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the part of a shadow in which there is no light from any light source.
a sharp appearance to the edges of a structure on a radiograph.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


radiology An image with sharply defined margins.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


(ŭm′bră) [L., shade, shadow]
The edge of the radiographic image proper.
Medical Dictionary, © 2009 Farlex and Partners


1. Region of very low illumination on a dark background.
2. Zone in which the brightness varies from some illumination to zero (umbra) in the shadow cast by an opaque object intercepting light from an extensive light source. See shadow.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
The Umbra fine is the result of a license agreement with the well-known Canadian designer of home furnishings.
By focusing on the next hot item, Umbra has broken many of the rules about product assortments, distribution and category specialization.
"This time around a high speed chase would not be necessary as the speed of the Umbra shadow over Gulf of Khambhat begins with Mach 50-60 slowing down to Mach 20 near Bhopal," said Dr.
The purpose of this education, he said, was to turn the members of his college-educated generation into "whites in brown skins by mastering white standards' ("Umbra Days" 105).
When the moon was completely in the umbra, the full aperture was used; however, when only part of the moon was in the umbra, the aperture was reduced to about 0.0007 meters.
* Umbra Cuscinetti, an East Granby, CT-based arm of the Umbra Group, has created ballscrews for electromechanical injection molding machines.
The darkest, central region of a sunspot, called the umbra, features tightly bundled magnetic field lines.
The path of the moon's umbra (the darkest central portion of the long, tapering lunar shadow caused by the passing of the moon between the earth and the sun which crosses our planet at twice the speed of sound), will begin in the south Atlantic Ocean at sunrise.
In the presence of larval dragonflies (Anax spp.) or caged mudminnows (Umbra limi), leopard frogs grew faster than wood frogs while total tadpole biomass production remained unchanged.
umbra (or figura): the sacraments of the Old Testament, which only foreshadowed things to come, signifying but not conferring grace;
Surgamus: solet esse grauis cantantibus umbra, iuniperi grauis umbra; nocent et frugibus umbrae.