Search results for "Flow"
showing 10 items of 5185 documents
Effect of Different Display Types on Vection and Its Interaction With Motion Direction and Field Dependence
2017
Illusory self-motion (vection) can be generated by visual stimulation. The purpose of the present study was to compare behavioral vection measures including intensity ratings, duration, and onset time across different visual display types. Participants were exposed to a pattern of alternating black-and-white horizontal or vertical bars that moved either in vertical or horizontal direction, respectively. Stimuli were presented on four types of displays in randomized order: (a) large field of view dome projection, (b) combination of three computer screens, (c) single computer screen, (d) large field of view flat projection screen. A Computer Rod and Frame Test was used to measure field depen…
MRI in the Diagnosis of Right Ventricular Dysplasia
2006
ARVD is part of the group of cardiomyopathies characterised pathologically by fibrofatty replacement of the right ventricular myocardium and clinically by right ventricular arrhythmias of the LBBB pattern. Pathogenesis, prevalence, and aetiology are yet not fully known. The diagnosis of ARVD is based on the presence of structural, histological, electrocardiographic, and genetic factors. Therapeutic options include antiarrhythmic medication, catheter ablation, implantable cardioverter defibrillation, and surgery. Angiography and echocardiography lack sensitivity and specificity in the diagnosis of ARVD. MR imaging allows a three-dimensional evaluation of especially the right ventricle, and p…
An FFR CT diagnostic strategy versus usual care in patients with suspected coronary artery disease planned for invasive coronary angiography at Germa…
2017
Aim Diagnostic evaluation practices for suspected coronary artery disease (CAD) may vary between countries. Our objective was to compare a CT-derived fractional flow reserve (FFRCT) diagnostic strategy with usual care in patients with planned invasive coronary angiography (ICA) enrolled in the PLATFORM (Prospective Longitudinal Trial of FFRCT: Outcome and Resource Impacts) study at German sites. Methods Patients were divided into two consecutive observational cohorts, receiving either usual care or CT angiography (CTA)/FFRCT. The primary endpoint was the percentage of patients planned for ICA, with no obstructive CAD on ICA within 90 days. Secondary endpoints included death, myocardial infa…
P729PD-1/PD-L1 axis contributes to infarct size in ST elevation myocardial infarction
2014
Programmed death-1 (PD-1) and Programmed death-1 ligand (PD-L1) regulate immune response. Previous studies associate an immune deregulation in ST-elevation myocardial infarction STEMI. We recruited 100 patients with a first STEMI treated with reperfusion. In all patients PD-1 and PD-L1 expression was studied 24 h post-reperfusion in peripheral blood mononuclear cells (PBMCs), by means of flow cytometry and molecular biology. PD-1 and PD-L1 expression was serially analyzed in the first 20 patients before reperfusion and 24h, 96h and 30 days afterwards. Results were compared with 30 age- and sex-matched controls. Cardiac Magnetic Resonance was used to quantify infarct size 1-week after infarc…
Clinical significance of the quantitative and qualitative determination of the cerebral blood flow through the use of isotopes
1966
Es wird über die bisher entwickelten Methoden zur bestimmung der Hirndurchblutung mit radioaktiven Isotopen berichtet, wobei die quantitativen Untersuchungsmethoden hinsichtlich ihrer klinischen Bedeutung den qualitativen gegenübergestellt werden. Während die quantitativen Methoden eine genaue Bestimmung des cerebralen Blutvolumens und damit der Gesamtdurchblutung des Hirns bzw. bestimmter Hirnareale ermöglichen, bieten die qualitativen Untersuchungsmethoden hinsichtlich der klinisch-diagnostischen Aussagekraft besondere Vorteile. Aus der Bestimmung der Zirkulationszeit des Hirns und dem Verlauf der über beiden Hemisphären registrierten Aktivitätskurven lassen sich differenzial-diagnostisch…
Determination of myocardial perfusion and coronary flow reserve by densitometric measurements: a selective classification of regions of interest
2002
To evaluate the functional effect of a coronary artery stenosis on the dependent myocardium, digitized coronary angiograms (DCAs) were recorded. The DCAs, acquired during heart catheterization, provide information about myocardial perfusion and coronary flow reserve of areas supplied by this coronary artery. For each analysis the myocardium is separated into different regions of interest (ROIs); 16 ROIs in the distribution of the LCA and 8 ROIs for the RCA. In addition to that, the ROIs of the diseased vessels are divided into ROIs which are proximal, within and distal to the stenosis. Using a semiautomatic procedure, densograms are constructed from which the parameter rise time is calculat…
Resting myocardial blood flow quantification using contrast-enhanced magnetic resonance imaging in the presence of stenosis: A computational fluid dy…
2015
Purpose: The extent to which atherosclerotic plaques affect contrast agent (CA) transport in the coronary arteries and, hence, quantification of myocardial blood flow (MBF) using magnetic resonance imaging (MRI) is unclear. The purpose of this work was to evaluate the influence of plaque induced stenosis both on CA transport and on the accuracy of MBF quantification. Methods: Computational fluid dynamics simulations in a high-detailed realistic vascular model were employed to investigate CA bolus transport in the coronary arteries. The impact of atherosclerosis was analyzed by inserting various medium- to high-grade stenoses in the vascular model. The influence of stenosis morphology was ex…
Transkranielle Dopplersonographie bei Kopf-Hals-Tumoren*
1991
Transcranial Doppler ultrasound (TCD) recording is a non-invasive diagnostic procedure for the evaluation of the cerebral collateral flow in patients, in whom therapeutic ligation or resection of the common and/or internal carotid artery is planned. Patients are first examined under resting conditions, and then under manual compression of the ipsilateral carotid artery. Since January 1989, 31 ENT and neurosurgical patients have been examined. In all patients an immediate decrease in flow velocity in the middle cerebral artery (mca) of about 25% to 90% was recorded. In 42.8% of the patients the mca flow velocity reached 90% or more of its value under normal conditions within a short period. …
[CT-angiography in carotid stenosis].
1997
Purpose: Prospective evaluation of the accuracy of CT angiography (CTA) with different postprocessing for extracranial carotid artery in comparison with DSA. Method: one hundred patients were studied with standarized CTA. For postprocessing, MPR, MIP, and 3D reconstruction based on segmentation with upper and lower threshold were used. Intravascular density profiles were considered. All CTA studies were correlated with intra-arterial angiography. The degree and classification of stenoses was determined using the guidelines established by the NASCET collaborators. Results: Measurement of stenosis was possible by MPR in 82.5 %, by MIP in 85 %, and 3D in 100 %. Correct classification was found…
Radiosurgery of Carotid-Cavernous Fistulae
1994
25 cases of carotid-cavernous fistulae (CCF) who underwent radiosurgery with a conventional gamma source from 1977 to 1992 are reported. 22 were low-flow, spontaneous CCFs and 3 were high flow fistulae which had undergone a previous trApplng. The total dose delivered was 30 to 40 Gy. 91% to patients with low-flow CCF cured after radiosurgery in a mean time of 7.5 months, presenting improvent in a mean time of 2.3 months. Only one of the high-flow fistulae was cured. Follow-up period ranged between 14 years and 15 months (mean: 50 months). No recurrence was recorded in any case. While intravascular embolotherapy is the treatment of choice for high-flow fistulae, stereotactic radiosurgery may…