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  • 1. Abtahi, F
    et al.
    Seoane, F
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Lindecrantz, K
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Electrical bioimpedance spectroscopy in time-variant systems: Is undersampling always a problem?2014Ingår i: Journal of Electrical Bioimpedance, ISSN 1891-5469, E-ISSN 1891-5469, Vol. 5, nr 1, s. 28-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During the last decades, Electrical Bioimpedance Spectroscopy (EBIS) has been applied mainly by using the frequency-sweep technique, across a range of many different applications. Traditionally, the tissue under study is considered to be time-invariant and dynamic changes of tissue activity are ignored by treating the changes as a noise source. A new trend in EBIS is simultaneous electrical stimulation with several frequencies, through the application of a multi-sine, rectangular or other waveform. This method can provide measurements fast enough to sample dynamic changes of different tissues, such as cardiac muscle. This high sampling rate comes at a price of reduction in SNR and the increase in complexity of devices. Although the frequency-sweep technique is often inadequate for monitoring the dynamic changes in a variant system, it can be used successfully in applications focused on the time-invariant or slowly-variant part of a system. However, in order to successfully use frequency-sweep EBIS for monitoring time-variant systems, it is paramount to consider the effects of aliasing and especially the folding of higher frequencies, on the desired frequency e.g. DC level. This paper discusses sub-Nyquist sampling of thoracic EBIS measurements and its application in the case of monitoring pulmonary oedema. It is concluded that by considering aliasing, and with proper implementation of smoothing filters, as well as by using random sampling, frequency-sweep EBIS can be used for assessing time-invariant or slowly-variant properties of time-variant biological systems, even in the presence of aliasing. In general, undersampling is not always a problem, but does always require proper consideration.

  • 2.
    Buendia, Ruben
    et al.
    Chalmers University of Technology.
    Seoane, Fernando
    Högskolan i Borås, Akademin för vård, arbetsliv och välfärd. KTH-School of Technology and Health.
    Lindecrantz, Kaj
    KTH-School of Technology and Health.
    Bosaeus, Ingvar
    University of Gothenburg.
    Gil-Pita, Roberto
    Universidad de Alcala.
    Johannsson, Gudmundur
    University of Gothenburg.
    Ellegård, Lars
    University of Gothenburg.
    Ward, Leigh
    University of Queensland.
    Estimation of body fluids with bioimpedance spectroscopy: state of the art methods and proposal of novel methods2015Ingår i: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 36, nr 10Artikel i tidskrift (Refereegranskat)
  • 3. Jiang, Wen jun
    et al.
    Wittek, Peter
    Högskolan i Borås, Institutionen Biblioteks- och informationsvetenskap / Bibliotekshögskolan.
    Zhao, Li
    Gao, Shi Chao
    Adaptive Thresholding with Inverted Triangular Area for Real-Time Detection of the Heart Rate from Photoplethysmogram Traces on a Smartphone2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Photoplethysmogram (PPG) signals acquired by smartphone cameras are weaker than those acquired by dedicated pulse oximeters. Furthermore, the signals have lower sampling rates, have notches in the waveform and are more severely affected by baseline drift, leading to specific morphological characteristics. This paper introduces a new feature, the inverted triangular area, to address these specific characteristics. The new feature enables real-time adaptive waveform detection using an algorithm of linear time complexity. It can also recognize notches in the waveform and it is inherently robust to baseline drift. An implementation of the algorithm on Android is available for free download. We collected data from 24 volunteers and compared our algorithm in peak detection with two competing algorithms designed for PPG signals, Incremental-Merge Segmentation (IMS) and Adaptive Thresholding (ADT). A sensitivity of 98.0 % and a positive predictive value of 98.8 % were obtained, which were 7.7 % higher than the IMS algorithm in sensitivity, and 8.3 % higher than the ADT algorithm in positive predictive value. The experimental results confirmed the applicability of the proposed method.

  • 4.
    Löfhede, Johan
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    The EEG of the neonatal brain: classification of background activity2009Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The brain requires a continuous supply of oxygen and nutrients, and even a short period of reduced oxygen supply can cause severe and lifelong consequences for the affected individual. The unborn baby is fairly robust, but there are of course limits also for these individuals. The most sensitive and most important organ is the brain. When the brain is deprived of oxygen, a process can start that ultimately may lead to the death of brain cells and irreparable brain damage. This process has two phases; one more or less immediate and one delayed. There is a window of time of up to 24 hours where action can be taken to prevent the delayed secondary damage. One recently clinically available technique is to reduce the metabolism and thereby stop the secondary damage in the brain by cooling the baby. It is important to be able to quickly diagnose hypoxic injuries and to follow the development of the processes in the brain. For this, the electroencephalogram (EEG) is an important tool. The EEG is a voltage signal that originates within the brain and that can be recorded easily and non-invasively at bedside. The signals are, however, highly complex and require special competence to interpret, a competence that typically is not available at the intensive care unit, and particularly not continuously day and night. This thesis addresses the problem of automatic classification of neonatal EEG and proposes methods that would be possible to use in bedside monitoring equipment for neonatal intensive care units. The thesis is a compilation of six papers. The first four deal with the segmentation of pathological signals (burst suppression) from post-asphyctic full term newborn babies. These studies investigate the use of various classification techniques, using both supervised and unsupervised learning. In paper V the scope is widened to include both classification of pathological activity versus activity found in healthy babies as well as application of the segmentation methods on the parts of the EEG signal that are found to be of the pathological type. The use of genetic algorithms for feature selection is also investigated. In paper VI the segmentation methods are applied on signals from pre-term babies to investigate the impact of a certain medication on the brain. The results of this thesis demonstrate ways to improve the monitoring of the brain during intensive care of newborn babies. Hopefully it will someday be implemented in monitoring equipment and help to prevent permanent brain damage in post asphyctic babies.

