Positioning Flashcards
Describe a mesoceophalic head shape.
- average head
- width 75-80% of length
Describe a Bradycephalic head shape.
-width is 80% or more of length
Describe a Dolichocephalic head shape.
-width is less than 75% of length
What are the positioning lines used on an AP axial Towne?
MSP perpendicular
OML or IOML perpendicular
What is the tube angle on an AP Axial Towne if the OML is perpendicular to the IR?
30 degrees caudal
What is the tube angle on an AP Axial Towne if the IOML is perpendicular to the IR?
37 degrees caudal
Where do you center on an AP axial Towne?
2 1/2 inches above the glabella
The AP axial Towne demonstrates what cranial bone?
the occipital
What is demonstrated within the foramen magnum on an AP axial Towne?
the dorsum sella
What is the alternative to the Towne Method?
PA axial Haas method
Why would you do use the Haas method over the Towne?
For patients that cannot flex their neck
What positioning lines are used for the PA axial Haas method?
OML perpendicular
MSP perpendicular
What is the tube angle for a PA axial Haas?
25 degrees cephalad
Where do you center for a PA axial Haas?
center to exit 1 1/2 inches above the nasion
What is the main difference in images between the Towne and Haas?
The dorsum sella within the foramen magnum are magnified. The occipital bone is also magnified.
How can you tell if rotation is present on an AP Towne or PA Haas?
the petrous ridges are symmetrical
What positioning lines are involved with the Lateral Skull?
MSP parallel
Interpupillary Line is perpendicular
IOML is perpendicular to front edge of IR
What is the centering point for the lateral skull?
2 inches superior to the EAM
Why might a sponge under the patients head be necessary on a lateral skull?
In order to reduce tilt on a patient with a large chest
If the entire skull is not in the 10x12 area on a lateral skull what other centering point can you use?
A midpoint between the nasion and the inion
How can you detect rotation on a lateral skull?
The two anterior clinoid processes not being superimposed show rotation
How can you detect tilt on a lateral skull?
the supraorbital ridges not being superimposed shows tilt
What positioning lines are involved with sella turcica?
IPL perpendicular
MSP parallel
IOML perpendicular to the front edge of the IR
Where do you center on a lateral sella turcica?
3/4th inch anterior and 3/4th inch superior to the EAM
What do you collimate for a sella turcica?
4x4
What ensures no rotation on the lateral sella turcica?
the anterior clinoid processes are superimposed
What ensures no tilt on the lateral sella turcica?
the greater wings of the sella turcica are superimposed
What positioning lines are used for a PA Caldwell projection?
OML perpendicular
MSP perpendicular
Where does the central ray exit on a PA Caldwell?
the nasion
What is the degree of angle on a PA Caldwell?
15 degrees caudal
What does using an angle on the PA caldwell demonstrate?
the petrous ridges in the lower 1/2 of the orbits
What positioning lines are used in a PA cranium projection?
OML perpendicular
MSP perpendicular
Where does the CR exit on a PA cranium?
the glabella
Where are the petrous ridges projected in a PA cranium?
fills the orbits
What positioning lines are used for a Submentovertex projection?
IOML parallel to IR
Where do you center for a SMV projection?
- 1 1/2 inches below the mental point
- between the gonions
What is the tube angle for the SMV projection?
angled to be perpendicular to the IOML
What structures are being viewed on a SMV projection of the skull?
the inferior temporal and base of the skull
