U.S. researchers say a portable X-ray source they\'ve developed could lead to inexpensive hand-held devices for medical diagnosis and terrorism prevention. Engineers at the University of Missouri say the compact source of X-rays and other forms of radiation, the size of a stick of gum, could be incorporated into portable X-ray scanners for use by doctors as well as in anti-terrorism efforts. \"Currently, X-ray machines are huge and require tremendous amounts of electricity,\" electrical and computer engineering Professor Scott Kovaleski said. \"In approximately three years, we could have a prototype hand-held X-ray scanner using our invention. The cellphone-sized device could improve medical services in remote and impoverished regions and reduce health care expenses everywhere.\" Such devices could be also be used at ports and border crossings to search cargoes for contraband or explosives being smuggled by terrorists, he said. The device uses a crystal of a material known as lithium niobate to produce more than 100,000 volts of electricity from only 10 volts of electrical input with low power consumption, the researchers said. \"Our device is perfectly harmless until energized, and even then it causes relatively low exposures to radiation,\" Kovaleski said. \"We have never really had the ability to design devices around a radioisotope with an on-off switch. The potential for innovation is very exciting.\"