- X-ray machine
An X-ray machine is a device used by
radiographers to acquire an x-rayimage. They are used in various fields, notably medicineand security.
Shay M. Andersonand Ryan W. Preuningerformulated mathematical equations for X-rays. Physicist Johann Hittorfobserved tubes with energy rays extending from a negative electrode. William Crookesinvestigated the effects of energy discharges on rare gases. Heinrich Hertzbegan experimenting and demonstrated that cathode rays could penetrate very thin metal foil (such as aluminium). In 1887, Nikola Teslabegan to investigate X-rays and produced the bremsstrahlungprocess. In 1895, Wilhelm Röntgenbegan observing and further documenting X-rays while experimenting with vacuum tubes.
One of the first X-ray photographs was made of the hand of Röntgen's wife. The image displayed both her wedding ring and bones. On
January 18, 1896an "X-ray machine" was formally displayed by H.L. Smith. Upon discovery in 1895, X-Rays were advertised as the new scientific wonder and seized upon by entertainers. Circus patrons viewed their own skeletons and were given pictures of their own bony hands wearing silhouetted jewelry. While many people were fascinated by this discovery, others feared that it would allow strangers to look through doors and invade people's privacy.
In the 1940s and 50s, (real time) X-ray machines were used in stores to help sell footwear. These were known as
fluoroscopes. However, as the harmful effects of X-ray radiationwere properly considered, they finally fell out of use. Shoe-fitting use of the device was first banned by the state of Pennsylvaniain 1957. (They were more a clever marketing tool to attract customers, rather than a fitting aid.)
An X-ray imaging system consists of a X-ray source or generator (
X-ray tube), and an image detection system which can either be comprised of film (analog technology) or a digital capture system (such as a picture archiving and communication system).
In the typical X-ray source of less than 450 kVFact|date=September 2008,
X-rayphotons are produced by an electron beamstriking a target. The electrons that make up the beam are emitted from a heated cathode filament. The electrons are then focused and accelerated towards an angled anode target. The point where the electron beam strikes the target is called the focal spot. Most of the kinetic energycontained in the electron beam is converted to heat, but around 1% of the energy is converted into X-ray photons, the excess heat is dissipated via a heat sink. [cite web | url = http://www.fnrf.science.cmu.ac.th/theory/radiation/Physics%20of%20X-RAY%20Production.html | title = Physics of X-RAY Production] At the focal spot, X-ray photons are emitted in all directions from the target surface, the highest intensity being around 60deg to 90deg from the beamClarifyme|date=September 2008. There is a small round window in the X-ray tube directly above the angled target. This window allows the X-ray to exit the tube with little attenuation while maintaining a vacuum seal required for the X-ray tube operation.
X-ray machines work by applying controlled
voltageand current to the X-ray tube, which results in a beam of X-rays. The beam is projected on matter. Some of the X-ray beam will pass through the object, while some are absorbed. The resulting pattern of the radiation is then ultimately detected by a detection medium including rare earth screens (which surround photographic film), semiconductor detectors, or X-ray image intensifiers.
In healthcare applications in particular, the x-ray detection system rarely consists of the detection medium. For example, a typical stationary radiographic x-ray machine also includes an ion chamber and grid. The
ion chamberis basically a hollow plate located between the detection medium and the object being imaged. It determines the level of exposure by measuring the amount of x-rays that have passed through the electrically charged, gas-filled gap inside the plate. This allows for minimization of patient radiation exposure by both ensuring that an image is not underdeveloped to the point the exam needs to be repeated and ensuring that more radiation than needed is not applied. The grid is usually located between the ion chamber and object and consists of many aluminum slats stacked next to each other (resembling a polaroid lens). In this manner, the grid allows straight x-rays to pass through to the detection medium but absorbs reflected x-rays. This improves image quality by preventing scattered (non-diagnostic) x-rays from reaching the detection medium, but using a grid creates higher exam radiation doses overall. Images taken with such devices are known as X-ray photographs or radiographs. The older term Röentgenogram continues to be used by radiologists.
technologyis used in health carefor visualising bone structures and other dense tissues such as tumours. Non-medicial applications include securityand material analysis.
The two main fields in which x-ray machines are used in medicine are
radiographyand dentistry. Radiographyis used for fast, highly penetrating images, and is usually used in areas with a high bone content. Some forms of radiography include:
orthopantomogram— a panoramic x-ray of the jawshowing all the teeth at once
mammography— x-rays of breast tissue
tomography— x-ray imaging in sections Radiotherapy— the use of x-ray radiation to treat malignant cancer cells, a non-imaging application Fluoroscopyis used in cases where real-time visualization is necessary (and is most commonly encountered in everyday life at airport security). Some medical applications of fluorography include:
angiography— used to examine blood vessels in real time
barium enema— a procedure used to examine problems of the colonand lower gastrointestinal tract
barium swallow— similar to a barium enema, but used to examine the upper gastroinstestional tract
biopsy— the removal of tissue for examination
X-rays are highly penetrating,
ionizing radiation, therefore X-ray machines are used to take pictures of dense tissues such as bones and teeth. This is because bones absorb the radiation more than the less dense soft tissue. X-rays from a source pass through the body and onto a photographic cassette. Areas where radiation is absorbed show up as lighter shades of grey (closer to white). This can be used to diagnose broken or fractured bones. In fluoroscopy, imaging of the digestive tract is done with the help of a radiocontrast agent such as barium sulfate, which is opaque to X-rays.
