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 Equipment Basic Concepts
Rotation center
Focal trough
Equipment
Basic Concepts

5. Basic Concepts Panoramic film Panoramic radiography
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
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
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 Collimator
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 Rare earth Emit blue light
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
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
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)
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 Solution
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 Solution
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

51. The patients head is incorrectly positioned; the chin is tipped up

52. A “reverse smile line” is seen on a panoramic film when the patients chin is tipped up

53. Positioning of the Frankfort Plane Downward
Problem
If the patient’s chin is positioned too low or is tipped down an “exaggerated smile line” is apparent on the radiograph
Solution
Position the patient so that the Frankfort plane is parallel with the floor

54. The patients head is incorrectly positioned; the chin is tipped down

55. An “exaggerated smile line” is seen on a panoramic film when the patients chin is tipped down

56. Positioning of the Teeth – Anterior to the Focal Trough
Problem
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
Position the patient so that the anterior teeth are placed in an end-to-end position in the groove on the bite-block

57. The patient is incorrectly positioned; the teeth are too far forward on the bite-block

58. The anterior teeth appear narrowed and blurred on a panoramic film when the patient is positioned too far forward on the bite-block

59. Positioning of the Teeth – Posterior to the Focal Trough
Problem
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
Position the patient so that the anterior teeth are placed in an end-to-end position in the groove on the bite-block

60. The patient is incorrectly positioned; the teeth are too far back and not on the bite-block

61. The anterior teeth appear widened and blurred on a panoramic film when the patient is positioned too far back on the bite-block.

62. Positioning of the Midsagittal Plane
Problem
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 film appears magnified
Solution
Position the patient’s head so that the midsagittal plane is perpendicular to the floor while the midline is centered on the bite-block

63. The patient is incorrectly positioned; the head is not centered

64. The patients posterior teeth and ramus appear to be magnified on a panoramic film when the head is not centered

65. Positioning of the Spine
Problem
If the patient is not standing or sitting with a straight spine, the cervical spine appears as a radiopacity in the center of the film and obscures diagnostic information
Solution
Instruct the patient to stand or sit “as tall as possible” with a straight back

66. If the patient is not standing erect, superimposition of the cervical spine (arrows) may be seen on the center of the panoramic film

67. Advantages of Panoramic Radiography
Field size
Simplicity
Patient cooperation
Minimal exposure

68. Panoramic radiograph of a pediatric patient

69. Disadvantages of Panoramic Radiography
Image quality
Focal trough limitations
Distortion
Equipment cost