Panoramic x ray
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Transcript of Panoramic x ray
Introduction to Panoramic
Radiography
• Commonplace in dental practice
• Considered essential in radiographic
diagnosis
• 30% of dental units sold are
panoramic
Introduction to Panoramic
Radiography
• “Panorama” means unobstructed
view of a region in any direction
• Panoramic radiograph show greater
coverage than periapical and
bitewing radiographs
Introduction to Panoramic
Radiography
• New technique
• Introduced in 1959
• Employs scanography (slit beam) &
curved surface rotational
tomography
Client Dose from Panoramic
Radiography
• 10 times less radiation than a complete intraoral survey using long, round PID & E+ film
• 4 time less radiation than a bitewing survey using long, round PID and E+ film
Indications for Panoramic
• Pathology-cysts, tumors
• Trauma-fractures
• Growth & development
• Client management
• Edentulous
• Localization: anatomy, objects, implant placement
• Carotid artery condition
Advantages of Panoramic
Radiography
• Field size
• Quality control
• Simplicity
• Time & rapidity of the procedure
• Client cooperation
• Dose
• Minimal infection control
• Gross anatomy & pathology visible
Disadvantages of Panoramic
Radiography
• Image quality
• Focal trough limitations
• Equipment costs
• Overuse
Disadvantages of Panoramic
Radiography
• Image quality
– Magnification
– Distortion
– Poor definition compared to intraoral
– Overlap
– Superimposition & ghost images
Disadvantages of Panoramic
Radiography
• Poor image quality due to
– Tomographic process
– Increased object-film distance
– Use of intensifying screens
– Faster film with larger crystals
Disadvantages of Panoramic
Radiography
• Focal Trough (Image Layer)
– Areas outside are not visible
– Size & shape limits imagery to those
structures which “fit” into the image
layer
– Size & shape not adjustable so not all
client’s arches image equally well
Disadvantages of Panoramic
Radiography
• Distortion
– Vertical & horizontal distortion with
variations causes uneven magnification
Disadvantages of Panoramic
Radiography
• Superimposition & Ghost Images
– All objects in the field of the beam, even
those outside of the image layer are
projected onto the film but most are not
seen.
– Objects with the greatest density are
projected in two places on the film
• Intended (useable image)
• Ghost image (reversed, higher, blurred)
Disadvantages of Panoramic
Radiography
• Superimposition & Other Imaging
Quirks
– Ghost images may hide pathosis
– Soft tissue shadows may mimic
pathosis
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 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.
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.
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.
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
