A substance opaque to X-rays, introduced into hollow or fluid-filled body parts to show them up on X-ray film. Barium is one of the most commonly used contrast media (see barium X-ray examinations).
| Contrast medium | 
|  | 
| Contrast medium | 
| A substance opaque to X-rays, introduced into hollow or fluid-filled body parts to show them up on X-ray film. Barium is one of the most commonly used contrast media (see barium X-ray examinations). | 
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