EXTRA-ORALEXTRA-ORAL RADIOGRAPHY RADIOGRAPHY

BY BHUPENDER SINGH NEGIBY BHUPENDER SINGH NEGI (MDS 3RD )

Guided by:-Dr.Anita Balan

Prof.& H.O.D.

Department Of Oral Medicine &Radiology

Government Dental College, Calicut.

Extra oral radiography means that the source as well as film are placed outside the mouth & an exposure is made in order to obtain the images on an recording medium.

INTRODUCTIONINTRODUCTION

INDICATIONSINDICATIONS

When it is not possible to place the film intraorally as during

trismus, gagging, loss of consciousness or unco-operative

patient.

To examine the extent of large lesions, especially when the

area of pathology is greater than which cannot be covered by

an intraoral periapical film.

When jaws or other facial bones have to be examined for

evidence of disease lesions and other pathological conditions.

To evaluate skeletal growth and development and its

disorders.

Pre-operative, intra-operative and post-operative

assessment in orthodontics, orthognathic surgery and

implantology. To study skull bones for concomitant involvement by disease.

To evaluate the status of impacted teeth.

To evaluate temporomandibular joint area and its disorders.

To detect and assess involvement of jaws by metastasis lesions.

To study diseases of maxillary sinuses.

To detect and study extent and nature of oral and maxillo-facial

trauma.

DRAWBACKSDRAWBACKS

Magnification occurs due to the greater object to film

distance used.

Details are not well-defined due to the use of cassettes and

intensifying screens. For optimum balance between loss of

image detail and reduction of patient exposure medium or

high speed screen film combinations should be used.

Contrast is reduced as the secondary radiation produced

by the soft tissues is more.

Extraoral Landmarks used for Patient Extraoral Landmarks used for Patient PositioningPositioning

The Median Plane of the Head: (Midsagittal Plane)The Infraorbital Line:The Orbitomeatal Line (Canthomeatal Line):The Frankfort Horizontal Line:

PATIENT PROCEDURE PATIENT PROCEDURE

Explain the radiographic procedure to be performed.

Remove all objects from the head and neck region.

Place lead apron without thyroid collar, lead apron must be placed low around the back of the neck so that it does not block the X-ray beam.

The patient must remove eyeglasses, earrings, necklaces, hearing aids, hairpins and CD/RPD.

EXTRAORAL RADIOGRPAHIC PROJECTIONS CAN BE EXTRAORAL RADIOGRPAHIC PROJECTIONS CAN BE CATEGORIZED INTO:CATEGORIZED INTO:A)A)Panoramic Imaging:Panoramic Imaging:

B) Posterioanterior Projection: B) Posterioanterior Projection: (also known as occipito

frontal projection of Nasal Sinuses) Posterior anterior Posterior anterior (Granger projection) Modified method, inclined Posterior anteriorModified method, inclined Posterior anterior

( Caldwell projection)

Radiography of the SkullRadiography of the Skull Lateral cephalogram

True lateral

PA cephaloaram

PA Skull

Towne’s projection

Radiography of the Maxillary Sinuses:Radiography of the Maxillary Sinuses: Standard Occipitomental projection ( 0 OM)

Modified method ( 30 OM)

PA Water’s

Bregma menton

Radiography of the Mandible:Radiography of the Mandible: PA Mandible Rotated PA Mandible Lateral Oblique Anterior body of mandible Posterior body of mandible Ramus of mandible

Radiography of Base of the Skull:Radiography of Base of the Skull:

Submento Vertex projection

Radiography of the Zygomatic ArchesRadiography of the Zygomatic Arches

Jughandle view (A Modification of submento vertex view)

Radiography of the Temporomandibular Joint Radiography of the Temporomandibular Joint

Transcranial Projection

Trans Pharyngeal Projection

Trans Orbital Projection

Reverse Towne's Projection

POSTERIOANTERIOR POSTERIOANTERIOR PROJECTION:PROJECTION:

Indications: To examine the skull for disease in trauma

or developmental abnormalities in frontal, temporal and parietal bone.

Provides a good record to detect progressive changes in the mediolateral dimensions of skull, including asymmetric growth.

For visualization of facial structures including the frontal and ethmoidal sinuses, nasal fossae and orbits

Film placement : The cassette is positioned vertically in a holding device.

Head position: Canthomeatal line parallel to the floor. For cephalometric applications the nose should be a little higher so that the anterior projection of the canthomeatal line is 10 degrees above the horizontal plane and Frankfort plane is perpendicular to the film.

