- Anything that does not let X-rays or other types of radiation penetrate. Radiopaque objects block radiation. They are opaque to radiation. A metal object, for example, is typically radiopaque. If a child swallows a coin and it goes down into the stomach, it is easily visible in the stomach on an X-ray because it is radiopaque. Radiopaque dyes are used in radiology to enhance the X-ray pictures of selected internal anatomic structures. For example, an intravenous pyelogram (IVP) is an X-ray study of the kidneys using a radiopaque dye injected intravenously that highlights the renal pelvis (where the kidney collects urine) and the ureters (the two tubes, one coming from each kidney, that transport the urine down to the bladder). Radiopaque is as opposed to radiolucent. A radiolucent object permits the penetration and passage of X-rays.
* * *Exhibiting relative opacity to, or impenetrability by, x-rays or any other form of radiation. Cf.:radiolucent. SYN: radiodense. [radio- + Fr. opaque fr. L. opacus, shady]
* * *ra·di·opaque -ō-'pāk adj being opaque to radiation and esp. X-rays <\radiopaque dyes> compare RADIOLUCENT
* * *adj.having the property of absorbing, and therefore being opaque to, X-rays. Radiopacity increases with atomic weight. Radiopaque materials, such as those containing iodine or barium, are used as contrast medium in radiography. Metallic foreign bodies in tissues are also radiopaque and can be detected by radiography. Such heavy elements as lead and barium can be used in shielding to protect people from unnecessary exposure to ionizing radiation.• radiopacity n.
* * *ra·di·opaque (ra″de-o-pākґ) [radio- + opaque] not penetrable by x-rays or other forms of radiant energy; radiopaque areas appear light or white on the exposed film.
Medical dictionary. 2011.