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Analog versus Digital

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sujatabyahatti's picture
Joined: 19 Dec 2010

A digital image consists of a number of collections of individual pixels organized in a matrix of rows and columns. Each pixel has a row and a column coordinate that uniquely identifies its location in the matrix. The electrons that make up the electronic detector can be visualized as being divided into an arrangement of blocks or picture elements known as pixels. A pixel is a small box or “well” into which the electrons produced by the x-ray exposure are deposited. A pixel is the digital equivalent of a silver crystal used in conventional radiography. As opposed to film emulsion that contains a random arrangement of silver crystals a pixel is structured in an ordered arrangement. The X-ray photons that come into contact with the electronic device cause electrons to be released from the silicon and produce a corresponding electronic charge. Consequently each pixel arrangement or electron potential well contains an electronic charge proportional to the number of electrons that react with in the well. Furthermore each electronic well corresponds to a specific area on the linked computer screen. When x-rays activate electrons and produce such electronic charges, an electronic latent image is then transmitted and stored in the computer and can be converted to a visible image on screen or printed on paper. The formation of a digital image requires several steps, beginning with the analog processes. At each pixel of an electronic detector, the absorption of x-rays generates a small voltage. At each pixel the voltage can fluctuate between a minimum and maximum value and is therefore an Analog signal.


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