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Extraoral radiography


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Extraoral radiography

  2. 2. CONTENTS-CONTENTS-• Introduction• Adjuncts in extraoral radiography– Intensifying screens– Grids– Digital radiography• Extraoral radiographic techniques– Panoramic radiograph– Skull viewsPA Skull PA CephalogramAP Skull Towne’s viewSubmentovertex view (base of the skull)Lateral skull Lateral cephalogram
  3. 3. • Maxillary sinus-– PA Water’s view– Modifications- Grenger’s view– Caldwell’s projection• Mandible-– PA Mandible– Lateral oblique views• Body• Ramus• TMJ views-– Transcranial– Transpharyngeal– Transorbital– Reverse Towne’s view
  4. 4. INTRODUCTION-INTRODUCTION-• Extraoral radiographs (outside the mouth) aretaken when large areas of the skull or jaw mustbe examined or when patients are unable to opentheir mouths for film placement.• Extraoral radiographs do not show the details aswell as intraoral films.• Extraoral radiographs are very useful forevaluating large areas of the skull and jaws butare not adequate for detection of subtle changessuch as the early stages of dental caries orperiodontal disease.• There are many type of extraoral radiographs.Some types are used to view the entire skull,whereas other types focus on the maxilla andmandible.
  5. 5. • It makes use of intensifying screens.• Cephalometric and skull views require atleast a 8X10 inch image receptor,whereas oblique lateral projections of themandible can be obtained with 5X7 inch.
  7. 7. Panoramic radiographsPanoramic radiographs• Most common.• It is a technique for producing a singletomographic image of facial structuresthat includes both maxillary andmandibular arches and their supportingstructures.• This is curvilinear variant of conventionaltomography and is also used on theprinciple of the reciprocal movement ofan x-ray source and an image receptoraround a central point or plane called theimage layer in which the object ofinterest is located.
  8. 8. Indications-Evaluation of-• Trauma• Location of third molars• Extensive dental or osseous disease• Known or suspected large lesions• Tooth development• Retained teeth or root tips• TMJ pain• Dental anomalies etc.
  10. 10. Lateral cephalometric projection-Lateral cephalometric projection-lmage Receptor and PatientPlacement• The image receptor ispositioned parallel to thepatient’s midsagittal plane.The site of interest is placedtoward the image receptor tominimize distortion.• In cephalometric radiography,a wedge filter at the tube headis positioned over the anterioraspect of the beam to absorbsome of the radiation and toallow visualization of softtissues of the face.• The central ray is directedperpendicular to the cassettethrough the external auditorymeatus.
  11. 11. • This view is used to evaluate facialgrowth and development, trauma,disease and developmentalanomalies.• This projection demonstrates thebones of the face, skull as well asthe soft tissue profile of the face.
  12. 12. True lateral skullTrue lateral skull• The image receptor ispositioned parallel to thepatient’s midsagittal plane.The site of interest is placedtoward the image receptorto minimize distortion.• The film is adjusted so thatthe upper circumference ofthe skull is half inch belowthe upper border of thecassette.• The central ray is directedperpendicular to thecassette and the midsagittalplane and towards theexternal auditory meatus.
  13. 13. INDICATIONS• Fractures of the cranium and the cranial base• Middle third facial fractures, to show possibledownward and backward displacement of themaxilla• Investigation of the frontal, sphenoidal andmaxillary sinuses• Conditions affecting the skull vault,– Paget’s disease– Multiple myeloma– Hyperparathyroidism• Conditions affecting the sella turcica,– Tumor of pituitary gland in acromegaly
  14. 14. PA skull projectionPA skull projection• The image receptor isplaced in front of thepatient, perpendicular tothe mid sagittal plane andparallel to coronal plane,so that the canthomeatalline is perpendicular tothe image receptor.• Central Ray is directed atright angles to the filmthrough the midsagittalplane through theocciput.
  15. 15. INDICATIONS• Fractures of the skull vault• Investigation of the frontal sinuses• Conditions affecting the cranium– Paget’s disease– Multiple myeloma– Hyperparathyroidism• Intracranial calcifications
  16. 16. PA cephalogramPA cephalogram
  17. 17. Towne’s viewTowne’s view• The cassette is placedperpendicular to thefloor.• The long-axis of thecassette is positionedvertically.• This is ananteroposterior view,with the back of thepatient’s head touchingthe film. Thecanthomeatal line isperpendicular to thefilm.• The central ray isdirected at 30degrees to thecanthomeatal lineand passes throughit at a point betweenthe external auditorymeatus.
  18. 18. • It is primarily usedto observe theoccipital area ofthe skull.• The necks of thecondyloid processcan also beviewed.
  19. 19. SubmentovertexSubmentovertex (base of the skull)(base of the skull)• The image receptor ispositioned parallel to patient’stransverse plane andperpendicular to themidsagittal and coronalplanes. To achieve this, thepatients neck is extended asfar backward as possible,with the canthomeatal lineforming a 10 degree anglewith the receptor.• The central beam isperpendicular to the imagereceptor, directed from belowthe mandible toward thevertex of the skull (hence thename submentoyertex, orSMV), and centered about 2cms anterior to a lineconnecting the right and leftcondyles.
