Here's why:

* Radioisotope: A radioactive form of an element.

* Radiopharmaceutical: A pharmaceutical drug (medicine) that contains a radioisotope. This radioisotope allows for imaging or therapeutic applications.

Example: A common radiopharmaceutical is Technetium-99m (Tc-99m), often used in medical imaging. It is incorporated into various molecules, like those targeting bone or the heart, to create images of these structures.

Let me know if you have any other questions!