Student Workbook for Digital Radiography in Practice [2 ed.] 0398094225, 9780398094225, 9780398078959, 9780398078966, 2009020443

Table of contents :
STUDENT WORKBOOK for DIGITAL RADIOGRAPHY IN PRACTICE
INTRODUCTION
How to Use this Student Workbook
1. IN-CLASS USE (RECOMMENDED):
2. HOMEWORK USE:
3. UNIT REVIEW AND SELF-TESTING:
CONTENTS
STUDENT WORKBOOK for DIGITAL RADIOGRAPHY IN PRACTICE
Chapter 1 NATURE OF THE DIGITAL RADIOGRAPH
Development of Digital Radiography
Nature of the Digital Image
Digitizing the Analog Image
Bit Depth, Dynamic Range, and Gray Scale
What is a Pixel?
Voxels, Dels and Pixels
Chapter 2 CREATING THE LATENT IMAGE
Overview of Variables
Creating Subject Contrast
Of Primary Interest for radiographic technique:
Role of Radiographic Technique in the Digital Age
Subject Contrast and Spatial Resolution (Sharpness)
Stages of Image Production
Chapter 3 QUALITIES OF THE DIGITAL RADIOGRAPH
Qualities of the Final Displayed Digital Image
Chapter 4 RADIOGRAPHIC TECHNIQUE FOR DIGITAL IMAGING
Understanding X-Ray Beam Penetration
Sensitivity of Digital Units to Subject Contrast
Subject Contrast and Exposure Latitude
Reducing Use of Grids
Sufficient Input Gray Scale
Effect of mAs and kVp on the Displayed Digital Image
Minimizing Patient Exposure with the 15% Rule
Benefits of High-kVp Radiography
Chapter 5 PREPROCESSING AND HISTOGRAM ANALYSIS
The Generic Steps of Digital Image Processing
Preprocessing
Histogram Analysis
Chapter 6 RESCALING (PROCESSING) THE DIGITAL RADIOGRAPH
Rescaling (Processing)
Chapter 7 DEFAULT POSTPROCESSING I: GRADATION PROCESSING
Digital Processing domains
Data Clipping
Dynamic Range Compression and Equalization
Chapter 8 DEFAULT POSTPROCESSING II: DETAIL PROCESSING
Understanding the Frequency Domain
Frequency Detail Processing
Spatial Detail Processing: Kernels as a Form of Band-Pass Processing
Preparation for Display
Chapter 9 MANIPULATING THE DIGITAL IMAGE:OPERATOR ADJUSTMENTS
Processing Algorithms
Windowing
Postprocessing Features
Chapter 10 MONITORING AND CONTROLLING EXPOSURE
Digital Speed Class
A Brief History of Exposure Indicators
The Deviation Index: Acceptable Parameters for Exposure
Limitations of the DI
Chapter 11 DIGITAL IMAGE ACQUISITION
Direct-Conversion DR Detectors
Indirect-Conversion DR Detectors
Computed Radiography (CR)
Background & Scatter Radiation
Characteristics of the Image Acquisition System
Sharpness of Digital Systems
Efficiency of Image Receptors
Digital Sampling and Aliasing
Other Digital Artifacts
Chapter 12 DISPLAYING THE DIGITAL IMAGE
The Liquid Crystal Display (LCD) Monitor
LCD Image Quality
Advantages of the LCD include:
Disadvantages of the LCD include:
The Nature of Display Pixels
Chapter 13 ARCHIVING PATIENT IMAGES AND INFORMATION
Picture Archiving and Communication Systems (PACS)
Medical Imaging Informatics
Chapter 14 DIGITAL FLUOROSCOPY
Image Recording from an Image Intensifier Tube
Charge-Coupled Devices (CCDs) have:
Dynamic Flat-Panel Detectors (DFPDs)
Optional Review: Direct DFP Detectors:
Optional Review: Indirect DFP Detectors:
Reducing Patient Dose
Chapter 15 QUALITY CONTROL FOR DIGITAL EQUIPMENT
Monitoring of Digital X-Ray Units
Monitoring of Electronic Image Display Systems

Citation preview

STUDENT WORKBOOK for

DIGITAL RADIOGRAPHY IN PRACTICE

Second Edition

STUDENT WORKBOOK for

DIGITAL RADIOGRAPHY IN PRACTICE

By

QUINN B. CARROLL, M.ED., R.T.

Published and Distributed Throughout the World by CHARLES C THOMAS • PUBLISHER, LTD. 2600 South First Street Springfield, Illinois 62704

This book is protected by copyright. No part of it may be reproduced in any manner without written permission from the publisher. All rights reserved.

