A radiotracer consists of two pieces: one half is the biologic side that travels through the blood to bind to a unique, designated target – in this case, a type of cancer cell. The other half is the radioactive component. During the diagnostic scan, that radioactive component emits a low amount of radiation that allows us to take pictures of the cancer cells onto which the radiotracer has latched. During the treatment, the biologic side is almost identical, but the radioactive component is a different, more powerful kind of radiation that kills cancer.
During both the diagnostic and treatment procedures, the biologic side must bind itself to that precise target on the tumor cells. Because most other healthy cells lack that target, the radiotracers do not attach to them.