patient preparation for panoramic x-ray ppt

By : Omar Alabood

Introduction Extraoral radiographs (outside the mouth) are taken

when large areas of the skull or jaw must be examined or when patients are unable to open their mouths for film placement.

Extraoral radiographs do not show the details as well as intraoral films.

Extraoral radiographs are very useful for 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 type of extraoral radiographs. Some types are used to view the entire skull, whereas other types focus on the maxilla and mandible.

Panoramic Radiography

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.

Basic Concepts

In panoramic radiography the film and tubehead rotate around the patient, and it produces 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.

move around the patient in opposite directions in panoramic radiography.

Focal Trough

An imaginary, three-dimensional curved area that is horseshoe shaped.

This is a very important concept because many technique errors 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 of this area, the images on the radiograph will appear blurred or indistinct.

Components of the Panoramic Unit Panoramic x-ray tubehead Head positioner Exposure controls

The main components of a panoramic unit.

The Head Positioner

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.

The head positioner is used to align the patient’s teeth in the focal trough.

Common Errors

Patient preparation errors • 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• Chin too high• Chin too low

Large hoop earrings (A) and ghost images (B). The ghost image of the earring appears on the opposite side of the film.

On a panoramic radiograph, a lead apron artifact appears as a large cone-shaped radiopacity obscuring the mandible.

The patient’s head is tipped too far upward.

The patient’s head is incorrectly positioned; the chin is tipped downward.

Positioning of the Teeth

Posterior to focal trough • 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 • 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.

The patient is biting too far back 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.

The anterior teeth appear narrowed and blurred on a panoramic film when the patient is positioned too far forward on the bite-block.

If the patient is not standing erect, superimposition of the cervical spine (arrows) may be seen on the center of the panoramic film.

Positioning of the Spine

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.