From the Guidelines
Glass is generally not visible on a plain radiograph, and other imaging modalities such as ultrasound, CT scans, or MRI are more effective for detecting glass foreign bodies. According to the most recent study 1, glass and ceramic are not always seen on radiographs, which is consistent with the findings of an earlier study 1 that glass is inconsistently visible radiographically, particularly if fragments are small or obscured by adjacent osseous structures. The main reasons for this are:
- Glass has a density similar to soft tissues in the human body, making it difficult to visualize on conventional X-rays
- Glass is considered radiolucent, meaning X-rays pass through it with minimal absorption or reflection
- However, some glass may contain lead or other heavy metals which could make it slightly more visible For detecting glass foreign bodies, other imaging modalities are preferred, including:
- Ultrasound, which is particularly useful for detecting superficial glass fragments in soft tissues
- CT scans, which can identify deeper glass fragments due to their superior contrast resolution
- MRI, which can also be used to evaluate concomitant soft-tissue infections.
From the Research
Visibility of Glass on Plain Radiographs
- The visibility of glass on plain radiographs has been studied in various research papers, with most concluding that glass is indeed visible on x-rays 2, 3.
- A study published in 1999 found that regular nonleaded glass is radiographically visible, with an overall sensitivity of 90% and a false-positive rate of 10% 2.
- Another study from 1985 assessed the radiopacity of modern glass and concluded that all glass fragments should be detectable on radiographs, although thin slivers of glass may be difficult to detect 3.
- These findings suggest that glass can be visible on plain radiographs, although the detection rate may vary depending on factors such as the size and location of the glass fragments.
Factors Affecting Detection
- The study from 1999 found that factors such as color and location of the glass have no effect on its detection, while a volume of less than 15 mm3 may have an effect on the detection of glass 2.
- The 1985 study noted that good radiography and careful scrutiny are necessary to detect thin slivers of glass 3.
- These findings highlight the importance of careful examination and high-quality imaging in detecting glass fragments on plain radiographs.
Comparison with Other Imaging Modalities
- A study from 2014 discussed the use of bedside ultrasound in identifying and guiding the management of retained soft tissue foreign bodies, including glass 4.
- However, this study did not directly compare the visibility of glass on plain radiographs with other imaging modalities.
- Other studies, such as those on acute appendicitis and COVID-19, do not provide relevant information on the visibility of glass on plain radiographs 5, 6.