penumbra


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penumbra

 [pĕ-num´brah]
1. the part of a shadow in which there is a small amount of illumination from a light source.
2. blurring at the edges of a structure on a radiograph.

pe·num·bra

(pe-nŭm'bră),
The region of partial illumination or radiation caused by light or x-rays not originating from a point source; also called 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.
[Mod. L., fr. L. paene, almost, + umbra, shadow]

penumbra 

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.

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.
[Mod. L., fr. L. paene, almost, + umbra, shadow]

penumbra

a blurred edge to an image, a halo effect, in an x-ray film caused usually by an overlarge focal spot exacerbated by a long object-to-film distance.
References in periodicals archive ?
The penumbra can be very well appreciated based on areas showing mild increase in cerebral blood volume, which is salvageable area by active arterial revascularisation/intervention.
It might be used to detect ischemic penumbra in patients with AIS, identify the type of a cerebral tumor, classify the stage of a malignant tumor, or evaluate the effects of chemotherapy or radiotherapy in patients with a cerebral tumor.
Along these lines, the new Penumbra includes films, panel discussions, one-off presentations of solo work, and discussions of visual art alongside the play programming.
Following their exposure on "PGT," El Gamma Penumbra was inundated with invitations to appear on TV shows, including "It's Showtime.
58% of these patients were identified as having a favourable penumbra region.
But the shading in the outer penumbra is so weak that you can't see anything yet.
El sistema Penumbra (Penumbra 2007) es reconocido como un sistema de trombectomia con una bomba de aspiracion y un separador que permite la fragmentacion del trombo para facilitar su extraccion.
Penumbra about what they've discovered, they are flung into a clash between technology and tradition--and the quest to discover the secret of eternal life.
Progress on Continental Coal's Penumbra coal project in South Africa as part of the EPCM contract to develop the underground room-and-pillar coal mine is well under way, after commencing with site work in September last year, reported Adam Wilkinson, project manager and mining engineer, TWP Projects.
This table was later expanded to include the penumbras only after the photos were taken because it was not initially expected that the penumbra would be as visible, as it turned out on the photos.
As a result of our numerous studies, carried out with powerful instruments and with close attention, we concluded that the penumbra was for the most part formed by filamentous currents of the single photosphere that enveloped the sun, or of the same material, rendered so thin that it was transparent.
In "Lunar Eclipse" the poet reflects on the disappearance and appearance of the moon--"slipping/ from penumbra to umbra/ to penumbra, reappearing/ newly created, from earth's shadow" and on the approaching end of her own life--"I too will slip/ from penumbra to umbra, but/ while the moon navigates the millennia/ for me there will be no return.