Berend Hillen

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PURPOSE To establish normal reference values for the presence of the anatomic variants of the circle of Willis and average diameters for its component vessels by using three-dimensional time-of-flight magnetic resonance (MR) angiography and to determine whether age- or sex-related differences exist in the circle's anatomy. MATERIALS AND METHODS One(More)
In adult human subjects, the correlations were determined between the cross-sectional areas of the jaw muscles (measured in CT scans) and a number of facial angles and dimensions (measured from lateral radiographs). Multivariate statistical analysis of the skeletal variables in a group of 50 subjects led to the recognition of six independent factors(More)
BACKGROUND This review seeks to provide a structured presentation of existing knowledge of leptomeningeal anastomoses from anatomic and functional points of view and to identify problems and possible research directions to foster a better understanding of the subject and of stroke mechanisms. SUMMARY OF REVIEW Available data show that leptomeningeal(More)
OBJECTIVE To relate local arterial geometry with markers that are thought to be related to plaque rupture. BACKGROUND Plaque rupture often occurs at sites with minor luminal stenosis and has retrospectively been characterized by colocalization of inflammatory cells. Recent studies have demonstrated that luminal narrowing is related with the mode of(More)
BACKGROUND AND PURPOSE The circle of Willis (CW) is considered an important collateral pathway in maintaining adequate cerebral blood flow in patients with internal carotid artery (ICA) obstruction. We aimed to investigate the anatomic variation of the CW in patients with severe symptomatic carotid obstructive disease and to analyze diameter changes of its(More)
STUDY OBJECTIVE Part 1: To describe cases of emphysema (subcutaneous and/or mediastinal) and pneumothorax after percutaneous dilational tracheostomy (PDT) in a series of 326 patients, and to review the existing literature describing the incidence and possible mechanisms. Part 2: To analyze the potential mechanisms for the development of emphysema and(More)
Cross-sectional areas of the masseter, temporalis and medial, and lateral pterygoid muscles were determined in 16 subjects by means of computer tomography. In each subject three scans were made, intersecting the thickest part of the muscles at right angles to the fiber direction. The masseter and medial pterygoid muscles are large in persons with(More)
A mathematical model of the flow in the circle of Willis has been designed and the effects of (a) the large anatomical variation of the communicating arteries and (b) physiological changes of the resistances of the vertebral arteries have been studied. The influence of the posterior perforating arteries on the flow in the posterior communicating arteries(More)
A very simple model of the flow in the circle of Willis is described in this paper. Disregarding pulsatility and vessel wall elasticity, fluxes in all segments of the circle of Willis and its afferent and efferent vessels are calculated by applying the Poiseuille-Hagen formula. Comparison with the fluxes calculated numerically from a more sophisticated(More)