Panoramic Tomography

Monday, August 18, 2014

DENTAL RADIOGRAPHY and Examination of Mandible

Pathology Demonstrated:
  • Fractures and infectious processes of the mandible and dental structures are shown.
  • Used as an adjuvant for pre-bone marrow transplants.
Technical Factors:
  • IR size - 23 x 30 cm (9 x 12 inches), crosswise 
  • Curved non-grid cassette 
  • 70 to 80 kV range 
  • Panoramic and Dental Radiography Unit Preparation:
  • Attach image receptor to panoramic unit.
  • Position tube and image receptor at standing position.
  • Raise chin rest to approximately same level as patient's chin.
  • Wrap vest type lead apron around patient.
Patient Position:
  • Remove all metal, plastic, and other removable objects from head and neck.
  • Explain to patient how tube and image receptor rotate and the time span needed for exposure.
  • Guide patient into unit, resting patient's chin on bite block.
  • Position patient's body, head and neck. Do not allow head and neck to stretch forward, but have patient stand in close, with spine straight and hips forward.
Part Position:
  • Adjust height of chin rest until Intra-Orbital Meatal Line (IOML) is aligned parallel with floor.
  • The occlusal plane (plane of biting surface of teeth) declines 10° from posterior to anterior.
  • Align MSP with the vertical center line of the chin rest.
  • Position bite block between patient's front teeth. see note.
  • Instruct patient to place lips together and position tongue on roof of mouth.
Central Ray:
  • X-ray beam direction is fixed and directed slightly cephalic to project anatomic structures, positioned at the same height, on top of one another.
  • Fixed SID, per panoramic unit.
  • A narrow, vertical-slit diaphragm is attached to tube, providing collimation.
  • Note: When the TJMs are of interest, a second panoramic image is taken with the mouth open.
  • This requires placement of a larger bite block between the patient's teeth.
Radiographic Criteria:
Structure Shown:
  • A single image of the teeth, mandible, TMJs, nasal fossae, maxillary sinus, zygomatic arches, and maxillae is shown.
  • A portion of the cervical spine is visualized.
Position of Patient in Dental Radiography:
  • The mandible visualized without rotation or tilting is indicated by the following:
  • TMJs on the same horizontal plane in the image.
  • Rami and posterior teeth equally magnified on each side of the image.
  • Anterior and posterior teeth sharply visualized with uniform magnification.
Correct Patient Position is indicated by the following:
  • Mandibular symphysis projected slightly below the mandibular angles
  • Mandible oval shape
  • Occlusal plane is parallel with long axis of the image
  • Upper and lower teeth positioned slightly apart with no superimposition
  • Cervical spine demonstrated with no superimposition of the TMJs.
Collimation and Central ray:
  • The mandible is located at the center of the image
  • The entire mandible in included in the collimation field.
Exposure Criteria:
  • Density of mandible and teeth is uniform across entire image.
  • No density loss is evident at the center.
  • No artifacts are superimposed on the image

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