The greatest feature of CT (or X-ray transmission computed tomography, XCT) (Hounsfield 1973; Radon 1917), compared with ordinary roentgenography, is its capability to image minute differences in X-ray attenuation coefficients. The reasons for this are, first, CT only takes cross section slices and reconstructs them into two-dimensional images for display so that redundant shadows do not overlap. Second, as it utilizes one or more thin X-ray beams, scattered radiation becomes reduced. Third, an X-ray detector which responds linearly to X-ray intensity over a wide range is used, and fourth, a digital computer system which performs superior image reconstruction is employed. Rotation radiography, according to Takahashi, can satisfy the first and second conditions above, while only part of the third condition can be met. It cannot, however, satisfy the fourth condition.
KeywordsAttenuation Coefficient Filter Back Projection Back Projection Iterative Approximation Beam Hardening
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