Basic principles of computed tomography
collimation - x ray beam width in z axis pitch = table travel / collimation pitch = 1 - coils of the helix are in contact pitch < 1 - coils of the helix overlap pitch > 1 - coils of the helix are separated
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www.columbia.eduV. Collimation A collimator is a metallic barrier with an aperture in the middle used to reduce the size and shape of the x-ray beam and therefore the volume of irradiated tissue within the patient. The round collimator is a thick plate of radiopaque material (usually lead) with a circular
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www.ncnr.nist.govcollimation and a simple neutron detector (end-window counter). Transmission measurements contain information about the sample content and the relative fractions of the various elements. For example, the relative ratio of carbon to hydrogen in crude oils (the so-called cracking ratio) could be measured accurately.
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