Panoramic Radiography

transcript

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.

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.

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

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

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.

Panoramic Radiography

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