Human Heart Pulse Wave Responses Measured Simultaneously at Several Sensor Placements by Two MR-Compatible Fibre Optic Methods

This paper presents experimental measurements conducted using two noninvasive fibre optic methods for detecting heart pulse waves in the human body. Both methods can be used in conjunction with magnetic resonance imaging (MRI). For comparison, the paper also performs an MRI-compatible electrocardiogram (ECG) measurement. By the simultaneous use of different measurement methods, the propagation of pressure waves generated by each heart pulse can be sensed extensively in different areas of the human body and at different depths, for example, on the chest and forehead and at the fingertip. An accurate determination of a pulse wave allows calculating the pulse transit time (PTT) of a particular heart pulse in different parts of the human body. This result can then be used to estimate the pulse wave velocity of blood flow in different places. Both measurement methods are realized using magnetic resonance-compatible fibres, which makes the methods applicable to the MRI environment. One of the developed sensors is an extraordinary accelerometer sensor, while the other one is a more common sensor based on photoplethysmography. All measurements, involving several test patients, were performed both inside and outside an MRI room. Measurements inside the MRI room were conducted using a 3-Tesla strength closed MRI scanner in the Department of Diagnostic Radiology at the Oulu University Hospital

A method for measuring blood pressure and cardiorespiratory oscillations

Studies with magnetoencephalography (MEG) are still quite rarely combined simultaneously with methods that can provide a metabolic dimension to MEG investigations. In addition, continuous blood pressure measurements which comply with MEG compatibility requirements are lacking. For instance, by combining methods reflecting neurovascular status one could obtain more information on low frequency fluctuations that have recently gained increasing interest as a mediator of functional connectivity within brain networks. This paper presents a multimodal brain imaging setup, capable to non-invasively and continuously measure cerebral hemodynamic, cardiorespiratory and blood pressure oscillations simultaneously with MEG. In the setup, all methods apart from MEG rely on the use of fibre optics. In particular, we present a method for measuring of blood pressure and cardiorespiratory oscillations continuously with MEG. The potential of this type of multimodal setup for brain research is demonstrated by our preliminary studies on human, showing effects of mild hypercapnia, gathered simultaneously with the presented modalities

Blood pressure estimation using pulse transit time models

Abstract. Blood pressure (BP) is an important indicator of human health. Common methods for measuring BP continuously are either invasive, intermittent or they require using a cumbersome cuff. Pulse Transmit Time (PTT) -based measurement can be an alternative for such methods, as it ensures continue and non-invasive monitoring. However, since the method is indirect, it requires careful modelling of PTT-BP relation. In this thesis, three approaches of BP estimation from PTT are tested: linear regression, nonlinear Moens and Korteweg model and nonlinear model developed by Gesche. In the experiments, cardiovascular pulses for PTT were sensed using two fiber optics based accelerometers developed at the University of Oulu. To evaluate feasibility of presented models, the results were compared with reference BP values, measured using methods accepted for the commercial use. There were two groups of data. One was compared with BP measured using invasive catheter. Second group was compared with BP measured using volume clamp method. Obtained results suggest, that the presented calculation methods in present state still require further development in order to provide accurate BP values, however, they can be potentially used for observation of BP changes

Measurement of Cerebral Circulation in Human

In this chapter, we review state-of-the-art non-invasive techniques to monitor and study cerebral circulation in humans. The measurement methods can be divided into two categories: direct and indirect methods. Direct methods are mostly based on using contrast agents delivered to blood circulation. Clinically used direct methods include single-photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance imaging (MRI) with contrast agents, xenon computed tomography (CT), and arterial spin labeling (ASL) MRI. Indirect techniques are based on measuring physiological parameters reflecting cerebral perfusion. The most commonly used indirect methods are near-infrared spectroscopy (NIRS), transcranial Doppler ultrasound (TCD), and phase-contrast MRI. In recent years, few more techniques have been intensively developed, such as diffuse correlation spectroscopy (DCS) and microwave-based techniques, which are still emerging as methods for cerebral circulation monitoring. In addition, methods combining different modalities are discussed and, as a summary, the presented techniques and their benefits for cerebral circulation will be compared

Jatkuva-aikainen vitaalielintoimintojen monitorointi pienillä lapsilla käyttäen rinnalle asetettavaa sensoria

