolved into hospital-based educational programs. obtain a patient’s radiographic images. To do this, the Formal classes and clinical experience were combined radiographer positions the patient’s anatomic area of to provide students with the knowledge and skills interest over the image receptor (IR) (Fig. 1.4A). The needed to take radiographs and to assist with radiation IR is placed on the tabletop to image small body parts, therapy (x-ray treatments). As the fields of diagnostic such as extremities. For larger anatomic areas, it can be and therapeutic radiology became more complex and placed in a tray beneath the table surface, or some digital specialized in the decade of the 1950s, education for tables have built-in IRs (see Chapter 2). The x-ray tube  CHAPTER 1 Introduction to Radiography 5 processor to produce a digital image. Processing converts the latent image into a visible one. All imaging systems include methods for identifying images with the patient’s name, the date, and the name of the facility. As you may have suspected, many details were omitted from the previous paragraphs. This is only a brief introduc- tion to the radiographic process. Next, we consider how x-rays are produced, their physical nature, and how their various characteristics relate to the process of radiography. X-RAY PRODUCTION Our tour will include a close look at a number of pieces of x-ray equipment. To better appreciate their purposes, A it will be helpful to understand how x-rays are produced. There are four basic requirements for the production of x-rays: 1. A vacuum 2. A source of electrons 3. A target for the electrons 4. A high potential difference (voltage) between the electron source and the target The container for the vacuum is the x-ray tube itself (Fig. 1.5), sometimes referred to as a glass envelope. It is made of borosilicate glass to withstand heat and is fitted on both ends with connections for the electrical supply. All the air is removed from the tube so that gas mol- ecules will not interfere with the process of x-ray pro- duction. The source of electrons is a wire filament at the elec- B trically negative cathode end of the tube. It is made of the element tungsten, a large atom with 74 electrons Fig. 1.4 A, A radiographer aligns patient anatomy to an image receptor in a bucky tray. B, A radiographer aligns an x-ray tube orbiting around its nucleus. An electric current flows to the patient and image receptor. through the filament to heat it; this accelerates the movement of the electrons and increases their distance position is adjusted to align the x-ray beam to the IR from the nucleus. Electrons in the outermost orbital (see Fig. 1.4B). The radiographer then goes to the con- shells get so far from the nucleus that they are no lon- trol booth, sets the exposure factors on the control con- ger held in orbit; instead, they are flung out of the atom, sole, and activates the exposure switch. forming an “electron cloud” around the filament. These During the exposure, x-rays from the tube pass through free electrons, called a space charge, provide the needed the patient. Different types of tissue absorb different electrons for x-ray production. amounts of the radiation, resulting in a pattern of varying The target is at the electrically positive anode end intensity in the x-ray beam that exits on the opposite side of of the tube, the end opposite the filament. The smooth, the patient. The radiation then passes to the IR and exposes hard surface of the target is the site to which the elec- it. The IR then has a pattern of exposure that is referred to trons travel and is the place where the x-rays are gen- as the latent image. Depending on the type of IR, a digital erated. The target is also made of tungsten, which has a image may appear immediately on a monitor or the photo- high melting point and withstands the heat produced at stimulable IR plate may be scanned by a laser in a special the anode during x-ray exposure. 6 PART 1 Introduction to Radiography Electron stream Target Heated Anode tungsten Amplitude a filament Crest Amplitude b Evacuated Valley glass envelope Fig. 1.5 Diagram of Coolidge tube simplifies understanding of Amplitude c x-ray production. Fig. 1.6 These three sine waves are identical except for their The voltage required for x-ray production is provided amplitudes. (From Bushong SC: Radiologic science for technol- by a high-voltage transformer. The two ends of the x-ray ogists, ed 11, St Louis, 2017, Elsevier.) tube are connected in the transformer circuit so that, during an exposure, the filament or cathode end is nega- tive and the target or anode end is positive. The high posi- tive electrical potential at the target attracts the negatively charged electrons of the space charge, which move rap- 1 cm idly across the tube, forming an electron stream. When these fast-moving electrons collide with the target, the kinetic energy of their motion must be converted into a different form of energy. The great majority of this kinetic energy is converted into heat (>99%), but a small amount is converted into the energy form known as x-rays. 0.5 cm When fast-moving electrons collide with the target of an x-ray tube, the kinetic energy of their motion is converted into other forms of energy: heat and x-rays. ELECTROMAGNETIC ENERGY 1.5 mm X-rays are among several types of energy described as electromagnetic energy, or electromagnetic