نتایج جستجو برای: physical penumbra

تعداد نتایج: 666538  

Journal: :Turkish neurosurgery 2016
Xudong Zhang Jun Wei Gao Pascal Jabbour

Mortality associated with the occlusion of large vessels in acute ischemic stroke is particularly high despite best available medical therapy. Early and safe revascularization of the primary occlusion is correlated with good clinical result. We report two patients with acute ischemic stroke in whom the mechanical device Penumbra System was used for thrombolysis and embolectomy. The Penumbra Sys...

Journal: :Comput. Graph. Forum 2005
Samuli Laine Timo Aila

We present a novel algorithm for rendering physically-based soft shadows in complex scenes. Instead of casting shadow rays, we place both the points to be shaded and the samples of an area light source into separate hierarchies, and compute hierarchically the shadows caused by each occluding triangle. This yields an efficient algorithm with memory requirements independent of the complexity of t...

2015
Kevin Cherry Robert Kooima

Real-time soft shadows have seen numerous improvements over the years. Post-process blurring of shadow edges are commonly used to hide aliasing artifacts, but in some cases, such as ours, it is used to mimic physical processes. Instead of generating penumbra regions uniformly, we scale key algorithmic components in screen space to allow the penumbra region to grow in accordance with occluder/re...

2009
G. B. Scharmer

Numerical simulations have by now revealed that the fine scale structure of the penumbra in general and the Evershed effect in particular is due to overturning convection, mainly confined to gaps with strongly reduced magnetic field strength. The Evershed flow is the radial component of the overturning convective flow visible at the surface. It is directed outwards – away from the umbra – becau...

2015
Jae-Hyung Choi Hyun-Seok Park Dae-Hyun Kim Jae-Kwan Cha Jae-Taeck Huh Myongjin Kang

BACKGROUND Higher reperfusion rates have been established with endovascular treatment for acute ischemic stroke patients. There are limited data on the comparative performance of mechanical thrombectomy devices. This study aimed to analyse the efficacy and safety of the stent retriever device (Solitaire stent) by comparing procedure time, angiographic outcome, complication rate and long term cl...

Journal: :Stroke 1999
R E Anderson W K Tan H S Martin F B Meyer

BACKGROUND AND PURPOSE During focal cerebral ischemia, the ischemic penumbra or border-zone regions of moderate cortical blood flow reductions have a heterogeneous development of intracellular cortical acidosis. This experiment tested the hypotheses that (1) this acidosis is secondary to glucose utilization and (2) this intracellular acidosis leads to recruitment of potentially salvageable tiss...

Journal: :Medical physics 2003
J E Bayouth S M Morrill

The objective of this work was to measure the performance characteristics of a double-focus multileaf collimator (MLC) for intensity modulated radiation therapy (IMRT), specifically the variation in penumbra and leakage for narrow fields as a function of field position over a 20x27 cm space available for segmented MLC IMRT. Measurements were made with 6 MV x rays through a MLC containing 29 lea...

Journal: :The neuroradiology journal 2014
José Eduardo Alves Ângelo Carneiro João Xavier

CT perfusion (CTP) is part of the initial evaluation of stroke patients, allowing differentiation between infarcted tissue and the ischaemic penumbra and helping in the selection of patients for endovascular treatment. This study assessed the reliability of the qualitative evaluation CTP maps in defining the ischemic penumbra and identified potential pitfalls associated with this technique. We ...

Journal: :Stroke 2005
Eng H Lo Michael A Moskowitz Thomas P Jacobs

It is now widely accepted that not all brain cells die immediately after stroke. Surrounding a core of severe and rapid tissue injury, brain cell death evolves more slowly in a heterogeneous area that has been called the penumbra.1,2 In 1977, Astrup et al provided one of the first experimental demonstrations of the penumbra in a baboon model of cerebral artery occlusion.3 This region of brain i...

2012
Youshi Fujita Takahiro Kuchimaru Tetsuya Kadonosono Shotaro Tanaka Yoshiki Hase Hidekazu Tomimoto Masahiro Hiraoka Shinae Kizaka-Kondoh Masafumi Ihara Ryosuke Takahashi

Within the ischemic penumbra, blood flow is sufficiently reduced that it results in hypoxia severe enough to arrest physiological function. Nevertheless, it has been shown that cells present within this region can be rescued and resuscitated by restoring perfusion and through other protective therapies. Thus, the early detection of the ischemic penumbra can be exploited to improve outcomes afte...

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