  20. 20. Jug handle viewJug handle view• Same as that insubmentovertex.• The exposure timefor the zygomaticarch is reduced toapproximately one-third the normalexposure time for asubmentovertexprojection.
  22. 22. Lateral oblique(body of mandible)Lateral oblique(body of mandible)• The cassette is positionedagainst the patients cheekoverlying the ascendingramus and the posterioraspect of the condyle of themandible under investigation.• The cassette is positioned sothat its lower border isparallel with the inferiorborder of the mandible butlies at least 2 cm below it
  23. 23. • The positioning achieves a l0-degree angle of separationbetween the median sagittalplane and the film.• The mandible is extended asfar as possible.• The centring position of thetube is the contralateral sideof the mandible at a point 2cm below the inferior border inthe region of the first/secondpermanent molar withangulation of 10 degreescephalad or caudal
  24. 24. Lateral oblique (ramus of mandible)Lateral oblique (ramus of mandible)
  25. 25. PA mandiblePA mandible• The cassette is placed in frontof the patient, so that themedian sagittal plane should beperpendicular to the cassette.The head is then adjusted tobring the orbito-meatal baselineperpendicular to the cassette• The cassette should bepositioned such that the middleof cassette, is centred at thelevel of the angles of themandible.• The central ray is directedperpendicular to the cassetteand centred in the midline atthe levels of the angles of themandible.
  27. 27. PA Water’s view (PNS)PA Water’s view (PNS)• The image receptor is placedin front of the patient andperpendicular to themidsagittal plane.• The patients head is tiltedupward so that thecanthomeatal line forms a 37degrees angle with theimage receptor.• If the patients mouth isopen, the sphenoid sinus willbe seen superimposed overthe palate.• The central beam isperpendicular to the imagereceptor and centered in thearea of maxillary sinuses.
  28. 28. Granger’s Modification-Granger’s Modification-
  29. 29. Caldwell’s Modification-Caldwell’s Modification-
  31. 31. TMJ panoramic viewTMJ panoramic view
  32. 32. Indications-• The panoramic projection serves as thescreening projection to identifyodontogenic disorders and otherdisorders that may be the source of TMJsymptoms• Gross osseous changes in the condylesmay be identified such as asymmetries,extensive erosions, large osteophytes,tumors or fractures.
  33. 33. TMJ- transcranial viewTMJ- transcranial view• The cassette is placed flat against the patient’sear and centered over the TM- joint of interest,against the facial skin parallel to the sagittalplane.• The patients head is adjusted so that thesagittal plane is vertical.• The ala-tragus line is parallel to the floor.• This view is taken with both open and closedposition.
  34. 34. • In Lindblom technic (1936), centralray entered half inch behind and 2inches above external auditorymeatus.
  35. 35. • In Grewcock technic (1953), centralray entry point is 2 inches aboveexternal auditory meatusperpendicular to occlusal plane
  36. 36. • In Gillis technic (1939), central rayentry point is 1/2 inch in front and 2inches above external auditorymeatus parallel and perpendicularto occlusal plane.
  37. 37. It depicts the lateral aspect of the TMJ.It helps to evaluate the joint’s bony relationship.Detecting arthritic changes on the articular surfaces.
  38. 38. TMJ- transpharyngeal viewTMJ- transpharyngeal view• The cassette is placed flat againstthe patient’s ear, over the TM jointof interest, against the facial skinparallel to the sagittal plane.• The patient is positioned so thatthe sagittal plane is vertical andparallel to the film. The patient isinstructed to slowly inhale throughthe nose during exposure.• The patient should open mouth• The central ray is directed from theopposite side cranially, at an angleof -5 to -10 degrees posteriorly.• It is directed through themandibular notch, that is a windowbetween the coronoid, condyle andthe zygomatic arch, of oppositeside below the base of the skull tothe TM joint of interest.
  39. 39. • It is a lateralprojectionshowing medialaspect of condylarhead and neck.
  40. 40. TMJ- transorbital viewTMJ- transorbital view• The film behind thepatient’s head at an angleof 45 degees to the sagittalplane.• The patient is positionedso that the sagittal plane isvertical.• The canthomeatel lineshould be 10 degrees tothe horizontal, with thehead tipped downwards.The mouth should be wideopen.• The tube head is placed infront of patient’s face.• The central ray is directed tothe joint of interest, at anangle of +20 degrees, tostrike the cassette at rightangles.• The point of entry may betaken at:– Pupil of the same eye, askingthe patient to look straightahead.– Medial canthus of the same eye– Medial canthus of the oppositeeye
  41. 41. The anterior view of the temporomandibular jointMedial displacement of fractured condyleFracture of neck of condyle
  42. 42. Reverse Towne’s viewReverse Towne’s view• The image receptor is placedin front of the patient,perpendicular to themidsagittal and parallel to thecoronal plane.• The patient’s head is tilteddownward so that thecanthomeatal line forms a 25to 30 degree angle with theimage receptor.• To improve visualization ofthe condyles, the patient’smouth is opened so that thecondylar heads are locatedinferior to the articulareminence.• The central beam isperpendicular to the imagereceptor and parallel topatient’s midsagittal planeand it is centered at thelevel of the condyles.
