Chapter 25: Digital Imaging

Chapter 25

1. Digital Imaging
Chapter 25

2. LEARNING OBJECTIVES
LESSON 25.1: DIGITAL IMAGING
1.Define the key terms associated with digital imaging.
2.Describe the purpose and use of digital imaging.
3.Discuss the fundamentals of digital imaging.
4.Describe radiation exposure in digital imaging.
5.List and describe the equipment used in digital imaging.
6.List and describe the two types of digital imaging.

3. LEARNING OBJECTIVES
LESSON 25.1: DIGITAL IMAGING (CONT.)
7.Describe the patient and equipment preparations required for
digital imaging.
8.List and discuss the advantages and disadvantages of digital
imaging.

4. INTRODUCTION
•Advances in technology have produced a significant
impact in the profession of dentistry as well as dental
imagine
•Digital imaging was introduced to dentistry in 1987
•Relatively new
•Digital imaging is a dependable and versatile technique
that provides clean, detailed images and enhance
interpretation and diagnoses
•An expensive investment for a dental office

5. BASIC CONCEPTS
•Digital imaging is a technique used to record
radiographic images
•No film or processing chemistry is used
•Uses an electronic sensor and computerized
imaging system that produces x-ray images almost
instantly on a computer monitor

6. TERMINOLOGY
•Analog image: Radiographic image produced by conventional
film.
•Charge-coupled device (CCD): Solid-state silicon chip detector
that converts light or x-ray photons into an electrical charge or
signal.
•Digital imaging: Filmless imaging system.
•Digital image: An image composed of pixels that can be stored in
a computer.
•Digital subtraction: One feature of digital imaging; a method of
reversing the gray scale as an image is viewed
•Digitize: In digital imaging, to convert an image into a digital form
that can be processed by a computer.

7. TERMINOLOGY (CONT.)
•Direct digital imaging: Method of obtaining a digital image, in which
an intraoral sensor is exposed to x-radiation to capture a dental image
that can be viewed on a computer monitor.
•Indirect digital imaging: Method of obtaining a digital image, in which
a sensor is scanned following exposure to x-radiation and then
converted into a digital form that can be viewed on a computer monitor.
•Sensor: In digital imaging, a receptor that is used to capture an
extraoralor intraoral image
•Storage phosphor imaging: Method of obtaining a digital image in
which the image is recorded on a phosphor-coated plate and then
placed into an electronic processor.

8. PURPOSE AND USE
•To generate images that can be used in the diagnosis and assessment of
dental disease
•To detect lesions, diseases, and conditions of the teeth and surrounding
structures
•To confirm or classify suspected disease
•To localize lesions or foreign objects
•To provide information during dental procedures
•To evaluate growth and development
•To illustrate changes secondary to caries, periodontal disease, or trauma
•To document the condition of a patient at a specific point in time
•To aid in the development of a clinical treatment plan

9. FUNDAMENTALS
•Digital imaging
•A method of capturing an image using a sensor, breaking it into electronic
pieces, and presenting and storing the image using a computer
•Film-based images are produced hen x-ray photons strike an intra oral film;
knows as an analog image
•Digital imaging receives the analog information and converts it a digital image
•The digital image is an array of pixel elements
•An electronic charge is produced on the surface of the sensor; this electronic
signal is digitized; or converted into digital form
•Software is used to store the image electronically and it is displayed within
seconds to minutes
•Can by manipulated to enhance its appearance for interpretation and
diagnoses

11. RADIATION EXPOSURE
•Digital imaging requires less x-radiation exposure than film-
based imaging
•The typical sensor is more sensitive to x-rays than conventional
film.
•Exposure times are 50% to 90% less than that required for
conventional radiography
•Supports the ALARA principle and therefore the use of digital
imaging is recommended

12. EQUIPMENT
•Digital imaging requires the use of specialized equipment
•X-ray unit
•Conventional intraoral dental x-ray unit may be used in both
film-based and digital imaging; timer must be adapted
•Units that are made for digital imaging are modern in
appearance and feature adjustments for shorter exposure
times

13. EQUIPMENT CONTINUED…
•Sensor
•A small detector that is placed in the mouth of the patient and used to capture
the radiographic image
•Most manufacturers produce sensors similar in dimension to size 0, 1, 2, and 4
intraoral films
•Wired
•The imaging sensor is linked by a fiber optic cable to a computer.
•Wireless
•The imaging sensor is not linked by a cable.
•Most popular types of direct sensor technologies
•Charge-coupled device
•Complementary metal oxide semiconductor/active pixel sensor

14. CHARGE-COUPLED DEVICE (CCD)
•The most common image receptor used in dental digital imaging
•A solid-state detector that contains a silicon chip with an electronic circuit
embedded in it
•The silicon chip is what is sensitive to x-rays or light
•Not new technology, developed in the 1960’s, CCD technology is also used in
fax machines, home video cameras, microscopes, and telescopes.
•The electrons that make up the silicon CCD can be visualized as being divided
into an arrangement of blocks or picture elements known as pixels
•Pixel
•A small box or “well” into which the electrons produced by the x-ray exposure
are deposited
•A pixel is the digital equivalent of a silver crystal in conventional radiography
•It is also more structured in an ordered arrangement, unlike the random
arrangement of silver crystals

15. CHARGE-COUPLED DEVICE (CCD) (CONT.)
•The x-ray photons that come into contact with the CCD cause
electrons to be released from the silicon and produce a
corresponding electronic charge.
•Each pixel arrangement, contains an electronic charge
proportional to the number of electrons that reacted within the
well.
•Each pixel arrangement corresponds to a specific area on the
linked computer screen
•Electronic latent image is produced

16. COMPLEMENTARY METAL OXIDE SEMICONDUCTOR/
ACTIVE PIXEL SENSOR (CMOS/APS)
•One manufacturer uses a CMOS/APS sensor instead of a CCD.
•The chip is less expensive to produce and offers greater durability than
the CCD
•Advantages are that the individual pixels can be made smaller, the power
requirements are less, and the production cost of the chip is lower
•CMOS sensors can be connected to a computer using a low-power external
connection such as a USB.

