Search results for "Digital"
showing 10 items of 3267 documents
Dynamical properties of the sleep EEG in different frequency bands.
1993
The information concerning the dynamic behavior of the sleep process gained by the usual evaluation of sleep EEGs according to the criteria of Rechtschaffen and Kales is limited. Therefore a new methodical approach is presented, which is a special case of spectral analyzed data processing. After digital band-pass filtering of the sleep EEG the root-mean-square (RMS) value of successive 20 s EEG epochs is calculated in defined frequency ranges. This procedure ensures to take into account the influence of the phase relation between different frequency components. The temporal course of these RMS values during the night reveals smooth curves with continuous transitions between different sleep …
Dimension reduction: additional benefit of an optimal filter for independent component analysis to extract event-related potentials.
2011
The present study addresses benefits of a linear optimal filter (OF) for independent component analysis (ICA) in extracting brain event-related potentials (ERPs). A filter such as the digital filter is usually considered as a denoising tool. Actually, in filtering ERP recordings by an OF, the ERP' topography should not be changed by the filter, and the output should also be able to be modeled by the linear transformation. Moreover, an OF designed for a specific ERP source or component may remove noise, as well as reduce the overlap of sources and even reject some non-targeted sources in the ERP recordings. The OF can thus accomplish both the denoising and dimension reduction (reducing the n…
The keyhole concept in aneurysm surgery: results of the past 20 years.
2011
Item does not contain fulltext BACKGROUND: Improvements in preoperative imaging and intraoperative visualization have led to a refinement in surgical techniques. OBJECTIVE: Report of a 20-year experience with application of the keyhole technique as a contribution to the ongoing debate on the impact of limited craniotomies in aneurysm surgery. METHODS: Over a 20-year period, 1000 consecutive patients with 1297 aneurysms were surgically treated in 1062 operations: 651 in the acute stage after SAH and 411 with unruptured aneurysms. The outcome was assessed with the modified Rankin scale and approach-related complications. RESULTS: The majority of the cases were treated by 4 different keyhole a…
Intraoperative C-arm CT imaging in angular stable plate osteosynthesis of distal radius fractures
2013
The purpose of this study was to analyze the practicability and benefit of intraoperative C-arm computed tomography (CT) imaging in volar plate osteosynthesis of unstable distal radius fractures. During a 1 year period, intraoperative three dimensional (3D) imaging with the ARCADIS Orbic 3D was performed in addition to standard fluoroscopy in 51 cases. The volar angular stable plate oesteosyntheses were analyzed intraoperatively and, if necessary, improved immediately. The duration of the scan and radiation exposure dose were measured. On average, performance of the scan and analysis of the CT dataset took 6.7 minutes. In 31.3% of the surgeries a misplacement of screws was detected and cor…
Noninvasive assessment of pulmonary hemodynamics in patients with chronic thromboembolic pulmonary hypertension by high temporal resolution phase-con…
2013
Background— Right heart catheterization is the gold standard for assessment of pulmonary hemodynamics in patients with chronic thromboembolic pulmonary hypertension. To date, MRI has not been able to produce precise measurements of mean pulmonary arterial pressure (mPAP). The purpose of the study was to create a model for estimating mPAP and pulmonary vascular resistance in patients with chronic thromboembolic pulmonary hypertension by high temporal resolution phase-contrast MRI (PC-MRI) and to correlate the results with simultaneously acquired, invasive catheter-based measurements (simultaneously measured mPAP) and with right heart catheterization measurements. Methods and Results— A tota…
Parametric assessment of myocardial perfusion during interventional cardiac catheterization by means of X-ray densitometry-short-and long-term result…
1990
X-ray densitometric evaluation of digital subtraction angiocardiograms allows an assessment of myocardial perfusion by means of the parameter 'MEAN RISE TIME' (MRT), defined as the time from the onset of local myocardial contrast medium opacification to the point of maximum opacification. Best results are obtained when the response of that parameter is compared before and after stimulation of coronary flow by papaverine. A prolongation of this parameter, especially after papaverine, was indicative of an impairment of myocardial perfusion, when compared to the results of TL-201 scintigraphy. In 50 patients with single vessel coronary artery disease the results of MRT pre and post papaverine …
A multicenter, site-independent, blinded study to compare the diagnostic accuracy of contrast-enhanced magnetic resonance angiography using 1.0M gado…
2007
Abstract Purpose Prospective evaluation of diagnostic accuracy of single field-of-view contrast-enhanced MR Angiography (ceMRA) with 1.0 M gadobutrol compared to intraarterial DSA in body arteries. Materials and methods In an European multicenter study 179 patients underwent ceMRA and DSA. For each indication five prospectively defined vessel segments were evaluated by local investigators onsite and by three site-independent blinded readers (BR) independently. Results The agreement between ceMRA and DSA diagnosis was statistically significant in the onsite (96.6%) and blinded reader (86.6–90.2%) evaluation. Sensitivity, specificity, accuracy, positive (PPV) and negative predictive values (N…
Diagnostic performance of gadobenate dimeglumine enhanced MR angiography of the iliofemoral and calf arteries: a large-scale multicenter trial
2007
OBJECTIVE. The purpose of this study was to compare gadobenate dimeglumine–enhanced MR angiography and unenhanced time-of-flight MR angiography for the detection of significant peripheral arterial occlusive disease using digital subtraction angiography as our reference standard. SUBJECTS AND METHODS. Two hundred seventy-two patients underwent MR angiography and digital subtraction angiography of the iliofemoral arteries. MR angiography was performed before (2D time-of-flight acquisitions) and after (spoiled gradient-echo acquisitions) the administration of 0.1 mmol/kg of gadobenate dimeglumine at 1–2 mL/s. Contrast-enhanced MR angiography and digital subtraction angiography of the calf arte…
Dose-response relationships and plasma concentrations of digitalis glycosides in man.
1978
An inter-individual, randomized, double-blind study of digitoxin (Dt) and β-acetyl digoxin (D) was performed in 120 healthy male volunteers. Groups of 10 persons each received orally D 0, 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6 mg and Dt 0.04, 0.08, 0.12, or 0.16 mg daily for 7 days; Loading doses were given for the first three days. Plasma levels were measured with an86Rb-erythrocyte assay 24 h after the last dose. ECG, carotid artery pulse and phonocardiogram were recorded prior to (b) and 24 h after (a) the last dose. QTc, amplitude of T-waves in V2 to V6, electromechanical systole (QS2c) and left ventricular ejection time (LVETc) were measured. The differences between a and b (Δ-values) reflect …
Detection of central pulmonary artery thromboemboli by transesophageal echocardiography in patients with severe pulmonary embolism.
1992
Transthoracic echocardiography generally provides only indirect signs of pulmonary embolism. In contrast, with transesophageal echocardiography the thromboembolus itself can be visualized in the central parts of the pulmonary artery. The aims of our study were to evaluate, first, the incidence of central pulmonary artery thromboemboli in patients with severe pulmonary embolism, and second, the accuracy of the echocardiographic diagnosis. Our study group comprised 60 patients with proved severe pulmonary embolism. All patients were examined by transthoracic and transesophageal echocardiography. The echocardiographic findings concerning the absence or presence of central pulmonary artery thro…