What do isotopes refer to in nuclear medicine?

Isotopes refer to variants of a chemical element that have the same number of protons but differ in the number of neutrons. This means they belong to the same element and have similar chemical properties, but their mass is different due to the varying number of neutrons. In nuclear medicine, isotopes are particularly important because some isotopes are unstable and radioactive, making them useful for diagnostics or treatment, as they can emit radiation that can be detected or used therapeutically.

While there are options that mention protons, mass numbers, and radioactivity, the defining characteristic of isotopes is specifically the variation in neutron count while maintaining the same proton count, which directly affects the element’s atomic mass. This fundamental understanding is crucial in the context of nuclear medicine, where different isotopes of an element can have different applications based on their radioactive properties.