Facial bones positioning quiz

The orientation of the radiation field size should be ______ for the lateral projection

Lengthwise

The plane of the IR should be parallel with the plane of the IR is the ________ plane for the lateral projection

Midsagittal

Which positioning line of the head should be perpendicular to the IR for the lateral projection?

Interpupillary

Which positioning line of the head should be parallel with the the transverse axis of the IR for the lateral projection?

Infraorbitomeatal

Which facial bone should be centered to the IR for the lateral projection?

Zygomatic

The central ray should be directed to the patient ________ for the lateral projection?

Perpendicularly

Where on the patients face should the central ray be directed for the lateral projection?

Halfway between the outer canthus and the EAM

Evaluation criteria for the lateral projection?

• the sella turcica should not be rotated

• The orbital roofs should be superimposed

• The mandibular rami should be almost perfectly superimposed

• All facial bones should be completely included with the zygomatic bone in the center

What’s wrong with image #43 “lateral”

• head is tilted

• Orbital roofs not superimposed

• Mandibular rami not superimposed

• IOML not perpendicular to the front edge of the cassette

• Chin raised a little too much

• Centered a little too anteriorly

• Rotated

Label image #37 “lateral”

C. Orbital roofs

D. Mentum

E. Maxillary sinus

F. sella turcica

Indicate how the OML should be positioned with reference to the IR for the PA waters

37 degree angulation with the IR

Indicate how the Midsagittal plane should be positioned with reference to the IR for the PA waters

Perpendicular to the IR

To which landmark of the head should the IR be centered for the PA waters?

Acanthion

How should the central ray be directed relative to the IR for the PA waters?

Perpendicularly

Describe where the petrous ridges most likely will appear in the image if the OML creates a 25 degree angle with the IR for the PA waters?

Too far under the maxillae

Describe where the petrous ridges most likely will appear in the image if the OML creates a 37 degree angle with the IR for the PA waters?

Immediately below the maxillae

Describe where the petrous ridges most likely will appear in the image if the OML creates a 55 degree angle with the IR for the PA waters?

Superimposing the maxillary sinuses

Evaluation criteria for the PA waters

• the petrous ridges should be projected immediately below the maxillary sinuses

• The distance between the lateral border of the skull and orbit should be equal on both sides

• Entire orbits and facial bones

• MSP of head aligned with long axis of collimated field

• No rotation or tilt

Label image #38 “PA waters”

G. Right petrous ridge

H. Left maxillary sinus

I. Right orbit

What’s wrong with image #41 “PA waters”

• chin tucked a little too much

• Petrous ridges in maxillary sinuses

• Rotated to the right

Position of patient for PA axial Caldwell

• patient in prone or seated position

• Center MSP of the patients body to the midline of the grid

• Rest the patients forehead and nose on the table or against the upright Bucky

• Flex the patients elbows and place the arms in a comfortable position

Position of part for PA axial Caldwell

• adjust flexion of the patients neck so the at the OML is perpendicular to the plane of the IR

• Align MSP of the head perpendicular to the IR by adjusting the lateral margins of the orbits or the EAM equidistant from tabletop

• Immobilize the head, and center the IR to the nasion

Central ray for PA axial Caldwell

• exits the nasion at an angle of 15 degrees caudad

• To show the orbital rims(orbital floors) use a 30 degree caudal angle

Evaluation criteria for PA axial Caldwell

• entire orbits and facial bones

• No rotation or tilt

• Equal distances from lateral borders of skull to lateral borders of orbits on both sides

• MSP of head aligned with long axis f collimated field

• Symmetric petrous ridges lying in lower third of orbit

What’s wrong with image #42 “PA axial Caldwell”?

• rotated to the right

• Unequal distance between lateral borders of skull and lateral border of orbits

• Not collimated enough

• Centered too inferiorly

True or false:

The SMV projection should demonstrate both zygomatic arches with one exposure

True

True or false:

Zygomatic arches should be demonstrated superimposed with the anterior frontal bone for the SMV projection

False

True or false:

The entire cranial base should be demonstrated for the SMV projection

False

True or false:

The MSP should be parallel with the IR for the SMV projection

False

Which positioning line of the head should be parallel with the IR for the SMV projection?

Infraorbitomeatal

Which part of the patient should be in contact with the grid device for the SMV projection?

Vertex of the skull

Which statement best describes how the central ray should be directed for the SMV projection?

Perpendicular to the IOML and centered on the MSP of the throat

For the SMV projection, what causes the zygomatic arches to be projected beyond the parietal eminence?

The divergent xray beam

Evaluation criteria for the SMV projection

• no rotation of the head should occur

• The zygomatic arches should be free from overlying structures

• The zygomatic arches should be symmetric and without foreshortening

Label image #36 “SMV”

A. Mentum and Frontal bone

B. Left zygomatic arch

What’s wrong with image #44 “SMV”

• tilted

• Chin not over midpoint of frontal bone

• Vertex tilted to the left

• Chin too much to the right

What’s wrong with image #45 “SMV”?

• chin tucked too much

• IOML not parallel to the IR

• Tilted to the left

• Distance between condyles and skull not equal

• Vertex tilted to the right

• Chin tilted to the left

True or false:

The patient should hyperextend the neck and rest the head on the vertex for the tangential projection

True

True or false:

The Midsagittal plane should be perpendicular to the IR for the tangential projection

False

Wha positioning line of the head should be as parallel as possible with the IR for the tangential projection?

Infraorbitomeatal line

Describe how the central ray should be directed for the tangential projection

Perpendicular to the IOML and centered to the zygomatic arch at a point approximately 1 inch posterior to the outer canthus

Evaluation criteria for tangential projection

The zygomatic arch should be free from overlying structures

Indicate how the OML should be positioned with reference to the IR for the Townes projection

Perpendicular to the IR

Indicate how the MSP should be positioned with reference to the IR for the Townes projection

Perpendicular to the IR

How many degrees and in which direction should the central ray be directed when the OML is placed perpendicular to the plane of the IR for the Townes projection?

30 degrees caudad

How many degrees and in which direction should the central ray be directed when the IOML is placed perpendicular to the plane of the IR for the Townes projection?

37 degrees caudad

The central ray should enter 1 inch above the landmark _____ for the Townes projection

Nasion

True or false:

Both zygomatic arches should be demonstrated on the image with a single exposure for the Townes projection

True

True or false:

The entire vertex should be included on the image for the Townes projection

False

Evaluation criteria for Townes projection

• no overlap of zygomatic arches by mandible

• No rotation or tilt

• symmetric arches

• Zygomatic arches projected lateral to mandibular rami

• MSP of head aligned with long axis of collimated field

Label image #40 “Townes”

M. Right zygomatic arch

N. Right mandibular ramus

What’s wrong with image #46 “Townes”?

• chin not tucked enough

• Dorsum sellae should be projected within shadow of foramen magnum

• Anterior portion of zygomatic arch is clipped

• Centered a little too superiorly

• Forgot to line up Bucky

• Zygomatic arches too dark