Final answer:
The synonym for 'contrast medium' in medical imaging is 'contrast agent,' also known as 'contrast dye,' used to enhance the visibility of internal body structures in imaging procedures.
Step-by-step explanation:
The synonym for contrast medium is contrast agent. A contrast agent, also known as contrast dye, is a substance used in medical imaging to improve the contrast of structures or fluids within the body in CT scans, MRIs, and X-rays, making them more visible on the images. Contrast substances can be administered in various ways, such as orally, intravenously, or rectally, depending on the type of imaging and the area of the body being investigated.