What best describes positive contrast media?

Positive contrast media are primarily composed of elements with high atomic numbers, such as iodine or barium. These high atomic number elements have a greater density, which enhances their visibility on imaging modalities like X-rays or CT scans. The increased density allows for a clearer distinction between the contrast-enhanced areas and surrounding tissues, making it easier for healthcare providers to identify abnormalities or conditions.

In contrast, options that mention low atomic numbers do not provide the necessary visualization properties needed for effective imaging. Additionally, while some positive contrast agents may be water-soluble and safe for many patients, this does not universally apply to all positive contrast media, as there can be exceptions and contraindications based on patient health. Furthermore, while some contrast materials can be used for therapeutic purposes, this does not define the primary characteristic of positive contrast media, which is their composition and effect on imaging.