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Ctp Lab Report

Satisfactory Essays
PHYSICAL PRINCIPLES
An x ray is similar to light and has both particle and wave nature. That basic working of a x ray CT scan is the photons of x ray radiation comes in contact with the electron clouds in atoms. This can happen either by photo electric effect or by scattering.
COMPTON SCATTERING
The first type of interaction of x rays in CT energy range is scattering and one of it is Compton scattering. In Compton scattering photons interact with the outer shell electrons of the atom an ejects it from the atom thereby ionising the atom. The ejected electron is then absorbed by a neighbouring atom. The probability of scattering depends on the electron density of the atom that is more the electron density more the chance of scattering.
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The filament adjacent to the cathode is heated up and the energy is absorbed by the electrons and gets ejected of the cathode. The electrons travel towards the anode and hits the tungsten target and rapid deceleration of electrons occurs and this deceleration results in production of electromagnetic radiation that is x-rays. The anode keeps on rotating so that the heat will be lost to a larger area.
SENSORS /DETECTORS
The x-rays leaving the object must be studied to create images. Basically there are three types of detectors.
• Ionisation chamber filled with gas
• Scintillation multiplier tube
• Solid state scintillation detector
IONISATION CHAMBER
Here a chamber is filled with compressed gas. Two electrodes with high potential difference between them is present. As the x-rays enter the chamber the atoms in the gas ionizes and current flows between the electrodes and detection takes place. The advantages of the gas chamber is that it is easier to manufacture and the response to beam density is linear.
SCINTILLATION MULTIPLIER TUBE.
Here a bismuth germinate crystal is used. When this crystal is struck by x-ray photon light is produced with is proportional to the energy of the hitting photon. Near to this is a photo emissive plane. The light produced from the crystal hits this plane and electrons are ejected from this plane. The intensity of the ejected electrons depends on the
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