17. CCD Sensor CMOS Sensor

18. COMPUTER
•Used to store the incoming electronic signal
•Converts the electronic signal from the sensor into a shade of
gray that is viewed on the computer monitor
•The computer digitizes, processes, and stores information received
from the sensor
•An image is recorded on a computer monitor in 0.5 to 120
seconds
•Has split screen and magnification capability
•Images may be stored permanently in the computer, printed on a
hard copy for the patient record, or transmitted electronically to
insurance companies or referring dental specialists.

22. TYPES OF DIGITAL IMAGING
•The difference between the methods lies in how the image is
obtained and in what size the receptor plates are available.
•Direct digital imaging
•Indirect digital imaging
•Scanning traditional images
•Storage phosphor imaging

23. DIRECT DIGITAL IMAGING
•Components include an intraoral
dental x-ray unit, a sensor, and a
computer with imaging software.
•A sensor is placed into the
mouth of the patient and
exposed.
•The sensor captures the image
and transmits it directlyto the
computer monitor.
•Within seconds of exposing the
sensor to radiation, an image
appears on the computer
screen.
•Software is used to enhance
and store the image.

24. INDIRECT DIGITAL IMAGING
•Components include a scanner and a computer.
•This concept is similar in theory to scanning an image, such as
a photograph, to a computer screen
•Extra step compared to direct digital imaging
•An existing x-ray film is digitized using a PSP plate
•The sensor is that put in the scanner
•The image is displayed on a computer monitor.

25. STORAGE PHOSPHOR IMAGING
•Also referred to as photo-stimulablephosphor imaging (PSP).
•A wireless digital imaging system
•A reusable imaging plate coated with phosphors is used instead
of a sensor with a fiber optic cable.
•The phosphor-coated plates are flexible and fit into the mouth.
•A high-speed scanner is used to convert the information into
electronic files.
•This type of digital imaging is less rapid than direct digital
imaging.
•It is recommended that the dental radiographer review the
mounted digital images and confirm the images with the clinical
findings while the patient is present in the dental chair.

26. PSP PLATE
•Following exposure, it converts x-ray energy into light
•The image remains on the reusable plate until it is erased after
the scanning process
•In past years, images were erased or cleared from the PSP
plates by exposure to viewboxlight for several minutes
•Currently, manufacturers use technology that scans and
retrieves the digital image, followed by the clearing step for
reuse of the PSP plate
•Can be damaged by bending or scratching

28. INTRAORAL SENSOR PREPARATION
•Each sensor is sealed and waterproofed.
•The sensor must be covered with a disposable barrier because
it cannot be sterilized.
•Rigid digital sensors, wired or wireless, must be covered with a
disposable barrier sleeve.
•The number and size of the sensor vary with different
manufacturers.
•Digital sensors cannot withstand heat sterilization

31. INTRAORAL SENSOR PLACEMENT
•The sensor is held in the mouth by bite-block attachments or
devices that aim the beam and sensor accurately.
•The paralleling technique is the preferred exposure method
•As with conventional intraoral film, the sensor is centered
over the area of interest.

34. ADVANTAGES OF DIGITAL IMAGING
•Superior gray-scale resolution
•Digital radiography uses up to 256 colors of gray compared with
the 16 to 25 shades of gray differentiated on a conventional film.
•The ability to manipulate the density and contrast of the image
without additional exposure to the patient is also an advantage.
•Reduced exposure to x-radiation
•The exposure of digital radiography is 50% to 80% less than that
required for conventional radiography.
•Increased speed of image viewing
•The images are able to be viewed instantaneously.

35. ADVANTAGES CONTINUED…
•Lower equipment and film cost
•No film cost or disposable necessary.
•Increased efficiency
•Requires less time
•Enhancement of diagnostic image
•Colorization, zoom, digital subtraction
•Effective patient education tool
•Eco-friendly tool
•A “greener” alternative because it doesn’t use any chemical
processing or generate any hazardous waste materials.

36. MAGNIFICATION

37. DIGITAL SUBTRACTION: THE GRAY-SCALE IS REVERSED TO THAT
RADIOLUCENT IMAGES APPEAR WHITE AND RAIOPAQUEIMAGES APPEAR
BLACK (ELIMINATES DISTRACTING BACKGROUND INFORMATION)

38. DISADVANTAGES OF DIGITAL IMAGING
•Initial setup costs
•Image quality
•Up for debate
•Sensor size and thickness
•Some digital x-ray sensors are thicker and less flexible than intraoral film.
•Infection control
•digital sensors cannot withstand heat sterilization, therefore sensors require
complete coverage with plastic sleeves that must be changed with each patient.
•Wear and tear
•Legal issues
•Because the original digital image can be enhanced, it is questionable whether
it can be used as evidence in court.

39. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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