wave radiation. They have both electrical and magnetic Fig. 1.7 These three sine waves have different wavelengths. properties, changing the field through which they pass The shorter the wavelength, the higher the frequency. (Note that the symbol for wavelength is the Greek letter lambda: λ.) both electrically and magnetically. These changes in (From Bushong SC: Radiologic science for technologists, ed the field occur in the form of a repeating wave, a pat- 11, St Louis, 2017, Elsevier) tern that scientists call a sinusoidal form or sine wave. Several characteristics of this waveform are signifi- the wave is the number of times per second that a crest cant. The distance between the crest and valley of the passes a given point. wave (its height) is called the amplitude (Fig. 1.6). More Because all electromagnetic energy moves through important to radiographers is the distance from one crest space at the same velocity—approximately 186,000 miles/ to the next, or wavelength (Fig. 1.7). The frequency of sec, which is 30 billion (3 × 1010) cm/sec—it is apparent  CHAPTER 1 Introduction to Radiography 7 that a relationship exists between wavelength and fre- Applications: Wavelength: quency. When the wavelength is short, the crests are closer Therapeutic x-ray 1/100,000 nm together; therefore more of them will pass a given point 1/10,000 nm each second, resulting in a higher frequency. Longer wave- Gamma rays 1/1000 nm Ionizing lengths will have a lower frequency; this can be expressed 1/100 nm Diagnostic x-ray 1/10 nm mathematically as follows: 1 nm Ultraviolet rays 10 nm Velocity (v) = Wavelength (λ) × Frequency (f) 100 nm Visible light 1000 nm Infrared rays 10,000 nm The more energy the wave has, the greater will be its fre- 100,000 nm Nonionizing 1/1000 m quency and the shorter its wavelength. We can therefore Radar 1/100 m use either wavelength or frequency to describe the energy 1/10 m of the wave. In radiologic science, wavelength is more often 1m Television 10 m used to describe the energy of the x-ray beam. The average Radio 100 m wavelength of a diagnostic x-ray beam is approximately 0.1 1 nanometer = 10-9 meters nanometer (nm), which is 10−10 (0.00000000001) m, or approximately one-billionth of 1 inch. Fig. 1.8 Electromagnetic spectrum. The wavelength of electromagnetic radiation varies from exceedingly short (shorter than that of diagnostic more harmful effects than light. Unlike light, x-rays can- x-rays) to very long (more than 5 miles). This range of ener- not be refracted by a lens. The x-ray beam diverges into gies is known as the electromagnetic spectrum; it includes space from its source until it is absorbed by matter. x-rays, gamma rays, visible light, microwaves, and radio Unlike light, x-rays cannot be detected by the human waves (Fig. 1.8). Radiation with a wavelength shorter than senses. This fact may seem obvious, but it is important to 1 nm (10−9 m) is said to be ionizing radiation because it consider. If x-rays could be seen, felt, or heard, we would has sufficient energy to remove an electron from an atomic have an increased awareness of their presence and radia- orbit. X-rays are one type of ionizing radiation. tion safety might be much simpler. Because they are unde- The smallest possible unit of electromagnetic energy tectable, however, safety requires that you learn to know (analogous to the atom with respect to matter) is the pho- when and where x-rays are present without being able to ton, which can be thought of as a minute “bullet” of energy. perceive them. Photons occur in groups or bundles called quanta (singu- X-rays can penetrate matter that is opaque to light. This lar, quantum). penetration is differential, depending on the density and thickness of the matter. For example, x-rays penetrate air readily. There is less penetration of fat or oil, even less of The smallest possible unit of electromagnetic ener- water, which is approximately the same density as muscle gy is the photon, which can be thought of as a minute tissue, and still less of bone. The effect on the x-ray beam “bullet” of energy. caused by passing through matter is called attenuation. X-rays that have passed through the body are referred to as remnant radiation or exit radiation. Attenuation results in the absorption of a portion of the radiation and produces a CHARACTERISTICS OF RADIATION pattern of intensity in the remnant radiation. This pattern Because x-rays and visible light are both forms of elec- reflects the absorption characteristics of the body through tromagnetic energy, they share some similar charac- which it has passed; this pattern is recorded to form the teristics. Both travel in straight lines, and both have a image. photographic effect. It is also important to remember X-rays cause certain crystals to fluoresce, giving off because accidental exposure can occur when image light when they are exposed. Among crystals that respond receptors are placed near x-ray sources. in this way are barium platinocyanide, barium lead sulfate, Both x-rays and light have a biologic effect; that is, calcium tungstate, and several salts consisting of rare earth they can cause changes in living organisms. Because of elements. These crystals are used to convert the x-ray pat- their greater energy, x-rays are capable of producing tern into a visible image that can be viewed directly, as in 8 PART 1 Introduction to Radiography fluoroscopy, or