Background: Due to the small size of the beamlets in IMRT (intensity modulated radiotherapy), physical penumbra is one of the important dosimetric parameters and small changes in the penumbra have a notable impact on the results. The physical penumbra width is defined as the lateral distance between two specified isodose curves at a specified depth of phantom. In this study, after demonstrating...

Introduction: Because of small size of the beamlets in IMRT, physical penumbra is one of the important dosimetric parameters and small changes in the penumbra will have a great impact on the results. The physical penumbra width is defined as the lateral distance between two specified isodose curves at a specified depth of phantom. In this study, after demonstrating the inconsi...

The uncombed penumbral model explains the structure of the sunspot penumbra in terms of thick magnetic fibrils embedded in a magnetic surrounding atmosphere. This model has been successfully applied to explain the polarization signals emerging from the sunspot penumbra. Thick penumbral fibrils face some physical problems, however. In this contribution we will offer possible solutions to these s...

Prel iminary results of tbe measurements of the electroQ and ion components of plasma obtained by means of wide-angle detectors onboard the Venera-9 and Venera-l0 satell ites are presented. Stable electron and fluctuating ion fluxes were detected in the optical and corpuscular umbra. As a result of the plasma characteristics ob­ served at a few hundred kilometers above the optical umbra, we ref...

Introduction: Penumbra is an important property of the radiation beam to obtain a suitable margin surrounding the target volume. Therefore, the precise penumbra width determination in stereotactic radiotherapy is necessary for treatment planning. This study aimed to compare the obtained results of penumbra width by in-house and standard circul...

one of the signifiant risk factor of ischemic stroke is carotid artery occlusion. although surgical treatment was disappointing in these patient but there is a growing reports of sucessful endovascular treatment recently. in this technical note 56 year-old man who suffered from bilateral carotid occlusion was revascularized. the penumbra thrombosuction system was applied to reduce the risk of d...

In a search for new genes involved in the regulation of erythropoiesis, we identified murine Penumbra cDNA from a multipotent hematopoietic cell line based on its predominant expression in erythroblasts. Subsequently, we identified the human PENUMBRA from a bone marrow cDNA library. Penumbra is a new member of the tetraspanin superfamily of membrane proteins, many of which are thought to functi...

Context. It is unclear why there a rather sharp boundary in sunspots between the umbra and penumbra. Both regions exhibit magnetoconvection, which manifests penumbral filaments penumbra umbral dots umbra. Aims. Here we compare physical properties of filaments. Our goal to understand how these convective features change across this related rapid increase brightness at umbra-penumbra boundary. Me...

BACKGROUND Penumbra characteristics play a significant role in dose delivery accuracy for radiation therapy. For treatment planning, penumbra width and radiation field offset strongly influence target dose conformity and organ at risk sparing. METHODS In this study, we present an analytical and numerical approach for evaluation of the rounded leaf end effect on penumbra characteristics. Based...