Extra oral radiographic techniques-Dr Joseph Johny.pptx

extraoral radiographic techniques

1. Extra oral radiographic techniques Dr Joseph Johny Dept of oral medicine & radiology

2. Definition Those techniques in which film is placed outside the oral cavity, against the side of the face to be radiographed and the X-ray beam is directed towards it.

3. Indications To evaluate skeletal growth and development Trauma TMJ Status of Impacted teeth Extent of large lesions Pathological conditions Trismus

4. Important landmarks

5. Frankfort horizontal line Infraorbital line Canthomeatal line Midsagittal plane

6. Postero anterior projection (Granger’s projection) Film placement: Placed perpendicular to the floor, long axis vertically Patient position: Mid- sagittal plane vertical and perpendicular to the plane of the cassette Canthomeatal line 10 degree to the plane Nose and forehead should touch the casette Central ray: Directed perpendicularly from backward Structures seen: frontal sinuses Sphenoidal sinuses Upper part of the antrum

7. Caldwell projection Film placement: Placed perpendicular to the floor, long axis vertically Patient position: Mid- sagittal plane vertical and perpendicular to the plane of the cassette Canthomeatal line 10 degree to the plane Nose and forehead should touch the casette Central ray: Directed 23 degree to the canthomeatal line, entering skull about 3cm above the external occipital protruberenceand exiting at the glabella Structures seen: Ethmoidal air sinuses Orbits

8. Water’s view Film placement: Placed perpendicular to the floor, long axis vertically Patient position: Mid- sagittal plane vertical and perpendicular to the plane of the cassette Canthomeatal line 37 degree from the plane of the casette Head extended, chin touches the casette Central ray: Directed perpendicular and to the midpoint of the film

9. Structures seen: maxillary sinuses, ethmoid sinus, frontal sinus Nasal cavity, coronoid process, zygomatic arch Open mouthwater’s view- sphenoidal sinuses Uses : Evaluation of sinus diseases (root pushed into antrum ) Fracture of coronoid , zygoma , orbit Extension of tumours , cysts, impaction

10. PA Mandible Film placement: Placed perpendicular to the floor, long axis vertically Patient position: Mid- sagittal plane vertical and perpendicular to the plane of the cassette Head tipped downwards, forehead and nose touch the film Radiographic base line is horizontal and perpendicular to the film Central ray: Right angles to the film through midsagittal plane through cervical spine; at the level of angles of the mandible Uses: Fractures of posterior third of body, rami,angles and condylar neck Mediolateral expansions, mandibular hypoplasia , hyperplasia

11. Lateral olique body Film placement: Cassette is placed against cheek and centered over the 1 st molar Lower border parallel with the inferior border of the mandible and extending at least 2cm below it Patient position: head is tilted towards the side being examined and the mandible is protruded Central ray: Directed towards 1 st molar region of the mandible on the side of interest from a point 2cm below the angle on the tube side Beam is directed perpendicular to the horizontal plane of the film Structures seen: Pre molar-molar region and the inferior border of the mandible

12. Lateral oblique ramus Film placement: Cassette is placed over the ramus and as far enough posteriorly to include the condyle Lower border parallel with the inferior border of the mandible and extending at least 2cm below it Patient position: head is tilted towards the side being examined until a line between mandibular angle next to the tube and the condyle away from the tube is parallel with the floor Central ray: Directed posteriorly towards centre of ramus on the side of interest from 2cm below 1 st molar region on the Beam is directed perpendicular to the horizontal plane of the film Structures seen: Ramus from angle of mandible to condyle 3rdmolar regions of maxilla and mandible

13. Reverse town Film placement: Perpendicular to the floor, long axis vertically Patient position: Mid- sagittal plane vertical and perpendicular to the film Canthomeatal line should be 25-30 degree angle with the casette Head touches the casette , patient’s mouth should be open Central ray: Beam is directed through mid- sagittal plane at the level of mandible perpendicular to the film Uses : Posterior of Condylar head and neck, high condylar fractures, mediolateral displacement, posterior wall of maxillary sinus, condylar hypoplasia and hyperplasia

14. Submentovertex Film placement: Placed perpendicular to the floor, long axis vertically Patient position: Head centered on the casette , head and neck tipped back as far as possible, vertex of the skull touches the cassette Mid- sagittal plane perpendicular to the cassette Canthomeatal line should be parallel to the cassette Central ray: Directed perpendicular to the film and through the midsagittal plane

