Download Chapter 7 Body Systems

Chapter 22
Panoramic Imaging
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
Dental Radiography
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Questions
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What equipment is used in panoramic imaging?
What is the focal trough?
What are the advantages and disadvantages of
panoramic imaging?
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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Dental Radiography
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Chapter 22 Reading
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Iannucci & Howerton (pp. 256-273)
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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Dental Radiography
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Chapter 22 Outline
Panoramic Imaging
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Basic concepts
 Step-by-step procedures
 Common errors
 Advantages and disadvantages
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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Introduction
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Purpose
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To present basic concepts of panoramic imaging
To describe the patient preparation, equipment
preparation, and patient positioning procedures
needed to perform this procedure
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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Basic Concepts
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Purpose and Use
Fundamentals
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Rotation center
 Focal trough
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Equipment
Basic Concepts
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Basic Concepts
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Panoramic image
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Iannucci & Howerton (pp. 256-257) (Fig. 22-1)
Shows a wide view of the upper and lower jaws.
Panoramic imaging
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Is used to examine the upper and lower jaws on a
single projection.
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Purpose and Use
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An overall image of the maxilla and mandible
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Iannucci & Howerton (p. 257)
Often used to supplement bite-wing and selected
periapical images
Images seen on a panoramic projection are
not as defined or sharp as the images seen
on intraoral projections.
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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Fundamentals
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
Iannucci & Howerton (pp. 257-258) (Fig. 22-2)
In panoramic imagng, the receptor and x-ray
tubehead move around the patient.
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The x-ray tube rotates around the patient’s head in
one direction while the receptor rotates in the
opposite direction.
The patient may stand or sit in a stationary position.
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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Fundamentals
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The movement of the receptor and the
tubehead produces an image through the
process known as tomography.
Tomography
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This is a radiographic technique that allows the
imaging of one layer or section of the body while
blurring images from structures in other planes.
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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Rotation Center
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
Iannucci & Howerton (pp. 258-259) (Fig. 22-3)
The pivotal point, or axis, around which the
cassette carrier and x-ray tubehead rotate
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There are three basic rotation centers depending
on the manufacturer:
• Double-center rotation
• Triple-center rotation
• Moving-center rotation
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Focal Trough
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
Iannucci & Howerton (p. 259) (Fig. 22-4)
Can be defined as a three-dimensional
curved zone in which structures are clearly
demonstrated on a panoramic radiograph
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Equipment
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Iannucci & Howerton (pp. 259)
Panoramic x-ray units
Film
Intensifying screens
Cassette
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Panoramic X-Ray Units
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Iannucci & Howerton (pp. 259-260) (Figs. 22-5,
22-6)
There are a number of different panoramic
x-ray units:
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All have similar components
• X-ray tubehead
• Head positioner
• Exposure controls
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Panoramic X-Ray Units
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X-Ray Tubehead
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Iannucci & Howerton (pp. 259-260) (Fig. 22-7)
Similar to an intraoral x-ray tubehead
Collimator
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Differs from the collimator used in the intraoral
x-ray tube head
• The collimator used in the panoramic x-ray machine is
a lead plate with an opening in the shape of a narrow
vertical slit
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Panoramic X-ray Units
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The x-ray beam emerges from the panoramic
tubehead through the collimator as a narrow
band.
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It passes through the patient and exposes the
receptor through another vertical slit in the
cassette carrier.
The vertical angulation is fixed so that the x-ray
beam is directed slightly upward.
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Head Positioner
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
Iannucci & Howerton (pp. 259-260) (Fig. 22-8)
A chin rest, notched bite-block, forehead rest,
and lateral head supports or guides
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Used to align the patient’s teeth as accurately as
possible
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Exposure Controls
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Iannucci & Howerton (pp. 259, 261) (Fig. 22-9)
Suggested exposure factors for
milliamperage and kilovoltage are provided
by the manufacturer and can be varied to
accommodate patients of different sizes.
Exposure time is fixed.
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Film
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Screen film is used in panoramic imaging.
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It is sensitive to the light from an intensifying
screen.
It is placed between two intensifying screens in a
cassette holder.
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Intensifying Screens
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Calcium tungstate
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Emit blue light
Rare earth
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Emit green light
Require less x-ray exposure than calcium
tungstate screens
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Cassette
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Iannucci & Howerton (pp. 261-262) (Figs. 22-10,
22-11)
A device used to hold the extraoral film and
intensifying screens
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May be rigid or flexible, curved or straight
Must be light-tight
Must be marked to orient the finished image
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Step-by-Step Procedures
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Equipment Preparation
Patient Preparation
Patient Positioning
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Equipment Preparation
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Iannucci & Howerton (pp. 261-262) (Procedure
22-1)
Load the panoramic cassette in the darkroom
under safelight conditions.
Cover the bite-block with a disposable plastic
coverslip or sterilize between patients.
Set the exposure factors.
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Patient Preparation
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Explain the radiographic procedures.
Place a lead apron without a thyroid collar on
the patient and secure it.
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Iannucci & Howerton (pp. 261, 263) (Fig. 22-12)
(Procedure 22-2)
A double-sided lead apron is recommended.
Remove all objects from the head and neck
area that may interfere with the procedure.
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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Patient Positioning
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Iannucci & Howerton (pp. 261-264) (Figs. 22-13,
22-14, 22-15) (Procedure 22-3)
Instruct the patient to sit or stand “as tall as
possible” with the back straight and erect.
Instruct the patient to bite on the plastic biteblock.
Position the midsagittal plane perpendicular
to the floor.
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Patient Positioning
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Position the Frankfort plane parallel with the floor.
Instruct the patient to position the tongue on the
roof of the mouth and keep the tongue in that
position during exposure of the receptor.
Instruct the patient to close the lips around the biteblock.
Instruct the patient to remain still while the machine
is rotating during exposure.
Expose the receptor and proceed with receptor
processing.
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Common Errors
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Patient Preparation Errors
Patient Positioning Errors
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Patient Preparation Errors
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Ghost Images
Lead Apron Artifact
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Ghost Images
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Iannucci & Howerton (pp. 262, 264) (Fig. 22-16)
A radiographic artifact seen on a panoramic
image that is produced when a radiodense
object is penetrated twice by the x-ray beam
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It is found on the opposite side of the receptor.
It appears indistinct, larger, and higher than its
actual counterpart.
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Ghost Images
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Problem
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If all metallic or radiodense objects are not
removed before exposure, a ghost image results
that obscures diagnostic information.
Solution
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The dental radiographer must instruct the patient
to remove all radiodense objects in the head and
neck region prior to positioning the patient.
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Lead Apron Artifact
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Problem
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Iannucci & Howerton (pp. 262, 265) (Fig. 22-17)
A radiopaque cone-shaped artifact that obscures
diagnostic information results if the lead apron is
incorrectly placed, or if a lead apron with a thyroid
collar is used.
Solution

