Cervical Spine - APThis is a featured page

Radiographic Positioning


Adult
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Name of projection Cervical Spine - AP
Area Covered The cervical vertebrae from C3 down to approximately T2
Pathology shown Some pathologies of the cervical vertebrae C3 through to C7
Radiographic Anatomy Cervical Spine Radiographic Anatomy
IR Size & Orientation 18 x 24 cm
Portrait
Film / Screen Combination Regular
(CR and DR as recommended by manufacturer)
Bucky / Grid Moving or Stationary Grid
Filter No
Exposure 65 kVp
16 mAs
FFD / SID 100 cm
Central Ray Directed to the level of C4, which is approximately the level of the angle of the mandible
15 degrees cephalad. (to match the lordotic curve of the cervical spine, to penetrate the intervertebral disc spaces)
Collimation Centre: C4, collimate to the 18 x 24cm film size
Shutter A: Open so that the light of the collimated field just includes the top of the ear. The light will appear to bend around due to the central ray being angled cephalad
Shutter B: Open to include the soft tissue of the neck laterally
Markers Lateral
Marker orientation AP
Shielding Gonadal (check your department's policy guidelines)
Respiration Suspended respiration
Positioning
In general,
  • Ensure the removal of artefacts that may superimpose the anatomy of interest
  • Only request the patient move into position if the possibility of spinal injury has been ruled out
  • Take care to ensure no rotation of either the head, neck or torso.
If the patient is erect,
  • Using the upright bucky, position the patient in an AP position. (This allows the patient to rest their back against the bucky, and may help to minimise patient movement)
  • Position the midsagittal plane so that it is perpendicular to the IR
  • Position the interpupillary line so that it is parallel to the IR (in an erect patient, this will also be parallel to the floor)
  • Raise the chin slighlty, so that the line of the occlusal plane superimposes the base of the skull
If the patient is supine,
  • Position the IR patient so that it is either in the table bucky, or is on the barouche posterior to the cervical spine
  • Position the midsagittal plane so that it is perpendicular to the IR
  • Position the interpupillary line so that it is parallel to the IR
Critique

Positioning
  • No rotation is evidenced by
    • The spinous processes are seen in the midline of the vertebral bodies (see notes below)
    • The pedicles are equidistant from the vertebral body edges (see notes below)
    • The mandibular angles are equidistant from the cervical spine
  • Correct alignment of the occlusal plane and the base of skull is evidenced by
    • The superimposition of the mandible over the base of the skull (see notes below)
  • Correct central ray angulation is evidenced by
    • The intervertebral disc spaces are seen open (see notes below)

Area Covered
  • Cervical vertebrae C3 through to C7 are visualised
Collimation
  • Centre: C4
  • Shutter A: Open to include the base of skull superiorly and approximately T2 inferiorly
  • Shutter B: Open to include the soft tissue of the neck laterally
Exposure
  • Bony trabecular patterns and cortical outlines are sharply defined
  • Soft tissues such as an air filled trachea are visualised
Special Notes Determining the direction of rotation
Using spinous process alignment:
When the spinous processes are not seen in the midline of the vertebral bodies this usually indicates rotation of that part of the cervical spine. As the head is rotated in a particular direction, the spinous process tip will move in the opposite direction. For example, if the spinous process tip is closer to the left vertebral body edge, then the patient's neck is rotated so they are looking towards the right side.

Using pedicle alignment:
In an AP view the pedicles are seen laterally in the area between the transverse process and the vertebral body. With correct positioning the pedicles should be equidistant from the vertebral body edges. Example: If the right pedicle is more towards the midline of the vertebral body (it is rolled under/behind the vertebral body), indicating the patient is rotated so they are looking towards the right side.

Demonstrating intervertebral disc spaces
Successful demonstration of the intervertebral disc spaces is largely dependent on correct central ray angulation.
Generally, the central ray is approximately 15 degrees up (cephalad). Consider varying this angle when:
  • the angle required to penetrate the intervertebral disc spaces is other than 15 degrees, as visualised on the lateral cervical spine image taken as part of the same examination
  • the patient is supine, there may be some reduction of the lordotic curve, that is, 'flattening' of the cervical spine. Reducing the central angle by approximately 5 degrees will compensate for this.
Superimposition of the mandible and base of skull
If the mandible is not superimposed over the base of skull, first determine which structure is the base of skull. Locating the mastoid tips will assist with this. If the mandible/chin is more inferior/lower, then raise the chin half the distance of the difference seen on the image. If the mandible/chin is more superior/higher than the base of skull margin, then lower the chin half the distance of the difference seen on the image




AndyC
AndyC
Latest page update: made by AndyC , Jun 3 2011, 4:22 AM EDT (about this update About This Update AndyC Edited by AndyC

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