Search results for " processing"
showing 10 items of 7549 documents
Effect of probe contact pressure on the photoplethysmographic assessment of conduit artery stiffness
2013
Currently, photoplethysmography (PPG) is a frequently studied optical blood pulsation detection tech- nique among biophotonic and biomedical researchers due to the fact that it shows high potential for estimating the arterial stiffness (AS). The extraction of diagnostically useful information requires standardized measurement pro- cedure with good repeatability. However, the effects of a crucially important factor—the optimal contact pressure (CP) of the probe—are often ignored. Also, CP values are not reported to evaluate those effects. It is hypothesized that AS estimated from PPG pulse wave 2nd derivative parameter b∕a is strongly inconsistent when recorded at nonoptimal probe CP. Our pi…
Cerebrovascular and cardiovascular variability interactions investigated through conditional joint transfer entropy in subjects prone to postural syn…
2017
Objective: A model-based conditional transfer entropy approach was exploited to quantify the information transfer in cerebrovascular (CBV) and cardiovascular (CV) systems in subjects prone to develop postural syncope. Approach: Spontaneous beat-to-beat variations of mean cerebral blood flow velocity (MCBFV) derived from a transcranial Doppler device, heart period (HP) derived from surface electrocardiogram, mean arterial pressure (MAP) and systolic arterial pressure (SAP) derived from finger plethysmographic arterial pressure device were monitored at rest in supine position (REST) and during 60° head-up tilt (TILT) in 13 individuals (age mean ± standard deviation: 28 ± 9 years, min-max r…
Correlation between fatigue and brain atrophy and lesion load in multiple sclerosis patients independent of disability.
2007
Abstract Background Fatigue is a major problem in multiple sclerosis (MS), and its association with MRI features is debated. Objective To study the correlation between fatigue and lesion load, white matter (WM), and grey matter (GM), in MS patients independent of disability. Methods We studied 222 relapsing remitting MS patients with low disability (scores ≤ 2 at the Kurtzke Expanded Disability Status Scale). Lesion load, WM and GM were measured by fully automated, operator-independent, multi-parametric segmentation method. T1 and T2 lesion volume were also measured by a semi-automated method. Fatigue was assessed by the Fatigue Severity Scale (FSS), and patients divided in high-fatigue (FS…
Semi-automated retinal vessel analysis in nonmydriatic fundus photography.
2013
Purpose Funduscopic assessment of the retinal vessels may be used to assess the health status of microcirculation and as a component in the evaluation of cardiovascular risk factors. Typically, the evaluation is restricted to morphological appreciation without strict quantification. Our purpose was to develop and validate a software tool for semi-automated quantitative analysis of retinal vasculature in nonmydriatic fundus photography. Methods matlab software was used to develop a semi-automated image recognition and analysis tool for the determination of the arterial–venous (A/V) ratio in the central vessel equivalent on 45° digital fundus photographs. Validity and reproducibility of the r…
Automatic detection and quantification of ground-glass opacities on high-resolution CT using multiple neural networks: comparison with a density mask.
2000
We compared multiple neural networks with a density mask for the automatic detection and quantification of ground-glass opacities on high-resolution CT under clinical conditions.Eighty-four patients (54 men and 30 women; age range, 18-82 years; mean age, 49 years) with a total of 99 consecutive high-resolution CT scans were enrolled in the study. The neural network was designed to detect ground-glass opacities with high sensitivity and to omit air-tissue interfaces to increase specificity. The results of the neural network were compared with those of a density mask (thresholds, -750/-300 H), with a radiologist serving as the gold standard.The neural network classified 6% of the total lung a…
Characterization of benign hepatic tumors arising in fatty liver with SonoVue and pulse inversion US.
2007
Background: We describe the spectrum of contrast-enhancement patterns of benign hepatic tumors arising in fatty liver on contrast-enhanced ultrasound (US). Methods: Sixteen patients (12 women and four men) with 27 benign hepatic tumors (17 hemangiomas, eight focal nodular hyperplasias, and two hepatocellular adenomas) arising in fatty liver underwent baseline and pulse inversion US after administration of SonoVue. Two experienced radiologists evaluated baseline echogenicity and dynamic enhancement pattern of each lesion in comparison with adjacent liver parenchyma. Results: After administration of SonoVue, in the arterial phase 13 of 17 hemangiomas showed peripheral globular enhancement and…
Do we truly see what we think we see? The role of cognitive bias in pathological interpretation
2008
In the histomorphological grading of prostate carcinoma, pathologists have regularly assigned comparable scores for the architectural Gleason and the now-obsolete nuclear World Health Organization (WHO) grading systems. Although both systems demonstrate good correspondence between grade and survival, they are based on fundamentally different biological criteria. We tested the hypothesis that this apparent concurrence between the two grading systems originates from an interpretation bias in the minds of diagnostic pathologists, rather than reflecting a biological reality. Three pathologists graded 178 prostatectomy specimens, assigning Gleason and WHO scores on glass slides and on digital im…
The influence of lorazepam medication upon the transfer properties of the brain during sleep in man
1993
In order to get better insight into the principles of information processing by the brain during sleep and its alterations under the influence of drugs we applied some tools from linear system theory to sleep EEG data. We investigated late components of auditory and visually evoked potentials (AEPs and VEPs) during different sleep stages and calculated from these the so-called amplitude-frequency characteristics (AFC). The main advantage of this analysis is that it enables one to detect functional differences during different sleep stages. This information can hardly be obtained by conventional spectral analysis. The result of our investigation was that the transfer properties of the brain …
One year longitudinal study of the straight gyrus morphometry in first-episode schizophrenia-spectrum patients
2012
Brief report.-- El pdf es la versión post-print.-- et al.
No short-term effects of digital mobile radio telephone on the awake human electroencephalogram
1997
A recent study reported the results of an exploratory study of alterations of the quantitative sleep profile due to the effects of a digital mobile radio telephone. Rapid eye movement (REM) was suppressed, and the spectral power density in the 8–13 Hz frequency range during REM sleep was altered. The aim of the present study was to illuminate the influence of digital mobile radio telephone on the awake electroencephalogram (EEG) of healthy subjects. For this purpose, we investigated 34 male subjects in a single-blind cross-over design experiment by measuring spontaneous EEGs under closed-eyes condition from scalp positions C3 and C4 and comparing the effects of an active (0.05 mW/cm2) and a…