CT Scan of the Thoracic and Lumbar Spine: Contrast Recommendations
CT scans of the thoracic and lumbar spine typically do not require contrast unless specific pathologies such as infection, malignancy, or post-surgical complications are suspected. 1
Standard Protocol for Spine CT Imaging
Non-Contrast CT is Appropriate for:
- Evaluation of osseous structures and anatomy
- Assessment of degenerative changes
- Fracture detection and characterization
- Preoperative planning for hardware fixation
- Spondylolysis evaluation
According to the ACR Appropriateness Criteria for thoracic back pain, "There is no relevant literature to support the use of CT thoracic spine without IV contrast in the initial imaging of thoracic back pain and myelopathy or radiculopathy." 1 However, CT without contrast remains useful for preoperative planning due to its excellent delineation of osseous structures.
Contrast-Enhanced CT is Indicated When:
- Infection is suspected (epidural abscess, discitis, osteomyelitis)
- Malignancy or metastatic disease is suspected
- Post-surgical evaluation for complications
- Assessment of soft tissue involvement around the spine
- Epidural abscess evaluation
The ACR guidelines state that "CT thoracic spine with IV contrast can provide complementary information that can be helpful in treatment planning, including for presurgical planning and postoperative assessment." 1
Decision Algorithm for Spine CT Contrast Use
Non-Contrast CT (first-line for most cases):
- Trauma/fracture evaluation
- Degenerative disease assessment
- Osseous abnormalities
- Spinal stenosis evaluation
- Hardware assessment
Contrast-Enhanced CT (specific indications):
- Clinical suspicion of infection with red flags (diabetes, IV drug use, immunosuppression) 1
- Known or suspected malignancy
- Post-surgical patients with suspected complications
- Soft tissue abnormalities requiring evaluation
Important Clinical Considerations
- MRI remains the gold standard for evaluating spinal cord, nerve roots, and soft tissue pathologies, with superior sensitivity compared to CT 1
- For suspected infection, MRI without and with IV contrast is preferred over CT due to its high sensitivity and specificity 1
- CT myelography (using intrathecal contrast) may be more appropriate than IV contrast CT for evaluating neural compression when MRI is contraindicated 1
Common Pitfalls to Avoid
- Ordering contrast-enhanced CT routinely without specific indications increases radiation exposure and risk of contrast-related complications
- Relying solely on CT (even with contrast) for soft tissue or neural pathology assessment when MRI would be more appropriate
- Using contrast when the clinical question can be answered with non-contrast imaging
- Failing to consider MRI as the first-line modality for suspected infection or malignancy
Technical Considerations
- When contrast is indicated, single-phase contrast-enhanced CT is sufficient; there is no diagnostic advantage to performing both non-contrast and contrast phases in a single study 1
- Iohexol (IV contrast) has a vascular compartment half-life of approximately 20 minutes, with peak enhancement occurring within 30-90 seconds after injection 2
In summary, while CT scanning of the thoracic and lumbar spine provides excellent osseous detail, contrast administration should be reserved for specific clinical scenarios where soft tissue pathology, infection, or malignancy is suspected.