recorded on photographic film. The use The x-ray beam size is restricted by the size of the port, of fluorescent intensifying screens to expose radiographs the opening in the tube housing. Attached to the housing greatly reduced the quantity of radiation needed to produce is the collimator, a device that enables the radiographer images compared with that required for direct exposure of to further control the size of the radiation field. film. The combination of film and intensifying screens was the conventional IR for decades, but is now largely replaced by filmless technology that produces digital images. This SCATTER RADIATION topic is explored further in Chapter 2. When the primary x-ray beam is attenuated by any solid matter, such as the patient or the x-ray table, a portion of its energy is absorbed. This results in the production of THE PRIMARY X-RAY BEAM scatter radiation (Fig. 1.10). Scatter radiation generally has X-rays are formed within a very small area on the target less energy than the primary x-ray beam, but it is not as (anode) called a focal spot. The actual size of the largest easily controlled. It emanates from the source (usually the focal spot is no more than a few millimeters in diameter. patient) in all directions, causing unwanted exposure to the From the focal spot, the x-rays diverge into space, form- IR and posing a radiation hazard to anyone in the room. ing the cone-shaped primary x-ray beam (Fig. 1.9). The cross section of the x-ray beam at the point where it is Scatter radiation is the principal source of occupa- used is called the radiation field. A photon in the center tional exposure to radiographers. of the primary beam and perpendicular to the long axis of the x-ray tube is called the central ray. The characteristics of primary radiation, scatter radi- ation, and remnant radiation are summarized for com- parison in Table 1.1. Radiation source Primary x-ray X-ray beam beam Central ray Scatter radiation Radiation field Remnant radiation Image receptor Fig. 1.9 A cross section of the x-ray beam is called the radiation Fig. 1.10 Scatter radiation forms when the primary x-ray beam field; an imaginary perpendicular ray at its center is called the interacts with matter. (From Bushong SC: Radiologic science central ray. for technologists, ed 11, St Louis, 2017, Elsevier)  CHAPTER 1 Introduction to Radiography 9 to a tiny focal spot on the target. The small filament RADIOGRAPHIC EQUIPMENT and focal spot provide finer image detail when a rela- X-ray rooms vary in design, depending on their pur- tively small exposure is appropriate—for example, when pose. For example, a room dedicated to upright chest imaging a small body part such as a toe or wrist. radiography might not have an x-ray table because the The large filament provides more electrons and is patients in this room would be standing for their exam- aimed at a somewhat larger target area. The combina- inations, not lying down. A room designed for gastro- tion of large filament and large focal spot is used when intestinal examinations would be equipped for both a large exposure is required, such as for radiographs of radiography and fluoroscopy. This dual-purpose equip- the lumbar spine or the abdomen, because the greater ment is described later in this chapter. A typical room number of electrons meets the exposure require- designed for general radiography (Fig. 1.11) is suitable ments of the larger body part and the large focal spot for many different types of x-ray examinations. In a hos- can better handle the resulting heat at the anode. The pital setting, the room will be fairly large, perhaps 18 × anode is disk-shaped and rotates during the exposure 20 feet in size, with wide doors to accommodate hos- (Fig. 1.14), distributing the anode heat over a larger pital beds and stretchers. Physical features will include area than the focal spot itself and increasing the heat the radiographic table, the x-ray tube and its support capacity of the tube. It is the rotation of the anode that system, an upright IR cabinet against one wall, and a causes the whirring sound heard just before and after shielded control booth that contains the control console. the exposure. The X-Ray Tube X-Ray Tube Housing The x-ray tube is the source of the radiation. Modern The x-ray tube is located inside a protective barrel-shaped multipurpose x-ray tubes (Fig. 1.12) are dual focus housing (Fig. 1.15). The housing incorporates shielding tubes. Their cathode assemblies contain two filaments, that absorbs radiation that is not a part of the useful x-ray one large and one small (Fig. 1.13). Each is situated in a beam. The housing protects and insulates the x-ray tube focusing cup that directs its electrons toward the same while providing a base for the attachments that allow the general area on the target portion of the anode. When radiographer to manipulate the x-ray tube and to control the small filament is activated, its electrons are directed the size and shape of the x-ray beam. TABLE 1.1 X-Ray Beam Attenuation Type of Radiation Definition Travel Pattern Energy Level Primary radiation The x-ray beam that It originates at the tube Its energy is controlled leaves the tube and is target and expands in a by the kilovoltage not attenuated, except cone-shaped beam that is setting. by air. perpendicular to the axis of the tube. Its direction and location are predictable and controllable. Scatter radiation Radiation scattered or It travels in all directions Generally, it has less created as a result of the from the scattering energy than the primary attenuation of the primary medium and is difficult beam. x-ray beam by matter. to control. Remnant (exit) What remains of the Its travel pattern is a Because the pattern of densities radiation primary beam after it continuation of the in the matter results in differ- has been attenuated pattern of the primary ential absorption, this pattern is by matter. beam. inherent in remnant radiation. The pattern of intensity of remnant radiation creates the radiographic image. 