Tiivistelmä. Tausta: Hengitystaajuus, sydämen syketaajuus ja happisaturaatio (SpO₂) ovat verenpaineen lisäksi kliinisesti tärkeitä indikaattoreita vastasyntyneiden ja kriittisesti sairaiden potilaiden tilan arvioimisessa ja ennustamisessa. Kliinisessä käytössä ei kuitenkaan ole yhdellä sensorilla toteutettavaa jatkuva-aikaista monitorointimenetelmää, joka avulla samanaikainen vitaalielintoimintojen seuranta olisi helposti ja nopeasti aloitettavissa. Työn tarkoitus: Tutkimuksen tavoitteena oli testata ja validoida mittausmenetelmää, jolla mitataan rintakehältä ei-invasiivisesti hengitys- ja syketaajuutta sekä happisaturaatiota. Tässä työssä rintakehälle asetettiin kiihtyvyysanturin lisäksi optinen happisaturaatioanturi sekä testattiin mittausmenetelmän soveltuvuutta erityisesti pienten lasten monitorointiin. Toisen kaulalle sijoitettavan kolmiaksiaalisen kiihtyvyysanturin avulla voidaan estimoida myöhemmin pulssin kulkuaikasignaalia. Tutkimuksen avulla myös pilotoidaan osa laajemman kliinisen tutkimuksen mittausasetelmasta. Menetelmät: Tutkimuksen aineisto kerättiin kotioloissa tehdyillä mittauksilla. Tutkimusjoukko koostui seitsemästä perusterveestä pienestä lapsesta (keskiarvo 2,7 v ja keskihajonta 2,1 v). Mittauksissa kerättiin signaalia rintakehältä sekä optisella anturilla että kiihtyvyysanturilla. Lisäksi kiihtyvyyssignaalia mitattiin kaulalle sijoitettavalla kiihtyvyysanturilla. Raakasignaalin laatua ja mittausasetelman käytettävyyttä arvioitiin eri mittaustilanteissa ja signaalinkäsittelyllä mittaussignaaleista estimoitiin hengitys- ja syketaajuus. Pilotoitavaa tutkimusta varten rakennettiin myös käyttöliittymä, johon yhdistettiin videokuvan tallennus synkronoidusti mittaussignaalien kanssa sekä suunniteltiin mittausasetelma. Tulokset: Mittausmenetelmän todettiin soveltuvan pienten lasten monitorointiin ja mittaukset suoritettiin onnistuneesti eri ikäisiltä lapsilta. Signaalien laatu eri mittaustilanteissa oli hyvää signaalinkäsittelyä varten lähes kaikissa mittauksissa, jolloin niistä voitiin laskea hengitys- ja syketaajuus sekä happisaturaatio. Signaalinkäsittely vaatii kuitenkin lisää kehittämistä, jotta vitaalielintoiminnoista kertovat parametrit ovat tarkkoja ja suodattavat liikehdinnästä aiheutuvat artefaktat riittävän hyvin. Tässä tutkimuksessa saadut happisaturaatioarvot eivät myöskään olleet uskottavia. Mittausasetelma kokonaisuudessaan oli käytännöllisesti toteutettavissa pienten lasten jatkuva-aikaiseen monitorointiin kotioloissa. Johtopäätökset: Käytettyä menetelmää on aiemmin testattu onnistuneesti mitattaessa vitaalielintoimintoja aikuisilta (Myllylä et al., 2017). Tähän tutkimukseen perustuen hengitystä, sydämen sykettä ja happisaturaatiota on mahdollista mitata helposti myös pieniltä lapsilta, mutta mittausmenetelmän validoinnille on vielä tarvetta. Jatkotutkimuksessa mittausmenetelmää soveltuvuutta tutkitaan keskosten monitoroinnissa sekä tutkitaan vastasyntyneiden kotimonitoroinnin mahdollisuuksia sähköisiin terveydenhuoltopalveluihin yhdistettynä.Continuous monitoring of vital functions in small children using wearable sensor on the chest. Abstract. Background: Respiratory rate, heart rate, and oxygen saturation (SpO₂) are important parameters for vital functions providing important information to identify a critically ill patient. However, neither in clinical nor in home use, there is a single sensor available that can monitor all these vital signals simultaneously and reliable. Objective: The aim of the study was to test and validate a measurement method for measuring respiratory rate, heart rate and oxygen saturation non-invasively on the chest. In this work, in addition to the accelerometer, an optical oxygen saturation sensor was placed on the chest and the applicability of the measurement method was tested, especially for monitoring of small children. The second tri-axial accelerometer located on the neck can be used to estimate the pulse transit time signal. The study also piloted part of a broader clinical trial measurement setup. Methods: The research material was collected by home measurements. The study group consisted of seven healthy small children (mean age 2,7 y and standard deviation 2,1 y). Measurements were taken from the chest using both an optical sensor and an accelerometer. In addition, the accelerometer was placed on the neck. The quality of the raw signal and the usability of the measurement setup were evaluated in different measurement situations, and the respiratory rate, heart rate and oxygen saturation were estimated from the measurement signals by signal processing. The user interface was also designed for a pilot study, which will combine video recording in synchronization with measurement signals. Results: The measurement method was found to be suitable for monitoring small children and measurements were successfully performed on children of different ages. The raw signal quality in various measurement situations was acceptable in almost all cases so that respiratory and heart rates as well as SpO₂ could be calculated. However, signal processing requires further development in order to ensure sufficiently accurate data also during movements of children which seemed to cause great deal of artefacts. Also, the oxygen saturation values were not credible. The whole measurement setup was practically feasible for continuous monitoring of small children at home. Conclusion: Based on this study, respiration, heart rate, and SpO₂ can be easily measured, even from small children, but there is still a need for further validation. In the follow-up study, the measurement method will be used also to monitor premature infants in hospital, as well as to explore the potential of home monitoring of small children and newborns in combination with eHealth services

