Abstract
Computed tomographic (CT) images are depictions of relative and not absolute tissue densities. These relative depictions are produced by measuring x-ray attenuation resulting from its travel through tissue. A tissue’s attenuation is expressed by its attenuation coefficient, μ. μ is an indicator of the likelihood that a photon will interact with an atom of a tissue rather than passing through it. The greater the density of a tissue, the greater its attenuation coefficient. However, specific tissues do not have constant attenuation coefficients. The attenuation coefficient of a tissue is also affected by the photon energy of an x-ray (KeV) and by the tissue thickness. Increasing photon energy and decreasing tissue thickness will reduce the attenuation coefficient of a specific tissue, thus allowing more photons to pass through to the detector (Fig. 2.1).
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Pelberg, R.A., Mazur, W. (2010). CT Basics. In: Vascular CT Angiography Manual. Springer, London. https://doi.org/10.1007/978-1-84996-260-5_2
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DOI: https://doi.org/10.1007/978-1-84996-260-5_2
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