For an AP axial Towne method skull projection, if the patient can depress their chin and align the OML perpendicular to the IR, what is the CR angulation?

For an AP axial Towne method skull projection, if the patient can depress their chin and align the OML perpendicular to the IR, what is the CR angulation?

• A. 30 degrees caudal
• B. 15 degrees caudal
• C. 37 degrees cephalad
• D. 0 degrees

Answer: (A)

The AP axial Towne projection relies on angling the CR so the beam passes through the foramen magnum and posterior fossa. When the chin is depressed so the OML is perpendicular to the IR, you use a 30-degree caudal tilt. This specific angle aligns the CR with the basilar skull in that positioning, producing the desired axial view of the occipital bone and foramen magnum. Using a smaller tilt (like 15 degrees) would not achieve the necessary axial projection, and 0 degrees would fail to superimpose the skull structures into the correct view. The 37-degree option involves a different reference (IOML) and a tilt in the opposite direction, which isn’t appropriate when the OML is perpendicular to the IR.

The AP axial Towne projection relies on angling the CR so the beam passes through the foramen magnum and posterior fossa. When the chin is depressed so the OML is perpendicular to the IR, you use a 30-degree caudal tilt. This specific angle aligns the CR with the basilar skull in that positioning, producing the desired axial view of the occipital bone and foramen magnum.

Using a smaller tilt (like 15 degrees) would not achieve the necessary axial projection, and 0 degrees would fail to superimpose the skull structures into the correct view. The 37-degree option involves a different reference (IOML) and a tilt in the opposite direction, which isn’t appropriate when the OML is perpendicular to the IR.