15. Uses : Fracture of zygomatic arches Destructive lesions of palate, pterygoid regions Sphenoidal sinus diseases Base of the skull condyle Assessment of thickness of mandible before osteotomy Contraindication: cervical spondilytis and neck injuries

16. Jug handle view To see the zygomatic arch Modification of submentovertex Central ray: cone is brought as close as possible to the patient(leads to magnification of structures at the base of the skull) kVp will be reduced to 50 kVp

17. Transcranial Film placement: Cassette flat against patient’s ear, centered over TMJ of interest parallel to sagittal plane Patient position: Mid- sagittal plane vertical, ala tragal line parallel to the floor Three positions; open mouth, closed mouth and rest position Central ray: caudally at an angle of +20 to +25 degree Post auricular/ Lindblom technique: point of entry- ½ inch behind and 2 inch abovethe auditory meatus . Directed posteriorly and passes along long axis of condyle Grewcock approach: 2 inch above external auditory meatus Gill’s approach: ½ inch anterior and 2 inch above EAM Structures seen: lateral aspect of condyle and temporal component

18. Transpharyngeal (modified Parma) Film placement: Cassette flat against patient’s ear, centered to a point ½ inch anterior to the EAM over TMJ of interest parallel to sagittal plane Patient position: Mid- sagittal plane vertical and parallel to the film Should open mouth Central ray: Directed at an angle -5 to -10 degree from sigmoid notch of contralateral side; 10 degree posterior to TMJ of interest Structures seen: medial aspect of condylar head and neck

19. Transorbital Film placement: Cassette behind patient’s head, perpendicular to the x-ray beam Patient position: Head tilted downward 10 degree so that canthomeatal line is horizontal Mouth wideopen Advice patient to turn face for 30 degree on the same side Central ray: Tube head is placed in front of face Central ray at an angle of +20 degree, to strike the cassette at right angle Point of entry: pupil of the same eye, ask to look straight Medial canthus of the same eye Medial canthus of the opposite eye Structures seen: mediolateral dimension of the condyle (anterior view of the condyle )

20. Lateral cephalogram Film placement: Placed perpendicular to the floor, long axis vertically Patient position: Mid- sagittal plane perpendicular to the floor and parallel to the film Right side of the head positioned against the cassette Teeth in occlusion Central ray: Directed perpendicular to the film through the external acoustic meatus Distance between thex -ray source and midsagittal plane of the patient is 60 inches Uses: To assess skeletal pattern, facial growth and developmental anomalies, assess nasal bone fractures , relationship of soft and hard tissues of face

21. True lateral Film placement: Film vertically held against the patient’s cheek and centered so that the entire skull along with the facial skeleton is seen on the resultant radiograph Patient position: Mid- sagittal plane vertical and parallel to the film Upper circumference of the skull is ½ inch below the upper border of the casette Teeth in occlusion, occlusal plane should be parallel to the floor Central ray: Directed perpendicular to the film and the midsagittal plane and towards the external auditory meatus Distance between the x-ray source and midcoronal plane of the patient is 36-40 inches Uses: To assess skull and facial bone fractures

22. PA Ceph Film placement: Placed perpendicular to the floor, long axis vertically Patient position: Mid- sagittal plane vertical and perpendicular to the film Head is tipped downwards so that only nose touches the film Radiographic base line is at 10 degree with the film Central ray: Directed perpendicular to the film through the midsagittal plane centered at the level of the bridge of the nose Uses: For assessment of facial assymetries

23. PA Skull Film placement: Placed perpendicular to the floor, long axis vertically Patient position: Mid- sagittal plane vertical and perpendicular to the film Head is tipped downwards so that forehead and nose touches the film Radiographic base line is horizontal and perpendicular to the film Central ray: Directed perpendicular to the film through the midsagittal plane through the occiput Uses: To assess skull vault

24. Town’s projection Film placement: Placed perpendicular to the floor, long axis vertically Patient position: Anteroposterior view, back of head touching the film Canthomeatal line perpendicular to the film Central ray: Directed at 30 degree to the canthomeatal line and passes through it at a point between the external auditory canals Uses: Occipital area of the skull Necks of condyloid process