What term describes isotopes that emit radiation and can be used in medical imaging?

The term that describes isotopes emitting radiation and used in medical imaging is radioisotopes. These isotopes are unstable and decay over time, releasing radiation in the form of particles or electromagnetic waves. In medical imaging, radioisotopes are employed in techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT), where they help to visualize and diagnose conditions based on how they interact with tissues in the body.

While the term radionuclides is also frequently used interchangeably with radioisotopes, it can refer more broadly to any radioactive nuclei, including ones not necessarily used for medical imaging. Nuclear isotopes can refer to any isotopes found in nuclear reactions or radioactive decay processes, but doesn't specifically denote their application in medicine. Stable isotopes, on the other hand, do not emit radiation and are therefore unsuitable for imaging purposes in a medical context.