Positioning of the Skull

What is the technique for the PA projection?

75 kVp @ 18-22 mAs

What is the technique for the PA axial (Caldwell method) projection?

75 kVp @ 18-22 mAs

What is the technique for the PA axial (Haas method) projection?

75 kVp @ 24-32 mAs

What is the IR size/orientation for the PA projection?

10 × 12 LW

What is the IR size/orientation for the PA axial (Caldwell) projection?

10 × 12 LW

What is the IR size/orientation for the PA axial (Haas) projection?

10 ×12 LW

What is the SID for all skull views?

40 inch

What is the collimation for all skull views?

Collimation of fours sides of anatomy

What is the tube angle for the PA axial (Caldwell)?

15 degrees caudad (75 on tube)

What is the tube angle for the PA axial (Haas)?

25 degrees cephalic (115 on tube)

Where is the CR for the PA projection?

Perpendicular exiting at the glabella

Where is the CR for the PA axial (Caldwell)?

Exits at the nasion

Where is the CR for the PA axial (Haas)?

Through level of EAMs and exits approximately 1 ½ inches superior to the nasion

How would you position for a PA projection?

• rest patients nose and forehead against upright bucky

• OML perpendicular to IR/Bucky (straight lines from EAM to outer canthus)

How would you position for a PA axial (Caldwell)?

• rest patients nose and forehead against upright Bucky

• OML perpendicular to IR/Bucky

• ensure to check for rotation or tilt

How would you position for a PA axial (Haas)?

• rest patients nose and forehead against upright Bucky

• Flex neck, bringing OML perpendicular to IR/Bucky and align the MSP to CR and to midlines of Bucky

Where is the marker placed for all skull views?

Bottom corner of IR

What is the breathing for all skull views?

Suspend respiration

Do you shield for skull views?

Yes

What should you see to know you have a correct PA projection?

Petrous ridges fill the orbits at level of the supraorbital margin

What should you see to know you have a correct PA axial (Caldwell)?

Petrous ridges projected in lower third of orbits

What is an alternate view for the Towne method?

Haas method

What does the Haas method demonstrate?

Dorsum sellae in shadow of the foramen magnum

What is important to note about the PA axial Haas method?

The occipital lobe is magnified but less dose to lens of eye and thyroid

What is the technique for the Towne method?

75 kVp @ 24-32 mAs

What is the technique for the lateral projection?

70 kVp @ 8-12 mAs

What is the technique for the SMV?

75 kVp @ 28-32 mAs

What is the SMV projection also called?

Full basal

What is the IR size/orientation for the Towne method?

10 ×12 LW

What is the IR size/orientation for the lateral projection?

10 × 12 CW

What is the IR size/orientation for the SMV?

10 × 12 LW

What is the tube angle for the Towne method?

• 37 degree caudal angle to IOML (53 degrees)

• 30 degrees caudal to OML

What is the tube angle for the SMV projection?

Only if pt is unable to extend neck, angle CR to remain perpendicular to IOML

Where is the CR for the Towne method?

2 ½ inches above glabella (near hairline)

Where is the CR for the lateral projection?

2 inches above EAM

Where is the CR for the SMV?

Perpendicular to IOML

How would you position for the Towne method?

• depress (tuck) chin

• IOML perpendicular to IR/Bucky

How would you position for a lateral projection?

• MSP parallel to IR

• interpupillary lline perpendicular to IR

• ensure minimal or no OID

• IOML perpendicular to the front edge of IR

How would you position for the SMV projection?

• raise chin and hyperextend neck until IOML is parallel to IR/Bucky

• rest patients head on vertex of skull

What does the Towne method demonstrate?

Dorsum sellae in shadow of the foramen magnum

What does the lateral projection demonstrate?

Sella turcica and clivus (superimposed)

How do you know you have rotation on the lateral projection?

There is anterior and posterior separation

How do you know you have tilt on the lateral projection?

There is superior and inferior separation