X-ray machines are used to screen objects non-invasively. Luggage at airports and student baggage at many schools are examined for possible weapons, including bombs. These machines are very low dose and safe to be around. The main parts of an X-ray Baggage Inspection System are the generator used to generate x-rays, the detector to detect radiation after passing through the baggage, signal processor unit (usually a PC) to process the incoming signal from the detector, and a conveyor system for moving baggage into the system.
When baggage is placed on the conveyor, it is moved into the machine by the operator. There is an
infraredtransmitter and receiver assembly to detect the baggage when it enters the tunnel. This assembly gives the signal to switch on the generator and signal processing system. The signal processing system processes incoming siginals from the detector and reproduce an image based upon the type of material and material density inside the baggage. This image is then sent to the display unit.
The colour of the image displayed depends upon the material and material density Fact|date=September 2008. Organic material such as paper, clothes and most explosives are dispayed in orange. Mixed materials such as aluminium are displayed in green. Inorganic materials such as copper are displayed in blue and non-penetrable items are displayed in black (some machines display this as a yellowish green or red). The darkness of the colour depends upon the density or thickness of the material.
Advances in X-ray technology
A film of
carbon nanotubes (as a cathode) that emits electrons at room temperature when exposed to an electrical field has been fashioned into an X-ray device. An array of these emitters can be placed around a target item to be scanned and the images from each emitter can be assembled by computer software to provide a 3-dimensional image of the target in a fraction of the time it takes using a conventional X-ray device. The carbon nanotube emitters also use less energy than conventional X-ray tubes leading to lower operational costs. [cite web | url = http://college.unc.edu/features/september2006/nanotube-x-ray-method-creates-ct-images-faster-than-traditional-scanners | title = Nanotube x-ray method creates CT images faster than traditonal scanners | accessdate = 2008-06-30 | author = Zhang, et al. ]
Backscatter X-rayeg for security scanning passengers (rather than baggage)
X-ray astronomyJust detectors.
# cite journal
author=Zhang, J; Yang, G; Cheng, Y; Gao, B Qiu, Q; Lee , YZ; Lu, JP and Zhou, O
title=Stationary scanning X-ray source based on carbon nanotube field emitters
journal=Applied Physics Letters
volume=86 | issue=May 2 | year=2005 | pages=184104
doi = 10.1063/1.1923750
url = http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000086000018184104000001&idtype=cvips&gifs=Yes
* [http://www.iuk.edu/~koalhe/img/Equipment/xray.jpgA picture of an X-ray machine]
* [http://www.thextremehosting.com/apt/viewec.php?no=8 X-ray baggage inspection system]
* [http://www.xraylinks.com Radiology Links]
* [http://www.radiologyworkers.com Radiology Job Outlook]
* [http://www.rtstudents.com Radiology Resources for Students and Professionals]
* [http://www.patient.co.uk/leaflets/roentgenogram.htm Patient leaflets regarding X-rays]
Wikimedia Foundation. 2010.
Look at other dictionaries:
X-ray machine — machine which produces X ray radiation … English contemporary dictionary
X-ray machine — noun an apparatus that provides a source of X rays (Freq. 1) • Hypernyms: ↑apparatus, ↑setup • Hyponyms: ↑fluoroscope, ↑roentgenoscope, ↑tomograph • Part Meronyms: ↑ … Useful english dictionary
X-ray machine — Mīkini nānā iā loko o ke kanaka … English-Hawaiian dictionary
machine — n. 1) to operate, run, work a machine 2) to shut down a machine 3) an adding; answering; calculating; composing, linotype, typesetting; copy, copying, duplicating; earth moving; heart lung; milking; milling; money access (AE); sanding; sewing;… … Combinatory dictionary
RAY (M.) — Pionnier, avec Marcel Duchamp et Picabia, du mouvement le plus radical de l’art moderne qui, de Dada au surréalisme, traverse jusqu’à notre époque tout le champ des arts visuels, Man Ray a largement contribué, par son œuvre polymorphe: tableaux,… … Encyclopédie Universelle
Ray Brown (designer) — Ray Brown (born September 27 1949) is an Australian custom tailor and rock clothing designer for numerous rock and roll, heavy metal, hard rock, teddy boy and pop stars and celebrities including Brian Setzer, Tony Iommi, Styx, Bon Jovi, Ozzy… … Wikipedia
Ray Reach — Reach (right) with Branford Marsalis. (Photo by Claudia Reach.) Background information Birth name Raymond Everett Reach, Jr … Wikipedia
Ray Bradbury — Born August 22, 1920 (1920 08 22) (age 91) Nationality American … Wikipedia
Ray Kurzweil — (2006) Raymond (Ray) Kurzweil (* 12. Februar 1948 in Queens, New York City) ist ein Pionier der optischen Texterkennung (OCR), Sprachsynthese (computervorgelesene Texte), Spracherkennung, Flachbettscannertechnologie und im Bereich elektronischer… … Deutsch Wikipedia
Ray Gun (magazine) — Ray Gun was an American alternative rock and roll magazine, first published in 1992 in Santa Monica, California. Led by founding art director David Carson, Ray Gun explored experimental magazine typographic design. The result was a chaotic,… … Wikipedia