Is there a way to detect diseases like cancer and Alzheimer’s before they advance too far? Doctors are using injected radioactive drugs that circulate through the body and act as a beacon for PET scanners. These diagnostic tools can detect the spread of diseases before they can be spotted with other types of imaging. So how exactly does this work, and is it safe? Pedro Brugarolas investigates. Lesson by Pedro Brugarolas, directed by Artrake Studio.