Absorbers of high atomic number are used to produce which type of contrast media?

• A. Negative contrast media
• B. Neutral contrast media
• C. Positive contrast media
• D. Radiopaque fluid

Answer: (C)

Materials with a high atomic number absorb more X‑ray photons, increasing local attenuation. When such agents are introduced, they make that area appear brighter on the image because they are radiopaque. This bright, white appearance is what we call positive contrast media. Common examples are iodine-based and barium-based agents, which outline structures like the GI tract by adding significant attenuation compared with surrounding tissues. In contrast, negative contrast uses low-density materials like air that appear dark, and neutral contrast would have attenuation similar to surrounding tissues, offering minimal intrinsic contrast. Radiopaque fluids are simply fluids that are radiodense and thus provide positive contrast.