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Monday, November 19, 2007


Researched by Alex
X-rays (or Röntgen rays) are a form of electromagnetic radiation with a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 PHz to 30 EHz. X-rays are primarily used for diagnostic radiography and crystallography. X-rays are a form of ionizing radiation and as such can be dangerous. In many languages it is called Röntgen radiation after one of the first investigators of the X-rays, Wilhelm Conrad Röntgen.

Units of Measure and Exposure

The rem is the traditional unit of Dose Equivalent. This describes the Energy delivered by γ or X - radiation (indirectly ionizing radiation) for humans. The SI counterpart is the Sievert (Sv). One Sievert is equal to 100 rem. Because the rem is a relatively large unit, typical equivalent Dose is measured in millirem (mrem), or one thousandth of a rem

The average person living in the United States is exposed to approximately 150 mrem annually from background sources alone.

Reported dosage due to dental X-rays seems to vary significantly. Depending on the source, a typical dental X-ray of a human results in an exposure of perhaps, 3, 40, 300, or as many as 900 mrems.

Medical Uses

Since Röntgen's discovery that X-rays can identify bony structures, X-rays have been developed for their use in medical imaging. Radiology is a specialized field of medicine. Radiographers employ radiography and other techniques for diagnostic imaging. Indeed, this is probably the most common use of X-ray technology.

X-rays are especially useful in the detection of pathology of the skeletal system, but are also useful for detecting some disease processes in soft tissue. Some notable examples are the very common chest X-ray, which can be used to identify lung diseases such as pneumonia, lung cancer or pulmonary edema, and the abdominal X-ray, which can detect ileus (blockage of the intestine), free air (from visceral perforations) and free fluid (in ascites). In some cases, the use of X-rays is debatable, such as gallstones (which are rarely radiopaque) or kidney stones (which are often visible, but not always). Also, traditional plain X-rays pose very little use in the imaging of soft tissues such as the brain or muscle. Imaging alternatives for soft tissues are computed axial tomography (CAT or CT scanning), magnetic resonance imaging (MRI) or ultrasound. Since 2005, X-rays are listed as a carcinogen by the U.S. government.

Radiotherapy, a curative medical intervention, now used almost exclusively for cancer, employs higher energies of radiation.

The efficiency of X-ray tubes is less than 2%. Most of the energy is used to heat up the anode.

Source: http://www.wikipedia.org

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