Cervical spine (AP view)
The AP cervical spine projection is part of the cervical spine series.
- patient positioned erect in AP position unless trauma the patient will be supine
- patient’s shoulders should be at equal distances from the image receptor to avoid rotation, the head facing straight forward.
- anterior posterior projection
- the central ray is midline centred at the level of C4 to enter immediately below the hyoid bone
- 15 degrees cephalad 1
laterally to include the entire cervical spine
superiorly to include C2 and inferiorly to include T2
- 18cm x 24cm
- 75 kVp
- 8-10 mAs
Image technical evaluation
- cervical spine intervertebral disk spaces should be open 1
- spinous processes should be midline, equidistant to the pedicles, indicating that there is no rotation
- make sure that any removable artefacts such as earrings, glasses or metal dentures are removed to avoid obscuring the anatomy of interest
Correcting rotational errors
Rotation can be detected by looking at the spinous processes in relation to the pedicles. The spinous process should be midline of the vertebral body, equidistant from both pedicles 2. Any deviation from the midline indicates rotation is present. The spinous process will rotate toward the pedicle of the side farther from the image receptor 2.
Correcting tube angle errors and head tilt errors
A lordotic curvature exists in the cervical spine. For this reason, a cephalic angle is required to project through the long axis of the vertebral column. This angle can and will vary between 5-20 degrees depending on the position of the head. To project the intervertebral disc spaces open, the central ray should be directed perpendicular to the long axis of the vertebral column 2,3. An excessive or insufficient angle can distort these disc spaces.
To achieve the best angle the central ray should be directed at an angle that parallels the plane of the mandible and then directed to just below the hyoid bone. This allows for discrepancies in the tilt of the head (flexion/extension of the cervical spine).
- 1. Joseph N. Film Critique of the CTL Spine - Part 1: Cervical Spine [Internet]. https://www.ceessentials.net. 2017 [cited 20 February 2017]. Available from: https://www.ceessentials.net/article20.html
- 2. McQuillen-Martensen KMcQuillen-Martensen K. Radiographic image analysis workbook. 2nd ed. St. Louis, Mo.: Elsevier Saunders; 2006.
- 3. Frank E, Long B, Smith B, Merrill V. Merrill's atlas of radiographic positioning & procedures. 12th ed. Jeanne Olson;.