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  • 201. Arvidsson, Anna
    et al.
    Sarve, Hamid
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Johansson, Carina B.
    Comparing and visualizing titanium implant integration in rat bone using 2D and 3D techniques2015Inngår i: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 103, nr 1, s. 12-20Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim was to compare the osseointegration of grit-blasted implants with and without a hydrogen fluoride treatment in rat tibia and femur, and to visualize bone formation using state-of-the-art 3D visualization techniques. Grit-blasted implants were inserted in femur and tibia of 10 Sprague-Dawley rats (4 implants/rat). Four weeks after insertion, bone implant samples were retrieved. Selected samples were imaged in 3D using Synchrotron Radiation-based CT (SRCT). The 3D data was quantified and visualized using two novel visualization techniques, thread fly-through and 2D unfolding. All samples were processed to cut and ground sections and 2D histomorphometrical comparisons of bone implant contact (BIC), bone area (BA), and mirror image area (MI) were performed. BA values were statistically significantly higher for test implants than controls (p<0.05), but BIC and MI data did not differ significantly. Thus, the results partly indicate improved bone formation at blasted and hydrogen fluoride treated implants, compared to blasted implants. The 3D analysis was a valuable complement to 2D analysis, facilitating improved visualization. However, further studies are required to evaluate aspects of 3D quantitative techniques, with relation to light microscopy that traditionally is used for osseointegration studies. (c) 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 12-20, 2015.

  • 202.
    Arvidsson, Daniel
    et al.
    University of Gothenburg.
    Fridolfsson, Jonatan
    University of Gothenburg.
    Börjesson, Mats
    University of Gothenburg.
    Andersen, Lars Bo
    Western Norway University of Applied Sciences, Campus Sogndal, Norway..
    Ekblom, Örjan
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet.
    Dencker, Magnus
    Lund University.
    Brønd, Jan Christian
    University of Southern Denmark, Odense, Denmark.
    Re-examination of accelerometer data processing and calibration for the assessment of physical activity intensity.2019Inngår i: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This review reexamines use of accelerometer and oxygen uptake data for assessment of activity intensity. Accelerometers capture mechanical work, while oxygen uptake captures the energy cost of this work. Frequency filtering needs to be considered when processing acceleration data. A too restrictive filter attenuates the acceleration signal for walking and, to a higher degree, for running. This measurement error affects shorter (children) more than taller (adults) individuals due to their higher movement frequency. Less restrictive filtering includes more movement related signals and provide measures that better capture mechanical work, but may include more noise. An optimal filter cut-point is determined where most relevant acceleration signals are included. Further, accelerometer placement affects what part of mechanical work being captured. While the waist placement captures total mechanical work and therefore contributes to measures of activity intensity equivalent by age and stature, the thigh and wrist placements capture more internal work and do not provide equivalent measures. Value calibration of accelerometer measures is usually performed using measured oxygen uptake with the metabolic equivalent of task (MET) as reference measure of activity intensity. However, the use of MET is not stringent and is not a measure of activity intensity equivalent by age and stature. A candidate measure is the mass-specific net oxygen uptake, VO2 net (VO2 tot - VO2 stand). To improve measurement of physical activity intensity using accelerometers, research developments are suggested concerning processing of accelerometer data, use of energy expenditure as reference for activity intensity, and calibration procedure with absolute versus relative intensity. This article is protected by copyright. All rights reserved.

