Panoramic Imaging Copyright 2012 2006 2000 1996 by

Basic Concepts Panoramic image n n n Most common extraoral projection used in general dentistry practices Shows a wide view of the upper and lower jaws. Is used to examine the upper and lower jaws on a single projection. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 2

Purpose and Use An overall image of the maxilla and mandible n n n Often used to supplement bite-wing and selected periapical images Used to examine large areas of the face and jaw Used to locate impacted teeth or retained root tips Used to evaluate trauma, lesions and diseases of the jaw Assessing growth and development Assessing any congenitally missing teeth Disadvantage: n Images seen on a panoramic projection are not as defined or sharp as the images seen on intraoral projections. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 3

Fundamentals In panoramic imaging, the receptor and x-ray tubehead move around the patient. n n n The x-ray tube rotates around the patient’s head in one direction while the receptor rotates in the opposite direction. The patient may stand or sit in a stationary position. The movement of the receptor and the tubehead produces an image through the process known as tomography. Tomography n This is a radiographic technique that allows the imaging of one layer or section of the body while blurring images from structures in other planes. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 4

Rotation Center The pivotal point, or axis, around which the cassette carrier and x-ray tubehead rotate n There are three basic rotation centers depending on the manufacturer: Double-center rotation Triple-center rotation Moving-center rotation Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 5

Focal Trough Defined: n Can be defined as a three-dimensional curved zone in which structures are clearly demonstrated on a panoramic radiograph Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 6

Equipment: Panoramic X-Ray Units There a number of different panoramic x-ray units: n All have similar components X-ray tubehead Head positioner Exposure controls Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 7

Parts of the Panoramic X-Ray Units X-Ray Tubehead n Similar to an intraoral x-ray tubehead Collimator n Differs from the collimator used in the intraoral x-ray tube head The collimator used in the panoramic x-ray machine is a lead plate with an opening in the shape of a narrow vertical slit The x-ray beam emerges from the panoramic tube head through the collimator as a narrow band. n n It passes through the patient and exposes the receptor through another vertical slit in the cassette carrier. The vertical angulation is fixed so that the x-ray beam is directed slightly upward. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 8

Parts of the Panoramic: Head Positioner A chin rest, notched bite-block, forehead rest, and lateral head supports or guides n Used to align the patient’s teeth as accurately as possible Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 9

Parts of the Panoramic: Exposure Controls Suggested exposure factors for milliamperage and kilovoltage are provided by the manufacturer and can be varied to accommodate patients of different sizes. Exposure time is fixed. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 10

Film Screen film is used in panoramic imaging. n n It is sensitive to the light from an intensifying screen. It is placed between two intensifying screens in a cassette holder. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 11

Intensifying Screens Types of intensifying screens: n Calcium tungstate Emit blue light n Rare earth Emit green light Require less x-ray exposure than calcium tungstate screens Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 12

Cassette A device used to hold the extraoral film and intensifying screens n n n May be rigid or flexible, curved or straight Must be light-tight Must be marked to orient the finished image Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 13

Step by Step: Equipment Preparation Load the panoramic cassette in the darkroom under safelight conditions. Cover the bite-block with a disposable plastic coverslip or sterilize between patients. Set the exposure factors. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 14

Step by Step: Patient Preparation 1. Explain the radiographic procedures. 2. Place a lead apron without a thyroid collar on the patient and secure it. n A double-sided lead apron is recommended. 3. Remove all objects from the head and neck area that may interfere with the procedure. 4. Instruct the patient to sit or stand “as tall as possible” with the back straight and erect. 5. Instruct the patient to bite on the plastic biteblock. 6. Position the midsagittal plane perpendicular to the floor. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 15

Patient Positioning Continued 7. Position the Frankfort plane parallel with the floor. n Frankfort plane: imaginary plane or line from the orbital ridge to the acoustic meatus of the ear 8. Instruct the patient to position the tongue on the roof of the mouth and keep the tongue in that position during exposure of the receptor. 9. Instruct the patient to close the lips around the biteblock. 10. Instruct the patient to remain still while the machine is rotating during exposure. 11. Expose the receptor and proceed with receptor processing. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 16

Patient Preparation Errors Ghost Images n A radiographic artifact seen on a panoramic image that is produced when a radiodense object is penetrated twice by the x-ray beam It is found on the opposite side of the receptor. It appears indistinct, larger, and higher than its actual counterpart. Problem n If all metallic or radiodense objects are not removed before exposure, a ghost image results that obscures diagnostic information. Solution n The dental radiographer must instruct the patient to remove all radiodense objects in the head and neck region prior to positioning the patient. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 17

Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 18

Lead Apron Artifact Problem n A radiopaque cone-shaped artifact that obscures diagnostic information results if the lead apron is incorrectly placed, or if a lead apron with a thyroid collar is used. Solution n The dental radiographer must always use a lead apron without a thyroid collar when exposing a panoramic projection. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 19

Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 20

Patient Positioning Errors Positioning of the Lips and Tongue Positioning of the Frankfort Plane – Upward Positioning of the Frankfort Plane – Downward Positioning of the Teeth – Anterior to the Focal Trough Positioning of the Teeth – Posterior to the Focal Trough Positioning of the Midsagittal Plane Positioning of the Spine Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 21

Positioning of the Lips and Tongue Problem n n If the patient’s lips are not closed on the biteblock during the exposure of a panoramic projection, a dark radiolucent shadow results that obscures the anterior teeth. If the tongue is not in contact with the palate during exposure of a panoramic projection, a dark radiolucent shadow results that obscures the apices of the maxillary teeth. Solution n Instruct the patient to close the lips around the bite-block and swallow and raise the tongue up to the palate during the exposure of the receptor. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 22

Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 23

Positioning of the Frankfort Plane Upward Problem n If the patient’s chin is positioned too high a “reverse smile line” is apparent on the image. Solution n Position the patient so the Frankfort plane is parallel with the floor. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 24

Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 25

Positioning of the Frankfort Plane Downward Problem n If the patient’s chin is positioned too low or is tipped down an “exaggerated smile line” is apparent on the image. Solution n Position the patient so that the Frankfort plane is parallel with the floor. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 26

Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 27

Positioning of the Teeth – Anterior to the Focal Trough Problem n If the patient’s teeth are positioned too far forward on the bite-block or anterior to the focal trough, the anterior teeth appear “skinny” and out of focus. Solution n Position the patient so that the anterior teeth are placed in an end-to-end position in the groove on the bite-block. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 28

Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 29

Positioning of the Teeth – Posterior to the Focal Trough Problem n If the patient’s teeth are positioned too far back on the bite-block or posterior to the focal trough, the anterior teeth appear “fat” and out of focus. Solution n Position the patient so that the anterior teeth are placed in an end-to-end position in the groove on the bite-block. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 30

Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 31

Positioning of the Midsagittal Plane Problem n If the patient’s head is not centered the ramus and posterior teeth appear unequally magnified on the panoramic radiograph. The side farthest from the receptor appears magnified. Solution n Position the patient’s head so that the midsagittal plane is perpendicular to the floor while the midline is centered on the bite-block. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 32

Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 33

Positioning of the Spine Problem n If the patient is not standing or sitting with a straight spine, the cervical spine appears as a radiopacity in the center of the receptor and obscures diagnostic information. Solution n Instruct the patient to stand or sit “as tall as possible” with a straight back. Copyright © 2012, 2006, 2000, 1996 by Saunders, an imprint of Elsevier Inc. 34