  • 5.
    Löfhede, Johan
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Degerman, Johan
    Löfgren, Nils
    Thordstein, Magnus
    Flisberg, Anders
    Kjellmer, Ingemar
    Lindecrantz, Kaj
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Comparing a Supervised and an Unsupervised Classification Method for Burst Detection in Neonatal EEG2008Ingår i: Proceedings of Engineering in Medicine and Biology Society, EMBS 2008. 30th Annual International Conference of the IEEE, 20-24 August, 2008, IEEE , 2008, s. 3836-3839Konferensbidrag (Refereegranskat)
    Abstract [en]

    Hidden Markov Models (HMM) and Support Vector Machines (SVM) using unsupervised and supervised training, respectively, were compared with respect to their ability to correctly classify burst and suppression in neonatal EEG. Each classifier was fed five feature signals extracted from EEG signals from six full term infants who had suffered from perinatal asphyxia. Visual inspection of the EEG by an experienced electroencephalographer was used as the gold standard when training the SVM, and for evaluating the performance of both methods. The results are presented as receiver operating characteristic (ROC) curves and quantified by the area under the curve (AUC). Our study show that the SVM and the HMM exhibit similar performance, despite their fundamental differences.

  • 6.
    Löfhede, Johan
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Löfgren, Nils
    Thordstein, Magnus
    Flisberg, Anders
    Kjellmer, Ingemar
    Lindecrantz, Kaj
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Classification of burst and suppression in the neonatal electroencephalogram2008Ingår i: Journal of Neural Engineering, ISSN 1741-2560, E-ISSN 1741-2552, Vol. 5, nr 4, s. 402-410Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fisher's linear discriminant (FLD), a feed-forward artificial neural network (ANN) and a support vector machine (SVM) were compared with respect to their ability to distinguish bursts from suppressions in electroencephalograms (EEG) displaying a burst-suppression pattern. Five features extracted from the EEG were used as inputs. The study was based on EEG signals from six full-term infants who had suffered from perinatal asphyxia, and the methods have been trained with reference data classified by an experienced electroencephalographer. The results are summarized as the area under the curve (AUC), derived from receiver operating characteristic (ROC) curves for the three methods. Based on this, the SVM performs slightly better than the others. Testing the three methods with combinations of increasing numbers of the five features shows that the SVM handles the increasing amount of information better than the other methods.

  • 7.
    Löfhede, Johan
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Löfgren, Nils
    Thordstein, Magnus
    Flisberg, Anders
    Kjellmer, Ingmar
    Lindecrantz, Kaj
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Classification of Burst Suppression and Tracé Alternant in Neonatal EEG2008Ingår i: Proceedings of Medicinteknikdagarna 2008. Annual conference of Svensk Förening för Medicinsk Teknik och Fysik, Göteborg, Oct., 2008, 2008Konferensbidrag (Refereegranskat)
  • 8.
    Sandsjö, Leif
    et al.
    Högskolan i Borås, Akademin för vård, arbetsliv och välfärd.
    Candefjord, Stefan
    SAFER/Chalmers University of Technology.
    Vulnerable Road Users: An eCall service for two-wheel vehicle users2015Rapport (Refereegranskat)
    Abstract [en]

    Vulnerable road users (VRUs) make up an increasing proportion of killed and severely injured in road traffic accidents. A way of reducing the consequences of road traffic accidents is to make efforts to reduce the time to find the crash site and perform appropriate rescue actions. Automatic Crash Notification (ACN) systems have been developed during the last two decades and are now featured in many modern cars. The European eCall initiative makes an automatic emergency call–function mandatory in all new cars introduced to the European market from 2017.

    The aim of this pre-study was to investigate the possibilities and the potential value of implementing an eCall functionality for VRUs with special focus on two-wheelers and bicyclists.

    This pre-study found a few existing products and services related to the ACN/eCall concept aimed at VRUs, but that there is still a vast potential for further initiatives and development. A pilot study performed as part of this pre-study demonstrated that smartphone technology can be used to detect an accident/fall and in addition also may provide information on the impact experienced by the VRU. Further, that this information can contribute significantly to the postcrash rescue activities and this way reduce the accident-related consequences to the individual.

