geometric unsharpness
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geometric unsharpness
image blur resulting from the finite size of the x-ray tube focal spot (as opposed to a point source).
pe·num·bra
(pĕ-nŭm'bră)1. radiology The blurred margin of an image.
2. radiation physics The region at the edges of a radiation beam over which a rapid change in dosage rate occurs.
Synonym(s): geometric unsharpness.
Synonym(s): geometric unsharpness.
[Mod. L., fr. L. paene, almost, + umbra, shadow]
pe·num·bra
(pĕ-nŭm'bră)1. radiology the blurred margin of an image.
2. radiation physics the region at the edges of a radiation beam over which a rapid change in dosage rate occurs.
Synonym(s): geometric unsharpness.
Synonym(s): geometric unsharpness.
[Mod. L., fr. L. paene, almost, + umbra, shadow]
geometric unsharpness,
n an impairment of image definition resulting from the geometric penumbra. See also penumbra, geometric and radiograph beam.