several soft-tissue foreign bodies, such as wood and plastic, are not radiopaque and may remain undetected on radiography; however, all foreign bodies are hyperechoic on sonography.
a non experienced operator may miss a foreign body. the sonographer must “heel and toe” the probe to ensure that they are looking at 90 degrees to the foreign body to ensure the shadowing artifact can be seen behind the foreign body along with the echogenic appearance of the object.
sonographic artifacts deep in relation to soft-tissue foreign bodies are related to the surface attributes rather than the composition of the foreign body and aid in their identification.
material such as wood or plastic tends to produce shadowing. metal objects tend to produce reverberation or comet tail artifact.
a high frequency linear transducer (7.5 to 18 mhz) is placed on the structure of interest with or without the use of a standoff pad. this allows better sound transmission and an improved view of the underlying soft tissues without the “big bang” effect.
the area is scanned throughout its entirety in search for a hyperechoic object in both the sagittal and transverse planes.