Siemens SOMATOM Spirit, Operator'S Manual, Page: 65 / 484

Safety Information about Personal Safety
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04/2012
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A.2-23
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Partial volume effects
A.2
Thick slices are often preferred instead of thin slices. This helps
to increase signal to noise ratio and to limit the examination
time by reducing the number of slices. However, this may result
in partial volume effects. These are caused by high density tis-
sues (such as a bone) or objects (such as pacemakers) projecting
only partly into the slice plane. One such well-known artifact is
the so-called Hounsfield bar between the petrous bones. Other
regions of the skull are also problematic with regard to partial
volume effects which are visible as dark streaks. Additional cor-
rection and / or special parameter settings (head modes) help to
minimize these effects.
A.2
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To avoid partial volume effects use thinner slices.