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THE PANORAMIC RADIOGRAPH

THE PANORAMIC RADIOGRAPH

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THE PANORAMIC RADIOGRAPH

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  1. THE PANORAMIC RADIOGRAPH

  2. The panoramic technique is used to show a continuous view of the lower half of the face. This includes the teeth, jaws and some soft tissue anatomy..

  3. ADVANTAGES & DISADVANTAGES OF THE PANORAMIC RADIOGRAPH • The principal advantages of the panoramic radiograph are: • the large area of coverage, • the bilateral view of anatomy, • low patient radiation dose, and • it can be used on handicapped patients, children, and on those who are unable to open their mouths. • Unfortunately, this radiograph has several disadvantages. • The definition of the x-ray is not as sharp as a periapical or a bitewing x-ray. Therefore, small caries, periapical disease along with other diseases, and abnormalities that would show up on intraoral x-rays would not be identified on a panoramic view. • Other problems would include magnification, distortion, and natural overlapping of some of the teeth.???!!! (Digital)

  4. Tooth germs or saliva stones? • What is the exact realtive position of the tooth germs? • Not possible to say from panoramic view.

  5. Tooth germs or saliva stones? These are no tooth germs, these are salivary stones in soft tissue

  6. USES OF THE PANORAMIC RADIOGRAPH The uses of the panoramic radiograph are numerous in the diagnosis of disease and abnormalities. A number of uses are as follows: 1- A complete survey can be made of the teeth and related structures, 2- Some tumors and cysts can be examined and evaluated, 3- The location and position of impacted teeth may be determined, 4- Fractures of the lower face may be located, and 5- Growth patterns of the jaws can be studied and evaluated. These uses make the panoramic radiograph a valuable tool.

  7. THE PANORAMIC UNIT There are various types and models of the panoramic unit on the market today. The operation of each machine will vary.

  8. POSITIONING • Patient positioning using Frankfurter Horizontal plane Is the inclination of the head correct?

  9. POSITIONING • Patient positioning using Frankfurter Horizontal plane Head bent to far backwards Head bent to far forwards

  10. POSITIONING Good position of a patient

  11. Everything You alwayswanted to know about … Panoramic X-ray but were afraid to ask...

  12. The possibilities of an intraoral x-ray are limited … Panoramic X-ray … why?

  13. Panoramic X-ray = global information

  14. As you see, there is always a really difference between an image of 3 x 4 cm...

  15. ... and an image of 15 x 30 cm.

  16. 1) The principle Represent a three-dimensional object in two dimensions

  17. 1) The principle Represent a three-dimensional object in two dimensions

  18. Tube Film 2) What is a sharp layer ? For intraoral and ceph exposures: All objects which are between the film (or sensor) and the tube head will be displayed. There is no movement of the X-ray beam.

  19. For panoramic X-ray the beam must be approximately at a right angle with the arch in order to display the teeth without overlapping. In order to display the left molars, the X-ray beam must also pass through the right side of the arch – but only the left side has to be visible on the image! When imaging the incisors the beam must also pass through the cervical vertebrae – but only the incisors has to be visible! Some objects have to be invisible on the image despite the fact that they have absorbed X-ray!

  20. Exemple: A is sharp, B is blurred, C is not visible Sharp layer A C B In panoramic X-ray due to special movement of the X-ray beam and of the film only objects in a defined region (layer) will be displayed sharp. The others are blurred or not visible. But they have also absorbed radiation. How is this possible?

  21. If you put the camera on a tripod and don't move it, you get a sharp image of the background but the fast moving cars in the foreground are completely blurred. It’s a simple trick! Like taking photographs of race cars with an old analog photo camera …(longer exposure times)

  22. It’s a simple trick! Like taking photographs of race cars with an old analog photo camera …(longer exposure times) If you “follow” the car with the camera, you get a sharp image of the car but the background is blurred.

  23. You cannot get a sharp image of the background and of the fast moving car on the same photograph, but you can decide which one will be sharp and which one almost invisible – by moving the camera or not.

