radiopacas

Radiopacas, or radiopaque substances, are materials that strongly attenuate X-ray photons and appear bright or white on radiographs and CT images. They contrast with radiolucent substances that allow more X-ray transmission and appear darker.

The degree of radiopacity depends on atomic number, electron density, and thickness. High atomic number elements (like lead, barium, iodine) and dense materials produce greater attenuation. In clinical imaging, radiopaque materials may be natural (bone) or introduced (contrast agents, implants).

Common examples include bone mineral, dental fillings, surgical implants made of metals, and contrast agents such as barium sulfate or iodinated compounds used to enhance visualization of the gastrointestinal tract or vessels.

Uses include diagnostic radiography, fluoroscopy, and computed tomography; radiopaque markers and fiducials assist in localization during planning and procedures; dental radiographs rely on radiopacity for tooth structures and materials; radiopaque implants provide lasting visibility across imaging sessions.

Safety and limitations: radiopaque materials increase tissue exposure to X-rays in the imaging region and can cause artifacts or streaks in CT; certain radiopaque substances may be toxic (e.g., lead) or cause allergic reactions (iodinated contrast). Distinguishing between different radiopaque materials can be challenging when densities are similar.