What are the two main types of contrast used in imaging?

The correct answer is positive and negative contrast, which refers to the two primary categories of contrast agents used in imaging studies. Positive contrast agents are substances that enhance the visibility of internal structures by appearing brighter than the surrounding tissues on imaging results. They typically contain elements with high atomic numbers, such as iodine or barium, which absorb X-rays more than the surrounding tissues. This makes them particularly useful in highlighting structures like blood vessels or the gastrointestinal tract.

Negative contrast agents, on the other hand, provide a different functionality by appearing darker on imaging. These agents, such as air or carbon dioxide, decrease the density of the structures they fill, creating a contrast effect against denser tissues. They are often utilized in conjunction with positive contrast agents to optimize the visibility of certain areas in imaging studies.

The classification into positive and negative types is fundamental in radiological practices, significantly improving the clarity and diagnostic value of the images produced.