Download Chapter 7 Body Systems

Extraoral and Digital
Radiography
Chapter 42
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Chapter 42
Lesson 42.1
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Learning Objectives
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Pronounce, define, and spell the Key Terms.
Describe the purpose and uses of panoramic
radiography.
Describe the equipment used in panoramic
radiography.
Describe the steps for patient positioning in
panoramic radiography.
Describe the errors caused during patient preparation
and positioning during panoramic radiography.
Discuss the advantages and disadvantages of
panoramic radiography.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Introduction
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Extraoral radiographs (outside the mouth) are taken
when large areas of the skull or jaw must be
examined or when a patient is unable to open his or
her mouth for film placement.
Extraoral radiographs do not show the details as well
as intraoral films do.
Extraoral radiographs are useful in evaluating large
areas of the skull and jaws but are not adequate for
detection of subtle changes such as the early stages
of dental caries or periodontal disease.
There are many types of extraoral radiographs. Some
types are used to view the entire skull, whereas other
types are focused on the maxilla and mandible.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Panoramic Radiography
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Panoramic radiographs show the entire dentition and
related structures on a single film.
Some types of panoramic units operate with the
patient in a seated position, and other types require
the patient to be in a standing position.
Regardless of the type of machine, you must follow
the manufacturer’s instructions carefully.
Because the images on a panoramic film are not as
clear or as well defined as the images on intraoral
films, bite-wing films are used to supplement a
panoramic film to detect dental caries or periapical
lesions.
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Basic Concepts
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In panoramic radiography the film and
tubehead rotate around the patient to
produce a series of individual images.
The term panorama means “an unobstructed
view of a region in any direction.” When the
series of images are combined onto a single
film, an overall view (panorama) of the
maxilla and mandible is created.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42–1 A, Panoramic radiograph. B, Panoramic anatomy.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-2 The film and x-ray tubehead move around the
patient in opposite directions in panoramic radiography.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
The Focal Trough
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The focal trough is an imaginary horseshoeshaped three-dimensional area.
This is a very important concept because
many errors in technique are caused by
improper positioning of the patient’s jaws
within the focal trough.
When the jaws are positioned within this
area, the radiograph will be clear.
When the jaws are positioned outside this
area, the images on the radiograph will
appear blurred or indistinct.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-3 Example of an image layer, or focal trough.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Components of the Panoramic Unit
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Panoramic x-ray tubehead
Head positioner
Exposure controls
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Fig. 42-4 Main components of a panoramic unit.
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The Head Positioner
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Each panoramic unit has a head positioner,
used to align the patient’s teeth as accurately
as possible.
Each head positioner consists of a chin rest,
notched bite-block, forehead rest, and lateral
head supports or guides.
Each panoramic unit is different, and the
operator must follow the manufacturer’s
instructions on how to position the patient in
the focal trough.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-5 The head positioner (notched bite-block, forehead rest,
and lateral head supports) is used to align the patient’s teeth
in the focal trough.
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Common Errors
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Patient-preparation errors
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Ghost images: A ghost image looks like the real
object, except that it appears on the opposite side
of the film.
Lead-apron artifact: If the lead apron is placed too
high, or if a lead apron with a thyroid collar is
used, a cone-shaped radiopaque artifact results.
Patient-seating errors
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Chin is too high.
Chin is too low.
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Fig. 42-6 Large hoop earrings (1) and ghost images (2).
The ghost image of the earring appears on the opposite side of the film and is
enlarged and laterally distorted.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-7 On a panoramic radiograph, a lead-apron artifact
appears as a large cone-shaped radiopacity obscuring the mandible.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-8 If the tongue is not placed on the roof of the mouth, a radiolucent
shadow will be superimposed over the apices of the maxillary teeth.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-9 Patient’s head is incorrectly positioned;
the chin is tipped upward.
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Fig. 42-10 “Reverse smile line” is seen on a panoramic
radiograph when the patient’s chin is tipped upward.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-11 Patient’s head is incorrectly positioned;
the chin is tipped downward.
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Positioning of the Teeth
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Posterior to focal trough
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If the patient’s anterior teeth are not positioned in
the groove on the bite-block and are either too far
back on the bite-block or posterior to the focal
trough, the anterior teeth appear “fat” and out of
focus on the radiograph.
Anterior to focal trough
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If the patient’s anterior teeth are not positioned in
the groove on the bite-block and are either too far
forward or anterior to the focal trough, the teeth
will appear “skinny” and out of focus.
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Fig. 42-14 This patient is biting too far back on the bite stick.
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Fig. 42-15 Anterior teeth appear widened and blurred on a panoramic radiograph
when the patient is positioned too far back on the bite-block.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-16 Anterior teeth appear narrowed and blurred on a panoramic radiograph
when the patient is positioned too far forward on the bite-block.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-17 If the patient is not standing erect, superimposition of the cervical spine
(arrows) may be seen on the center of the panoramic radiograph.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Positioning of the Spine
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If the patient’s spine is not straight,
the cervical spine will appear as a radiopaque
artifact in the center of the film and obscure
diagnostic information.
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Chapter 42
Lesson 42.2
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Learning Objectives
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Describe the purposes and uses of extraoral
radiography.
Describe the equipment used in extraoral radiography.
Identify the specific purpose of each of the extraoral
film projections.
Describe the purposes and uses of digital radiography.
Discuss the fundamentals of digital radiography.
List and describe the equipment used in digital
radiography.
