The Radiographic Detection of Glass in Soft Tissue

The Physical basis of radiology rests on the unequal absorption of x rays as they pass through objects of different densities and effective atomic numbers. It is not generally appreciated that all types of commercial glass possess physical characteristics that are different from those of human tissues. The higher density and effective atomic number of glass compared to those of surrounding soft tissue cause it to be visible on the appropriately exposed radiograph.

A review of the American radiologic literature uncovered only one reference concerning the radiopacity of glass, and that was written in 1932 (6). In 1958 two articles appeared, one in The Archives of Industrial Health (9) and the other in The British Journal of Surgery (4), reporting the radiopacity of glass and its detection in soft tissues. The German literature contains a report published in 1964 which concluded that all ordinary glass, when embedded in the tissues of the hand, could be detected radiographically (3).

Information gained from consulting several of the standard texts is confusing and often inaccurate. Zatzkin states that ordinary glass used in windows and bottles usually can be demonstrated in soft tissues (12). He illustrates multiple varieties of glass that are radiopaque. Another text states that plate glass, glass utilized in lenses and chemical apparatus, and glass containing manganese may be faintly visible but that small pieces in thick parts of the body are not (10). Köhler and Zim-mer suggest that glass is either invisible or barely visible radiographically and do not include it among those objects that are easily visualized (5). Brodeur states that glass must contain iron, lead, or titanium in order to have a density greater than that of soft tissues and therefore cast a shadow (1). Caffey shows a picture of glass from a beer bottle in the hand. He concludes that, “The heavy density of this glass fragment is due to its lead content; glass free of lead is usually invisible in soft tissues because it has a density similar to that of soft tissues” (2). Other texts make no mention of the radiopacity of glass in soft tissue (7, 8, 11).

The value of using a simple device such as an x ray to locate glass particles in the body should be apparent to all who treat glass-induced injuries. An informal survey of pediatric and surgical residents as well as some trained radiologists revealed that most did not consider all types of glass to be radiopaque. This is not surprising in view of the confusing information published in the standard radiology texts as well as the absence of any recent publication in the radiologic or pediatric literature. Contrary to general opinion, glass need not contain lead to be radiopaque. Ordinary machine-made glass contains no lead but is made of a mixture of soda-lime, silicates, and potash.²