  • 203.
    Asan, Noor Badariah
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Noreland, Daniel
    Hassan, Emadeldeen
    Redzwan, Syaiful
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Blokhuis, Taco J.
    Carlsson, Per-Ola
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Augustine, Robin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Intra-body microwave communication through adipose tissue2017Inngår i: Healthcare Technology Letters, E-ISSN 2053-3713, Vol. 4, nr 4, s. 115-121Artikkel i tidsskrift (Fagfellevurdert)
  • 204. Asan, Noor Badariah
    et al.
    Noreland, Daniel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hassan, Emadeldeen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Department of Electronics and Electrical Communications, Menoufia University, Menouf, Egypt.
    Shah, Syaiful Redzwan Mohd
    Rydberg, Anders
    Blokhuis, Taco J.
    Carlsson, Per-Ola
    Voigt, Thiemo
    Augustine, Robin
    Intra-body microwave communication through adipose tissue2017Inngår i: Healthcare technology letters, E-ISSN 2053-3713, Vol. 4, nr 4, s. 115-121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The human body can act as a medium for the transmission of electromagnetic waves in the wireless body sensor networks context. However, there are transmission losses in biological tissues due to the presence of water and salts. This Letter focuses on lateral intra-body microwave communication through different biological tissue layers and demonstrates the effect of the tissue thicknesses by comparing signal coupling in the channel. For this work, the authors utilise the R-band frequencies since it overlaps the industrial, scientific and medical radio (ISM) band. The channel model in human tissues is proposed based on electromagnetic simulations, validated using equivalent phantom and ex-vivo measurements. The phantom and ex-vivo measurements are compared with simulation modelling. The results show that electromagnetic communication is feasible in the adipose tissue layer with a low attenuation of approximate to 2 dB per 20 mm for phantom measurements and 4 dB per 20 mm for ex-vivo measurements at 2 GHz. Since the dielectric losses of human adipose tissues are almost half of ex-vivo tissue, an attenuation of around 3 dB per 20 mm is expected. The results show that human adipose tissue can be used as an intra-body communication channel.

  • 205.
    Asan, Noor Badariah
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Redzwan, Syaiful
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Augustine, Robin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Noreland, Daniel
    Hassan, Emadeldeen
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Human fat tissue: A microwave communication channel2017Inngår i: Proc. 1st MTT-S International Microwave Bio Conference, IEEE, 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we present an approach for communication through human body tissue in the R-band frequency range. This study examines the ranges of microwave frequencies suitable for intra-body communication. The human body tissues are characterized with respect to their transmission properties using simulation modeling and phantom measurements. The variations in signal coupling with respect to different tissue thicknesses are studied. The simulation and phantom measurement results show that electromagnetic communication in the fat layer is viable with attenuation of approximately 2 dB per 20 mm. 

  • 206.
    Asan, Noor Badariah
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Velander, Jacob
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Redzwan, Syaiful
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Augustine, Robin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Hassan, Emadeldeen
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Noreland, Daniel
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Blokhuis, Taco J.
    Department of Surgery, Maastricht University Medical Center+, Maastricht, The Netherland.
    Reliability of the fat tissue channel for intra-body microwave communication2017Inngår i: 2017 IEEE Conference on Antenna Measurements & Applications (CAMA), IEEE, 2017, s. 310-313Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recently, the human fat tissue has been proposed as a microwave channel for intra-body sensor applications. In this work, we assess how disturbances can prevent reliable microwave propagation through the fat channel. Perturbants of different sizes are considered. The simulation and experimental results show that efficient communication through the fat channel is possible even in the presence of perturbants such as embedded muscle layers and blood vessels. We show that the communication channel is not affected by perturbants that are smaller than 15 mm cube.

  • 207.
    Ashfaq, Awais
    KTH, Skolan för teknik och hälsa (STH).
    Segmentation of Cone Beam CT in Stereotactic Radiosurgery2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    C-arm Cone Beam CT (CBCT) systems – due to compact size, flexible geometry and low radiation exposure – inaugurated the era of on-board 3D image guidance in therapeutic and surgical procedures. Leksell Gamma Knife Icon by Elekta introduced an integrated CBCT system to determine patient position prior to surgical session, thus advancing to a paradigm shift in facilitating frameless stereotactic radiosurgeries. While CBCT offers a quick imaging facility with high spatial accuracy, the quantitative values tend to be distorted due to various physics based artifacts such as scatter, beam hardening and cone beam effect. Several 3D reconstruction algorithms targeting these artifacts involve an accurate and fast segmentation of craniofacial CBCT images into air, tissue and bone.

