Answer the following question given this paragraph: 

Despite its dangers, radioactivity has several uses. It can be used to determine the ages of ancient rocks and fossils. This use of radioactivity is explained in this chapter’s "Radioactive Decay" lesson. Radioactivity can also be used as a source of power to generate electricity. This use of radioactivity is covered later on in this chapter in the lesson "Nuclear Energy. " Radioactivity can even be used to diagnose and treat diseases, including cancer. Cancer cells grow rapidly and take up a lot of glucose for energy. Glucose containing radioactive elements can be given to patients. Cancer cells will take up more of the glucose than normal cells do and give off radiation. The radiation can be detected with special machines (see Figure below ). Radioactive elements taken up by cancer cells may also be used to kill the cells and treat the disease. You can learn more about medical uses of radiation at the URL below.


Q: What type of disease can be treated by radioactive elements in glucose?


A:
cancer