PANORAMIC
RADIOGRAPHY
DA 105
Dental Radiography

Questions
What equipment is used in panoramic
radiography?
 What is the focal trough?
 What are the advantages and
disadvantages of panoramic
radiography?

Introduction

Purpose
To present basic concepts of
panoramic radiography
 To describe the patient preparation,
equipment preparation, and patient
positioning procedures needed to
perform this procedure

Basic Concepts
Purpose and Use
 Fundamentals

Rotation center
 Focal trough

Equipment
 Basic Concepts

Basic Concepts

Panoramic film


Shows a wide view of the upper and
lower jaws
Panoramic radiography

Used to examine the upper and lower
jaws on a single film
A, Panoramic radiograph. B, Panoramic anatomy
Purpose and Use

An overall image of the maxilla and
mandible


Often used to supplement bite-wing
and selected periapical films
Images seen on a panoramic film are
not as defined or sharp as the images
seen on intraoral films
Fundamentals

In panoramic radiography, the film and xray tubehead move around the patient
The x-ray tube rotates around the patient’s
head in one direction while the film rotates
in the opposite direction
 The patient may stand or sit in a stationary
position

The film and x-ray tubehead move around the
patient in opposite directions in panoramic
radiography
Fundamentals
The movement of the film and the
tubehead produces an image through
the process known as tomography
 Tomography


A radiographic technique that allows
the imaging of one layer or section of
the body while blurring images from
structures in other planes
Rotation Center

The pivotal point, or axis, around
which the cassette carrier and x-ray
tubehead rotate

There are three basic rotation centers
depending on the manufacturer
• Double-center rotation
• Triple-center rotation
• Moving-center rotation
Types of panoramic x-ray machines. A, Double-center rotation machines
have two rotational centers, one for the right and one for the left side of the
jaws. B, Triple-center rotation machines have three centers of rotation and
create an uninterrupted radiographic image of the jaws. C, Moving-center
rotation machines rotate around a continuously moving center that is similar
to the arches, creating an uninterrupted image of the jaws
Focal Trough

Can be defined as a threedimensional curved zone in which
structures are clearly demonstrated
on a panoramic radiograph
Example of an “image layer” or “focal
trough
Equipment
Panoramic x-ray units
 Film
 Intensifying screens
 Cassette

Panoramic X-ray Units

There are a number of different
panoramic x-ray units

All have similar components
• X-ray tubehead
• Head positioner
• Exposure controls
A, Orthophos XG Plus extraoral x-ray
machine. B, Orthoralix 8500 extraoral x-ray
machine. C, Example of a digital
panoramic system
Main components of the Orthophos XG 5: A, x-ray
tubehead; B, head positioner; C, exposure
controls
Panoramic X-ray Units

X-ray Tubehead


Similar to an intraoral x-ray tubehead
Collimator

Differs from the collimator used in the
intraoral x-ray tube head
• The collimator used in the panoramic xray machine is a lead plate with an
opening in the shape of a narrow vertical
slit
The collimater on the Orthophos XG 5 has
a narrow slit opening
Panoramic X-ray Units

The x-ray beam emerges from the
panoramic tubehead through the
collimator as a narrow band
It passes through the patient and
exposes the film through another
vertical slit in the cassette carrier
 The vertical angulation is fixed so that
the x-ray beam is directed slightly
upward

Head Positioner

A chin rest, notched bite-block,
forehead rest, and lateral head
supports or guides

Used to align the patient’s teeth as
accurately as possible
The head positioner (notched bite-block, forehead
rest, and lateral head supports) is used to align
the patients teeth in the focal trough
Exposure Controls
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

Exposure controls on the Orthophos XG
5 can be used to adjust exposure factors
Film

Screen film is used in panoramic
radiography
It is sensitive to the light from an
intensifying screen
 It is placed between two intensifying
screens in a cassette holder

Intensifying Screens

Calcium tungstate


Emit blue light
Rare earth
Emit green light
 Require less x-ray exposure than
calcium tungstate screens

Cassette

A device used to hold the extraoral
film and intensifying screens
May be rigid or flexible, curved or
straight
 Must be light-tight
 Must be marked to orient the finished
radiograph


