For a pulmonary nodule >8mm, when Low-Dose Computed Tomography (LDCT) is not an option, should a noncontrast Computed Tomography (CT) chest or a contrast-enhanced CT chest be used for surveillance?

Noncontrast CT is Recommended for Surveillance of Pulmonary Nodules >8mm

For pulmonary nodules >8mm, noncontrast CT chest should be used for surveillance when LDCT is not available. 1

Rationale for Noncontrast CT

• The American College of Chest Physicians (ACCP) guidelines explicitly state that CT surveillance of solid nodules >8mm should use noncontrast techniques 1
• Contrast administration can artificially affect nodule volume measurements, potentially masking true growth patterns:
  • Studies show that nodules ≤200mm³ (approximately 8mm) appear significantly larger on contrast-enhanced CT compared to noncontrast CT 2
  • Measured volume of small nodules was 13.7-15.5% lower on noncontrast CT compared to contrast-enhanced CT 2

Clinical Implications

• Using different techniques (contrast vs. noncontrast) between baseline and follow-up scans can lead to:
  • Underestimation of nodule growth
  • Masking of potentially malignant growth rates 3
  • Inaccurate calculation of doubling times

Surveillance Protocol for Nodules >8mm

For solid nodules >8mm, follow this protocol:

1. Initial evaluation may include:

   • PET scan if nodule is suspicious
   • Nonsurgical biopsy when clinical probability and imaging findings are discordant
   • Surgical diagnosis when clinical probability of malignancy is high (>65%) 1

2. For follow-up surveillance:

   • Use noncontrast CT technique
   • Maintain consistent technical parameters between scans
   • Use thin sections (≤1.5mm) through the nodule of interest 4

Special Considerations

• For part-solid nodules >8mm:

  • Repeat chest CT at 3 months
  • If persistent, proceed with PET, nonsurgical biopsy, or surgical resection 1
  • Use noncontrast techniques with thin sections 1

• For nonsolid (pure ground glass) nodules >5mm:

  • Annual surveillance with noncontrast CT for at least 3 years 1
  • Early follow-up at 3 months may be indicated for nodules >10mm 1

Pitfalls to Avoid

1. Inconsistent imaging techniques: Always use the same CT protocol (noncontrast) for baseline and follow-up scans to ensure accurate assessment of growth 3, 2

2. Inadequate slice thickness: Thin-section CT (≤1.5mm) should be used for accurate characterization of nodules 4

3. Misinterpretation of apparent growth: Be aware that comparing contrast-enhanced CT with subsequent noncontrast CT may falsely suggest stability when growth is actually occurring 3

By following these evidence-based recommendations, you can optimize surveillance of pulmonary nodules >8mm while minimizing radiation exposure and ensuring accurate assessment of potential malignant transformation.