Radiograph Revolution

A new method of creating x-rays under development by MXISystems in Nashville, TN, could make this oldest of medical imaging technologies safer and more accurate, improving diagnosis of everything from broken arms to breast cancer. Each pulse from a conventional medical x-ray machine generates radiation at a wide range of frequencies, only a small subset of which are diagnostically useful. Lower frequencies that don't contribute to the image do yield harmful radiation, and higher frequencies that bounce around inside the body blur radiographs, making the images harder to read. MXISystems' machine produces x-rays that span an extremely narrow frequency band; its emission can be tuned to the frequency best suited for each specific imaging task-a chest x-ray, say, or a mammogram. The system works by colliding a beam of electrons with an infrared laser beam; their interaction creates x-rays at a frequency that is related to the speed of the electrons, which can be easily adjusted. Based on technology from Vanderbilt University's W.M. Keck Free-Electron Laser Center, the machine emits less harmful radiation than standard x-ray units. It also produces high-resolution radiographs with sharper contrast between tissues of different densities, making it easier to distinguish tumors from healthy tissue, for example. The company plans to begin trials of the machine for mammography next year.

MiniMicrowave

Communications devices use microwaves, which are tricky to amplify. Vacuum tube hardware weighing hundreds of kilograms is needed to produce the highest-power signals for military radar. Semiconductor devices made of silicon or gallium arsenide work well for the few-kilometer transmissions required by cell phones, but they have too little power to send signals over long distances. A new microwave amplifier built at General Electric's Global Research Center in Niskayuna, NY, packs the amplifying power of vacuum tubes into a semiconductor package. GE developed techniques for reducing defects in gallium nitride as it is manufactured; the team also built computer models to design devices that work well despite such defects. The result: gallium nitride devices that provide about seven times the power of other semiconductors at certain microwave-communications frequencies. GE is collaborating with Lockheed Martin to deliver high-power radar for lightweight, unmanned military aircraft in five to ten years.