Film cassettes. A and B,
Rigid cassettes.
Intensifying screens are
attached to the inside
cover and base of a rigid
cassette. When the
panoramic film is placed
in the cassette, it lies
between the screens. C,
Flexible cassette has an
opening at one end,
creating a pouch. The
panoramic film is placed
between two removable,
flexible intensifying
screens, which are then
slid into the pouch
This panoramic film is labeled with two metal
letters indicating the patients right (R) and left (L)
sides
Step-by-Step Procedures
Equipment Preparation
 Patient Preparation
 Patient Positioning

Equipment Preparation
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

Patient Preparation
Explain the radiographic procedures
 Place a lead apron without a thyroid collar on
the patient and secure it



A double-sided lead apron is recommended
Remove all objects from the head and neck
area that may interfere with film exposure
A double-sided lead apron is recommended for
use during exposure of a panoramic film
Patient Positioning
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 bite-block
 Position the midsagittal plane
perpendicular to the floor

The patients teeth must be positioned in
the grooves on the bite-block
Frankfort and midsagittal planes. The Frankfort plane
passes through the floor of the orbit and the external
auditory meatus. The midsagittal plane divides the body in
half into right and left sides
The patients Frankfort plane must be
positioned so that it is parallel to the floor
Patient Positioning
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 film
 Instruct the patient to close the lips
around the bite-block
 Instruct the patient to remain still while
the machine is rotating during exposure
 Expose the film and proceed with film
processing

Common Errors
Patient Preparation Errors
 Patient Positioning Errors

Patient Preparation Errors
Ghost Images
 Lead Apron Artifact

Ghost Images

A radiographic artifact seen on a
panoramic film that is produced when
a radiodense object is penetrated
twice by the x-ray beam
It is found on the opposite side of the
film
 It appears indistinct, larger, and higher
than its actual counterpart

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
Ghost Images

Problem


If all metallic or radiodense objects are
not removed before exposure, a ghost
image results that obscures diagnostic
information
Solution

The dental radiographer must instruct
the patient to remove all radiodense
objects in the head and neck region
prior to positioning the patient
Lead Apron Artifact

Problem


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 film
On a panoramic radiograph, a lead apron artifact
appears as a large cone-shaped radiopacity
obscuring the mandible
Patient Positioning Errors
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

Positioning of the Lips and
Tongue


Problem
 If the patient’s lips are not closed on the biteblock during the exposure of a panoramic
film, 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 film, a dark
radiolucent shadow results that obscures the
apices of the maxillary teeth
Solution
 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 film
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
Positioning of the
Frankfort Plane Upward

Problem


If the patient’s chin is positioned too high a
“reverse smile line” is apparent on the
radiograph
Solution

Position the patient so the Frankfort plane
is parallel with the floor
The patients head is incorrectly
positioned; the chin is tipped up
A “reverse smile line” is seen on a panoramic film
when the patients chin is tipped up
Positioning of the
Frankfort Plane Downward

Problem


If the patient’s chin is positioned too low or
is tipped down an “exaggerated smile line”
is apparent on the radiograph
Solution

Position the patient so that the Frankfort
plane is parallel with the floor
The patients head is incorrectly positioned;
the chin is tipped down
An “exaggerated smile line” is seen on a
panoramic film when the patients chin is tipped
down
Positioning of the Teeth –
Anterior to the Focal Trough

Problem


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
The patient is incorrectly positioned; the teeth are
too far forward on the bite-block
The anterior teeth appear narrowed and blurred
on a panoramic film when the patient is positioned
too far forward on the bite-block
Positioning of the Teeth –
Posterior to the Focal Trough

Problem


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
The patient is incorrectly positioned; the teeth are
too far back and not on the bite-block
The anterior teeth appear widened and blurred on
a panoramic film when the patient is positioned
too far back on the bite-block.
Positioning of the Midsagittal
Plane


Problem
 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 film 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 biteblock
The patient is incorrectly positioned; the
head is not centered
The patients posterior teeth and ramus appear to
be magnified on a panoramic film when the head
is not centered
Positioning of the Spine

Problem


If the patient is not standing or sitting
with a straight spine, the cervical
spine appears as a radiopacity in the
center of the film and obscures
diagnostic information
Solution

Instruct the patient to stand or sit “as
tall as possible” with a straight back
If the patient is not standing erect, superimposition
of the cervical spine (arrows) may be seen on the
center of the panoramic film
Advantages of
Panoramic Radiography
Field size
 Simplicity
 Patient cooperation
 Minimal exposure

Panoramic radiograph of a
pediatric patient
Disadvantages of
Panoramic Radiography
Image quality
 Focal trough limitations
 Distortion
 Equipment cost