  24. I5 cm The x-ray beam is high (15 cm) and slim (4 mm). Panoramic X-ray = 15x30 cm 30 cm Now the geometrical explanation Rotation of tube, beam and film holder Sliding movement of the film during the rotation, in order to expose all parts of the film

  25. The principle :An object will be sharp displayed when the central beam moves on this object with the same linear speed as onthe film (sensor). It’s a rotational move. The linear speed of the beam on the objects A, B, C depends on the distance between these objects and the center of rotation. Rotation of tube, beam and film holder B A C Sliding of film

  26. But the linear speed of the beam on the film (due to the sliding movement of the film) can have only one given value at this moment. Only these objects for which both speeds have the same value are located on the line of maximum sharpness. In this example the object A will be sharp.All other objects will be less sharp, or blurred, or even invisible depending on their location. Rotation of tube, beam and film holder B A C Sliding of film

  27. The object D is invisible on the image because the sliding movements of the beam on the object and on the film are in two opposite directions – creating a big speed difference. B A C D Glissementdu film

  28. The change from sharpness to unsharpness is progressive. The zone of diagnostic relevant sharpness can be determined by a lead lines phantom. In this way the thickness of the sharp layer is determined. The speed of the film movement is preprogrammed in order to place the sharp zone at a necessary place. In this way it is possible to represent objects with complex shape. Rotation of tube, beam and film holder B A C Sliding of film

  29. Line of maximum sharpness Objects situated beyond the limits of the layer are represented as unsharp and provide little diagnostic value. Example :Sharp layer of a standard panoramic program We will see later the reason why the thickness of the layer is not constant.

  30. Complexity of a maxillary arch Zone of the sharp layer Spinal column

  31. Film Central beam Tube Tube + film cassette rotate around the object Object Calculated speed delay of the film movementBy sensors: programmed output rate of the vertical sensor pixel lines in order to simulate a movement 3) How is a panoramic unit working?

  32. The left side will be displayed ... ... but the radiation has to pass first the right side – without making an image of it!

  33. The left side will be displayed … ... but the radiation has to pass first the right side.

  34. The left side is displayed … ... but the radiation has to pass first the right side.

  35. The ideal projection prevents overlappingin the molar region.

  36. The ideal projection prevents overlappingin the molar region.

  37. Strong radiation absorption due to the spinal column. Therefore it’s necessary to compensate this area to prevent white zones.

  38. Strong radiation absorption due to the spinal column. Therefore it’s necessary to compensate this area to prevent white zones.

  39. The movement goes until the final position is reached (just opposite the starting point).

  40. Due to the jaw form complex rotational and translational movements are necessary.

  41. Rotation point of the beam at the present moment The thickness of the sharp layer 1) Is defined by the collimator of the tube 2) and varies with the distance between the object and the rotation point of the beam at the moment (see previous slide). 4) Why is the thickness of the sharp layer not constant?

  42. On panoramic X-rays, the magnification coefficient depends on the distance between the sensor and the object. 5) On what depends the magnification factor?

  43. 6) The double projection The axis of the X-ray beam is slightly inclining (5 to 6°) to pass the patients shoulders. This principle is used for all panoramic brands.

  44. Because of the radiation inclination (and the form of the mandible) some of the radiation passes below the mandible and darkens the film strongerbecause the beam hits onlyone side of the mandible. When starting an exposure, the mandible which is just before the tube head absorbs some of the radiation.

  45. This effect depends more or less on the patients bone density and the shape of his jaw. It may be unaesthetic but it doesn't interfere the diagnosis.

  46. Another effect: phantom images due to double projection from ear rings.

  47. The principle of (standard panoramic program):orthoradial radiation (without overlapping of teeth) for an exact image . The artifact-reduced programs prevent the double projection due to a modified radiation angle. But overlapping of the crowns can appear in molar and premolar region.

  48. 7) How compensate the absorption of the spinal column? On the image it is important to avoid a white zone in the anterior region.