10 PART 1 Introduction to Radiography X-Ray Tube Support The tube housing can either be attached to a ceil- ing-mounted tube hanger or mounted on a tube stand. Both types of mountings provide support and mobility for the tube. A tube hanger (Fig. 1.16) is suspended from the ceiling on a system of tracks to allow positioning of the tube at locations throughout the room. This ceil- ing mount is useful when positioning the tube over a stretcher or when moving the tube for use in different locations. A tube stand is a vertical support with a hori- zontal arm that supports the tube over the radiographic table. The tube stand rolls along a track that is secured to the floor (and sometimes also the ceiling or wall), per- Fig. 1.11 A typical room designed for general radiography. mitting horizontal motion. A Glass envelope Rotor Molybdenum disk Cathode Focal B track Fig. 1.12 A, Modern rotating-anode x-ray tube. B, Diagram of typical x-ray rube with key parts labeled.  CHAPTER 1 Introduction to Radiography 11 A system of electric locks holds the tube support in R  otation—allows the entire tube support to turn position. The control system for all, or most, of these on its axis, changing the direction in which the locks is an attachment on the front of the tube housing. tube arm is extended To move the tube in any direction, the locking device Roll (tilt, angle)—permits angulation of the must be released. Moving the tube without first releasing tube along the longitudinal axis and allows the the lock can damage the lock, making it impossible to tube to be aimed at the wall rather than the secure the tube in position. table A detent is a special mechanism that tends to stop Do not attempt to move the x-ray tube without first a moving part in a specific location. Detents are built releasing the appropriate lock. into tube supports to facilitate placement at standard locations. For example, a vertical detent will indicate when the distance from tube to IR is 40 or 48 inches, Typical tube motions (Fig. 1.17) include the follow- common standard distances. Other detents provide ing: “stops” when the transverse tube position is centered to Longitudinal—along the long axis of the table the table and when the tilt motion is such that the cen- Transverse—across the table, at right angles to tral ray is perpendicular to the table or to the upright longitudinal IR cabinet. Vertical—up and down, increasing or decreasing the distance between the tube and the table Collimator Another attachment to the tube housing is the collimator, a boxlike device mounted beneath the port. Collimators allow the radiographer to vary the size of the radiation field and to indicate with a light beam the size, location, and center of the field (Fig. 1.18) There is usually also a centering light that helps to align the IR. Controls on the front of the collimator allow the radiographer to adjust the size of each dimension of the radiation field. The col- limator has a scale that indicates each dimension of the field at specific source-image distances. A timer controls the collimator light, turning it off after a certain length Fig. 1.13 Dual focus x-ray tube has focusing cups with large and of time—usually 15 to 30 seconds. This helps to avoid small filaments. (From Long B, Frank E, Ehrlich RA: Radiography accidental overheating of the unit by prolonged use of essentials for limited practice, ed 5, St Louis, 2017, Elsevier.) its high-intensity light. Anode stem Focal track Focal A B spot Fig. 1.14 Rotating anode. Electrons strike the anode in the tiny focal spot area, but the heat is spread around the entire focal track of the spinning anode face. A, Side view. B, View from cathode. (From Long B, Frank E, Ehrlich RA: Radiography essentials for limited practice, 5th ed, St Louis, 2017, Elsevier.) 12 PART 1 Introduction to Radiography detent position after lowering it for patient access. Not all tables are capable of vertical motion. A tilting table (Fig. 1.20) also uses a hydraulic motor to change position. In this case, the table turns on a central axis to attain a vertical position; this allows the patient to be placed in a horizontal or vertical position or at any angle in between. The table can also tilt in the opposite direction, allowing the patient’s head to be lowered at least 15 degrees into the Trendelenburg position. A detent stops the table in the horizontal position. Tilting is an essential feature of fluoroscopic tables and may also be a feature of a radio- graphic unit. Special attachments for the tilting table include a foot- Fig. 1.15 The tube housing (arrow) shields the tube and pro- vides mounting for tube motion controls and collimator. board and a shoulder guard system to provide safety for the patient when tilting the table (Fig. 1.21). Pay