Ultrasound examination of foreign bodies. An in vitro investigation.

Ultrasound examination of foreign bodies most frequently encountered in the human body was performed when they were contained within a transmission medium acoustically resembling human soft tissues. All the foreign bodies evaluated (lead and plastic pellets, pieces of wire, nails, needles, small fragments of rock and glass, wooden slivers, surgical sponges and surgical threads) were detectable with ultrasound. Strong echoes were reflected from their surface when they were positioned favourably, although in some positions the echoes from a needle, fragment of glass, wooden silver, or surgical thread could not be distinguished from those of the surroundings. Acoustic shadows were also seen behind the foreign bodies. A striking column of reverberation echoes was demonstrated behind lead pellets and nails while behind a glass plate there was an acoustic shadow that was often difficult to detect because it was concealed by a mirror image. With modern grey-scale real-time equipment it is possible to demonstrate objects from various angles, a fact which should facilitate the detection of foreign bodies in vivo circumstances.