Projection of central ray:

Coincident with the midsagittal plane at the level of the

bridge of the nose.

Exposure parameter: kvp : 84, mA : 13, sec.-1.5.

Modified method, inclined Posterior anterior ( Caldwell projection)

This angulation will cause the petrous ridges to be superimposed on the maxillary sinuses, thus allowing the accurate examination of the orbits & ethomidal air cells.

Film placement: The cassette is positioned vertically in a holding device.

Position of the Patient: The midsagittal plane is vertical

and perpendicular to the cassette. Canthomeatal line is perpendicular to the cassette.

Central Ray: Is directed to the 23 to the canthometal

line, entering the skull about 3 cm above the external occipital protuberance & exiting at glabella.

Exposure parameters: kvp : 70-80 , mA :- 60 to 80 sec. :-

1.6(Bucky grid.)

LATERAL SKULL PROJECTION (LATERAL LATERAL SKULL PROJECTION (LATERAL CEPHALOMETRIC PROJECTION CEPHALOMETRIC PROJECTION

To survey the skull and facial bones for evidence of trauma, disease, or developmental abnormality.

Nasopharyngeal soft tissues, paranasal sinuses, hard palate.

In orthodontics, to assess facial growth, pretreatment and post treatment records.

Conditions affecting the sella turcica such as tumor of the pituitary gland in acromegaly

The lateral cephalometric projection reveals the facial soft tissue profile.

Film placement :Head position:Left side of the face near the cassette

and midsagittal plane parallel to the plane of the film.

For cephalometric projection: patient is positioned with in the cephalostat with the sagittal plane of the head vertical and parallel to the film.

FH plane horizontal

Teeth should be in maximum intercuspation

Head is immobilized with plastic ear rods

Wedge filter is placed – absorb some of the radiation in the anterior region and helps to reveal the soft tissue outlines

Lateral skull projection: cephalostat are not placed and wedge filter is removed

Projection of Central rayDistance between the X-ray source

and midsagittal plane is 36-40 inches.

Central ray is directed toward the external auditory meatus

Perpendicular to the film and the midsagittal plane

Exposure parameter:

kvp of 70-80, mA :- 60-50. sec. :-1.6 (Bucky grid).

Water’s View Water’s View

Occipitomental view.

It is particularly useful for evaluating maxillary sinuses.

In addition frontal and ethmoidal sinuses, the orbit, the zygomaticofrontal suture, nasal cavity.

Demonstrates the position of the coronoid process of the mandible between the maxilla and the zygomatic arch.

Film placement:The long axis of the cassette is

positioned vertically.

Head Position:The midsagittal plane should be

vertical & 90 to the plane of the film. The canthomeatal line should be 37 above the horizontal.

Central Ray:The central ray should be

perpendicular to the film, through the midsagittal plane, and at the level of the maxillary sinus.

Exposure parameters:

kVp: 65 & mA: 10 & Sec:

2-3

Bregma Menton Bregma Menton

This projection is primarily used to demonstrate the walls of the maxillary sinus ( especially in the posterior areas), the orbits, the zygomatic arches & the nasal septum

Also demonstrates medial or lateral deviations of any part of the mandible

Film placement:The cassette is placed in a horizontal

position on top of a metal tableThe image receptor is tucked under the

chin as far back as possible.Position of the Patient:The midsagittal plane should be vertical

& 90 to the plane of the film & the chin is extended as far as comfortable to make the lower border of the mandible as parallel to the cassette as possible

Only the chin touches the cassette

Central Ray:

Enters at the Bregma & exits at the menton

Exposure parameters: kVp: 65 & mA: 10 & Sec.: 2-3

Reverse Towne'sReverse Towne's

Indications:

High fractures of the condylar necksMedially displaced condyle Intracapsular fractures of the TMJ Investigation of the quality of the articular surfaces of

the condylar heads in TMJ disorders.Condylar hypoplasia or hypertrophy.

Film placement:Position of the patient:The patient is in the PA position,

i.e. the head tipped forwards in the forehead-nose position, but in addition the mouth is open.

The radiographic baseline is horizontal and at right angles to the film. Opening the mouth takes the condylar heads out of the glenoid fossae so they can be seen.

