CT of the Spine¶
Definition¶
Computed tomography (CT) of the spine uses X-ray beams and computer reconstruction to produce detailed cross-sectional images of the vertebral column. It provides superior osseous detail compared to radiography and is the gold standard for evaluating fractures, bony stenosis, and hardware positioning.
Technique¶
Acquisition¶
- Helical (spiral) CT is standard — continuous data acquisition as the patient moves through the gantry
- Thin-section acquisition (0.5–1.25 mm slice thickness) allows high-quality multiplanar reformats
- Multiplanar reformats (MPR): sagittal and coronal images reconstructed from axial data are essential for spinal imaging
- 3D volume rendering: useful for complex deformities, fractures, and surgical planning
Scan Parameters¶
| Parameter | Typical Value |
|---|---|
| Slice thickness | 0.5–1.25 mm (bone); 2–3 mm (soft tissue) |
| Reconstruction kernels | Sharp/bone kernel for osseous detail; soft tissue kernel for disc/canal evaluation |
| Window settings | Bone window (W:2000, L:400); soft tissue window (W:400, L:40) |
| Contrast | Not routinely used for spine CT; reserved for CT myelography or vascular evaluation (CTA) |
Region-Specific Protocols¶
- Cervical: occiput through T1; thin sections essential for craniocervical junction
- Thoracic: T1 through T12; often combined with chest CT in trauma
- Lumbar: T12 through sacrum; standard for low back pain evaluation
- Whole spine: occiput through sacrum in polytrauma
Indications¶
- Trauma: fracture detection and characterization (sensitivity >99% for fractures)
- Degenerative disease: bony stenosis, foraminal narrowing, facet arthropathy, spondylolisthesis
- Post-surgical: hardware positioning, fusion assessment, pseudarthrosis
- Osseous lesions: primary bone tumors, metastatic disease, infection (osteomyelitis)
- Congenital anomalies: segmentation defects, transitional vertebrae
- CT myelography: when MRI is contraindicated
- Pre-surgical planning: pedicle screw trajectory, deformity correction
Advantages Over Radiography¶
- Cross-sectional imaging eliminates superimposition
- Superior fracture detection — CT detects occult fractures missed on radiographs
- Precise measurement of canal dimensions, foraminal size, and fragment retropulsion
- Multiplanar reformats provide comprehensive anatomic evaluation
- Fast acquisition — critical in trauma settings
Imaging Findings by Pathology¶
Fractures¶
- Vertebral body fractures: compression, burst (retropulsed fragment), chance (horizontal split)
- Posterior element fractures: pedicle, lamina, facet, spinous process, transverse process
- Percent canal compromise can be measured on axial images
Degenerative Disease¶
- Disc calcification, vacuum phenomenon (gas in the disc)
- Osteophytes and endplate sclerosis
- Facet hypertrophy, joint space narrowing, subchondral cysts
- Bony foraminal and central canal stenosis
Post-Surgical¶
- Screw positioning relative to pedicle cortex and spinal canal
- Interbody cage positioning
- Fusion assessment — bridging bone vs. lucency around hardware (loosening)
Clinical Pearl
In trauma, CT has a sensitivity >99% for detecting spinal fractures, compared to approximately 50–70% for plain radiographs. The American College of Radiology recommends CT as the primary imaging modality for spine clearance in blunt trauma patients with a high-risk mechanism, altered mental status, or distracting injuries. Plain radiographs are no longer considered adequate for definitive spine clearance in high-risk patients.
Limitations¶
- Radiation exposure — significantly higher than radiography; cumulative dose is a concern with repeated studies
- Poor soft tissue contrast — cannot adequately evaluate the spinal cord, nerve roots, ligaments, or intervertebral discs (MRI is superior)
- Beam hardening artifacts from metallic hardware can obscure adjacent structures
- Cannot evaluate the spinal cord — cord compression, myelopathy, and intrinsic cord lesions require MRI
- Weight limitations for the scanner table
Key Points¶
- CT is the gold standard for evaluating spinal fractures, with sensitivity >99%
- Thin-section acquisition with multiplanar reformats is essential for comprehensive spinal evaluation
- CT is preferred for acute trauma spine clearance in high-risk patients
- Bone and soft tissue reconstruction kernels should both be reviewed
- CT cannot adequately evaluate the spinal cord, discs, or ligaments — MRI is required for soft tissue assessment
- Post-surgical hardware evaluation is a major indication
References¶
- Hassankhani A, Freeman CW, Banks J, et al. ACR Appropriateness Criteria® Acute Spinal Trauma: 2024 Update. J Am Coll Radiol. 2025;22(5S):S48-S66. doi:10.1016/j.jacr.2025.02.013. PMID: 40409895.
- Beckmann NM, West OC, Nunez D Jr, et al. ACR Appropriateness Criteria® Suspected Spine Trauma. J Am Coll Radiol. 2019;16(5S):S264-S285. doi:10.1016/j.jacr.2019.02.002. PMID: 31054754.
- Dreizin D, Letzing M, Sliker CW, et al. Multidetector CT of blunt cervical spine trauma in adults. RadioGraphics. 2014;34(7):1842-1865. doi:10.1148/rg.347130094. PMID: 25384284.
- Ghodasara N, Yi PH, Clark K, Fishman EK, Farshad M, Fritz J. Postoperative Spinal CT: What the Radiologist Needs to Know. RadioGraphics. 2019;39(6):1840-1861. doi:10.1148/rg.2019190050. PMID: 31589573.
- Dieckmeyer M, Sollmann N, Kupfer K, et al. Computed Tomography of the Spine: Systematic Review on Acquisition and Reconstruction Techniques to Reduce Radiation Dose. Clin Neuroradiol. 2023;33(2):271-291. doi:10.1007/s00062-022-01227-1. PMID: 36416936.
- Radiopaedia. CT cervical spine (protocol). Available at: https://radiopaedia.org/articles/ct-cervical-spine-protocol-1
- Radiopaedia. CT lumbar spine (protocol). Available at: https://radiopaedia.org/articles/ct-lumbar-spine-protocol-1