Safety of Simultaneous Scalp and Intracranial Electroencephalography Functional Magnetic Resonance Imaging

Understanding the brain and its activity is one of the great challenges of modern science. Normal brain activity (cognitive processes, etc.) has been extensively studied using electroencephalography (EEG) since the 1930’s, in the form of spontaneous fluctuations in rhythms, and patterns, and in a more experimentally-driven approach in the form of event-related potentials allowing us to relate scalp voltage waveforms to brain states and behaviour. The use of EEG recorded during functional magnetic resonance imaging (EEG-fMRI) is a more recent development that has become an important tool in clinical neuroscience, for example, for the study of epileptic activity. The primary aim of this thesis is to devise a protocol in order to minimise the health risks that are associated with simultaneous scalp and intracranial EEG during fMRI (S- icEEG-fMRI). The advances in this technique will be helpful in presenting a new imaging method that will allow the measurement of brain activity with unprecedented sensitivity and coverage. However, this cannot be achieved without assessing the safety implications of such a technique. Therefore, five experiments were performed to fulfil the primary aim. First, the safety of icEEG- fMRI using body transmit RF coil was investigated to improve the results of previous attempts using a head transmit coil at 1.5T. The results of heating increases during a high-SAR sequence were in the range of 0.2-2.4 °C at the contacts with leads positioned along the central axis inside the MRI bore. These findings suggest the need for careful lead placement. Second, also for the body transmit coil we compared the heating in the vicinity of icEEG electrodes placed inside a realistically-shaped head phantom following the addition of scalp EEG electrodes. The peak temperature change was +2.7 °C at the most superior icEEG electrode contact without scalp electrodes, and +2.1 °C at the same contact and the peak increase in the vicinity of a scalp electrode contact was +0.6 °C (location FP2). These findings show that the S-icEEG-fMRI technique is feasible if our protocol is followed carefully. Third, the heating of a realistic 3D model of icEEG electrode during MRI using EM computational simulation was investigated. The resulting peak 10 g averaged SAR was 20% higher than without icEEG. Moreover, the superior icEEG placed perpendicular to B0 showed significant local SAR increase. These results were in line with previous studies. Fourth, the possibility of simplifying a complete 8-contact with 8 wires depth icEEG electrode model into an electrode with 1-contact and 1 wire using EM simulations was addressed. The results showed similar patterns of averaged SAR values around the electrode tip during phantom and electrode position along Z for the Complete and Simplified models, except an average maximum at Z = ~2.5 W/kg for the former. The SAR values during insertion depth for the Simplified model were double those for the Complete model. The effect of extension cable length is in agreement with previous experiments. Fifth, further simulations were implemented using two more simplified models: 8-contact with 1 wire shared with all contact and 8-contact 1 wire connected to each contact at a time as well as the previously modelled simplified 1-contact 1 wire. Two sets of simulations were performed: with a single electrode and with multiple electrodes. For the single electrode, three scenarios were tested: the first simplified model used only, the second simplified models used only and the third model positioned in different 13 locations. The results of these simulations showed about 11.4-20.5-fold lower SAR for the first model than the second and 0.29-5.82-fold lower SAR for the first model than the complete model. The results also showed increased SAR for the electrode close to the head coil than the ones away from it. For the multiple electrodes, three scenarios were tested: two 1-contact and wire electrodes in different separations, multiple electrodes with their wires separated and multiple electrodes with their wires shorted. The results showed interaction between the two tested electrodes. The results of the multiple electrodes presented 2 to ~10 times higher SAR for the separated setup than the shorted. The comparison between the 1-contact with 1 wire model and the complete model is still unknown and more tests are required to show it. From the findings of this PhD research, we conclude that a body RF coil can be utilized for icEEG-fMRI at 1.5 T; however, the safety protocol has to be implemented. In addition, scalp EEG can be used in conjunction with icEEG electrodes inside the body RF coil at 1.5 T and the safety protocol has to be followed. Finally, it is feasible to perform EM computational simulations using realistic icEEG electrodes on a human model. However, simplifying the realistic icEEG electrode model might result in overestimations of the heating, although it is possible that the simplification of the model can help to simulate more complex implantations such as the implantation of multiple electrodes with their leads open circuited or short circuited, which can provide more information about the safety of implanted patients inside the MRI

