X-Ray Machines

موضوع: X-Ray Machines الأحد فبراير 21, 2010 10:15 pm

X-Ray Machines
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
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

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

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.

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
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