Neon is a chemical element with a chemical symbol Ne and atomic number 10. Neon is a member of the noble gas family. Neon was discovered in 1898 by British chemists William Ramsay (1852-1916) and Morris Travers (1872-1961). It occurs naturally in the atmosphere, but only in very small amounts. The reddish-orange color emitted in neon lights is widely used to make advertising signs. Neon is also used generically for these types of lights when in reality many other gases are used to produce different colors of light. Other uses of neon include high-voltage indicators, lightning arrestors, wave meter tubes and television tubes. Neon and helium are used to make a type of gas laser. Liquefied neon is commercially used as an economical cryogenic refrigerant. Neon lighting is now used for many other purposes. For example, neon tubes are used in instruments used to detect electric currents. Neon is also used in the manufacture of lasers. A laser is a device for producing very bright light of a single color. Lasers now have many uses in industry and medicine. They are very efficient at cutting metal and plastic. They can also be used to do very precise kinds of surgery. Neon may be used in the clinical setting as a diagnostic tracer gas in a gas analyzer for a lung diffusion test. Neon 19, 17-second positron-emitting radioelement, is produced continuously by 23MeV alpha particle bombardment of oxygen. For a 12 muA particle current the method of preparation described delivers 14 mCi of neon 19 per min to the functional exploration room. The radiochemically pure radioactive gas is diluted in air and breathed continously by the patient lying under a positron tomographic camera. The regional lung ventilation distribution is obtained on 2 cm thick sections of organ with a transverse resolution of 17 mm. Quantification of the ventilation output per unit lung volume is contemplated. Helium-neon laser radiation was used for the combined treatment of the patients with atrophic rhinitis. Other clinical application of neon is radiotherapy in various cancers. Neon ion radiotherapy possesses biologic and physical advantages over megavoltage X rays. Biologically, the neon beam reduces the oxygen enhancement ratio and increases relative biological effectiveness. Cells irradiated by neon ions show less variation in cell-cycle related radiosensitivity and decreased repair of radiation injury. The physical behavior of heavy charged particles allows precise delivery of high radiation doses to tumors while minimizing irradiation of normal tissues. In 1979 a Phase I-II clinical trial was started at Lawrence Berkeley Laboratory using neon ions to irradiate patients for whom conventional treatment modalities were ineffective. Treatment of malignant gliomas, pancreatic, gastric, esophageal, lung, and advanced or recurrent head and neck cancer has been less successful; results for these tumors appear no better than those achieved with conventional x-ray therapy. This gas is inert and is classified as a simple asphyxiant. Inhalation in excessive concentrations can result in dizziness, nausea, vomiting, loss of consciousness, and death. Death may result from errors in judgment, confusion, or loss of consciousness which prevent self-rescue. At low oxygen concentrations, unconsciousness and death may occur in seconds without warning.