Panoramic imaging (1)
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Transcript of Panoramic imaging (1)
Panoramic Imaging
Panoramic Imaging• It is a technique for producing a single tomographic
image of the facial structures that includes both the maxillary and mandibular dental arches and their supporting structures.
Or Pantomography
Panoramic ImagingAdvantages:• Broad coverage • Low patient radiation dose• Convenience of the examination• Useful in patients who are unable to open their mouths• Short time required: 3-4 mins• Useful visual aid
Panoramic ImagingIndications:• Evaluation of trauma• Location of third molars• Extensive dental or osseous disease• Known or suspected large lesions• Tooth development• Retained teeth or root tips• TMJ pain• Study of sinuses• Developmental anomalies
Panoramic ImagingDisdvantages:Disdvantages:• Magnification, Geometric distortion &
overlapped images.• Resolution of fine anatomic details of peri-apical
area and periodontal structures is less.• The spinal cord superimpose the anterior region.• Common to have overlapped teeth images
especially in premolars.• Expensive
Principles of Panoramic Image Formation• First described by Numata and independently by Paatero
in the late 1940s• Movement of the film and objects about 2 fixed centers
of rotation.
Principles of Panoramic Image Formation
Movement of the film and objects (A, B, C, and D) about two fixed centers of rotation. Pb, Lead collimator
Principles of Panoramic Image Formation
Movement of the film and x-ray source about one fixed center of rotation. Pb, Lead collimator
Principles of Panoramic Image Formation
Movement of the film and x-ray source about a shifting center of rotation. Pb, Lead collimator
Principles of Panoramic Image Formation
Movement of the x-ray source and beam.
Image Layer• Is a 3-D curved zone, or “focal
trough” where the structures lying within this layer are reasonably well defined on final panoramic image.
• The images seen on the OPG consists largely of anatomic structures located within the focal trough
• Objects out of focal trough are blurred, magnified, reduced or distorted.
• The shape of the focal trough varies with the brand of equipments used.
Or Focal Trough
Image LayerFactors that affect image layer size:• Arc path• Velocity of the receptor and x-ray tube head• Alignment of the x-ray beam• Collimator width
Image Layer
• Mandible supporting a metal ring positioned at the center of the focal trough.
• The incisal edges of the mandibular teeth are indexed by a bite rod-positioning device.
• The Mandible is positioned at the center of the trough.
Image Layer
• Ring 5 mm anterior to Focal Trough
Image Layer
• Ring 5 mm posterior to Focal Trough
Image Layer• This distortions result from the reciprocal horizontal
movements of the receptor and x-ray source.
• When the mandible is displaced to the lingual side of its optimal position in the image layer, the beam passes more slowly through it. The images of the structures are elongated horizontally thus, appear wider.
• When the mandible is displaced toward the buccal, the beam passes at a rate faster than normal through the structures, thus appear thinner.
PANORAMIC MACHINES
• Othoralix 8500• Proline XC• Orthophos XG-PLUS
Panoramic Machines
A number of companies manufacture high-quality film-based and digital panoramic machines.These are:• Othoralix 8500• Proline XC • Orthophos XG-PLUS
Panoramic Machines• These machines are highly versatile.• They have the capability of adjusting to patients of
various sizes making frontal and lateral images of TMJs.
• They are also capable of producing tomographic views through the sinuses and cross-sectional views of the maxilla and mandible.
• Views are acquired by having special tube head and film movements programmed into the machine.
• Each machine also has the capablity for adding on a cephalometric attachment to allow exposure of standardized skull views.
Panoramic Machines
Orthoralix 8500
Panoramic Machines
Proline XC
Panoramic Machines
Orthophos XG-PLUS
Patient Positioning and Head Alignment
Patient Positioning and Head Alignment
• To obtain diagnostically useful panoramic radiographs, it is necessary to properly prepare patients and to position their heads carefully in the image layer.• Dental appliances, earrings, necklaces, hairpins
and any other metallic objects in the head and neck region should be removed.• It may also be wise to demonstrate the machine
to the patient by cycling it while explaining the need to remain still during the procedure.• Children should be instructed to look forward
and to not follow the tube head with their eyes.
Patient Positioning and Head Alignment
• The patient’s head must be centered in three different planes in order to uniformly record the maxillofacial complex. The head alignment planes include the midsagittal, occlusal and the anteroposterior.
Midsagittal plane • is positioned perpendicular or at a
right angle to the floor and centered right to left.
• Failure to position the midsagittal plane in the rotational midline of the machine results in a radiograph showing right and left sides that are unequally magnified in the horizontal dimension.
Patient Positioning and Head AlignmentOcclusal plane• Is angled 20 to 30 degrees• A general guide for chin positioning is
to place the patient so that a line from the tragus of the ear to the outer canthus of the eye is parallel with the floor.
• If the chin is tipped too high, the occlusal plane on the radiograph appears flat or inverted, and the image of the mandible is distorted.
• If the chin is tipped too low, the teeth become severely overlapped, the symphyseal region of the mandible may be cut off the film and both mandibular condyles may be projected off the superior edge of the film.
Patient Positioning and Head Alignment
Anteriorposterior• is achieved typically by having
patients place the incisal edges of their maxillary and mandibular incisors into a notched positioning device.
• Patients should not shift the mandible to either side when making this protrusive movements.
Image Receptor
Image Receptor• Intensifying screens are routinely used in panoramic
radiography because they significantly reduce the amount of radiation required for properly exposing a radiograph.
Panoramic Film Darkroom Techniques• Special darkroom procedures are needed when panoramic film is
being processed. • These films are far more light sensitive than intraoral films,
espicially after they have been exposed.• A reduction in dark room lighting from that used for conventional
intraoral film is necessary.• A KODAK GBX-2 filter can be installed with a 15-watt bulb at least
four feet from the working surface. • An ML-2 filter should not be used because it fogs panoramic films.• Panoramic films should be developed either manually or in
automatic film process.• Obtaining optimal results relies on the same care to develop,
rinse, fix and wash panoramic films as is taken with intraoral films.
Interpreting the Panoramic ImageThe FOUR Diagnostic Regions in a Panoramic Image:
Maxillary Region
Mandibular RegionDentoalveolar Region
TMJ, including retromaxillaryand cervical region
Interpreting the Panoramic ImageMaxillary Region:
Interpreting the Panoramic ImageMaxillary Region:
Interpreting the Panoramic ImageMandibular Region:
Interpreting the Panoramic ImageMandibular Region:
Interpreting the Panoramic ImageDentoalveolar Region:
• Shape and angulation of roots• Alveolar bone and periodontium• Shows gentle curve of occlusal plane• Missing 3rd molars• Presence of metallic restorations
Interpreting the Panoramic ImageSoft Tissue Images:
Interpreting the Panoramic ImageSoft Tissue Images:
Interpreting the Panoramic ImageAirspace:
Interpreting the Panoramic ImageAirspace:
Interpreting the Panoramic Image Dentition