The dental radiographer must always use a lead
apron without a thyroid collar when exposing a
panoramic projection.
Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc.
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Patient Positioning Errors
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Positioning of the Lips and Tongue
Positioning of the Frankfort Plane – Upward
Positioning of the Frankfort Plane – Downward
Positioning of the Teeth – Anterior to the Focal
Trough
Positioning of the Teeth – Posterior to the
Focal Trough
Positioning of the Midsagittal Plane
Positioning of the Spine
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Positioning of the Lips and Tongue
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Problem
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Iannucci & Howerton (p. 265) (Fig. 22-18)
If the patient’s lips are not closed on the bite-block
during the exposure of a panoramic projection, a
dark radiolucent shadow results that obscures the
anterior teeth.
If the tongue is not in contact with the palate
during exposure of a panoramic projection, a dark
radiolucent shadow results that obscures the
apices of the maxillary teeth.
Solution
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Instruct the patient to close the lips around the
bite-block and swallow and raise the tongue up to
the palate during the exposure of the receptor.
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Positioning of the
Frankfort Plane Upward
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Problem
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Iannucci & Howerton (pp. 265-266) (Figs. 22-19,
22-20)
If the patient’s chin is positioned too high a
“reverse smile line” is apparent on the image.
Solution

Position the patient so the Frankfort plane is
parallel with the floor.
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Positioning of the
Frankfort Plane Downward
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Problem
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Iannucci & Howerton (pp. 266-267) (Figs. 22-21,
22-22)
If the patient’s chin is positioned too low or is
tipped down an “exaggerated smile line” is
apparent on the image.
Solution

Position the patient so that the Frankfort plane is
parallel with the floor.
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Positioning of the Teeth –
Anterior to the Focal Trough
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Problem
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
Iannucci & Howerton (pp. 266-268) (Figs. 22-23,
22-24)
If the patient’s teeth are positioned too far forward
on the bite-block or anterior to the focal trough, the
anterior teeth appear “skinny” and out of focus.
Solution

Position the patient so that the anterior teeth are
placed in an end-to-end position in the groove on
the bite-block.
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Positioning of the Teeth –
Posterior to the Focal Trough
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Problem
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Iannucci & Howerton (pp. 266, 268-269) (Figs. 2225, 22-26)
If the patient’s teeth are positioned too far back on
the bite-block or posterior to the focal trough, the
anterior teeth appear “fat” and out of focus.
Solution

Position the patient so that the anterior teeth are
placed in an end-to-end position in the groove on
the bite-block.
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Positioning of the Midsagittal Plane
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Problem
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
Iannucci & Howerton (pp. 266-267, 269-270)
(Figs. 22-27, 22-28)
If the patient’s head is not centered the ramus and
posterior teeth appear unequally magnified on the
panoramic radiograph.
• The side farthest from the receptor appears magnified.
Solution

Position the patient’s head so that the midsagittal
plane is perpendicular to the floor while the
midline is centered on the bite-block.
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Positioning of the Spine
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Problem
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Iannucci & Howerton (pp. 267, 270) (Fig. 22-29)
If the patient is not standing or sitting with a
straight spine, the cervical spine appears as a
radiopacity in the center of the receptor and
obscures diagnostic information.
Solution

Instruct the patient to stand or sit “as tall as
possible” with a straight back.
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39
Advantages of
Panoramic Radiography
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
Iannucci & Howerton (pp. 267-268, 270) (Fig. 2230)
Field size
Simplicity
Patient cooperation
Minimal exposure
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Disadvantages of
Panoramic Radiography
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



Iannucci & Howerton (p. 268)
Image quality
Focal trough limitations
Distortion
Equipment cost
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