    The objective of the thesis is to investigate the performance of deep learning based convolutional neural networks (CNN) in relation to conventional image processing and machine learning algorithms in segmenting CBCT images. CBCT data for training and testing procedures was provided by Elekta. A framework of segmentation algorithms including multilevel automatic thresholding, fuzzy clustering, multilayer perceptron and CNN is developed and tested against pre-defined evaluation metrics carrying pixel-wise prediction accuracy, statistical tests and execution times among others. CNN has proven its ability to outperform other segmentation algorithms throughout the evaluation metrics except for execution times. Mean segmentation error for CNN is found to be 0.4% with a standard deviation of 0.07%, followed by fuzzy clustering with mean segmentation error of 0.8% and a standard deviation of 0.12%. CNN based segmentation takes 500s compared to multilevel thresholding which requires ~1s on similar sized CBCT image.

    The present work demonstrates the ability of CNN in handling artifacts and noise in CBCT images and maintaining a high semantic segmentation performance. However, further efforts targeting CNN execution speed are required to utilize the segmentation framework within real-time 3D reconstruction algorithms.

  • 208.
    Ashfaq, Awais
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR Centrum för tillämpade intelligenta system (IS-lab). KTH Royal Institute of Technology, Stockholm, Sweden.
    Adler, Jonas
    KTH Royal Institute of Technology, Stockholm, Sweden & Elekta Instrument AB, Stockholm, Sweden.
    A modified fuzzy C means algorithm for shading correction in craniofacial CBCT images2017Inngår i: CMBEBIH 2017: Proceedings of the International Conference on Medical and Biological Engineering 2017 / [ed] Almir Badnjevic, Singapore: Springer, 2017, Vol. 62, s. 531-538Konferansepaper (Fagfellevurdert)
    Abstract [en]

    CBCT images suffer from acute shading artifacts primarily due to scatter. Numerous image-domain correction algorithms have been proposed in the literature that use patient-specific planning CT images to estimate shading contributions in CBCT images. However, in the context of radiosurgery applications such as gamma knife, planning images are often acquired through MRI which impedes the use of polynomial fitting approaches for shading correction. We present a new shading correction approach that is independent of planning CT images. Our algorithm is based on the assumption that true CBCT images follow a uniform volumetric intensity distribution per material, and scatter perturbs this uniform texture by contributing cupping and shading artifacts in the image domain. The framework is a combination of fuzzy C-means coupled with a neighborhood regularization term and Otsu’s method. Experimental results on artificially simulated craniofacial CBCT images are provided to demonstrate the effectiveness of our algorithm. Spatial non-uniformity is reduced from 16% to 7% in soft tissue and from 44% to 8% in bone regions. With shading-correction, thresholding based segmentation accuracy for bone pixels is improved from 85% to 91% when compared to thresholding without shading-correction. The proposed algorithm is thus practical and qualifies as a plug and play extension into any CBCT reconstruction software for shading correction. © Springer Nature Singapore Pte Ltd. 2017.

  • 209.
    Ashfaq, Awais
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR Centrum för tillämpade intelligenta system (IS-lab). Halland Hospital, Region Halland, Halmstad, Sweden.
    Nowaczyk, Sławomir
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR Centrum för tillämpade intelligenta system (IS-lab).
    Machine learning in healthcare - a system’s perspective2019Inngår i: Proceedings of the ACM SIGKDD Workshop on Epidemiology meets Data Mining and Knowledge Discovery (epiDAMIK) / [ed] B. Aditya Prakash, Anil Vullikanti, Shweta Bansal, Adam Sadelik, Arlington, 2019, s. 14-17Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A consequence of the fragmented and siloed healthcare landscape is that patient care (and data) is split along multitude of different facilities and computer systems and enabling interoperability between these systems is hard. The lack interoperability not only hinders continuity of care and burdens providers, but also hinders effective application of Machine Learning (ML) algorithms. Thus, most current ML algorithms, designed to understand patient care and facilitate clinical decision-support, are trained on limited datasets. This approach is analogous to the Newtonian paradigm of Reductionism in which a system is broken down into elementary components and a description of the whole is formed by understanding those components individually. A key limitation of the reductionist approach is that it ignores the component-component interactions and dynamics within the system which are often of prime significance in understanding the overall behaviour of complex adaptive systems (CAS). Healthcare is a CAS.

