Radiodensity

Radiodensity is the property of relative transparency to the passage of X-raysthrough a material. Radiolucent indicates greater transparency to X-ray photons. Radiodense indicates greater opacity to X-rayphotons.

X-rays are part of the electromagnetic spectrum, with photon energies above visible(and ultraviolet) light photons. They are distinguished from gamma raysin that they are produced not by transitions within the atomic nucleus, but either by deceleration of a charged particle or by the transition of state of orbital electrons. Diagnostic X-rays are produced using X-ray tubes.

The radio wavesportion of the electromagnetic spectrum represent much lower energy/frequency photons than visible light. Thus, referring to the property of X-raydensity as radiodensity appears contradictory by current knowledge, but is still used as a historical artifact.

Though radiodensity is commonly used in a qualitative comparison perspective, it can also be quantified according to the Hounsfield scale, which is fundamental to CT scanningapplications. Specifically, distilled wateris specified on the Hounsfield scale, as a reference, as 0 units ("HU", or Hounsfield units), airis specified as -1000 HU. These were chosen as universally available references and were oriented to the key application CT was developed for: imaging the internal anatomy of living creatures based on organized waterstructures and mostly living in air, e.g. humans.

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It uses material from the http://en.wikipedia.org/wiki/Radiodensity Wikipedia article Radiodensity.