In an AP cervical spine radiograph, the patient is positioned supine or upright and the CR is perpendicular to which level, including skull base through which vertebra?

In an AP cervical spine radiograph, the patient is positioned supine or upright and the CR is perpendicular to which level, including skull base through which vertebra?

• A. Perpendicular to C4; skull base through T1
• B. Perpendicular to C2; skull base through T3
• C. Perpendicular to C6; skull base through T1
• D. Perpendicular to C1; skull base through C7

Answer: (A)

Centering the CR at the midcervical region and directing it perpendicular to C4 ensures the entire cervical spine is captured from the skull base down to the C7–T1 area. C4 sits roughly in the middle of the cervical column, so this beam orientation provides even projection of all seven cervical vertebrae and the lower limit at T1. It minimizes distortion and keeps the superior border at the skull base while including the inferior cervical region (C7–T1). If the beam were aimed at a higher level (C1 or C2), the lower cervical spine might be cropped out; if aimed at a lower level (C6), the skull base and upper cervical segments could be inadequately visualized.

Centering the CR at the midcervical region and directing it perpendicular to C4 ensures the entire cervical spine is captured from the skull base down to the C7–T1 area. C4 sits roughly in the middle of the cervical column, so this beam orientation provides even projection of all seven cervical vertebrae and the lower limit at T1. It minimizes distortion and keeps the superior border at the skull base while including the inferior cervical region (C7–T1). If the beam were aimed at a higher level (C1 or C2), the lower cervical spine might be cropped out; if aimed at a lower level (C6), the skull base and upper cervical segments could be inadequately visualized.