    Though the application of ML on health data have shown incremental improvements for clinical decision support, ML has a much a broader potential to restructure care delivery as a whole and maximize care value. However, this ML potential remains largely untapped: primarily due to functional limitations of Electronic Health Records (EHR) and the inability to see the healthcare system as a whole. This viewpoint (i) articulates the healthcare as a complex system which has a biological and an organizational perspective, (ii) motivates with examples, the need of a system's approach when addressing healthcare challenges via ML and, (iii) emphasizes to unleash EHR functionality - while duly respecting all ethical and legal concerns - to reap full benefits of ML.

  • 210.
    Ask, P.
    et al.
    Department of Biomedical Engineering, Linköping University, Sweden.
    Ekstrand, K.
    ?.
    Hult, P.
    Department of Biomedical Engineering, Linköping University, Sweden.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Pettersson, N. -E
    Örebro County Council, Sweden.
    NovaMedTech - A regional program for supporting new medical technologies in personalized health care2012Inngår i: Studies in Health Technology and Informatics, 2012, s. 71-75Konferansepaper (Fagfellevurdert)
    Abstract [en]

    NovaMedTech is an initiative funded from EU structural funds for supporting new medical technologies for personalized health care. It aims at bringing these technologies into clinical use and to the health care market. The program has participants from health care, industry and academia in East middle Sweden. The first three year period of the program was successful in terms of product concepts tried clinically, and number of products brought to a commercialization phase. Further, the program has led to a large number of scientific publications. Among projects supported, we can mention: Intelligent sensor networks; A digital pen to collect medical information about health status from patients; A web-based intelligent stethoscope; Methodologies to measure local blood flow and nutrition using optical techniques; Blood flow assessment from ankle pressure measurements; Technologies for pressure ulcer prevention; An IR thermometer for improved accuracy; A technique that identifies individuals prone to commit suicide among depressed patients; Detection of infectious disease using an electronic nose; Identification of the lactate threshold from breath; Obesity measurements using special software and MR camera; and An optical probe guided tumor resection. During the present three years period emphasis will be on entrepreneurial activities supporting the commercialization and bringing products to the market.

  • 211.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Low-compliance perfusion pump for oesophageal manometry.1978Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 16, nr 6, s. 732-738Artikkel i tidsskrift (Fagfellevurdert)
  • 212.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Measurement techniques for urodynamic investigations.1989Inngår i: Critical reviews in biomedical engineering, ISSN 0278-940X, E-ISSN 1943-619X, Vol. 17, nr 5, s. 413-449Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Important measurement techniques for investigating lower urinary tract function are flow and pressure measurements. The demands on urinary flowmeters and the measurement principles of balance type, rotating disc, dipstick, and air-displacement type are described. Urological pressure measurements are performed in the bladder, in the urethra, and in the abdominal cavity. Various fluid-filled and microtransducer systems are reviewed and demands for performance given. Differences in measuring a mechanical pressure, like in the urethra, and a fluid pressure in the bladder are discussed. Electromyography (EMG) technique is used to investigate various neurological disturbances in the lower urinary tract. The electrode technique is also described. Furthermore, techniques for incontinence detection are reviewed.

