Search results for "Biomedical"
showing 10 items of 2328 documents
Surrogate data approaches to assess the significance of directed coherence: Application to EEG activity propagation
2009
This paper addresses the topic of evaluating the significance of frequency domain measures of causal coupling in multivariate time series through generation of surrogate data. The considered approaches are the traditional Fourier Transform (FT) algorithm and a new causal FT (CFT) algorithm for surrogate data generation. Both algorithms preserve the FT modulus of the original series; differences are in the phase relationships, that are completely destroyed for FT surrogates and imposed after switching off the link over the considered causal direction for CFT surrogates. The ability of the algorithms to assess causality in the frequency domain was tested using the directed coherence as discri…
Testing Frequency-Domain Causality in Multivariate Time Series
2010
We introduce a new hypothesis-testing framework, based on surrogate data generation, to assess in the frequency domain, the concept of causality among multivariate (MV) time series. The approach extends the traditional Fourier transform (FT) method for generating surrogate data in a MV process and adapts it to the specific issue of causality. It generates causal FT (CFT) surrogates with FT modulus taken from the original series, and FT phase taken from a set of series with causal interactions set to zero over the direction of interest and preserved over all other directions. Two different zero-setting procedures, acting on the parameters of a MV autoregressive (MVAR) model fitted on the ori…
Inability of Laplace's law to estimate sub-bandage pressures after applying a compressive bandage: a clinical study
2021
Objective: The aim of the current study was to compare pressures exerted on the lower limb by a high compression bandage as recorded by sub-bandage sensors and those estimated by Laplace's law. The correlation between pressures obtained in each anatomical zone and the corresponding limb perimeters were explored. Method: For the measurement of sub-bandage pressures, four anatomical zones in the lower right limb were determined. Pressures were recorded by nine pneumatic sensors and a PicoPress transducer. A two-layer compression bandage system (UrgoK2, Urgo Group, France) was used for the dressing. Pressures were registered in supine position. Sensor pressures were compared with those estimat…
Imaging photoplethysmography for clinical assessment of cutaneous microcirculation at two different depths
2016
The feasibility of bispectral imaging photoplethysmography (iPPG) system for clinical assessment of cutaneous microcirculation at two different depths is proposed. The iPPG system has been developed and evaluated for in vivo conditions during various tests: (1) topical application of vasodilatory liniment on the skin, (2) skin local heating, (3) arterial occlusion, and (4) regional anesthesia. The device has been validated by the measurements of a laser Doppler imager (LDI) as a reference. The hardware comprises four bispectral light sources (530 and 810 nm) for uniform illumination of skin, video camera, and the control unit for triggering of the system. The PPG signals were calculated and…
Whole-body MRI radiomics model to predict relapsed/refractory Hodgkin Lymphoma: A preliminary study.
2022
Purpose A strong prognostic score that enables a stratification of newly diagnosed Hodgkin Lymphoma (HL) to identify patients at high risk of refractory/relapsed disease is still needed. Our aim was to investigate the potential value of a radiomics analysis pipeline from whole-body MRI (WB-MRI) exams for clinical outcome prediction in patients with Hodgkin Lymphoma (HL). Materials and methods Index lesions from baseline WB-MRIs of 40 patients (22 females; mean age 31.7 ± 11.4 years) with newly diagnosed HL treated by ABVD chemotherapy regimen were manually segmented on T1-weighted, STIR, and DWI images for texture analysis feature extraction. A machine learning approach based on the Extra T…
Mass Output and Particle Size Distribution of Glucocorticosteroids Emitted from Different Inhalation Devices Depending on Various Inspiratory Paramet…
2002
Efficient inhalation therapy depends on successful delivery of the drug to the lung. The efficacy of drug delivery is not only influenced by the characteristics of the inhalation device, but also by the patient's handling of the device and by the inspiratory maneuver achieved through the device. We analyzed the output characteristics of three different chlorofluorocarbon (CFC)-free breath-actuated inhalers for inhaled glucocorticosteroids (BUD Turbohaler, FP Diskus/Accuhaler and HFA-BDP Autohaler, respectively). Mass output and particle size distribution of drug aerosol delivered by the inhalers were determined depending on different inhalation parameters in vitro using an Andersen cascade …
Complications of Poly Implant Prothèse breast implants: the current discussion
2013
Against the background of the current discussion about Poly Implant Prothèse (PIP, Seyne-sur-mer, France) breast implants, we want to present a case demonstrating the complications such as implant rupture, silicone dissemination and level III silicone lymphadenopathy. A 29-year-old woman with cosmetic breast augmentation with PIP implants 5 years previously showed a sensitive swelling in her right axilla and neck region. All tests to detect an infectious or lymphomatous lymphadenopathy were negative. After ultrasound and MRI, rupture of the right implant was assumed and multiple pathologically enlarged lymph nodes up to supraclavicular region were shown. An excision biopsy of one axillary l…
A study protocol for applying the co-creating knowledge translation framework to a population health study
2013
Background: Population health research can generate significant outcomes for communities, while Knowledge Translation (KT) aims to expressly maximize the outcomes of knowledge producing activity. Yet the two approaches are seldom explicitly combined as part of the research process. A population health study in Port Lincoln, South Australia offered the opportunity to develop and apply the co-KT Framework to the entire research process. This is a new framework to facilitate knowledge formation collaboratively between researchers and communities throughout a research to intervention implementation process. Design: This study employs a five step framework (the co-KT Framework) that is formulate…
Mixed predictability and cross-validation to assess non-linear Granger causality in short cardiovascular variability series
2006
A method to evaluate the direction and strength of causal interactions in bivariate cardiovascular and cardiorespiratory series is presented. The method is based on quantifying self and mixed predictability of the two series using nearest-neighbour local linear approximation. It returns two causal coupling indexes measuring the relative improvement in predictability along direct and reverse directions, and a directionality index indicating the preferential direction of interaction. The method was implemented through a cross-validation approach that allowed quantification of directionality without constraining the embedding of the series, and fully exploited the available data to maximise th…
Phase information of time-frequency transforms as a key feature for classification of atrial fibrillation episodes
2015
[EN] Patients suffering from atrial fibrillation can be classified into different subtypes, according to the temporal pattern of the arrhythmia and its recurrence. Nowadays, clinicians cannot differentiate a priori between the different subtypes, and patient classification is done afterwards, when its clinical course is available. In this paper we present a comparison of classification performances when differentiating paroxysmal and persistent atrial fibrillation episodes by means of support vector machines. We analyze short surface electrocardiogram recordings by extracting modulus and phase features from several time-frequency transforms: short-time Fourier transform, Wigner-Ville, Choi-…