Central ray: Is aimed upwards from below the occipit, with the

central ray at 30 to the horizontal, centered through the condyles

Exposure parameters: kVp: 70-80 & mA: 60-50 & Sec.:- 1.6

(Bucky grid)

Submento Vertex Projection Submento Vertex Projection

Structures: Symmetrical projection of the petrosa Mastoid process Spinosum canals Foramen ovale Carotid canals Sphenoidal sinuses

Curvature of Mandible Lateral wall of Maxillary sinuses Nasal septum Odontoid process of the atlas Axial inclination of the mandibular condyles

Indications:Destructive expansile lesions

affecting the palate, pterygoid region or base of skull.

Any displacement of a fractured zygomatic arch.( Jug Handle View).

Investigation of the sphenoidal sinus.Assessment of the thickness (medio-

lateral) of the posterior part of the mandible before osteotomy.

Film placement:Position of the patient: The patient is positioned

facing away from the film. The head is tipped backwards as far as possible, so the vertex of the skull touches film. In this position, the radiographic baseline is vertical and parallel to the film.

Central ray: Is aimed upwards from below the chin, with the

central ray at 5 to the horizontal, centered on an imaginary line joining the lower first molars.

Exposure parameters: kVp: 50 & mA: 20-30 & Sec.: 0.4

RADIOGRAPHY OF THE MANDIBLE:RADIOGRAPHY OF THE MANDIBLE:

PA Mandible Rotated PA Mandible Lateral Oblique

A. Anterior body of mandible

B. Posterior body of mandible

C. Ramus of mandible

PA MandiblePA Mandible

Shows the posterio-anterior projection of the mandibular body & the ramus. It is not suitable for showing the facial skeleton, because of superimposition of the base of the skull & the nasal bones.

Indications:

Fractures of the mandible involving the: Posterior 3rd of the body Angles Rami Low condylar necks lesions such as cysts or tumours in the

posterior 3rd of the body or rami to note medio-lateral expansion

Mandibular hypoplasia or hyperplasia Maxillofacial deformities

Film placement:Is centered so that the lips are

centered to the film.Position of the Patient :The sagittal plane should be

vertical & 90 to the film.The head is tipped forward so

that radiographic baseline horizontal and perpendicular to the film in the forehead-nose position.

Central Ray:

Centered through the cervical spine at the level of

the rami of the mandible

Exposure parameters : kVp: 65-80 & mA: 60-80

Sec.:-1.6(Bucky grid)

Rotated PA Mandible

This projection shows the tissues of one side of the face and is used to investigate the parotid gland and the ramus of the mandible.

Main indications: Stones/calculi in the parotid glands. Lesions such as cysts or tumours in the ramus

to note any medio-lateral expansion. Submasseteric infection to note new bone

formation.

Film placement:

Position of the Patient: The patient is positioned facing the film, with the

occlusal plane horizontal and the tip of the nose touching the film in the so-called normal head position.

The head is then rotated 10 to the side of interest. This positioning rotates the bones of the back of the skull away from the side of the face under investigation.

Central Ray:Is directed at 90 to the film,

aimed down the side of the face which is of interest.

Exposure parameters: kVp: 65-80 & mA:60-80 &

Sec.: 1.6(Bucky grid)

MANDIBULAR OBLIQUE LATERAL PROJECTIONS

Two oblique lateral projections commonly used to examine the mandible, one for the body and one for the ramus.

A dental X-ray machine with an open ended aiming cylinder is best for these projections.

The film : 13 x 18cm ( 5 x 7” ) or larger.The patient should hold the cassette.

Indications: Assessment of the presence and/or position of unerupted

toothDetection of fractures of the mandibleEvaluation of lesions or conditions affecting the jaws

including cysts, tumors, giant cell lesions & osteodystrophies

As an alternative when intraoral views are unobtainable, because of severe gagging/if the patient is unable to open the mouth

As specific views of the TMJ

Oblique laterals are categorized into: A. Anterior body of mandible

B. Posterior body of mandible C. Ramus of mandible

Structures: Anterior body of the mandible Position of teeth in the same area

Helps to evaluate impacted teeth, fractures & lesions located in the inferior border of the mandible

Anterior body of mandibleAnterior body of mandible

Film placement:The cassette is placed flat against

the patient’s cheek & is centered over the body of the mandible overlying the canine teeth.

Should be positioned parallel to the body of the mandible & inferior border of the cassette should be parallel to the lower border & below it.

Position of the patient:The patient is normally seated

upright in the dental chair & is then instructed to:• Rotate the head to the side of

interest: to bring the contra lateral ramus forwards avoiding it’s superimposition & to increase the space available between the neck & shoulder to position the X-ray set.

