Radiology Lecture 16: Extraoral Radiography

What should the length of extraoral films be?

20 by 25 cm

What is the line drawn from the inferior aspect of the orbit to the superior border of external auditory meatus?

Frankfurt plane

What is the line drawn from the canthus (corner) of the eye to the center of the external auditory meatus?

Canthomeatal line

What are the standardized projections that allow for reproducible imaging of the craniofacial region?

Cephalometric projections

What are cephalometric projections made by?

Cephalostat

What should the source to object distance be for cephalometric projections?

5 ft

What should the object to receptor distance be for cephalometric projections?

10 to 15 cm

What two diagnoses could be done with lateral cephalometric projections?

1. Orthodontic

2. Prosthetic

What two conditions are indicators found with lateral cephalometric projections?

1. Trauma

2. Developmental anomalies

Which three structures can be examined using lateral cephalometric projections?

1. Nasopharyngeal tissues

2. Paranasal sinuses

3. Hard palate

Where is the image receptor positioned for lateral cephalometric projections?

Parallel to midsagittal plane

What side of the patient should be positioned toward the receptor in lateral cephalometric projections?

Left side

Where is the x-ray beam positioned for lateral cephalometric projections?

Perpendicular to midsagittal plane and receptor

Where is the x-ray beam centered for lateral cephalometric projections?

External auditory meatus

Is exact superimposition of right and left sides possible?

No

What dimension can be examined with posterioanterior cephalometric projections?

Mediolateral

What three conditions are indicators found with posterioanterior cephalometric projections?

1. Trauma

2. Developmental anomalies

3. Asymmetrical growth

Which two structures can be examined using posterioanterior cephalometric projections?

1. Nasal cavity

2. Orbits

Where is the image receptor positioned for posterioanterior cephalometric projection relative to the patient?

Front of patient

What should the image receptor for posterioanterior cephalometric projections be parallel to?

Coronal plane

What should the image receptor for posterioanterior cephalometric projections be perpendicular to?

Midsagittal plane

What plane is perpendicular to the image receptor in posterioanterior cephalometric projections?

Frankfurt plane

What should the x-ray beam for posterioanterior cephalometric projections be perpendicular to?

Image receptor

What should the x-ray beam for posterioanterior cephalometric projections be parallel to?

Midsagittal plane

Where should the x-ray beam for posterioanterior cephalometric projections be centered?

Level of the bridge of nose

Which three sinuses can be examined using Waters projections?

1. Maxillary sinus

2. Frontal sinus

3. Ethmoid sinus

Which four structures can be examined using Waters projections?

1. Orbits

2. Zygomaticofrontal suture

3. Nasal cavity

4. Coronoid process

Where is the image receptor positioned for Waters projection relative to the patient?

Front of patient

What angle should the patient's head tilt up in Waters projection?

37°

What should the x-ray beam for Waters projections be perpendicular to?

Image receptor

Where should the x-ray beam for Waters projections be centered?

Region of maxillary sinuses

What part of the skull could you examine using Submentovertex projections?

Base of skull

Which four skull structures could you examine using Submentovertex projections?

1. Condyle

2. Zygomatic arch

3. Pterygoid plates

4. Foramina

Which two sinuses could you examine using Submentovertex projections?

1. Sphenoid sinus

2. Lateral wall maxillary sinus

What should the image receptor for Submentovertex projections be perpendicular to?

Coronal and midsagittal plane

What should the image receptor for Submentovertex projections be parallel to?

Axial plane

What should the patient's position be for Submentovertex projections?

Neck extended far back

What line on the patient should be parallel to the image receptor?

Canthomeatal line

From where to where should the x-ray beam for Submentovertex projections travel?

Mandible to vertex of the skull

Where should the x-ray beam for Submentovertex projections be centered?

2 cm anterior to line connecting right and left condyles

What is the indicator found in reverse-towne projection?

Condylar neck