© 2023 by CHARLES C THOMAS • PUBLISHER, LTD. ISBN 978-0-398-0398-09422-5 (comb/paper) ISBN 978-0-398-0398-09423-2 (ebook)

With THOMAS BOOKS careful attention is given to all details of manufacturing and design. It is the Publisher’s desire to present books that are satisfactory as to their physical qualities and artistic possibilities and appropriate for their particular use. THOMAS BOOKS will be true to those laws of quality that assure a good name and good will. Printed in the United States of America CM-C-1

Sapp, Marty, 1958Psychodynamic, affective, and behavioral theories to psychotherapy / by Marty Sapp. p. cm. Includes bibliographical references and index. ISBN 978-0-398-07895-9 (hard) -- ISBN 978-0-398-07896-6 (pbk.) 1. Psychodynamic psychotherapy. 2. Behavior therapy. 3. Cognitive therapy. 4. Psychotherapy. I. Title. RC489.P72S27 2009 616.89’14–dc22 2009020443

INTRODUCTION How to Use this Student Workbook The Workbook is entirely organized in a “fill-in-the-blank” format. The wording of each question almost exactly matches the lecture slide series Digital Radiography in Practice: Instructor PowerPoint™ Slides, and closely matches the progression of concepts in the textbook. The guiding philosophy is to provide immediate or short-term reinforcement of lecture and reading material by focusing on keywords. The Workbook should therefore be used on a daily basis, not as a self-test or review after whole units have been covered. Following are specific recommendations on how the student (and instructor) can most fully benefit from the Workbook and other ancillaries to Digital Radiography in Practice: 1. IN-CLASS USE (RECOMMENDED): This is the most recommended method, for use with the Digital Radiography in Practice Instructor PowerPoint Slides. The workbook and slides are designed to work in tandem with each other to actively engage the student in classroom learning while at the same time minimizing the amount of notetaking so that the student is allowed to concentrate on the lecture. The sequence and wording of questions almost exactly matches the slides, using a fill-in-the-blank approach connected to highlighted keywords on the slides. Instructors may elect to require this type of classroom participation and award points for completion of each unit. 2. HOMEWORK USE: If the Workbook is used as a reinforcement tool for homework, it is strongly recommended that the student answer the corresponding questions after reading each major section of a chapter. If you wait until completing an entire chapter, you may have trouble recalling the keywords elicited by each question and are more likely to confuse different concepts. To facilitate this, the major unit subheadings are included in the Workbook to match the textbook.

v

vi

Student Workbook for Digital Radiography in Practice 3. UNIT REVIEW AND SELF-TESTING: For the purposes of review, self-testing or preparation immediately prior to a test, Chapter Review Questions are provided at the end of each chapter in the textbook. Answer keys to these questions may be made available from your instructor. These are better suited to unit review and test preparation than the workbook material.

CONTENTS Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Chapter 1. NATURE OF THE DIGITAL RADIOGRAPH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. CREATING THE LATENT IMAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3. QUALITIES OF THE DIGITAL RADIOGRAPH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4. RADIOGRAPHIC TECHNIQUE FOR DIGITAL IMAGING . . . . . . . . . . . . . . . . . . . . . . . 23 5. PREPROCESSING AND HISTOGRAM ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 6. RESCALING (PROCESSING) THE DIGITAL RADIOGRAPH . . . . . . . . . . . . . . . . . . . . 38 7. DEFAULT POSTPROCESSING I: GRADATION PROCESSING . . . . . . . . . . . . . . . . . . 41 8. DEFAULT POSTPROCESSING II: DETAIL PROCESSING . . . . . . . . . . . . . . . . . . . . . 49 9. MANIPULATING THE DIGITAL IMAGE: OPERATOR ADJUSTMENTS . . . . . . . . . . . . 56 10. MONITORING AND CONTROLLING EXPOSURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 11. DIGITAL IMAGE ACQUISITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 12. DISPLAYING THE DIGITAL IMAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 13. ARCHIVING PATIENT IMAGES AND INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . 97 14. DIGITAL FLUOROSCOPY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 15. QUALITY CONTROL FOR DIGITAL EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

vii

STUDENT WORKBOOK for

DIGITAL RADIOGRAPHY IN PRACTICE

Chapter 1 NATURE OF THE DIGITAL RADIOGRAPH Development of Digital Radiography 1. 1979 – First application of digital tech: Digital _________________ unit. 2. 1982 – PACS and ____________________. 3. 1980s – Computed radiography (CR): Initially led to a ____________ of exposure. 4. 1996 – Digital radiography (DR): Advanced miniaturization of ______________ elements. 5. For CR, x-ray energy stored by a phosphor is emitted as ________ when stimulated by a laser beam. 6. For direct-conversion DR, x-ray energy is converted directly into stored _________ charge. 7. For indirect-conversion DR, a __________ first converts x-rays to light, then the light is converted into electrical charge. 8. Both direct-conversion and indirect-conversion systems use an _________ ___________ _________ of miniature detectors. 9. All CR and DR systems ultimately produce an ____________ image signal that is “fed” into a computer for processing.