  • 213.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Edwall, G
    Johansson, K E
    Tibbling, Lita
    On the use of monocrystalline antimony pH electrodes in gastro-oesophageal functional disorders.1982Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 20, nr 3, s. 383-389Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Monocrystalline antimony electrodes have been shown to be suitable for thein vivo determination of pH in blood, tissue and in the upper gastro-intestinal canal. Thanks to their small dimensions it has been possible to mount them into conventional manometry catheters for oesophageal investigation. The monocrystalline antimony pH electrode has several advantages over the conventional pH glass electrode; better accuracy, shorter rise time, smaller dimensions. The monocrystalline antimony electrode has been used for long-term registration of gastro-oesophageal reflux, for the oesophageal acid clearing test and for identification of the pH gradient zone between the gastric and oesophageal mucosa. Its use in combination with pressure sensors has added a new dimension to the diagnosis of functional disorders in the gastro-oesophageal region.

  • 214.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hägglund, Sture
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system. Linköpings universitet, Tekniska högskolan.
    Olsson, Jan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Filosofiska fakulteten.
    Pettersson, Nils-Erik
    Sjöqvist, Bengt-Arne
    Åhlfeldt, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    36-nätet och "pensionärsdatorer" kan bidra till att lösa sjukvårdens problem2003Inngår i: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, Vol. 100, nr 14, s. 1257-1258Artikkel i tidsskrift (Fagfellevurdert)
  • 215.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Regurgitant flow through heart valves: a hydraulic model applicable to ultrasound Doppler measurements.1986Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 24, nr 6, s. 643-646Artikkel i tidsskrift (Fagfellevurdert)
  • 216.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Skogh, Marcus
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Undersökning av EKG-elektroners elektriska och mekaniska långtidsegenskaper1974Rapport (Annet vitenskapelig)
  • 217.
    Askfors, Ylva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Hälsoinformatik.
    Samverkan för innovation: En fallstudie av mötet mellan akademi, industri och sjukvård2018Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [sv]

    Samverkan kan leda till innovation, konkurrenskraftiga företag, förstklassig forskning samt välfungerande myndigheter och institutioner. I den politiska debatten idag finns en förväntan att Sverige ska upprätthålla sin konkurrenskraft och bemöta samhällets utmaningar genom innovation och att vägen till innovation går via samverkan. Avhandlingen bygger på en studie av ett samverkansprojekt vars syfte var att skapa innovation för att minska antalet vårdrelaterade infektioner i Sverige. Projektet som studerats ses som en transdisciplinär ansats med aktörer som representerade akademi, industri samt hälso- och sjukvård.

    Syftet med avhandlingen är att vidareutveckla kunskapen om interorganisatorisk samverkan för innovation. Detta görs genom ett tredelat bidrag, till teoribildningen kring samverkan för innovation som börjat växa fram, till den samverkande praktiken inom både privat och offentlig sektor samt till politiker och beslutsfattare som styr fördelning av statliga anslag till forskning och innovation.

    Fallstudien som ligger till grund för avhandlingen är baserad på en etnografiskt inspirerad studie. Empiriskt material samlades in och skapades tillsammans med aktörerna i projektet under drygt två års tid genom intervjuer och deltagande observation.

    Studien visar att interorganisatorisk samverkan består av flera dimensioner och kan förstås på flera nivåer. Interorganisatorisk samverkan innebär inte bara att det är olika organisationer som ska göra en gemensam ansträngning. Organisationerna består av olika människor med olika discipliner och professioner vilka bygger på olika utgångspunkter och sätt att se på världen. Samverkan kan ses som ett sätt att fylla mellanrummen mellan organisationer istället för att bygga broar över gränser. I de organisatoriska mellanrummen kan aktörer från olika organisationer, med olika discipliner och professioner mötas utan institutionaliserade roller, i en receptiv kontext där innovation kan skapas.

