Dr. James F. Hainfeld claims that an injection containing nanoparticles followed by 3 minutes in a magnetic field "completely cured" test animals of cancer. This is possible because when an iron particle is inserted into an alternating magnetic field, it spins in a manner which generates enough heat to burn the tumor. However, the toxic levels of iron in the nanoparticles would prove to be harmful in a human patient. Hence, Hainfeld and his colleagues spent 6 years engineering a nanoparticle with an iron core and a biocompatible shell. This could be injected into the bloodstream without adverse effects. An experiment using an infrared camera to measure the temperature inside of tumors after being treated with the nanoparticles demonstrated a rise in temperature hot enough to melt the cancer away. This technology is also being used to cross the blood-brain barrier and attack brain cancers.