Search results for " volunteers"
showing 10 items of 229 documents
Realization of administration unit for3He with gas recycling
2011
Hyperpolarized (HP) noble gases (3He,129Xe) are used for MR-imaging of the lung. In the majority of case the HP gas is filled in Tedlarbags and directly inhaled by the patients. Starting from an earlier pilot device, an administration unit was built respectively to the Medical Devices Law to administer patients HP noble gas boli in defined quantities and at a predefined time during inspiration with high reproducibility and reliability without reducing MR-quality. The patient's airflows are monitored and recorded. It is possible to use gas admixtures, measure the polarization on-line and collect the exhaled gas for later recycling. The first images with healthy volunteers were taken with thi…
Optical multichannel sensing of skin blood pulsations
2004
Time resolved detection and analysis of the skin back-scattered optical signals (reflection photoplethysmography or PPG) provide information on skin blood volume pulsations and can serve for cardiovascular assessment. The multi-channel PPG concept has been developed and clinically verified in this study. Portable two- and four-channel PPG monitoring devices have been designed for real-time data acquisition and processing. The multi-channel devices were successfully applied for cardiovascular fitness tests and for early detection of arterial occlusions in extremities. The optically measured heartbeat pulse wave propagation made possible to estimate relative arterial resistances for numerous …
Magnesium concentration in saliva — an indicator of digitalis toxicity
1981
In a prospective study salivary magnesium was measured by atomic absorption spectrophotometry in 168 patients on chronic digoxin therapy. Magnesium concentration in saliva was correlated with clinical data and plasma digoxin levels. A significant elevation in salivary magnesium concentration was caused by digoxin therapy (0.58 +/- 0.39 mmol/l, n = 93) in comparison to patients with no digitalis treatment (0.17 +/- 0.07 mmol/l, n = 35). Magnesium concentrations in saliva were significantly higher in toxic patients (1.1 +/- 0.68 mmol/l, n = 32) than in nontoxic patients. Possibly toxic patients showed a magnesium level of saliva of 0.63 +/- 0.39 mmol/l (n = 40). In 89% of the intoxicated pati…
Scalp, basal epidural and intravascular far-field recordings after median nerve stimulation: evidence for a separate N18a potential
2000
Far-field somatosensory evoked potentials (SSEPs) after median nerve stimulation were recorded from scalp- (Fz), epidural- (ED) and intravascular electrodes (basilar artery [Bas]) to study the nature of the controversial N18a component of the widespread N18 potential. In healthy volunteers frequently an N18a potential was recorded at Fz. Simultaneous Fz and ED recordings at the pontomesencephalic junction as well as Bas-recordings at the caudal basilar artery showed N18a components identical in latency and shape. With intravascular recordings the shapes differed between the top of the basilar artery and the caudal artery recordings. These findings support the existence of a separate N18a po…
Explaining the unique nature of individual gait patterns with deep learning
2019
Machine learning (ML) techniques such as (deep) artificial neural networks (DNN) are solving very successfully a plethora of tasks and provide new predictive models for complex physical, chemical, biological and social systems. However, in most cases this comes with the disadvantage of acting as a black box, rarely providing information about what made them arrive at a particular prediction. This black box aspect of ML techniques can be problematic especially in medical diagnoses, so far hampering a clinical acceptance. The present paper studies the uniqueness of individual gait patterns in clinical biomechanics using DNNs. By attributing portions of the model predictions back to the input …
Quantification of Myocardial Blood Flow Using Magnetic Resonance Imaging with Different accelerated Pulse Sequences
2009
The aim of this study was to compare SRTurboFLASH, SR-TrueFISP, and SR-segEPI pulse sequences using a twofold TSENSE-acceleration with regard to their use in quantification of myocardial blood flow (MBF). Six healthy volunteers were examined at 1.5T by first pass myocardial perfusion MRI at rest using all three TSENSE-accelerated pulse sequences. For absolute quantifi-cation of MBF XSIM software with the MMID4 model has been used. MBF analyses revealed significant MBF differences between SRTurboFLASH and SR-segEPI compared to SR-TrueFISP (p<0.005 and p<0.001, respectively). Differences between SRTurboFLASH and SR-segEPI were not statistically significant. The median MBF values for SR-TurboF…
Multilevel assessment of mental stress via network physiology paradigm using consumer wearable devices
2019
Mental stress is a physiological condition that has a strong negative impact on the quality of life, affecting both the physical and the mental health. For such a reason, accurate measurements of stress level can be helpful to provide mechanisms for prevention and treatment. This paper proposes a procedure for the classification of different mental stress levels by using physiological signals provided by low invasive wearable devices. 17 healthy volunteers participated in this study. Three different mental states were elicited in them: a resting condition, a stressful cognitive state, and a sustained attention task. The acquired physiological signals were: a one lead electrocardiogram (ECG)…
Reliability of automated optical determination of capillary refill time
2021
The present study is devoted to assessment of automated optical capillary refill time determination by custom developed optoelectronic device prototype. Study comprised fifteen healthy volunteers; To induce capillary refill time changes the hand position challenge was utilized. During rest conditions slight inter-subject variation was observed: T90 (0.75±0.27 s), TSTB (2.20±0.58 s) and temperature at the measurement site (32.21±1.87 Co), however during hand position challenge results were more consistent. Rising hand substantially increased, while lowering slightly decreased capillary refill time. We conclude that automated determination of refill time have high clinical potential, however …
Transcribing the "Estoria de Espanna" using crowdsourcing: Strategies and aspirations
2015
This paper examines the specific strategies for recruitment and retention of volunteer transcribers in use in two collaborative transcription projects: Transcribe Bentham (University College, London) and the Estoria de Espanna Digital Project (University of Birmingham). The aim of the paper is to review the strategies used by Transcribe Bentham, a more mature crowdsourced electronic transcription project, with a view to informing the strategies put into place in the Estoria project, which has started transcribing using crowdsourcing more recently. The paper discusses the difficulties faced by crowdsourced electronic transcription projects and how these have been and are being resolved in th…
Causal brain-heart information transfer during visual emotional elicitation in healthy subjects: Preliminary evaluations and future perspectives
2017
Complex heartbeat dynamics is known to reflect subject's emotional state, thanks to numerous links to brain cortical and subcortical regions. Likewise, specific brain regions are deeply involved in vagally-mediated emotional processing and regulation. Nevertheless, although the brain-heart interplay has been studied during visual emotion elicitation, directional interactions have not been investigated so far. To fill this gap, in this study we investigate brain-heart dynamics during emotional elicitation in healthy subjects through measures of Granger causality (GC) between the two physiological systems. Data were gathered from 22 healthy volunteers who underwent pleasant/ unpleasant affect…