panoramic radiography
DESCRIPTION
radiographyTRANSCRIPT
PANORAMIC RADIOGRAPHY
DR. LUBNA F. ALFALEH
Panoramic means “Wide View”
.
Panoramic radiography:
An Extraoral technique which produces a
radiograph with wide view of the maxilla
and mandible.
it's also known “pantomography”
“Rotational panoramic radiography”
Both film and Tube head rotate around the
patient
Purpose and use:
To evaluate impacted teeth
To evaluate eruption patterns, growth,
and Development.
To Detect Diseases , lesions, and
conditions of the jaws
To Examine the extent of Large lesions
To Evaluate Trauma.
Panoramic film are not as Defined or
sharp as the images seen on intraoral films,
consequently
a panoramic film should not be used to
evaluate and diagnose caries, periodontal
disease , or periapical lesions.
Normal anatomic landmarks
In Panoramic radiography the film and x-
rays Tube head 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 and
patient ( sit or stand ) in stationary
position.
The movement of the film and the tube head produces an image through the process known as tomography, the term tomo means section
The change in rotation of the tube head allow producing the image layer that confirms elliptical shape of the dental arches.
Different machines
Focal trough
The focal trough (image layer) is Defined as an
invisible area 3 dimensional curved zone in
which structures are clearly demonstrated on a
panoramic radiograph
Focal trough
The shape of the Focal trough varies depending
on the equipment manufacturer
The structures (teeth and jaws) located within
the focal trough appear reasonably well defined
in the panoramic radiograph
Focal trough
Structures positioned inside or out side the
Focal trough appear blurred or not visible on
the panoramic film
In most x-ray machines, the Focal trough is
narrow in the anterior region and wide in the
posterior region.
Equipment:
1. X-ray unit.2. Intensifying screens3. Screen film4. Cassette
1. Panoramic X ray Unit
X-ray tube head
Head positioner
Exposure controls
X ray tube head
Consists of a tube head which is similar to an
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
The Tube head always rotates behind the patient‟s
head as the film rotates in the front of the patient.
X ray tube head
Head positioner: consists of chin rest, notched Bite-block, forehead rest and lateral head supports
Exposure factors are determined by the manufacturer who suggests the (Kvp and Milliamperage).
The Kvp and milliamperage settings are adjustable and can be varied to accommodate patients of different sizes
The Exposure time is fixed and can‟t be changed
2.Intensifying screens , cassette
Cassette is the device that holds the Extra oral
film and the intensifying screens, and it‟s either
rigid or Flexible, curved or straight
Depending on the used panoramic x-ray unit.
The Screen film is placed between 2 intensifying
screens in a cassette holder.
Each intensifying screen contains a phosphor
layer that fluoresces when activated by x-radiation
which has penetrated the cassette.
2.Intensifying screens , cassette
This Exposure methods differs from conventional
intraoral radiographs in which x-rays directly
exposes the film.
Therefore the amount of radiation needed to
produce a high quality film is less when using
intensifying screens
The green light intensifying screens require less
x-rays exposure then the blue one so it‟s faster,
that‟s why it‟s recommended.
2.Intensifying screens , cassette
All cassette should be light tight to protect the
film from exposure, one intensifying screen is
placed on each side of the film
Before exposure a metal letter R can be attached
to the front of the cassette to indicate Right from
left side of the patient, around with special
labeling of patient name., dentist name and the
date.
3.Film
Screen film used in panoramic radiography
is sensitive to light emitted from intensifying
screens
Some Screen film are sensitive to green
light others for blue .
The film is available in 2 sizes 5x12
inch6x12 inch.
Step by step preparations
Equipment preparation
Patient preparation
Patient positioning
A. Equipment preparation:
1.Load the panoramic cassette in the dark
room under safelight conditions, one extraoral
film and 2 intensifying screens must be placed in
the cassette, and the cassette must be securely
closed.
2.set the Exposure factors according to the
manufacturer‟s recommendations
e.g. obese patient or patient with large
bone>> use the next highest Kvp or mA
3. adjust the machine to the height of the
patient, the cassette is loaded in the cassette
carrier in the panoramic unit.