  • 218.
    Asklöf, Madeleine
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Barn- och kvinnocentrum, Kvinnokliniken i Linköping.
    Kjölhede, Preben
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för barns och kvinnors hälsa. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Barn- och kvinnocentrum, Kvinnokliniken i Linköping.
    Borendal Wodlin, Ninnie
    Linköpings universitet, Medicinska fakulteten. Region Östergötland, Barn- och kvinnocentrum, Kvinnokliniken i Linköping. Linköpings universitet, Institutionen för klinisk och experimentell medicin.
    Nilsson, Lena
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för läkemedelsforskning. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Sinnescentrum, Anestesi- och intensivvårdskliniken US.
    Bioelectrical impedance analysis; a new method to evaluate lymphoedema, fluid status, and tissue damage after gynaecological surgery - A systematic review2018Inngår i: European Journal of Obstetrics, Gynecology, and Reproductive Biology, ISSN 0301-2115, E-ISSN 1872-7654, Vol. 228, s. 111-119Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The aim of this descriptive review is to summarise the current knowledge of non-invasive bioelectrical impedance analysis (BIA) used with gynaecological surgical patients in regard to postoperative development of lymphoedema and determination of perioperative fluid balance, and as a prognostic factor in cancer mortality and a predictor of postoperative complications. The databases PubMed, MEDLINE, Scopus Web of Science, the Cochrane Library, and reference lists of selected articles were searched for relevant articles published during the period January 2008-April 2018. Only papers published in English were retrieved. Thirty-seven articles were evaluated. Where gynaecological studies were lacking, studies with a study population from neighbouring clinical fields were used instead. Studies on the clinical use of BIA with gynaecological surgical patients were divided into three categories: the postoperative development of lower limb lymphoedema (n = 7), perioperative hydration measuring (n = 3), and the BIA parameter phase angle as a prognostic factor in cancer survival and as predictive for postoperative complications (n = 6). Of these 16 studies only three used a pure gynaecological study population. Three different methods of BIA were used in these articles: single frequency-BIA, multifrequency-BIA and bioimpedance spectroscopy. BIA was found to detect lymphoedema with a sensitivity of 73% and a specificity of 84%. Studies indicated that BIA was able to detect lower limb lymphoedema at an early stage even before it became clinically detectable. During postoperative hydration measurements, an increase in extracellular fluid volume and extracellular fluid volume in relation to total body fluid volume, as well as a decrease in phase angle, were associated with higher frequencies of postoperative complications. Moreover, low values for the phase angle have been associated with increased mortality in cancer patients. However, the number of studies in this field was limited. From our review, BIA seems to be a useful tool for use in the clinical setting of the gynaecological surgical patient. The theoretical approach of using bioelectrical impedance values to measure the fluid distribution in the body compartments offers wide opportunities in the clinical setting. However, so far, all studies have set up cut-off limits within the study population, and reference values for a general population need to be defined. There are also rather few studies on a gynaecological study population. Hence, there is a need for further studies within gynaecological surgery focusing on early detection of lower limb lymphoedema, perioperative fluid balance, and postoperative complications in order to establish the value of BIA in clinical praxis. (C) 2018 Elsevier B.V. All rights reserved.

  • 219. Aslund, M.
    et al.
    Fredenberg, Erik
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Telman, M.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Detectors for the future of X-ray imaging2010Inngår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, nr 1-3, s. 327-333Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In recent decades, developments in detectors for X-ray imaging have improved dose efficiency. This has been accomplished with for example, structured scintillators such as columnar CsI, or with direct detectors where the X rays are converted to electric charge carriers in a semiconductor. Scattered radiation remains a major noise source, and fairly inefficient anti-scatter grids are still a gold standard. Hence, any future development should include improved scatter rejection. In recent years, photon-counting detectors have generated significant interest by several companies as well as academic research groups. This method eliminates electronic noise, which is an advantage in low-dose applications. Moreover, energy-sensitive photon-counting detectors allow for further improvements by optimising the signal-to-quantum-noise ratio, anatomical background subtraction or quantitative analysis of object constituents. This paper reviews state-of-the-art photon-counting detectors, scatter control and their application in diagnostic X-ray medical imaging. In particular, spectral imaging with photon-counting detectors, pitfalls such as charge sharing and high rates and various proposals for mitigation are discussed.

