What are the different types of Computed Tomography (CT) spine scans?

Types of CT Spine Imaging

CT spine imaging can be categorized into several distinct types, each with specific clinical applications and advantages, with CT myelography being particularly valuable for assessing spinal canal patency when MRI is contraindicated or in cases with significant hardware artifacts.

Standard CT Spine Protocols

• CT Spine Without IV Contrast: The most common type, used to evaluate osseous integrity, fractures, alignment, and bony destructive changes. It provides detailed analysis of fractures extending to the posterior column of the vertebra and for evaluating pedicle integrity and posterior cortex. However, intradural and spinal cord pathologies are poorly depicted 1.

• CT Spine With IV Contrast: Used to evaluate for epidural abscess in patients with suspected infection. Addition of IV contrast may help assess for epidural abscess but generally doesn't provide significant additional information for fracture evaluation 1.

• CT Spine Without and With IV Contrast: Not typically performed as there is no diagnostic advantage to performing a single study with both protocols compared to either alone 1.

Specialized CT Spine Techniques

• CT Myelography: Involves lumbar puncture with intrathecal contrast injection followed by CT imaging. This technique:

  • Assesses patency of the spinal canal/thecal sac, subarticular recesses, and neural foramina 1
  • Has safety advantages over MRI for patients with implanted medical devices that are not MRI safe/conditional 1
  • Is useful in patients with significant artifact from metallic surgical hardware 1
  • Is occasionally more accurate than MRI in diagnosing nerve root compression in the lateral recess 1
  • Has the disadvantage of requiring lumbar puncture and intrathecal contrast injection 1

• Discography and Post-Discography CT: Involves injection of contrast into intervertebral discs followed by CT imaging. This technique has limited application and is not supported by literature for most clinical scenarios including low back pain evaluation 1.

CT Spine by Anatomical Region

• CT Cervical Spine: Specialized protocols may be used, such as shoulder pull-down techniques to improve visualization of lower cervical segments 2.

• CT Thoracic Spine: Used to assess integrity of fusion, hardware position, and spinal alignment in post-surgical patients 1.

• CT Lumbar Spine: Commonly used to evaluate for osseous abnormalities, hardware assessment, and spinal stenosis 1.

Advanced CT Applications

• CT with SPECT or SPECT/CT: Not typically used as initial imaging but can be helpful in:

  • Evaluating for widespread osseous metastatic disease 1
  • Assessing radiographically occult fractures 1
  • Evaluating acuity of vertebral fractures 1
  • Cases of painful pseudoarthrosis or periprosthetic loosening in patients with previous lumbar fusion 1

• FDG-PET/CT: Not typically an initial imaging study but can be used to:

  • Evaluate for widespread metastatic disease 1
  • Distinguish between benign versus malignant compression fractures 1
  • Help differentiate benign from pathologic compression fractures when other imaging modalities are indeterminate 1

Clinical Considerations

• CT spine imaging provides excellent detail of cortical bony structures but is less sensitive for spinal cord and soft tissue evaluation compared to MRI 3, 4.

• With advancements in multidetector CT (MDCT) technology, unenhanced CT can now provide sufficient stratigraphic details of the spinal cord and epidural space without requiring subarachnoid opacification in many cases 5.

• CT is generally equal to MRI for predicting significant spinal stenosis and excluding cauda equina impingement, but inferior for evaluating marrow abnormalities, infection, and intradural pathologies 1, 4.