Which of the following describes negative contrast media?

Negative contrast media are substances used in imaging that decrease the density of tissues in radiographic examinations. This is achieved by incorporating agents that are less dense than the surrounding bodily tissues, allowing for enhanced visualization of structures during imaging studies. In particular, negative contrast agents, such as air or carbon dioxide, create a contrast that highlights areas by creating shadows or outlines against denser materials.

Using negative contrast helps differentiate between tissues and structures by providing a stark contrast with the surrounding areas that may appear denser with other materials. This characteristic is essential in various imaging modalities where clear delineation of structures is crucial for accurate diagnosis and assessment.

The other options do not accurately describe the nature of negative contrast media. For example, increasing tissue density would involve positive contrast media, while the assertion that negative contrast is always iodine-based is misleading, as negative contrast media do not rely on iodine at all and often use gases or low-density materials instead. Lastly, the claim that negative contrast is only used in cardiac imaging is incorrect, as these media can be applied in various imaging fields, including gastrointestinal imaging and others that require differentiation of anatomical structures.