Gamma rays have the shortest wavelengths and the highest amount of energy of all types of electromagnetic radiation. They are able to penetrate most materials and aren't easily blocked. When they pass through matter, they eject electrons from the atoms they collide with. This is called ionization, and it's dangerous to living cells; prolonged gamma radiation can lead to grave illness and even death. Yet we use gamma rays from cobalt-60 for cancer treatment. We also use gamma rays in industry to test castings and welded joints for tiny, almost invisible cracks or defects.
Gamma rays were discovered by physicist Paul Villard in 1900. They can be produced by antimatter destroying matter or by a nuclear reaction and move at the speed of light. Gamma rays can travel hundreds or even thousands of yards or meters while maintaining their energy [source: EPA]. They can be identified by a Geiger counter or a scintillation counter, or with photographic film or plates.
Traditional radiation treatment for cancer isn't the only way gamma rays are used by medical professionals. In Gamma Knife surgery, more than 200 beams of gamma radiation are directed at small tumors, causing 90 to 95 percent of them to cease growing and a majority of them to shrink [source: University of Maryland Medical Center]. Among the conditions treated with the Gamma Knife are malignant and benign tumors and Parkinson's disease. Gamma rays also figure in a PET (Positron Emission Tomography) scan. The patient is injected with a radioactive substance and placed on a table that slides into a gamma ray detector. Doctors can then track blood flow and other biochemical processes within the body [source: Cleveland Clinic].
Gamma Rays also pay a role in international security and food safety. The Container Security Initiative was announced by U.S. customs officials in 2002. By 2008, 58 ports worldwide were equipped with X-ray and gamma ray screening devices, giving security officers access to 86 percent of all maritime cargo in containers [source: U.S. Customs and Border Protection]. Food irradiation -- passing food through a beam of gamma rays -- is also called "irradiation pasteurization" or "cold pasteurization," and kills bacteria that could spoil food or render it poisonous [source: EPA]. The process has a long history, as patents for a food preservation process using radioactive materials were issued in 1905. Food that is irradiated today does not become radioactive itself, and is considered safe.
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