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PANORAMIC RADIOGRAPHY

PANORAMIC RADIOGRAPHY. DA 105. Dental Radiography. Questions What equipment is used in panoramic radiography? What is the focal trough? What are the advantages and disadvantages of panoramic radiography?. Introduction. Purpose To present basic concepts of panoramic radiography

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PANORAMIC RADIOGRAPHY

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  1. PANORAMIC RADIOGRAPHY DA 105

  2. Dental Radiography • Questions • What equipment is used in panoramic radiography? • What is the focal trough? • What are the advantages and disadvantages of panoramic radiography?

  3. Introduction • Purpose • To present basic concepts of panoramic radiography • To describe the patient preparation, equipment preparation, and patient positioning procedures needed to perform this procedure

  4. Basic Concepts • Purpose and Use • Fundamentals • Rotation center • Focal trough • Equipment • Basic Concepts

  5. Basic Concepts • Panoramic film • Shows a wide view of the upper and lower jaws • Panoramic radiography • Used to examine the upper and lower jaws on a single film

  6.   A, Panoramic radiograph. B, Panoramic anatomy

  7. Purpose and Use • An overall image of the maxilla and mandible • Often used to supplement bite-wing and selected periapical films • Images seen on a panoramic film are not as defined or sharp as the images seen on intraoral films

  8. Fundamentals • In panoramic radiography, the film and x-ray tubehead move around the patient • The x-ray tube rotates around the patient’s head in one direction while the film rotates in the opposite direction • The patient may stand or sit in a stationary position

  9. The film and x-ray tubehead move around the patient in opposite directions in panoramic radiography

  10. Fundamentals • The movement of the film and the tubehead produces an image through the process known as tomography • Tomography • A radiographic technique that allows the imaging of one layer or section of the body while blurring images from structures in other planes

  11. Rotation Center • The pivotal point, or axis, around which the cassette carrier and x-ray tubehead rotate • There are three basic rotation centers depending on the manufacturer • Double-center rotation • Triple-center rotation • Moving-center rotation

  12. Types of panoramic x-ray machines. A, Double-center rotation machines have two rotational centers, one for the right and one for the left side of the jaws. B, Triple-center rotation machines have three centers of rotation and create an uninterrupted radiographic image of the jaws. C, Moving-center rotation machines rotate around a continuously moving center that is similar to the arches, creating an uninterrupted image of the jaws

  13. Focal Trough • Can be defined as a three-dimensional curved zone in which structures are clearly demonstrated on a panoramic radiograph

  14. Example of an “image layer” or “focal trough

  15. Equipment • Panoramic x-ray units • Film • Intensifying screens • Cassette

  16. Panoramic X-ray Units • There are a number of different panoramic x-ray units • All have similar components • X-ray tubehead • Head positioner • Exposure controls

  17. A, Orthophos XG Plus extraoral x-ray machine. B, Orthoralix 8500 extraoral x-ray machine. C, Example of a digital panoramic system

  18. Main components of the Orthophos XG 5: A, x-ray tubehead; B, head positioner; C, exposure controls

  19. Panoramic X-ray Units • X-ray Tubehead • Similar to an intraoral x-ray tubehead • Collimator • 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

  20. The collimater on the Orthophos XG 5 has a narrow slit opening

  21. Panoramic X-ray Units • The x-ray beam emerges from the panoramic tubehead through the collimator as a narrow band • It passes through the patient and exposes the film through another vertical slit in the cassette carrier • The vertical angulation is fixed so that the x-ray beam is directed slightly upward

  22. Head Positioner • A chin rest, notched bite-block, forehead rest, and lateral head supports or guides • Used to align the patient’s teeth as accurately as possible

  23. The head positioner (notched bite-block, forehead rest, and lateral head supports) is used to align the patients teeth in the focal trough

  24. 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

  25.    Exposure controls on the Orthophos XG 5 can be used to adjust exposure factors

  26. Film • Screen film is used in panoramic radiography • It is sensitive to the light from an intensifying screen • It is placed between two intensifying screens in a cassette holder

  27. Intensifying Screens • Calcium tungstate • Emit blue light • Rare earth • Emit green light • Require less x-ray exposure than calcium tungstate screens

  28. Cassette • A device used to hold the extraoral film and intensifying screens • May be rigid or flexible, curved or straight • Must be light-tight • Must be marked to orient the finished radiograph

  29. Film cassettes. A and B, Rigid cassettes. Intensifying screens are attached to the inside cover and base of a rigid cassette. When the panoramic film is placed in the cassette, it lies between the screens. C, Flexible cassette has an opening at one end, creating a pouch. The panoramic film is placed between two removable, flexible intensifying screens, which are then slid into the pouch

  30. This panoramic film is labeled with two metal letters indicating the patients right (R) and left (L) sides

  31. Step-by-Step Procedures • Equipment Preparation • Patient Preparation • Patient Positioning

  32. 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

  33. Patient Preparation • Explain the radiographic procedures • Place a lead apron without a thyroid collar on the patient and secure it • A double-sided lead apron is recommended • Remove all objects from the head and neck area that may interfere with film exposure

  34. A double-sided lead apron is recommended for use during exposure of a panoramic film

  35. Patient Positioning • Instruct the patient to sit or stand “as tall as possible” with the back straight and erect • Instruct the patient to bite on the plastic bite-block • Position the midsagittal plane perpendicular to the floor

  36. The patients teeth must be positioned in the grooves on the bite-block

  37. Frankfort and midsagittal planes. The Frankfort plane passes through the floor of the orbit and the external auditory meatus. The midsagittal plane divides the body in half into right and left sides

  38. The patients Frankfort plane must be positioned so that it is parallel to the floor

  39. Patient Positioning • Position the Frankfort plane parallel with the floor • Instruct the patient to position the tongue on the roof of the mouth and keep the tongue in that position during exposure of the film • Instruct the patient to close the lips around the bite-block • Instruct the patient to remain still while the machine is rotating during exposure • Expose the film and proceed with film processing

  40. Common Errors • Patient Preparation Errors • Patient Positioning Errors

  41. Patient Preparation Errors • Ghost Images • Lead Apron Artifact

  42. Ghost Images • A radiographic artifact seen on a panoramic film that is produced when a radiodense object is penetrated twice by the x-ray beam • It is found on the opposite side of the film • It appears indistinct, larger, and higher than its actual counterpart

  43. Large hoop earrings (1) and ghost images (2). The ghost image of the earring appears on the opposite side of the film and is enlarged and laterally distorted

  44. Ghost Images • Problem • If all metallic or radiodense objects are not removed before exposure, a ghost image results that obscures diagnostic information • Solution • The dental radiographer must instruct the patient to remove all radiodense objects in the head and neck region prior to positioning the patient

  45. Lead Apron Artifact • Problem • 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 • The dental radiographer must always use a lead apron without a thyroid collar when exposing a panoramic film

  46. On a panoramic radiograph, a lead apron artifact appears as a large cone-shaped radiopacity obscuring the mandible

  47. 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

  48. Positioning of the Lips and Tongue • Problem • If the patient’s lips are not closed on the bite-block during the exposure of a panoramic film, 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 film, a dark radiolucent shadow results that obscures the apices of the maxillary teeth • Solution • 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 film

  49. If the tongue is not placed on the roof of the mouth, a radiolucent shadow will be superimposed over the apices of the maxillary teeth

  50. Positioning of the Frankfort Plane Upward • Problem • If the patient’s chin is positioned too high a “reverse smile line” is apparent on the radiograph • Solution • Position the patient so the Frankfort plane is parallel with the floor

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