• Raise the chin: to increase the triangular space between the back of the ramus & the cervical spine through which the X-ray beam will pass.

• The sagittal plane is tilted so that it is 5 to the vertical & rotated 30 from the true lateral position.

• The patient must hold the cassette in position with the thumb placed under the edge of the cassette & the palm against the outer surface of the cassette.

Central ray: Is directed from under the mandible

opposite the side of examination from 2 cm behind the angle of the mandible

The beam is directed upwards (-10 to -15 ) & centered on the anterior body of the mandible. The beam must be directed 90 to the horizontal plane of the film.

Exposure parameters: kVp: 65 to 75 & mA: 7-10 & Sec.: 0.8

Structures: Posterior body of the mandiblePosition of teeth in the same areaRamus of the mandible Angle of the mandible

Posterior body of the mandible

Film placement:Position of the patient: The patient head is so adjusted that the

ala tragus line is parallel to the floor. The mandible is protruded slightly to

separate it from the vertebral column. The sagittal plane is tilted so that it is 5

to the vertical & the head is rotated 10 to 15 from the true lateral position.

The patient must hold the cassette in position with the thumb placed under the edge of the cassette & the palm against the outer surface of the cassette.

Central ray: Is directed from under the

mandible opposite the side of examination, from 2 cm below the angle of the mandible.

The beam is directed upwards (-10 to 15 & centered on the body of the mandible & directed 90° to the horizontal plane of the film.

Exposure parameters: kVp: 65 to 70 & mA: 7-10 & Sec.:

0.8

Structures: Ramus from angle of the mandible to condyles

Film placement:

Position of the patient: Ala tragus line The mandible is protruded slightly The sagittal plane is tilted to 10 to vertical Head tilted 5

Ramus of mandible

Central ray: Is directed from under the mandible

opposite the side of examination, from behind the angle of the mandible to a point posterior to the 3rd molar region on the side opposite the cassette.

The beam is directed upwards ( -10 to 15 ) & centered on the ramus of the mandible & directed 90 to the horizontal plane of the film.

Exposure parameters : kVp: 65 to 70 & mA: 7-10 & Sec.: 0.8

HARD TISSUE IMAGING Panoramic Projection Transcranial Projection Trans Pharyngeal Projection Trans Orbital Projection Convenional Tomography Computed Tomography

SOFT TISSUE IMAGING Arthrography MRI

Radiography of the Temporomandibular Joint

Transcranial Projection:

Sagittal view of the lateral aspects of the condyle and temporal component.

Gross osseous changes on the lateral aspect of the joint. Displaced condylar fractures Range of motion

Film placement: The cassette is placed flat against

the patient’s ear & centered over the TMJ of interest, against the facial skin parallel to the sagittal plane.

Head Position: The patient is placed with the head

rotated through 90 so that TMJ under investigation is touching the film & the saggital plane of the head is parallel to the film.

In open view, the patient’s mouth is opened as far as comfortable & even a bite block can also be used for stability.

Central ray: The X-ray beam is directed

downward from the opposite side, through the cranium & above the petrous ridge of the temporal bone, at a +25 angulation through the joint.

Post auricular / Lindblom technique:Point of entry of the central ray is ½’’ behind & 2’’

above the auditory meatusIs directed from posteriorly so that it passes along

the long axis of the condyle i.e. the medial pole of the condyle is more posterior to the lateral pole.

Grewcock approach: The central ray enters through a point 2’’ above the

external auditory meatus.

Gill’s approach: The central ray enters through a point ½ ’’ anterior &

2’’ above the external auditory meatus. An average 20 anterior angle may be used.

Because of the positive beam angulation, the central & medial aspects of the joint are projected inferiorly & only lateral joint contours are visible in this projection.

The image of the condyle, temporal component & joint space is distorted & condylar position cannot be reliably determined, particularly if the horizontal beam angle is not individualized for each patient.

Transpharyngeal (Infracranial or McQueen Dell Technique or Parma )

Structures : Lateral projection of the sagittal view of the medial pole

of the condylar head and neck, usually taken in the mouth open position, so that the joint is projected into the shadow of air containing spaces of the nasopharynx, which helps to increase the contrast of the various parts of the joint.

Film Placement:The cassette is placed flat

against the patient's ear and is centered to a point ½” anterior to the external auditory meatus, over the TMJ of interest, against the facial skin parallel to the sagittal plane.

Position of the Patient:The patient is positioned so that the sagittal plane is

vertical and parallel to the film, with the TMJ of interest adjacent to the film.

