Which substances are used to create positive contrast media?

• A. Calcium and magnesium
• B. Iodine and barium
• C. Carbon and nitrogen
• D. Water and air

Answer: (B)

Positive contrast media are substances that enhance the contrast of structures or fluids within the body in radiographic imaging. Iodine and barium are commonly used for this purpose due to their high atomic numbers, which increase their opacity to X-rays. This property allows the surrounding structures to appear more clearly on the radiographic image.

Iodine-based contrast agents are particularly effective because they can be administered intravenously and are well-absorbed by vascular structures, making them ideal for enhancing visibility in various diagnostic imaging studies. Barium, on the other hand, is typically used for gastrointestinal tract imaging, as it is effective in delineating the contours of the digestive organs.

The other substances listed do not possess the appropriate properties needed for positive contrast in radiography. Calcium and magnesium, while important elements in the body, do not provide the necessary density differences when imaged with X-rays. Carbon and nitrogen are gaseous substances that do not enhance contrast. Similarly, water and air do not provide sufficient contrast in imaging studies, as their densities are too similar to that of surrounding tissues.

Therefore, iodine and barium are the correct choices for positive contrast agents in radiographic procedures.