This article was taken from the May issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content bysubscribing online
Millions of diagnostic CT scans are made every year in the UK, but their widespread use is also a cause for concern -- the high doses of X-ray radiation used during the tests are suspected of causing cancers. The new scanner from General Electric, the CT750 HD, delivers high-resolution images, but reduces radiation dosage by 50 percent thanks to a better photon detector and smarter rendering algorithms.
How it worksThe high-definition tube and Gemstone detector rotate around the patient taking a series of X-rays. Photons are absorbed by parts of the body in varying degrees according to their electron density (bones are especially dense), allowing the detector to convert those photons it does receive into electrical impulses. In turn, these impulses are processed into a 3D view of the patient.
1. Performix HD TubeIn HD mode the X-ray tube deflects its stream of photons so that the focal point is sampled from two different angles simultaneously. This delivers higher spatial resolution by better determining a point's location in 3D space.
2. Spectral Imagine ModeSpectral imaging identifies an object's composition by checking the attenuation of its high- and low-energy photons against known attenuation profiles for various materials. This improves diagnosis.
3. Xtream 3D ConsoleThe CT750 HD's various scan settings are programmed in the console. An onboard processor lets the operator measure particular objects or review live 3D models of the patient before sending the digital results directly to a doctor's reading room.
4. Adaptive Statistical Iterative Reconstruction (ASIR)Algorithms running on a dedicated processor assemble images from the data acquisition system into the final 3D image. In the process the algorithms remove 50 per cent of noise and 40 per cent of the errors introduced by the scanner itself. Because fewer scans are needed for a clear picture, there is less exposure to radiation.
5. Volume Helical ShuttlingBy continuously scanning and shuttling the patient backwards and forwards, the CT750 can model the body in live 3D. This allows specialists to observe the operation of a patient's organs -- ideal for locating blood clots in the brain or analysing joint movement.
6. GE Gemstone DetectorGE synthesised the structure of garnet to take advantage of the mineral's optical properties. The detector took eight years and $110 million to develop, but its 0.03μs sampling time reduces blurring and streaks.
7. Volara Data Acquisition System (DAS)After removing interference, the DAS converts light information into digital 3D images, capturing both light intensity and depth. The DAS takes samples 7,131 times per second.
This article was originally published by WIRED UK
