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