OPG and Extraoral radiography

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Thorough knowledge of the indications of various extra oral techniques allows accurate and timely diagnosis of various maxillofacial pathologies. Further, we can arrive at a diagnosis with minimum number of x-rays there by reducing patient exposure to radiation.

Transcript of OPG and Extraoral radiography

  • Radiographs (Part 2) Presented by Dr. Neha Sharma PG II YR
  • CONTENTS 3 PANORAMIC IMAGING EXTRAORAL RADIOGRAPHS CEPHALOMETRIC LANDMARKS LATERAL SKULL PROJECTION SUBMENTOVERTEX PROJECTION PA WATERS PROJECTION REVERSE TOWNES PROJECTION TMJ IMAGING CONCLUSION
  • HISTORY OF - EXTRAORAL RADIOGRAPHIC TECHNIQUES
  • EXTRA-ORAL SOURCE Discovered by Dr. Hisatugu Numata of Japan, 1933
  • Father of Panoramic Radiography 1949, extra-oral films X-ray source - stationary Dr Yrjo Veli Paatero
  • What is panoramic imaging /pantomography??? A technique for producing a single tomographic image of the facial structures that includes both the maxillary and mandibular dental arches and their supporting structures.
  • Panorama Tomography An unobstructed view of a region in every direction An X-ray technique for making radiographs of layers of tissue in depth without the interference of tissues above and below the level PANTOMOGRAPHY
  • Equipment 1. Panoramic X-ray unit
  • 2. Screen film
  • 3. Intensifying screens
  • 4. Cassette
  • BONY LANDMARKS IN MANDIBLE 14 1 1. Condylar head 2. Sigmoid notch 3. Coronoid process 4. External oblique ridge 5. Mandibular canal 2 3 4 5 6. Post. Border of Ramus 8. Lower border7. Gonial Angle 6 7 9. Mental ridge 11. Mental foramen10. Genial tubercle 13. Lingula 12. External Oblique Ridge 14. Hyoid bone 8 9 10 11 12 13
  • BONY LANDMARKS IN MAXILLA 15 15 15. Glenoid fossa 19. Floor of Max.Sinus 17. Zygomatic Arch16. Articular eminence 18.Post. wall max. sinus 20. Zygomatic process of max. forming innominate line 21. Hard palate 22. Floor of the orbit 23. Nasal septum 24. Incisive foramen 25. Inferior choncha 26. Meatus 27. Frontal process of Z.bone 16 17 18 19 20 21 22 23 29 25 24 26 28.Pterygo max. fissure 30. Maxillary tuberosity29.Spine of the sphenoid bone 31. Lateral pterygoid plate 31 30 28 27
  • OTHER STRUCTURES 16 32 32. External acoustic meatus 34. Shadow of ear lobe33. Styloid process 35. nose 36. Shadow of Cervical spine 33 34 35 36 37 37. Cervical vertebrae 38 38. Nasopharyngeal space 39. Shadow of uvula 40 39 40 Submandibular fossa
  • A panoramic film is not as useful as periapical radiography for detecting small carious lesions, periodontal diseases, or periapical lesions. It should not be used as a substitute for intraoral films.
  • Impacted teeth and its relation with the mandibular canal.
  • To evaluate eruption patterns
  • To detect diseases, lesions, conditions of the jaws and the extent of large lesions.
  • to evaluate trauma
  • Retainedteethor root tips in edentulous patients
  • Post-operative examination and patient education.
  • Implants
  • ROTATION CENTER The pivotal point or axis, around which the cassette carrier and X-ray tubehead rotate, is termed a ROTATION CENTER.
  • Double center of rotation
  • Three stationary centers of rotation
  • Continously moving center of rotation
  • During the exposure cycle, the machine shiftsto one or more additional rotation centers. This rotational change allowsthe image layer to conformto the shape of the dental arches. The location and no. of rotational centers influence the size and shape of the focal trough.
  • Focal trough The focal trough (also known as the Image layer) is defined as a 3-D curved zone in which structures are clearly demonstrated on a panoramic radiograph.
  • Advantages 1. Fieldsize 2. Minimal exposure 3. Simplicity 4. Patient cooperation 5. Useful in patients with trismus & gagging 6. Valuable visual aid for patient education
  • Disadvantages 1. Cannot be usedin detection of caries and periodontal disease. 2. Overlapping of teethin premolar region 3. Focal trough limitations 4. Shadowof cervical spine in the lower anterior region. 5. Ghost images 6. Equipment cost
  • 34 COMMON ERRORS
  • PATIENT POSITIONING ERRORS
  • Positioning of lips and tongue
  • Positioning of Frankfort plane upward
  • Positioning of Frankfort plane downward
  • Positioning of teeth anterior to focal trough
  • Positioning of teeth posterior to focal trough
  • Positioning of midsagittal plane
  • Patient movement
  • Positioning of spine
  • Processing Errors Underexposed, light, washed out image Very dark film, Overexposed Film Fog Improper filter in daylight loader
  • Panoramic Image= Right lateral image+ PA image+ Left Lateral image
  • EXTRAORA L RADIOGRA PHIC TECHNIQUE S 7/29/2014 46
  • LATERAL CEPHALOMETRIC PROJECTION Film position - cassette is placed perpendicular to the floor with long axis of the cassette placed vertically. Position of patient - left side of the face is positioned against the cassette. Mid sagittal plane is perpendicular to the floor and parallel to film. Central ray - perpendicular to the film.
  • Exposure parameters KVp= 84 mAs= 13 Seconds =1.6
  • INDICATIONS To evaluate facial growth and development, trauma, disease and developmental anomalies. Demonstrates the bones of the face, skull as well as the soft tissue profile of the face.
  • Film position - cassette is perpendicular to the floor with long axis of the cassette placed vertically. Position of patient The film is adjusted so that the upper circumference of the skull is .5 inch below the lower border of the cassette. Central ray - perpendicular to the film towards the E.A.M. TRUE LATERAL SKULL
  • LATERAL SKULL PROJECTION 51 Exposure parameters KVp= 65 mAs= 10 Seconds =.5-2 sec
  • To survey skull and facial bone for trauma or pathology. Nasopharangeal soft tissue, paranasal sinus and hard palate. Condition affecting sella turcica, such as tumour of pitutary gland in acromegaly. Indications
  • 7/29/2014 53 PA WATERS PROJECTION Film position - cassette is perpendicular to the floor with long axis of the cassette placed vertically. Position of patient - mid sagittal plane perpendicular to the floor and parallel to film. Head is extended so that only the chin touches the casette. The tip of nose is .5 to 1.5 cm away from the cassette Central ray- perpendicular and to the midpoint of the film.
  • 54 Exposure parameters KVp= 65 mAs= 10 Seconds =2-3 sec
  • INDICATIONS 55 Demonstrate the maxillary , frontal and ethmoidal sinuses. The orbit, frontozygomatic suture, nasal cavity, coronoid process of the mandible and the zygomatic arch are also seen.
  • 56 Film position- cassette is placed perpendicular to the floor with long axis of the cassette placed horizontally. Position of patient- head is centered on the cassette (Head and neck tipped back).Vertex of the skull touches the cassette. Central raY- perpendicular to the film. It enters via between angle of mandible and i