3

4

Student Workbook for Digital Radiography in Practice

Nature of the Digital Image 10. All forms of digital image acquisition result in an image ___________. 11. Each ________ (picture element) is a single location designated by its column and row. 12. Each pixel is assigned a pixel value that will become its _____________ upon display. 13. Light images enter a camera, and x-rays enter a detector, in _____________ form. 14. To manipulate these images with a computer, they must first be converted into __________ form. 15. Analog: Continuous, and infinitely ______________, like the rails of a railroad track. 16. Digital: Discrete (separated into ____________ units), limited in subdivision and in scale, like the wooden ties of a railroad track. 17. Mathematically, digitization means ______________ all measurements to the nearest available digital value in a pre-set scale. 18. This rounding out makes digital information inherently less ______________ than analog information. 19. However, as long as the discrete units for a digital computer are smaller than the human eye can detect, digitizing the information improves ______________ accuracy. 20. This is why ___________ equipment is used to clock the winner of a race in the Olympics. 21. Rounding these input values (A) out to the nearest allowable discrete unit (B) so the computer can manage them is the function of an ___________-to___________ converter (ADC).

Nature of the Digital Radiograph

5

Digitizing the Analog Image 22. Three Steps to Digitizing the Image: 1. ________________ 2. ________________ 3. ________________ 23. Scanning: Image is divided up into a(n) ___________ of pixel cells. 24. Sampling: _______________ of light (or x-rays) is measured for each cell. 25. Scanning: In CR, the reader (processor) is set to scan the PSP plate in a predesignated number of _______, and samplings per ______. 26. In DR (and DF using CCDs), since the number of available pixels is the number of detector elements (dels) embedded in the image receptor plate, collimation of the x-ray beam is analogous to _____________. 27. Sampling Aperture: Opening through which ___________________ are taken. 28. DR: Sampling aperture determined by _____________ ______________ (dels) in the IR, which are square in shape and do not overlap adjacent samplings. 29. CR: Sampling aperture determined by reading __________ beam in CR reader, which is circular in shape, overlapping adjacent samplings that must then be “cropped.” 30. Quantizing: Discrete numerical value is assigned to each cell from a pre-designated _______ _________. Bit Depth, Dynamic Range, and Gray Scale 31. The terms bit depth and dynamic range are often used interchangeably by physicists and ______________________, which can be confusing for the student. For clarity, we will define them according to their most dominant use by experts.

6

Student Workbook for Digital Radiography in Practice

32. Bit Depth: The maximum range of pixel values a computer, display monitor, DR detector or other _________________ device can store, expressed as an exponent of base 2. “6 bits deep” = 2__ = 64 values “7 bits deep” = 2__ = 128 values “8 bits deep” = 28 = ____ values 33. The human eye can only discern about 2__ = ___ shades of gray or levels of brightness (a bit depth of __). 34. By not using the full range of bit depth of the computer, image processing ________ can be accelerated. 35. Dynamic range compression ________ off the extreme ends of the bit depth that are not needed to construct images, to save processing speed. This does not affect the displayed image. 36. Dynamic Range: The range of pixel values (from the bit depth) that the entire system makes _______________ to build up images. 37. Dynamic range is determined by _______________ as well as hardware. 38. Dynamic range is also the number of gray shades with which each _________ can be represented by the system. 39. Gray Scale: The range of pixel values actually present in a ______________ image. 40. Dynamic range is a ____________ of Bit Depth. Gray Scale is a subset of ____________ __________. 41. The greater the dynamic range, the ___________ the gray scale in the displayed image. 42. The longer the gray scale, the more ___________ can be represented in the image. 43. Excessive dynamic range _________ down image processing time. Insufficient dynamic range causes loss of image ___________.

