Petr Vanek

OBJECTIVES: CT angiography (CTA) is recommended as a standard of stroke imaging. We investigated accuracy and precision of standard or single-phase CTA as compared with novel technique or multiphase CTA in clot detection in the middle cerebral artery.

METHODS: Twenty single-phase CTA and twenty multiphase CTA with prevailing M2 occlusion were assessed by 10 radiologists and 10 neurologists blinded to clinical information (7 less experienced and 3 experienced). Sensitivity, specificity, ...

In geoid computation, effects of real three-dimensional topographic masses on the Earth’s gravity field must be accurately quantified and, in the Stokes–Helmert scheme, replaced with effects of those masses condensed on the geoid. The most comprehensive modern schemes for evaluation of topographical effects account for terrain effects, use a spherical model of topography, and incorporate two-dimensionally varying models of topographical mass density. In this contribution, we employ a ...

The precision and accuracy of positions obtained from the least-squares adjustment of Global Positioning System (GPS) data are dependent on the fidelity of the algorithms used to model the data. They are also dependent on the a priori covariance matrix of the data that is used in the adjustment. This matrix describes not only the uncertainty of the data but also the correlation among themboth mathematical and physical. In this paper we present a summary of a study of the effect of ...

Statistically rigorous densification of horizontal geodetic networks must consist of a simultaneous adjustment of both the densification and the densified networks. Equivalently, the effect of the already adjusted existing network to be densified may be rigorously propagated into the densification network, through an appropriately derived weight matrix of the common station positions. The nonrigorous schemes utilize information available on the existing network in a statistically ...