penumbra


Also found in: Dictionary, Thesaurus, Legal, Encyclopedia, Wikipedia.

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]
References in periodicals archive ?
!Todo aparece de una forma u otra en Un blues en la penumbra!"
After femoral puncture a large guide catheter [Penumbra Neuron 088 Max (Penumbra Inc., Alameda, CA, USA)] was navigated to the carotid bulb.
Areas having delay in peak enhancement and slightly abnormal cerebral blood volume suggested ischaemic penumbra, which is recoverable brain parenchyma.
Diffusion-weighted imaging (DWI) is the most sensitive MRI technique by which to identify the acute ischemic core.[sup][1] When used together, perfusion-weighted imaging (PWI) and DWI can identify brain tissue with hypoperfusion, which is defined as "ischemic penumbra," from normal diffusion.[sup][2] The role of perfusion neuroimaging in the management of AIS is to confirm the presence of reduced regional blood flow and contribute to the identification of the ischemic penumbra that might be salvaged by thrombolytic and/or endovascular recanalization therapy.[sup][3]
The moon will begin to leave from the shadows at 7:27am and exit the penumbra at 8:22am.
IF THEY DON'T PROVIDE CAUTIONARY tales, the leadership transitions at Mu, the Jungle, Penumbra, and the Guthrie do offer observers a range of different models for charting a theatre's future.
La obra de Fernando de Szyszlo es una indagacion en el destello y la penumbra como aspectos del ser de la America Latina.
Cotabato City, (PNA) - Asia's renowned El Gamma Penumbra, an all-male Filipino shadow play group, is set to display their exceptional skill before constituents of the Autonomous Region in Muslim Mindanao (ARMM) depicting relevant issues on peace and reforms.
The Apollo system is the result of decades of research and development work in the field of advanced aspiration and vibrational energy technology by researchers at Penumbra. The Apollo system adds internal energy generation to a specialized advanced aspiration tool to surgically address deep bleeding in the brain, a particularly devastating form of acute hemorrhagic stroke.
And Mr Penumbra's bookstore is at the heart of Robin Sloan's novel, never closed, its light always aglow in downtown San Francisco's dark.