Because of the granulomatous, inflammatory response to foreign bodies within soft tissues, surrounding fluid signal, edema, peripheral enhancement is a dominant pattern on MRI, which can be used to help localize foreign bodies. MRI with IV contrast can also assess complications of foreign bodies in soft tissues and bone, including cellulitis, fasciitis, abscesses, sinus tracts, osteomyelitis, and vascular or tendon injuries. Compared with US and CT, MRI has a lower sensitivity and inferior spatial resolution for detection of foreign bodies. Radiodense foreign bodies are better visualized on radiography [46]. Metallic foreign bodies and air produce susceptibility artifact, which can limit MRI quality. With metallic objects and MRI, there is a potential for severe soft tissue heating and motion of the foreign body because of the magnetic field. The severity of this risk is dependent on the ferromagnetic properties and location of the metallic foreign body, how long the foreign body has been in place, and the strength of the MRI unit [47]. Therefore, radiographic screening for metallic foreign bodies is recommended before MRI. US Area of Interest If a foreign body is not visualized on radiographs, US can be used for further evaluation especially in the acute, emergency setting [46,47]. US has a reported sensitivity of 95% for the detection of foreign bodies [48]. Tantray et al [48] reported out of 120 patients that went to surgery for foreign body exploration, US visualized foreign bodies in 114 patients. Among the 6 patients with negative US, only 1 patient had a foreign body on surgery. In addition, US can further characterize foreign body morphology, depth, and location in relation to adjacent structures like Suspected Osteomyelitis, Septic Arthritis vessels, bone, joints, tendons, or nerves. Furthermore, US can provide image guidance for removal of the foreign bodies.
Suspected Osteomyelitis Septic Arthritis or Soft Tissue Infection Excluding Spine and Diabetic Foot PCAs. Because of the granulomatous, inflammatory response to foreign bodies within soft tissues, surrounding fluid signal, edema, peripheral enhancement is a dominant pattern on MRI, which can be used to help localize foreign bodies. MRI with IV contrast can also assess complications of foreign bodies in soft tissues and bone, including cellulitis, fasciitis, abscesses, sinus tracts, osteomyelitis, and vascular or tendon injuries. Compared with US and CT, MRI has a lower sensitivity and inferior spatial resolution for detection of foreign bodies. Radiodense foreign bodies are better visualized on radiography [46]. Metallic foreign bodies and air produce susceptibility artifact, which can limit MRI quality. With metallic objects and MRI, there is a potential for severe soft tissue heating and motion of the foreign body because of the magnetic field. The severity of this risk is dependent on the ferromagnetic properties and location of the metallic foreign body, how long the foreign body has been in place, and the strength of the MRI unit [47]. Therefore, radiographic screening for metallic foreign bodies is recommended before MRI. US Area of Interest If a foreign body is not visualized on radiographs, US can be used for further evaluation especially in the acute, emergency setting [46,47]. US has a reported sensitivity of 95% for the detection of foreign bodies [48]. Tantray et al [48] reported out of 120 patients that went to surgery for foreign body exploration, US visualized foreign bodies in 114 patients. Among the 6 patients with negative US, only 1 patient had a foreign body on surgery. In addition, US can further characterize foreign body morphology, depth, and location in relation to adjacent structures like Suspected Osteomyelitis, Septic Arthritis vessels, bone, joints, tendons, or nerves. Furthermore, US can provide image guidance for removal of the foreign bodies.