X-Ray Machines - Basic
| Abbreviation / other names What does "X-ray" mean? |
Mobile X-Ray or Fixed X-Ray (General Screening, Angiography, Fluoroscopy, Mammography and CT Scanners) In an X-Ray tube an electron gun fires electrons at a target.
The electrons are accelerated by using high voltage and strike
the target with very high energy. This produces high energy
photons of electromagnetic radiation called X-Rays |
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| What does it do? |
X-Rays are directed through the body onto a film resulting
in a ‘picture’ (called an X-Ray) of the internal parts of that part of the body |
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| Physiology |
The Human body has different densities of tissue, Hard (eg
Bones and tendons) and Soft (eg Skin, Muscle and Internal Organs).
The X-Ray is used to form an image of the dense tissue in the
body. |
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| How it works |
The X-Ray tube is placed on one side of the patient and a
film is placed on the other side. As the X-Rays pass through
the body they are absorbed more by the hard tissue than the
soft tissue. The X-Rays that are not absorbed travel through
the body and hit the X-Ray film. The X-Ray film is exposed less
in the areas where the X-Rays have been absorbed by the hard
tissue and when the film is developed these areas look lighter.
This gives a very good picture of the Bones and Tendons in that
part of the body. |
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| Units of measurement |
X-Rays are measured photographically. There are two common
sets of units, Rads and Sieverts (typically milliSieverts, mS)
X-Ray Machine Outputs are measured with test equipment in kilovolts (kV) and milliamp seconds (mAs) Higher values of kV and mAs produce more X-Rays than lower values |
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| Typical values |
The output required of an X-Ray Machine depends on the thickness
of the Body part being X-Rayed. Higher power is needed for thicker
parts (eg a Chest X-Ray requires more power than an Arm)
Outputs vary from 70 – 130 kV and 20 – 95 mAs |
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| Picture of equipment |
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