Extraoral radiographs are used to examine areas not fully covered by intraoral films and to evaluate the cranium, face, and cervical spine. There are several types of extraoral projections defined by the anatomical plane they image. Key criteria for selecting a projection include spatially localizing pathology and obtaining at least two images at right angles. Proper patient positioning and central beam alignment are required to obtain diagnostic images and minimize distortion. Lateral skull, posteroanterior skull, submentovertex, Waters, and reverse-Towne projections are described in terms of image receptor placement, patient positioning, central beam alignment, and the resultant anatomy visualized.

1. In The Name Of God

2. Extraoral projections
Chapter 9 white
Present by :
dr. Maedeh Aminian
dr. Maryam Ghazizadeh

3. Types according to planes :
• Sagittal or median plane
Lateral ceph. / skull
• Travsverse or horizontal plane
SMV
• Coronal or frontal plane
PA ceph. / skull
Waters
Reverse-towne

4. Selection criteria:
 To examine areas not fully covered by intraoral
films
 To evaluate the cranium, face (including the
maxilla and mandible), or cervical
 To evaluate the relationship between various oro-
facial and dental structures, growth and
development of the face, or treatment progression
• First step in obtaining and interpreting a radiograph
=> Selecting the appropriate extraoral
radiographic examination
• For spatially localizing pathology, usually at least
two radiographs taken at right angles to each
another are obtained

5. TECHNIQUE
Cephalometric and skull views require at
least a 20 cm x 25 cm (8 inch x 10 inch)
image receptor

6. The proper Exposure parameters
depend on:
• the patient's size, Anatomy & head
orientation
• image receptor speed
• x-ray source to receptor distance
• grids +/-
Patient kV mA
Hand Wrist 60 2
Child(6 and under) 64 5
Adult Female / Small Male 66 5
Adult Male 68 5
Large Adult 70 5

7. Grids
 reduce scattered radiation
 improve contrast and resolution
 higher patient exposure
 improve the radiographic appearance of fine
structures, such as trabecular architecture
 aid in the diagnosis of disease
 Cephalometry does not require the use of grids

8. Proper positioning
Main Anatomic landmark:
Cantho-meatal line =
Orbito-meatal line =
radiographic baseline

10. EVALUATION OF THE IMAGE
Extraoral images should first be evaluated for
overall quality
The first step in the interpretation of
radiographic images is the identification of
anatomy

11. EVALUATION OF THE IMAGE

12. LATERAL SKULL/CEPHALOMETRIC PROJECTION
DIFFERENCE?
Cephalostat

13. LATERAL SKULL/CEPHALOMETRIC PROJECTION
Image Receptor and Patient positioning
Position of Central X-Ray Beam
• The image receptor parallel to the patient's midsagittal
plane
• The site of interest toward the image receptor ( minimize
distortion)
• In cephalometric radiography => 1. the left side toward
the image receptor 2. a wedge filter at the tube head
over the anterior aspect of the beam
• perpendicular to the midsagittal plane and
the image receptor
• centered over the external auditory
meatus

14. LATERAL SKULL/CEPHALOMETRIC PROJECTION
RESULTANT IMAGE

15. LATERAL SKULL/CEPHALOMETRIC PROJECTION

16. LATERAL SKULL/CEPHALOMETRIC PROJECTION

17. LATERAL SKULL/CEPHALOMETRIC PROJECTION

18. LATERAL SKULL/CEPHALOMETRIC PROJECTION

19. PA SKULL/CEPHALOMETRIC PROJECTION
PA Cephalogram
=> mainly used for evaluation of
facial asymmetries and for
assessment of orthognathic surgery
outcomes involving the patient's
midline or mandibular-maxillary
relationship

20. PA SKULL/CEPHALOMETRIC PROJECTION
Image Receptor and Patient positioning
Position of Central X-Ray Beam
• Image receptor => in front of the patient / perpendicular to the
midsagittal plane / parallel to the coronal plane
• PA cephalometric => the Canthomeatal line 9-degree with the
horizontal plane/ The Frankfurt plane perpendicular to receptor
• standard PA skull => the canthomeatal line perpendicular to
receptor
• perpendicular to the receptor from the post. to the ant.
• parallel to the patient's midsagittal plane
• centered at the level of the bridge of the nose

21. PA SKULL/CEPHALOMETRIC PROJECTION
RESULTANT IMAGE

22. PA SKULL/CEPHALOMETRIC PROJECTION
INTERPRETATION

23. SUBMENTOVERTEX (SMV or base) PROJECTION
Image Receptor and Patient positioning
Position of Central X-Ray Beam
• Receptor parallel to the patient's transverse plane
• Perpendicular to the midsagittal and coronal planes
• The patient's neck extended as far backward as possible
• The canthomeatal line 10-degree with the receptor
• Perpendicular to the receptor
• from below the mandible toward the vertex of the skull
• 2 cm anterior to a line connecting the right and left condyles

24. SUBMENTOVERTEX (SMV or base) PROJECTION
RESULTANT IMAGE

25. SUBMENTOVERTEX (SMV or base) PROJECTION
RESULTANT IMAGE

26. WATERS PROJECTION
Image Receptor and Patient positioning
Position of Central X-Ray Beam
• The receptor in front of the patient
• Perpendicular to the midsagittal plane
• The patient's head tilted upward
• The canthomeatal line 37-degree with the image receptor
• Open mouth => the sphenoid sinus seen over the palate
• Perpendicular to the receptor
• Centered in the area of the maxillary sinuses

27. WATERS PROJECTION
RESULTANT IMAGE

28. REVERSE-TOWNE PROJECTION
(OPEN MOUTH)
Image Receptor and Patient positioning
Position of Central X-Ray Beam
• The receptor in front of the patient
• Perpendicular to the midsagittal plane
• Parallel to the coronal plane
• Patient's head tilted downward
• the canthomeatal line 25 – 30 degree with the receptor
• Open mouth => improve the visualization of the condyles
• Perpendicular to the receptor
• Parallel to the patient's midsagittal plane
• Centered at the level of the condyles

29. REVERSE-TOWNE PROJECTION(OPEN MOUTH)
RESULTANT IMAGE

31. Thanks for
your
attention