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Computed tomography provides axial cross-sectional representations of the body according to the X-ray density of the tissues.
At each level to be visualised, the X-ray source and detector record the penetration of a narrow beam of X-rays through a 180 degree arc around the patient. From this data a computer is able to reconstruct the cross-section of the body.
CT is particularly good for the thorax and abdomen. Skull CT is good for supratentorial pathology but bone artifact limits the quality of views in the posterior fossa.
High resolution CT is particularly good for examining the air spaces in the thorax. Narrow slices and line-enhancing software greatly clarify the airways but obscure soft tissue details.