The quality of being
transparent to
x-rays and thus invisible on x-ray film or
fluoroscopes, or an object having this quality. Contrast
radiopaque.
Of interest in a medical context for a couple of reasons. Chairs, headrests, surgical tables etc. made from radiolucent material allow patients to be examined or operated on more comfortably and effectively in situ.
Radiolucent surgical materials can also be used inside the body to protect or support body structures that need repair, while allowing an unimpaired (x-ray) view later from the outside.