Siemens SOMATOM Emotion syngo CT 2007E, Operator'S Manual, Page: 77 / 574

Safety Information about Personal Safety
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syngo CT 2007E Emotion Operator Manual
02/2008
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Beam hardining
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When X-ray beams pass through tissue, the average energy of
the radiation spectrum is shifted towards higher energy. This is
known as
beam hardening . It depends on the material density
and thickness of the tissue through which the X-ray beam
passes.
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For body parts similar in density to water, e.g., soft tissue, the
effect on the CT image can be compensated. In areas of high
density such as hips, shoulders or lower skull, hypodense
streaks and areas with reduced CT values can be seen. Along
the sides of the upper part of the skull, the so-called “cupping
effect” can be seen as a brightening of the CT values. The cup-
ping effect also occurs in rare cases such as infant skull tomo-
grams, due to residual extra focal radiation.
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Additional corrections and/or special kernel parameter settings
(head modes) help to minimize these effects. Yet, they cannot
fully eliminate them.
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