A contrast agent is a substance used in medical imaging to enhance the visibility of internal structures in the body. It helps improve the clarity of images obtained through techniques like X-rays, CT scans, and MRI. By highlighting specific areas, contrast agents allow healthcare professionals to better diagnose and monitor various conditions. These agents can be administered orally or through injection, depending on the type of imaging required. Common types of contrast agents include iodine-based solutions for X-rays and CT scans, and gadolinium for MRI. Their use is essential for accurate assessments in medical evaluations.