particu- lar attention to the attachment mechanisms so that you will be able to apply these devices correctly when needed. Before tilting a patient on the table, always test the footboard and shoulder guards to be certain that they are securely attached. The motor that tilts the table is powerful and can overcome the resistance of obstacles placed in the way. Many step stools and other pieces of movable equip- ment have been damaged because they were under the end of the table and out of view when the table motor was activated. Such a collision can also damage the Fig. 1.16 Ceiling-mounted tube support. table motor. Radiographic Table The radiographic table (Fig. 1.19) is a specialized unit that Be certain that the spaces under the head and foot of the table are clear before activating the tilt motor. is more than just a support for the patient. Although the table is usually secured to the floor, it may be capable of several types of motion: vertical, tilt, and “floating” table- A floating tabletop allows the top of the table to move top. independently of the remainder of the table for ease in For vertical table motion, a hydraulic motor, activated aligning the patient to the x-ray tube and the IR. This by a hand, foot, or knee switch, raises or lowers the height motion may involve a mechanical release, allowing the of the table. This motion allows the lowering of the table radiographer to shift the position of the tabletop man- so that the patient can sit on it easily and permits the table ually, or it may be power-assisted, activated by a small to rise to a comfortable working height for the radiogra- control pad with directional switches. Power-assisted pher. Adjustments to exact stretcher height can be made movement is usual for fluoroscopic tables. to facilitate patient transfers. There will be a detent at the standard height for routine radiography. This standard Grids and Buckys table position corresponds to indicated distances from the You will recall from an earlier part of this chapter that x-ray tube. Because it is important that standard tube–IR when primary radiation encounters matter, such as distances be used, it is necessary to return the table to the the patient or the x-ray table, the resulting interaction  CHAPTER 1 Introduction to Radiography 13 Vertical verse Trans Lo ng itud ina l A B C Fig. 1.17 Tube motions. A, Longitudinal, transverse, and vertical. B, Rotation. C, Angulation. (From Long B, Frank E, Ehrlich RA: Radiography essentials for limited practice, ed 5, St Louis, 2017, Elsevier.) Fig. 1.19 Radiographic table. produces scatter radiation. Most of the scatter pro- duced during an exposure originates within the patient. This scatter radiation causes fog on the radiographic image, a generalized exposure that compromises the visibility of the anatomic structures. Grids and buckys Fig. 1.18 Collimator light defines the radiation field and aids in are devices to prevent scatter radiation from reaching the alignment of the bucky tray. the IR. 14 PART 1 Introduction to Radiography units, the grid moves during the exposure. The purpose Grids and buckys prevent scatter radiation from of moving the grid is to blur the image of the thin lead reaching the IR and producing fog that degrades the image. strips so that they are not visible on the radiograph. When the table has a floating tabletop, the bucky mech- anism and IR tray do not move with the tabletop. A bucky is usually located beneath the table surface; it is a moving grid device that incorporates a tray to hold the IR (Fig. 1.22). The entire unit can be moved along the length of the table and locked into position where desired. The grid that is incorporated into the bucky device is situated between the tabletop and the IR (Fig. 1.23). It is a plate made of tissue-thin lead strips, mounted on edge, with radiolucent interspacing mate- rial (Fig. 1.24). The strips must be carefully aligned to the path of the primary x-ray beam, so precise align- ment of the x-ray tube is essential. In most radiographic A A B B Fig. 1.21 Table attachments must be secured carefully for patient Fig. 1.20 The hydraulic fluoroscopic table tilts to change the safety before tilting the table. A, Footboard. B, Shoulder guard. patient’s position. A, Semi-upright position. B, Trendelenburg position.  CHAPTER 1 Introduction to Radiography 15 Stationary grids that do not move during the expo- Upright Image Receptor Units sure serve the same purpose as a bucky. A grid can also An upright device holds the IR in position for upright be incorporated into a device called a grid cap, which radiography (Fig. 1.25). It is adjustable in height and can is a grid mounted in a frame that can be attached to the incorporate a grid. Even if the table tilts to the upright posi- front of an IR for mobile radiography and other special tion, it is common to have a separate upright unit for some applications. examinations, such as those of the cervical spine and the Grids or buckys are generally used only for body chest. When the patient is sitting or standing at the upright parts that measure more than 10 to 12 cm in thick- device, the tube is angled to direct the x-ray beam toward ness. (The average adult’s neck or knee measures 12 the IR. The distance may be adjusted to 40, 48, or 72 inches, cm.) When a grid is not needed, the IR is placed on depending on the requirements of the procedure. the tabletop. Transformer