Cerebral Circulation

Diagnostics and diseases related to the cerebrovascular system are constantly evolving and updating. 3D augmented reality or quantification of cerebral perfusion are becoming important diagnostic tools in daily practice and the role of the cerebral venous system is being constantly revised considering new theories such as that of “the glymphatic system.” This book provides updates on models, diagnosis, and treatment of diseases of the cerebrovascular system

The Public Service Media and Public Service Internet Manifesto

This book presents the collectively authored Public Service Media and Public Service Internet Manifesto and accompanying materials.The Internet and the media landscape are broken. The dominant commercial Internet platforms endanger democracy. They have created a communications landscape overwhelmed by surveillance, advertising, fake news, hate speech, conspiracy theories, and algorithmic politics. Commercial Internet platforms have harmed citizens, users, everyday life, and society. Democracy and digital democracy require Public Service Media. A democracy-enhancing Internet requires Public Service Media becoming Public Service Internet platforms – an Internet of the public, by the public, and for the public; an Internet that advances instead of threatens democracy and the public sphere. The Public Service Internet is based on Internet platforms operated by a variety of Public Service Media, taking the public service remit into the digital age. The Public Service Internet provides opportunities for public debate, participation, and the advancement of social cohesion. Accompanying the Manifesto are materials that informed its creation: Christian Fuchs’ report of the results of the Public Service Media/Internet Survey, the written version of Graham Murdock’s online talk on public service media today, and a summary of an ecomitee.com discussion of the Manifesto’s foundations

Structural Health Monitoring Damage Detection Systems for Aerospace

This open access book presents established methods of structural health monitoring (SHM) and discusses their technological merit in the current aerospace environment. While the aerospace industry aims for weight reduction to improve fuel efficiency, reduce environmental impact, and to decrease maintenance time and operating costs, aircraft structures are often designed and built heavier than required in order to accommodate unpredictable failure. A way to overcome this approach is the use of SHM systems to detect the presence of defects. This book covers all major contemporary aerospace-relevant SHM methods, from the basics of each method to the various defect types that SHM is required to detect to discussion of signal processing developments alongside considerations of aerospace safety requirements. It will be of interest to professionals in industry and academic researchers alike, as well as engineering students. This article/publication is based upon work from COST Action CA18203 (ODIN - http://odin-cost.com/), supported by COST (European Cooperation in Science and Technology). COST (European Cooperation in Science and Technology) is a funding agency for research and innovation networks. Our Actions help connect research initiatives across Europe and enable scientists to grow their ideas by sharing them with their peers. This boosts their research, career and innovation