In a patient with increased FDG uptake adjacent to a coronary stent seen on both attenuation‑corrected and non‑attenuation‑corrected PET images, how does the presence of a metallic versus a drug‑eluting stent affect interpretation?

Metallic vs Drug-Eluting Stents: Impact on FDG-PET Interpretation

Both metallic and drug-eluting stents can cause CT attenuation correction artifacts on PET images, but the key to accurate interpretation is reviewing BOTH non-attenuation-corrected (NAC) and attenuation-corrected (AC) images together—if uptake persists on NAC images, it represents true pathology rather than artifact. 1, 2

Understanding the Artifact Problem

The type of stent material (metallic bare-metal vs drug-eluting) is less important than recognizing that any dense metallic object causes overcorrection artifacts in CT-based attenuation correction, creating false "hot spots" on AC PET images that mimic infection 3. This occurs because:

• The CT-based attenuation correction algorithm overcompensates for the high-density metal
• Artifactual FDG uptake appears surrounding the metallic object on AC images only
• True pathologic uptake will be visible on BOTH AC and NAC images

Critical Interpretation Algorithm

When evaluating coronary stent uptake on FDG-PET/CT:

1. First, check NAC images: If increased FDG uptake is present on AC images adjacent to the stent, immediately review the NAC images 1, 2

2. Compare uptake patterns:

   • Artifact: Uptake visible only on AC images, disappears on NAC images 3
   • True infection/inflammation: Uptake persists on both AC and NAC images 2, 4

3. Assess uptake characteristics on NAC images:

   • Location relative to stent (focal at stent site vs diffuse)
   • Intensity compared to adjacent tissue
   • Pattern (focal, linear along stent, or diffuse) 2

4. Correlate with CT findings: Look for supporting anatomical evidence such as:

   • Soft tissue mass around stent
   • Pericardial fluid collection
   • Abscess formation 5

Drug-Eluting Stent Considerations

While drug-eluting stents contain metal and cause the same attenuation artifacts as bare-metal stents, they have additional interpretive considerations:

• Drug-eluting stents can cause local inflammatory reactions from the polymer coating or drug itself, potentially showing FDG uptake even without infection 6
• This inflammation-associated uptake may represent sterile inflammation rather than infection
• Clinical context (timing post-procedure, symptoms, inflammatory markers) becomes crucial for differentiation

Practical Pitfalls to Avoid

Common error: Interpreting any uptake near a stent on AC images as infection without checking NAC images—this leads to false positives 3

Modern scanners: Newer PET/CT devices with improved metal artifact reduction algorithms produce fewer artifacts, but NAC review remains essential when doubt exists 1

SUV measurements: Do not rely on SUV values or target-to-background ratios to differentiate infection from artifact or sterile inflammation—these are not validated for this purpose 2

When Stent Infection is Confirmed

If true FDG uptake is confirmed on NAC images with supporting clinical/anatomical findings 5, 7:

• Consider ECG-gated acquisition for better anatomical localization 5
• Evaluate for complications: in-stent restenosis, pseudoaneurysm, pericardial involvement 7
• Assess whole body for septic emboli and infection source 2

The distinction between metallic and drug-eluting stents matters less for artifact generation than for understanding potential causes of true uptake—both require the same rigorous NAC/AC comparison for accurate interpretation.