Grids or buckys are generally used only for body Cables from the tube housing connect the x-ray tube parts that measure more than 10 to 12 cm in thickness. to the transformer, which provides the high voltage necessary for x-ray production. Some transformers look like a large box or cabinet, which may be located within the x-ray room. Newer transformer designs are much smaller and may be incorporated into the control console. Control Console The control console, located in the control booth, is the access point for the radiographer to determine the expo- sure factors and to initiate the exposure (Fig. 1.26). Radio- graphic control consoles have buttons, switches, dials, or digital readouts for some or all of the following functions: Off/On—controls the power to the control panel mA—allows the operator to set the milliamper- age, the rate at which the x-rays are produced; Fig. 1.22 The bucky tray holds the image receptor within the x-ray table. determines the focal spot size Grid position under tabletop Bucky tray Cassette Fig. 1.23 The bucky device for scatter radiation control incorporates a tray for the image receptor and is mounted under the tabletop. Note that the lead strips are parallel to the long axis of the table. (From Long B, Frank E, Ehrlich RA: Radiography essentials for limited practice, ed 5, St Louis, 2017, Elsevier.) 16 PART 1 Introduction to Radiography A Fig. 1.24 Lead strips in the grid absorb scatter radiation emit- ted from the patient; remnant radiation passes through the grid and exposes the image receptor. (From Bushong SC: Radio- logic science for technologists, ed 11, St Louis, 2017, Elsevier.) B Fig. 1.26 Examples of x-ray control consoles. (A) Simple com- puterized radiographic controls. (B) Controls for filmless radiog- raphy with digital fluoroscopy. k Vp—controls the kilovoltage, and thereby the wave- length and penetrating power, of the x-ray beam Timer—controls the duration of the exposure mAs—some units have an mAs control instead of mA and time settings; the mAs (the product of mA and time) determines the total quantity of radiation produced during an exposure Bucky—activates the motor control of the bucky device so that the grid will move during the ­exposure Automatic exposure controls—special settings available on units that allow termination of expo- sure when a certain quantity of radiation has reached the IR Meters or digital readouts to indicate the status of the settings Prep (ready or rotor) switch—prepares the tube for exposure and must be continuously activated Fig. 1.25 Upright image receptor device. until exposure is complete  CHAPTER 1 Introduction to Radiography 17 E xposure switch—initiates the exposure and must be continuously activated until the exposure is complete Accessories—other controls may also be present, depending on the equipment and its specific features FLUOROSCOPY Whereas routine radiography produces still or static images, fluoroscopy permits the viewing of dynamic images, or x-ray images in motion. Fluoroscopy is usu- ally performed by radiologists with the assistance of radiographers. Fluoroscopic procedures are a routine aspect of every radiographer’s clinical education. Fluoroscopic Equipment A fluoroscope is an x-ray machine designed for direct viewing of the x-ray image. This equipment permits the radiologist to view and record radiographic images in Fig. 1.27 Typical radiographic/fluoroscopic unit. The tower (arrow) contains the image intensifier. motion in real time. Early fluoroscopes consisted simply of an x-ray tube mounted under the x-ray table and a flu- of photomultiplier tubes that brighten and enhance the orescent screen mounted over the patient. The physician image formerly seen by looking directly at the fluoro- watched the radiographic image on the screen while turn- scopic screen. The enhanced image is digitized or pho- ing the patient into the desired positions to view various tographed by a video camera to provide direct viewing anatomic areas. Because the fluoroscopic image was dim, on a video monitor. A computer or video recorder can dark adaptation was required and the procedure was per- be used to make a record of the entire study. The fluoro- formed in a darkroom. scope and spot film device can be moved out of the way when the table is used for radiography. A fluoroscope is an x-ray machine designed for direct The control console of an R/F unit is more com- viewing of the x-ray image. This equipment permits the plex than that of a basic radiography unit. There must radiologist to view and record x-ray images in motion in be separate mA and kVp settings for the control of the real time. radiographic (overhead) and fluoroscopic (under-table) tubes, and special settings for spot film radiography. Modern equipment is far more sophisticated. Most fluo- The radiologist activates the fluoroscope intermittently roscopic units are properly called radiographic/fluoroscopic during an examination. When the fluoroscope is acti- (R/F) units because they can be used for both radiography vated so that x-rays are being produced, a timer on the and fluoroscopy. This is convenient because most fluoro- control advances and an alarm sounds after a preset scopic examinations also have a radiographic component. period, usually 5 minutes. This warning is a reminder to “Spot films” are taken during fluoroscopy to record reduce fluoroscopy time, and thus minimizes the radia- the image as seen on the fluoroscope. These are static tion exposure received by all involved. images taken by the radiologist that use the under-table fluoroscopic tube. After the fluoroscopic portion of the study is completed, additional images may be taken by When the fluoroscope is activated so that x-rays are be- the radiographer, using the spot images. ing produced, a timer on the control advances and an The radiation required for a fluoroscopic study has alarm sounds after a preset period of exposure, usually been greatly reduced by the use of the image intensifier. 