CT cervical spine (protocol)

The CT cervical spine or C-spine protocol serves as an examination for the assessment of the cervical spine. It is usually performed as a non-contrast study. In certain situations, it might be combined or simultaneously acquired with a CT angiography of the cerebral arteries or a CT of the neck. It also forms a part of a polytrauma CT or might rarely be done as a CT myelogram in situations where MRI is contraindicated.

Note: This article aims to frame a general concept of a CT protocol for the assessment of the cervical spine. Protocol specifics will vary depending on CT scanner type, specific hardware and software, radiologist and perhaps referrer preference, patient factors e.g. implants, specific indications.

A typical CT of the cervical spine might look like as follows:

Indications

Typical indications include the following ^1-4:

• cervical spine injury
  • cervical spine fractures
  • discoligamentous injuries
• cervical spine implants and complications
• spinal tumours and/or vertebral metastasis
• congenital anomalies
• if MRI is contraindicated
  • inflammatory arthritis or spondylodiscitis
  • degenerative disk disease
• image guidance (e.g. cervical spinal epidural injections)
• CT myelography
  • if MRI is contraindicated or metallic implants prevent sufficient image quality
  • spinal cord compression

Purpose

The most common purpose of a CT of the cervical spine is the timely diagnosis and classification or exclusion of cervical spine injuries and the evaluation of the osseous spinal canal including ^1-3:

• upper cervical injuries
• subaxial injuries
• cervical canal stenosis

In the setting of vertebral metastasis or spinal tumours this also includes the assessment of the following: 

• fracture risk: spinal instability neoplastic score (SINS)
• cord compression risk: epidural spinal cord compression (ESCC) scale

Technique

• patient position
  • supine position 
  • both arms next to the body, shoulders pulled down
• tube voltage
  • ≤120 kVp
• tube current
  • as suggested by the automated current adjustment mode 
• scout
  • from above the temporal bone to the manubrium sterni 
• scan extent
  • should include the base of the skull and the first thoracic vertebra
• scan direction
  • craniocaudal
• scan geometry
  • field of view (FOV): 120-200 mm (should be adjusted to increase in-plane resolution)
  • slice thickness: ≤1 mm, interval: ≤0.75 mm
  • reconstruction kernelalgorithm: bone kernel (e.g. B70), soft tissue kernel (e.g. B40)
• multiplanar reconstructions/reformats
  • sagittal images: sagittal aligned through the centre of the dens and the vertebral bodies
  • coronal images: coronal aligned to the transverse processes
  • axial images:perpendicular to the cervical spine and the neck
  • slice thickness: ≤1.5 mm, overlap 50%

Practical points

• patient positioning prior to scanning might reduce and facilitate multiplanar reconstructions
• shoulder pull-down might allow for safe dose reduction
• dose optimisation ^5-8
  • use iterative reconstruction algorithms if available
  • tube current might be lowered to as low as 105-150 mAs ^6-8
• imaging of implants ⁵
  • use metal artifact reduction algorithms
  • use monochromatic reconstructions in dual-energy CT scans
  • use additional wide window setting
  • might require a higher tube potential
• the threshold for a CT instead of radiographic cervical spine series should be low in the setting of an adequate cervical spine trauma (as determined by clinical criteria e.g. NEXUS criteria or Canadian C-spine rule)  ^1-3