how are radioactive materials used to diagnose a disorder

Question

most cancer cells are detected by introducing a radioactive material into the body. How specifically can one tell if the cell has cancer or not with the help of the radioactive substances

Answer 1

Cancer cells have a higher metabolic rate that is consistent with rapid growth and division. Therefore tumors and cancer cells will incorporate radio-labeled compounds (such as nucleotide precursors or glucose for energy) at a higher rate than normal tissues.

 

Thus the specificty depends on the difference between the metabolism of the tumor tissue and the surrounding healthy tissue.

Answer 2

Using radioactive substances (via isotopes), you can monitor where the material is being absorbed/consumed. Cancer cells grow and divide much faster than 'normal' cells. So it is more likely that the cancer cells will consume/absorb the radioactive material. By testing to see where those known isotopes are located, it can suggest the location of the tumor growth.