5 minutes. This warning is a reminder to reduce fluoros- This electronic device is in the form of a tower that fits copy time, and thus minimizes the radiation exposure received by all involved. over the fluoroscopic screen (Fig. 1.27). Inside is a series 18 PART 1 Introduction to Radiography Radiographer’s Duties in Fluoroscopic P  reparing the equipment for fluoroscopy, includ- Examinations ing attaching the footboard and shoulder guard. Entering patient data into the computer image For a fluoroscopic examination, the duties of the radiog- rapher can include the following: acquisition Taking the patient’s history, including informa- Preparing contrast agents as needed Assisting the radiologist as needed, which can involve tion on the success of dietary or bowel cleansing preparation (see Chapter 18). helping the patient assume various positions; assisting Filling out necessary preprocedural paperwork the patient and/or the radiologist with the contrast such as Contrast Media Consent, Time-Out, and medium; or electronically handling digital images Taking follow-up radiographs, if applicable Patient Education forms Assisting the patient to undress and don a Providing postprocedural care and instructions to gown the patient Explaining the procedure to the patient Your orientation to the fluoroscopy suite may be to Taking and processing any required preliminary observe or assist with fluoroscopic studies of the gastro- images intestinal tract. These x-ray examinations of the stomach Setting the control panel correctly for fluoroscopy and/or the bowel are described in detail in Chapter 18. and spot film radiography Other examinations involving fluoroscopy are discussed Positioning the patient for the start of the proce- in Chapters 19 through 22. dure SUMMARY W.C. Roentgen discovered x-rays in Würzburg, Ger- E lectromagnetic sine wave characteristics include many, in 1895, while experimenting with a Crookes amplitude, wavelength, frequency, and velocity. The tube. wavelength multiplied by the frequency equals the Other x-ray pioneers include the following: velocity (the speed of light). Edison, who experimented with many phosphors The characteristics of x-rays are similar to those of Snook, who invented the interrupterless trans- light except that x-rays cannot be refracted by a lens, former are not detectable by the human senses, and are capa- Eastman, who made the first x-ray film ble of ionizing matter. Coolidge, who invented the hot cathode x-ray The primary x-ray beam is that which exits the x-ray tube tube and is unattenuated except by air; its location R adiography education began in hospitals as phy- and direction are predictable and controllable. sicians trained their assistants to help with x-ray Scatter radiation is that created by the interaction examinations. Hospital-based programs still between radiation and matter; it travels in all directions exist, but most radiography education today takes from the scattering medium and is difficult to control. place in college programs affiliated with medical ­ Remnant radiation is what remains of the primary centers. beam after it has been attenuated by the patient; its pat- A simple x-ray tube contains a vacuum, a filament tern of intensity represents the pattern of absorption to provide a source of free electrons, and a target at and is the pattern that creates the radiographic image. which the electrons are directed. When a high volt- Ceiling mounts or tube stands support x-ray tubes age is applied to the tube, the free electrons collide and provide a means to secure them in position. Tube with the target, decelerate suddenly, and produce motions include horizontal, vertical, angulation, and both heat and x-rays. rotational movements. X-rays are a form of electromagnetic energy that A collimator is a device attached to the x-ray tube occurs in units called photons. Photons occur in housing for the purpose of controlling the field size; bundles called quanta. X-ray energy occurs in a sine it has a light that indicates the location of the field, waveform, changing the field through which it passes the location of the central ray, and the alignment of both magnetically and electrically. the x-ray beam to the IR.  