Nature of the Digital Radiograph

7

44. Insufficient dynamic range prevents full post ________________ capabilities for the image: 45. We must be able to double or cut in half both the brightness and contrast of the image _____________ times without running out of dynamic range (data clipping). Complex features such as subtraction require still more. 46. The dynamic range of the remnant x-ray beam is approximately 2___. 47. The enhanced contrast resolution and processing features of CT and MRI systems require a ____-bit deep range. 48. Most digital imaging systems have dynamic ranges set at 28 = 256, 210 = 1024 (___ and ___), or 212 = 4048. What is a Pixel? 49. To a computer expert, a pixel has no particular shape or dimensions - It is a point location or ______________ which has been assigned a numerical value. 50. For displayed medical images, however, we define a pixel as the ____________ screen element which can represent all gray levels within the dynamic range of the imaging system. 51. These elements do have both a shape and an area _______. 52. For the radiographer, it is best to visualize pixels as generally __________ in shape and having a set size. 53. For an LCD display monitor, each hardware pixel is formed by the __________________ of two flat, transparent wires. Their dimensions are typically ____mm square. Voxels, Dels and Pixels 54. Attenuation Coefficient: The ________ or __________________ of original x-ray beam intensity absorbed by a particular tissue area in the patient. 55. The attenuation coefficient is determined by data acquired from 3-dimensional volumes of tissue within the patient called __________, an acronym for “______________-elements.”

8

Student Workbook for Digital Radiography in Practice

56. Each __________ in a radiographic image represents a voxel within the patient. 57. CT scanners can isolate a 3-D cube of tissue because they combine multiple ______________ from hundreds of angles. 58. Since DR and CR only use a single projection, the 3-D voxels sampled are in the shape of long, square tubes that pass from the __________ to the ________ of the patient. 59. To assign a gray level to a pixel in the final image, within each voxel the attenuation coefficients for various tissues must be ________________. 60. These attenuation coefficients must then be rounded out by the ADC to _____________ values from the system’s dynamic range. 61. The ultimate brightness of each pixel brought up on the display monitor is controlled by the amount of electrical voltage applied to it, which depends on the _______ ________ number stored in the computer for that pixel. 62. We might say that to form a digital radiographic image, data from the __________ in the patient are collected by the dels of the image receptor, then computer processed to become the __________ of the displayed image.

Chapter 2 CREATING THE LATENT IMAGE Overview of Variables 1. Projected Image: Information carried by the __________ x-ray beam to the image receptor, just prior to capture, after passing through the ___________ and ______. 2. List the three general types of radiographic variables for the projected image: __________ __________ __________ 3. Give two examples for each of the three general types of radiographic variables for the projected image: __________ __________ __________ __________ __________ __________ 4. X-ray absorption by air is ___________, less than ___% of the geometrical effect of the inverse square law. 5. Nearly ALL the effect of increased SID is due to the simple ___________ of the inverse square law. 6. Within the patient, _______________ interactions are primarily responsible for production of subject contrast in the remnant x-ray beam.

9

10

Student Workbook for Digital Radiography in Practice

7. Compton and Thompson interactions generate scatter radiation and are ___________ to subject contrast. 8. Attenuation: The ___________ absorption of x-rays by body tissues. 9. Attenuation is essential to production of an image ________ in the projected image carried by the remnant x-ray beam. 10. Without attenuation, rather than various shades of gray representing different tissues, a silhouette image would result with little ______________ in it. Creating Subject Contrast 11. Within the patient, photoelectric Interactions are primarily responsible for creating _________ shades. 12. Compton scatter: Responsible for ___% of all scatter radiation. 13. Thompson scatter produces only 2-3% of __________ radiation. 14. Characteristic interactions result only in low-energy ultraviolet rays that do not ________ the patient’s body. Of Primary Interest for radiographic technique: 15. Penetrating X-rays: Responsible for creating subject contrast (_______). 16. Photoelectric Interactions: Responsible for creating subject contrast (_______). 17. Compton Scatter: Mostly responsible for destroying subject contrast by adding “fog” to the latent image reaching the _________ ____________. 18. In the remnant x-ray beam, the useful signal is created by variations in the photoelectric/penetration _______ for different tissues of the body. 19. Compton Scatter carries no useful signal, but is a ___________-distributed form of noise that hinders visibility of the useful image. 20. A “hardened” x-ray beam with higher __________ energy can be created by either increasing the set kVp OR by adding filtration. 21. kVp is the primary controlling factor for x-ray beam ______________.

Creating the Latent Image

11

22. kVp is essential for adequate ______________ _______________. 23. As average x-ray beam energy is increased, ALL x-rays have increased ____________ of penetration. 24. Therefore, _____ types of interactions within the patient’s body decrease in probability. 25. However, as x-ray beam energy (keV) increases, the probability of photoelectric interactions ___________. 26. While …the probability of Compton interactions only decreases slightly (