B. Patient preparation:
1.Explain the radiographic procedures to be
performed.
2.place lead apron, without thyroid collar not to
block the the x-ray beam and also double sided
lead apron is recommended ( one that protect
the patient from the front and the back.
3.remove all objects from the head and neck
area. earrings , necklaces, napkin chain
eyeglasses. And complete and partial dentures
C .Patient positioning:
1.instruct the patient to Stand or sit ( as tall as
possible) with straight back , the vertebral
column must be straight to prevent white
shadow to appear over the middle of the
radiograph.
2. patient must bite a plastic bite block, the
front teeth should be placed in end to end
position in the notch found on the bite block,
this groove will align the teeth and the jaw in
the focal trough area .
3. position the midsagittal plane perpendicular
to the floor, and the head should not be tilted
4.position the Frankfort plane (an imaginary
plane that passes through the top of the ear
canal and the bottom of the eye socket)
parallel with floor so that occluasl plane is in
correct angle.
5. Instruct the patient to swallow and feel the
tongue rise up the roof of the mouth and
keep it in that position and close lips around
the bite block.
6. patient should remain stand still.
COMMON ERRORS
A. Patient preparation errors
B. patient positioning errors.
COMMON ERRORS
A. Patient preparation errors
1.Ghost images:
Radiopaque artifact that appear
only if the objects Ex (eye glass,
orthodontic retainer.. ) are not removed.
2.Lead apron artifact:
only if the dental radiographer used lead
apron with thyroid collar.
Ghost image
Lead apron artifact
B. Patient positioning errors
1.positioning of lips and tongue :
- If patient lips are not closed on Bite blocks during the
Exposure, Dark radiolucent shadow results that
obscure the anterior teeth.
- If tongue is not in contact with palate , dark
radiolucent shadow will Obscure the apices of
maxillary teeth.
2.Positinong of Frankfort plane Upward :
If patient „s chin is too high or tipped up, Frankfort
plane is angled Upward the following will result:
The hard palate and floor of nasal cavity appear
superimposed over the roots of maxillary teeth.
there is a loss of detail in the maxillary incisors region
The maxillary incisors appear blurred and magnified
“A reverse smile line “ will appear on the radiograph
3.Positinong of Frankfort plane Downward :
If the patient „s chin is too low, the Frankfort plane is
angled down ward it will result in:
the mandibular incisors appear blurred
There is a loss if detail in the anterior apical region
The mandibular condyles may not be visible
A “curved Upward smile line” will appear.
4.Postinong of teeth Anterior to Focal trough
(not in the groove in the Bite block)
The teeth will appear blurred
if too far anterior to the focal trough it will appear
“skinny” and out of focus.
Teeth Anterior to the Focal trough
5. Positioning of teeth posterior to Focal trough:
The teeth will appear blurred
If too far the anterior teeth will appear “Fat”
Teeth posterior to the focal trough
Teeth posterior to the focal trough
6. Positioning of Midsagittal plane:
if the patient head is not centered the ramus
and the posterior teeth appear unequally
magnified on the panoramic radiograph
The side farthest from the film appears
magnified and the closer appear smaller.
7.Postioning of spine:
If patient is not sitting or standing with stright
back ,cervical spine appears as radiopacity in
the center of the film
END OF LECTURE
ADVANTAGES AND
DISADVANTAGES
Advantages:
1. Field size: coverage of the Entire Maxilla
and mandible , so more anatomical
structures and lesion can be viewed
2. Simplicity.
3. Patient cooperation (no discomfort)
especially children.
4. Minimal exposure: minimal radiation
Exposure for the patient.
Disadvantages:1. Image quality: not as sharp as intraoral
radiographs (because of the intensifying
screens). That‟s why You can‟t evaluate Details
like ( dental caries , periodontal disease or
periapical lesions.
2. Focal trough limitations: any object outside
focal trough can‟t be seen.
3. Distortion: A certain amount of magnification,
distortion , overlapping is present even if
proper technique is used
4. Equipment cost: high compared to intraoral
radiography Unit.