Radiographs should be obtained with an underpenetrated "soft tissue technique," producing a lighter film that increases the contrast between the foreign body and surrounding tissue.1 Plain films should be taken in multiple projections to separate the shadow of the foreign body from underlying bone and to help gauge the depth of the object in the tissue. Chronic inflammatory changes may create secondary bony changes such as osteolytic and osteoblastic lesions, pseudotumor formation, and periosteal reaction, revealing the object's location.
Many common or highly reactive materials such as wood, thorns, cactus spines, fish bones, most plastics, and other organic matter are not visible on plain films. 1 Sometimes there is indirect evidence of their presence; a radiolucent filling defect may occur when the object is less dense than surrounding tissue. Even radiopaque foreign bodies may be invisible on plain films if they are projected over bone or impacted in bone.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.