  • 9.
    Sandsjö, Leif
    et al.
    Högskolan i Borås, Akademin för vård, arbetsliv och välfärd. MedTech West/SAFER.
    Candefjord, Stefan
    Signals and Systems, Chalmers.
    Sjöqvist, Bengt Arne
    Signals and Systems/Chalmers.
    Statistikinsamling och automatiskt olyckslarm för trafik med fyrhjulingar via en smartmobilplattform2016Rapport (Övrigt vetenskapligt)
  • 10.
    Seoane, Fernando
    et al.
    Högskolan i Borås, Akademin för vård, arbetsliv och välfärd. KTH-School of Technology and Health.
    Abtahi, Shirin
    Karolinska University Hospital.
    Abtahi, Farhad
    KTH-School of Technology and Health.
    Ellegård, Lars
    Sahlgrenska University Hospital.
    Johannsson, Gudmundur
    Sahlgrenska University Hospital.
    Bosaeus, Ingvar
    University of Gothenburg.
    Ward, Leigh
    University of Queensland.
    Slightly superior performance of bioimpedance spectroscopy over single frequency regression equations for assessment of total body water2015Konferensbidrag (Refereegranskat)
  • 11.
    Seoane, Fernando
    et al.
    Högskolan i Borås, Akademin för vård, arbetsliv och välfärd. KTH-School of Technology and Health.
    Abtahi, Shirin
    Karolinkska University Hospital.
    Abtahi, Farhad
    KTH-School of Technology and Health.
    Ellegård, Lars
    University of Gothenburg.
    Johannsson, Gudmundur
    University of Gothenburg.
    Bosaeus, Ingvar
    University of Gothenburg.
    Ward, Leigh C
    University of Queensland.
    Mean Expected Error in Prediction of Total Body Water.: A True Accuracy Comparison between Bioimpedance Spectroscopy and Single Frequency Regression Equations.2015Ingår i: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, Vol. 2015Artikel i tidskrift (Refereegranskat)
  • 12.
    Seoane, Fernando
    et al.
    Högskolan i Borås, Akademin för vård, arbetsliv och välfärd. KTH-School of Technology and Health.
    Atefi, Seyed Reza
    Harvard Univsersity.
    Tomner, Jens
    Karolinska Hospital.
    Kostulas, Konstantinos
    Karolinska Hospital.
    Lindecrantz, Kaj
    KTH-School of Technology and Health.
    Electrical Bioimpedance Spectroscopy on Acute Unilateral Stroke Patients: Initial Observations regarding Differences between Sides2015Ingår i: BioMed research international, Vol. 2015Artikel i tidskrift (Refereegranskat)
  • 13. Thordstein, Magnus
    et al.
    Flisberg, Anders
    Inganäs, L.
    Mourtzis, A.
    Karlsson, L.
    Rex, K.
    Löfhede, Johan
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Löfgren, Nils
    Förbättrad användning av aEEG för övervakning av centralnervös funktion hos nyfödda barn. En prospektiv, populationsbaserad studie.2008Ingår i: Proceedings of Medicinteknikdagarna 2008, 2008Konferensbidrag (Refereegranskat)
  • 14. Thordstein, Magnus
    et al.
    Kjellmer, Ingemar
    Löfgren, Nils
    Löfhede, Johan
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Lindecrantz, Kaj
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Dean, Justin
    Mallard, Carina
    Effects of inflammation on cerebral electric activity in fetal sheep2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    OBJECTIVE Intrauterine infections can by themselves induce fetal brain damage but also potentiate the effects of other harmful influences such as asphyxia and seizures. Using an EEG technique that permits the recording of extremely low frequencies, often called DC EEG, changes in the level, i.e. DC shifts can be detected. The DC level has been suggested to depend mainly on the potential over the blood brain barrier (BBB), in turn decided primarily by the arterial level of pCO2. Fetuses affected by infection/inflammation that produce detrimental effects on the brain, may have elevated levels of pCO2 and disturbance of the BBB. We aimed at investigating the possibility that the DC EEG could be used to detect the effects of inflammation on the fetal brain. METHODS Fetal sheep were instrumented at 97 days of gestation with catheters, four active EEG electrodes placed on the dura mater as well as extracranial reference and ground electrodes. After three days of recovery, the bacterial endotoxin lipopolysaccharide (LPS) was given to the fetus (200 ng i.v.). RESULTS Exposure to LPS induced a positive DC shift in parallel to the assumed affection of cerebral function and to the pCO2 elevation. This change was not always obvious in standard EEG. CONCLUSIONS These recordings of fetal DC EEG appear to be the first to be done. They indicate that the effects of inflammation on cerebral function can be monitored by DC EEG. Such monitoring might be feasible also during late stages of labour and in neonates.

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