The occlusal plane should be parallel to the transverse axis of the film so that the soft parts of the nasopharynx are in one line with the TMJ.

The patient is instructed to slowly inhale through the nose during exposure, so as to ensure filling of the naso pharynx with air during the exposure.

The patient should open his mouth so that the condyles move away from the base of the skull and the mandibular notch of the opposite side is enlarged.

Central Ray: Is directed superiorly at -5°

through the sigmoid notch of the opposite side & 7-8° from the anterior.

Exposure Parameters: kVp- 70, mA-7 & Seconds-0.8

Parma Modification:The lead lined open ended cone is removed and the

tube head is brought close to the skin surface, producing magnification of the tube side structures and there by reducing super imposition.

This is the conventional frontal TMJ projection which is most successful in delineating the joint with minimal super impositions, leading to the production of a relatively true 'enface' projection.

Structures :The articular surface (convex) and

the articular eminence (flat or convex).

Transorbital (Zimmer Projection)

Film Placement:

The film is positioned behind the patient's head at an angle of 45° to the sagittal plane & perpendicular to the X-ray beam.

Position of Patient:The patient is positioned so that the

sagittal plane is vertical. The canthomeatal line should be 10° to the horizontal, with the head tipped downwards.

The mouth should be wide open or as an alternative protrudes the mandible, thereby positioning the condyle at the summit of the articular eminence & avoiding superimposition of the articular eminence or skull base on the condyle.

Central ray:

The X-ray is directed from the front of the patient through the ipsilateral orbit & TMJ of interest.

The point of entry may be taken at: Pupil of the same eye, asking the patient to look straight

ahead. Medial canthus of the same eye.

Exposure Parameters:kVp-70, mA-7 & Seconds-0.8

Structures: Primarily used to observe the

occipital area of the skull. The necks of the condyloid process can also be viewed.

Film Position:The cassette is placed

perpendicular to the floor in a cassette holding device. The long-axis of the cassette is positioned vertically.

Towne’s projection

Position of Patient: This is an anteroposterior ( AP) view,

with the back of the patient's head touching the film. The canthomeatal line is perpendicular to the film.

Central ray: Is directed at 30° to the canthomeatal

line and passes through it at a point between the external auditory canals.

Exposure Parameters: kVp:-70-80 & mA:-60-50 & Seconds-

1.6(Bucky grid)

CONVENTIONAL TOMOGRAPHY

Tomography is a radiographic technique that produces multiple thin image slices, permitting visualization of an anatomic structures.

Provide multiple image slices at right angles through the joint.

Typically are exposed in the sagittal plane with several image slices in the closed position and usually one image in the maximal open position.

Particularly indicated when morphologic abnormalities or erosive changes of the condylar head are suspected.

COMPUTED TOMOGRAPHY

Indications: When more information is needed about the three-

dimensional shape and internal structure of the osseous components of the joint.

They are useful for assessing osseous deformities of the jaws or surrounding structures.

The presence and extent of ankylosis Neoplasms

Extent of bony involvment in some arthritides

Imaging complex fractures

To evaluate complications from the use of polytetrafluoroethylene or silicon sheet implants such as erosions into the middle cranial fossa and ectopic bone growth

SOFT TISSUE IMAGING

It is indicated when TMJ pain and dysfunction are present or when the clinical findings suggest disc displacement that are non responsive to conservative treatment.

ARTHROGRAPHY

MAGNETIC RESONANCE IMAGING

ARTHROGRAPHY

Indirect image of the disc is obtained by injecting a radiopaque contrast agent in to one or both joint spaces under fluoroscopic guidance.

A perforation is detected by the flow of contrast agent into superior joint space from the lower space.

Adhesions are detected by the manner in which contrast agents fills the joint space.

After both the joint spaces are filled, disc function is studied using fluoroscopy during opening and closing movements

Indications:

Disc position, function, morphology and the integrity of discal attachments to aid in treatment planning.

MAGNETIC RESONANCE IMAGING

Uses a magnetic field and radiofrequency pulses rather than IR to produce multiple digital image slices.

Indications:Articular discMedial disc displacements

Contraindications:Pregnant, who have pacemakers, intracranial vascular clips

or metal particles in vital structures.

References:-

Oral Radiology: Principles and Interpretation (Mosby) (Hardback) By (author) Stuart C. White, By (author) Michael J. Pharoah

Essentials of oral and maxillofacial radiology ( Freny R Karjodker)

Essentials of Dental Radiography and Radiology BY Eric Whaites