List and discuss the advantages and disadvantages of
digital radiography.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Extraoral Radiography
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Extraoral radiographs provide images of larger areas
such as the skull and jaws.
In some instances an extraoral film may be
necessary in a handicapped patient who cannot open
his or her mouth for film placement or in a patient
with swelling or severe pain who is unable to tolerate
the placement of intraoral films.
Extraoral films are also useful in patients who are
uncooperative and may refuse to open their mouths.
Images seen on an extraoral films are not as clear or
as well defined as the images seen on intraoral
radiographs.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Equipment
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Extraoral radiographs may be taken with the
use of a standard intraoral x-ray machine.
Special head positioning and beam alignment
devices can be added to the standard x-ray
unit to aid patient positioning.
Panoramic x-ray units may also be fitted with
a special device known as a cephalostat.
The cephalostat includes a film holder and
head positioner that allow the operator to
easily position the patient.
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The Grid
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A grid is a device used to decrease film fog
and increase the contrast of the radiographic
image.
It does this by reducing the amount of scatter
radiation that reaches an extraoral film during
exposure.
Scatter radiation causes film fog and reduces
film contrast.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 42-19 A grid decreases the amount of scatter
radiation that reaches the extraoral film.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
The Lateral Jaw Projection
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The lateral jaw projection is used to view the
posterior region of the mandible. This type of
projection is very useful in patients with limited
jaw opening and in patients who cannot or will
not tolerate intraoral film placement.
A lateral jaw projection does not provide as
much diagnostic information as a panoramic
radiograph.
The advantage is that the lateral jaw projection
can be taken with a standard x-ray unit.
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Lateral Jaw Projection Techniques
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Body of mandible projection
Ramus of mandible projection
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Fig. 42-20 A, For the lateral jaw projection of the body of the mandible, proper
patient and film positioning is shown as viewed from the front and side of
the patient.
B, Lateral jaw radiograph of mandibular body.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
B
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The Ramus of the Mandible
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This film is used to evaluate impacted third
molars, large lesions, and fractures that
extend into the ramus of the mandible.
The ramus from the angle of the mandible to
the condyle is visible in this projection.
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Fig. 42-21 A, For the lateral jaw projection of the ramus of the mandible,
proper patient and film positioning is shown as viewed from the front and
side of the patient. B, Lateral jaw radiograph of mandibular ramus.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
B
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Skull Radiography
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Lateral cephalometric projection
Posteroanterior projection
Water projection
Submentovertex projection
Reverse Towne projection
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Fig. 42-22 B, Lateral cephalometric radiograph.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
B
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Fig. 42-23 B, Posteroanterior skull radiograph.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
B
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Fig. 42-25 B, Submentovertex radiograph.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
B
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Fig. 42-26 B, Reverse Towne radiograph.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
B
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Temporomandibular Joint
Radiography
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Radiographs of the temporomandibular joint (TMJ)
can be very difficult to examine because of the
multiple adjacent bony structures.
The articular disc and other soft tissues
of the TMJ cannot be examined radiographically.
Special imaging techniques (e.g., arthrography,
magnetic resonance imaging) must be used.
Radiographic projections of the TMJ can be used to
show the bone and the relationship
of the jaw joint.
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Fig. 42-28 Patient positioned for a transcranial radiograph
of the TMJ.
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Digital Radiography
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Advances in digital technology have led to a
unique “filmless” imaging system known as
digital radiography.
Introduced in 1987, digital radiography has
influenced both how dental disease is
recognized and how it is diagnosed.
In the last 2 years, the use of digital
radiography has increased rapidly in both
general and specialty dental practices.
Several companies are producing digital
radiography systems.
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The Basics of Digital Radiography
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Digital radiography uses a sensor (instead of
film) to capture a radiographic image,
breaking it into electronic pieces and storing
the image in a computer.
The patient is exposed to less x-radiation
than with conventional radiography.
The image is displayed on a computer screen
rather than on film.
The term image (not radiograph) is used to
describe the pictures that are produced.
(Cont’d)
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The Basics of Digital Radiography
(Cont’d)
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The x-ray beam strikes the sensor.
An electronic charge is produced on the
surface of the sensor, and this electronic
signal is digitized.
The digital sensor in turn transmits this
information to the computer.
Software on the computer is used to store the
image electronically.
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Fig. 42-29 Digital radiographic system.
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Fig. 42-30 A, Size of the electronic sensor is compared with traditional intraoral film in sizes
0, 1, and 2. B, Electronic sensor is protected with a plastic barrier and is ready for
positioning in the patient’s mouth in the same manner as that of a traditional film and
holder.
(Courtesy of Michael Danford, Santa Rosa, Calif.)
A
B
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Radiation Exposure
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Digital radiography requires much less xradiation than conventional radiography does
because the sensor is more sensitive to xrays than is conventional film.
Exposure times for digital radiography are
50% to 80% less than that required for
radiography using conventional film.
With less radiation, the dose absorbed by the
patient is significantly lower.
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Equipment
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For digital radiography, special equipment is
required. The essential components include:
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Dental x-ray unit
Intraoral sensor
Computer
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Types of Digital Imaging
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There are three types of digital imaging:
Direct
Indirect
Storage phosphor
The difference between the methods lies in
how the image is obtained and in what size
the receptor plates are available (e.g.,
panoramic).
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Fig. 42-31 All types of radiographs may be produced in
digital format.
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