An AP axial (Towne method) cranial projection with poor positioning demonstrates the dorsum sellae superior to the foramen magnum. How was the positioning setup mispositioned for such a projection to be obtained?
1)The patient's face was rotated toward the left side.
2)The chin was not adequately tucked.
3)The OML was not aligned perpendicular to the IR.
4)The central ray was angled too caudally.
A) 1 only
B) 4 only
C) 2 and 3 only
D) 2, 3, and 4 only

Question

Quizplus · Accepted Answer

The dorsum sellae being superior to the foramen magnum indicates that the central ray was angled too anteriorly. This could result from inadequate chin tuck (option 2) and OML alignment (option 3), leading to the skull being positioned too far away from the IR in the z-axis. However, rotation (option 1) would cause the entire skull to be obliquely positioned, whereas this misalignment is localized to a specific region. Therefore, options 2 and 3 only are the most likely causes of the positioning error. Option 4 is incorrect because angling the central ray too caudally would have resulted in the dorsum sellae being inferior to the foramen magnum.

An AP Axial (Towne Method) Cranial Projection with Poor Positioning