  43. 43. • Condylar neckand head• High fractures ofcondylar neck,intracapsularfractures of theTMJ• Condylarhypoplasia orhypertrophy
  45. 45. • CT• MRI• USG• CBCT
  46. 46. COMPUTED TOMOGRAPHYCOMPUTED TOMOGRAPHYIndications-The diagnosis and extent of• Variety of infections• Osteomyelitis• Cysts• Benign and malignant tumors• Trauma in the maxillofacial region• Lesions involving the bone• 3D CT has been applied to trauma andcraniofacial reconstructive surgery andused for treatment of congenital andacquired deformities.
  47. 47. MRIMRIIndications-• To evaluate the position and integrity ofthe disk in the TMJ.• Neoplasia involving the soft tissues,such as tongue, cheek, salivary glands,and neck.• Determining malignant involvement oflymphnodes.• Determining perineural invasion bymalignant neoplasms.• With contrast, enhances the imageresolution of neoplasia.
  48. 48. ULTRASONOGRAPHYULTRASONOGRAPHYIndications-For the evaluation of• Neoplasms in the thyroid, paathyroid orsalivary glands or lymphnodes.• Stones in salivary glands or ducts• Vessels of neck• To guide fine-needle aspiration in theneck
  49. 49. CONE-BEAM COMPUTEDCONE-BEAM COMPUTEDTOMOGRAPHYTOMOGRAPHY• Cone-beam computedtomography (CBCT) isa recent technologyinitially developed forangiography in 1982and subsequentlyapplied to maxiilofacialimaging.
  50. 50. It constitutes of• Two-dimensionaldigital arrayproviding an areadetector fixed on arotating gantry• A three-dimensional (3D)cone shaped x-raybeam
  51. 51. PRINCIPLE-• Cone-beam scanners use a two-dimensional digital array providing anarea detector rather than a lineardetector as CT does.• This is combined with a three-dimensional (3D) x-ray beam withcircular collimation so that the resultantbeam is in the shape of a cone, hencethe name "cone beam."
  52. 52. • Because the exposureincorporates the entireregion of interest (ROI), onlyone rotational scan of thegantry is necessary toacquire enough data forimage reconstruction.• CBCT produces an entirevolumetric dataset fromwhich the voxels areextracted.• Voxel dimensions aredependent on the pixel sizeon the area detector.• Therefore CBCT units ingeneral provide voxelresolutions that areisotropic-equal in all threedimensions.
  53. 53. How the image acquisition occurs?How the image acquisition occurs?
  54. 54. • End Result– 3-D visualization of the oral and maxillofacialcomplex from any plane– A stack of 360 images or exposurescompiled into a volumetric dataset through acomputer process known as primaryreconstruction– This data volume is then converted into apatient-study by accompanying software– Can be visualized as• 2D trans-axial, multi-planar reformatted• 3D techniques such as surface reconstruction andvolume rendering• A combination of 2D and 3D techniques
  55. 55. APPLICATIONSAPPLICATIONS– Orthodontic treatment planning– Dental implants– Temporomandibular joints for osseousdegenerative changes– Evaluation of wisdom teeth vs. mandibularnerve– Endodontic assessment– Assesment of impacted teeth, fractured teethand jaws, periapical infections andperiodontal diseases.- Benign calcifications (tonsilloliths, lymphnodes, salivary gland stones) can also beidentified)
  56. 56. C B C T - ORTHOC B C T - ORTHOCeph TracingCeph Tracing
  57. 57. C B C TC B C TNerve MappingNerve Mapping
  58. 58. CBCTCBCT TMJ viewTMJ view
  59. 59. ADVANTAGES-• Lower dose than helical• Compact design• Superior images to Panoramic• Low cost• Low heat load• High speed scanning (less than 30 secs)
  60. 60. DISADVANTAGES-• Worse low contrast detectability• Poor soft tissue contrast• Long scan times = motion artifacts• Slightly Inferior quality toconventional CT• Image noise• Metal artifacts
  61. 61. C B C TC B C T versusversus Medical C TMedical C T• Med CT– Conventional linearfan beam– Single row or a series(4, 8, 12, 32, 64) ofsolid state detectors– Provides a set ofconsecutive slices ofthe patient• CBCT– Cone beam– Square 2 dimensionalarray of detectors– Provides a volume ofdata
  62. 62. C B C TC B C T versusversus Medical C TMedical C T• Med CT– Greater contrastresolution• Morediscriminationbetween differenttissue types (i.e.bone, teeth, andsoft tissue)• CBCT– Equipment• Cost 3-5x less thanMDCT• Lighter & Smaller• No special electrical• No floorstrengthening• No special cooling– Ease of operation– Dedicated to dental– Patient sits or stands– Both jaws can beimaged at the sametime– Lower radiation burden
  63. 63. NewTom 3G by AFP MercuRay by Hitachi3D Accuitomoby J. MoritaGalileos by SironaI-CAT by ISI Iluma by IMTECVARIOUS CBCT UNITS