Is glass radiopaque?

Is Glass Radiopaque?

Yes, glass is radiopaque and should be visible on plain radiographs with approximately 98% sensitivity, though visibility depends on size, thickness, and surrounding tissue. 1, 2

Factors Affecting Glass Visibility on Imaging

Glass is considered radiodense, but its visibility on imaging depends on several important factors:

• Size and thickness: Thin slivers of glass may be more difficult to detect but should still be visible with proper radiographic technique 3
• Surrounding tissue: The contrast between glass and surrounding tissue affects visibility 4
• Type of glass: Both leaded and non-leaded glass are radiopaque 1
• Quality of imaging: Proper radiographic technique is essential for detection 5

Optimal Imaging Approach for Glass Foreign Bodies

When a glass foreign body is suspected, the following imaging approach is recommended:

1. Initial imaging: Plain radiographs in at least two perpendicular planes (biplanar radiography) should be the first-line imaging modality 2

   • Sensitivity for detecting radiopaque foreign bodies is approximately 98% 1
   • False-negative rates can be reduced with biplanar views 2

2. If radiographs are negative but clinical suspicion remains high:

   • Ultrasound: Excellent for precise localization with 90-100% sensitivity for foreign bodies 2
   • CT scan: 5-15 times more sensitive than radiography, with thin slice thickness (1 mm) recommended to avoid missing small glass fragments 2

Evidence on Glass Visibility

Research studies have demonstrated the radiopacity of glass:

• A cadaver study found 90% overall sensitivity for detecting non-leaded glass fragments on plain radiographs, with color and location having no significant effect on detection 5
• Glass fragments with volume less than 15 mm³ may be more difficult to detect 5
• All glass fragments should be detectable with good radiographic technique and careful examination 3

Common Pitfalls to Avoid

• Relying solely on a single radiographic view: Using at least two perpendicular views significantly improves detection rates 2
• Assuming all glass is equally visible: Very small or thin fragments may be more challenging to detect 5
• Confusing radiopacity as binary: Radiopacity is relative and depends on comparative X-ray attenuation rather than being simply present or absent 4
• Inadequate imaging technique: Poor quality radiographs may miss glass foreign bodies that would otherwise be visible 3

In clinical practice, understanding that glass is radiopaque but with variable visibility based on these factors will help guide appropriate imaging selection and interpretation when glass foreign bodies are suspected.