CHAPTER 1 Introduction to Radiography 19 G rids and buckys are devices placed between the typical of all control consoles and should be recog- patient and the IR to prevent scatter radiation from nized and understood by radiographers. degrading the image; they are located beneath the Fluoroscopes are special x-ray machines that permit top of the radiographic table, in upright cabinets, viewing of the x-ray image in motion in real time. and in grid caps for mobile radiography. Radiographic units are often combined with fluoro- The control console is the access point for the radiog- scopes, and fluoroscopic examinations often have a rapher to control the exposure settings and initiate radiographic component. the x-ray exposure. Certain settings and readings are REVIEW QUESTIONS 1. X -rays were discovered in 1895 in: C. Microwaves A. the United States D. Ultraviolet light B. England 8. Which of the following is not an accurate state- C. Germany ment regarding the characteristics of x-rays? D. China A. They can penetrate matter that is impenetrable to 2. The inventor of the hot cathode x-ray tube was: light. A. Crookes B. They can be refracted by a lens. B. Roentgen C. They have an exposure effect on photographic C. Coolidge emulsions. D. Edison D. They cannot be detected by the human senses. 3. The majority of radiography education programs are 9. The characteristic most often used to describe the based in/on: energy of an x-ray beam is its: A. colleges A. velocity B. clinics B. space charge C. hospitals C. wavelength D. the Internet D. amplitude 4. A cassette containing a photostimulable phosphor 10. An x-ray beam that has been attenuated by matter is plate is one form of: called: A. fluoroscope A. remnant radiation B. image receptor B. primary radiation C. grid device C. secondary radiation D. transformer D. scatter radiation 5. Which of the following is not a basic requirement 11. A device used to indicate the location of the radia- for the production of x-rays? tion field and to control its size is called a: A. A vacuum A. grid B. A source of electrons B. collimator C. A photostimulable phosphor C. transformer D. A target D. control console 6. When fast-moving electrons collide with the target 12. An x-ray machine that permits viewing of the x-ray of an x-ray tube, the kinetic energy of their motion image in motion in real time is called a: is converted into x-rays and: A. control console A. a space charge B. fluoroscope B. heat C. collimator C. potential difference (voltage) D. bucky D. scatter radiation 7. Of the following types of electromagnetic energy, Answers can be found in the Answer Key on pages which has the shortest wavelength? ________. A. Radio waves B. Gamma rays 20 PART 1 Introduction to Radiography CRITICAL THINKING EXERCISES 1. C rookes and others worked with Crookes tubes before 3. L ist characteristics of x-rays that are similar to those Roentgen did. Why didn’t one of them discover x-rays? of light and those that are different. Which character- What important characteristics of x-rays did Roentgen istics of x-rays are useful in radiography? display during and after the discovery? 4. Compare and contrast radiography and fluoroscopy. 2. When did your radiography program begin? How    does its history correspond with the history of radi- ography education in this chapter?  2 Image Quality Factors OBJECTIVES At the conclusion of this chapter, the student will be able D efine OID and state its significance with respect to to: radiographic quality. Define milliamperage and state its significance with Explain the effect of an increase in source-image respect to radiographic exposure. distance on both optical density and image detail. Explain the significance of exposure time with List three types of image receptor system and respect to optical density. describe each. Explain the significance of mAs with respect to List the two types of image distortion and state the image quality. cause of each. Describe the effects of an increase in kVp with Differentiate between images that exhibit high respect to both the x-ray beam and the radiographic contrast and those with low contrast. image. List factors that influence image contrast. State the content and purpose of an x-ray technique List possible causes of poor image detail. chart. List three digital pitfalls and explain how they should be avoided. CHAPTER OUTLINE Factors of Radiographic Exposure, 22 Digital Radiography, 25 Exposure Time, 22 Image Quality, 26 Milliamperage, 22 Optical Density, 26 Kilovoltage, 23 Image Contrast, 26 Distance, 23 Image Detail, 27 Technique Charts, 24 Distortion, 27 Image Receptor Systems, 24 Digital Pitfalls, 29 Computed Radiography, 25 Summary, 32 KEY TERMS annotation exposure time (T) automatic exposure control (AEC) image contrast computed radiography (CR) image detail cropping inverse-square law digital radiography (DR) kilovoltage (kV or kVp) distortion milliamperage (mA) electronic masking milliampere-seconds (mAs) exposure index (EI) number object-image distance (OID) 21 22 PART 1 Introduction to Radiography optical density (OD) shuttering picture archiving and communication system (PACS) source-image distance (SID) postprocessing    As radiographers are responsible for controlling the Exposure time is a measure of how long the expo- quality of the images they produce, it is important sure will continue and is measured in units of seconds, to understand the terms used to discuss image qual- fractions of seconds, or milliseconds. When all other ity and the factors that can be changed to influence factors are equal, a longer exposure time will produce the appearance of the image. This chapter introduces more exposure and a darker radiographic image; a image quality factors and the language you will need shorter exposure time will result in less radiation expo- to learn more about this important aspect of radiog- sure and a lighter image. raphy. Most x-ray table and upright IR units have automatic FACTORS OF RADIOGRAPHIC EXPOSURE timers calle