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建立人际资源圈Imaging_Receptors_In_X-ray_And_MRI
2013-11-13 来源: 类别: 更多范文
Imaging Receptors In X-ray And MRI
Introduction:
Two landmarks in non-invasive medical diagnosis took place with the introduction of x-ray and Magnetic Resonance Imaging (MRI) facilities. Each system has its pros and cons and its unique features making it invaluable.
Operational overview:
X-ray machines have several components including the source, an intensifying grid and a film. The source is the x-ray tube, a glass or metal envelope containing the anode and cathode within a vacuum. X-rays are generated by converting electrical energy into intense heat in the cathode where electrons leave its external surfaces. This stream of electrons is shot against the tungsten anode with the great force created from the large potential difference. When the electrons collide with tungsten atoms they dislodge electrons from the atoms lower orbits. Electrons from higher orbitals fill the lower energy level and release energy in the form of x-ray photons with high energy levels. Electrons slowed by other atoms nuclei also give off extra energy as x-ray photons which are focused through a window in the x-ray tube onto the target area of the patient.
The x-rays produced by the tube pass through objects to create images of their structures. The bodys tissues have varying densities; each absorbs and transmits
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