  • 220.
    Asplund, Maria
    KTH, Skolan för teknik och hälsa (STH), Neuronik.
    Conjugated Polymers for Neural Interfaces: Prospects, possibilities and future challenges2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Within the field of neuroprosthetics the possibility to use implanted electrodes for communication with the nervous system is explored. Much effort is put into the material aspects of the electrode implant to increase charge injection capacity, suppress foreign body response and build micro sized electrode arrays allowing close contact with neurons. Conducting polymers, in particular poly(3,4-ethylene dioxythiophene) (PEDOT), have been suggested as materials highly interesting for such neural communication electrodes. The possibility to tailor the material both mechanically and biochemically to suit specific applications, is a substantial benefit with polymers when compared to metals. PEDOT also have hybrid charge transfer properties, including both electronic and ionic conduction, which allow for highly efficient charge injection.

     

    Part of this thesis describes a method of tailoring PEDOT through exchanging the counter ion used in electropolymerisation process. Commonly used surfactants can thereby be excluded and instead, different biomolecules can be incorporated into the polymer. The electrochemical characteristics of the polymer film depend on the ion. PEDOT electropolymerised with heparin was here determined to have the most advantageous properties. In vitro methods were applied to confirm non-cytotoxicity of the formed PEDOT:biomolecular composites. In addition, biocompatibility was affirmed for PEDOT:heparin by evaluation of inflammatory response and neuron density when implanted in rodent cortex.

     

    One advantage with PEDOT often stated, is its high stability compared to other conducting polymers. A battery of tests simulating the biological environment was therefore applied to investigate this stability, and especially the influence of the incorporated heparin. These tests showed that there was a decline in the electroactivity of PEDOT over time. This also applied in phosphate buffered saline at body temperature and in the absence of other stressors. The time course of degradation also differed depending on whether the counter ion was the surfactant polystyrene sulphonate or heparin, with a slightly better stability for the former.

     

    One possibility with PEDOT, often overlooked for biological applications, is the use of its semi conducting properties in order to include logic functions in the implant. This thesis presents the concept of using PEDOT electrochemical transistors to construct textile electrode arrays with in-built multiplexing. Using the electrolyte mediated interaction between adjacent PEDOT coated fibres to switch the polymer coat between conducting and non conducting states, then transistor function can be included in the conducting textile. Analogue circuit simulations based on experimentally found transistor characteristics proved the feasibility of these textile arrays. Developments of better polymer coatings, electrolytes and encapsulation techniques for this technology, were also identified to be essential steps in order to make these devices truly useful.

     

    In summary, this work shows the potential of PEDOT to improve neural interfaces in several ways. Some weaknesses of the polymer and the polymer electronics are presented and this, together with the epidemiological data, should point in the direction for future studies within this field.

  • 221.
    Asplund, Maria
    et al.
    KTH, Skolan för teknik och hälsa (STH), Neuronik.
    Hamedi, Mahiar
    Inganäs, Olle
    Forchheimer, Robert
    von Holst, Hans
    KTH, Skolan för teknik och hälsa (STH), Neuronik.
    Neural microcontacts with wire electrodes and woven logic2007Konferansepaper (Fagfellevurdert)
  • 222.
    Asplund, Raquel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Evaluation of a cloud-based image analysis and image display system for medical images2015Independent thesis Basic level (university diploma), 180 hpOppgave
  • 223.
    Atefi, Seyed Reza
    KTH-School of Technology and Health.
    Electrical Bioimpedance Cerebral Monitoring: From Hyopthesis and Simulation to First Experimental Evidence in Stroke Patients2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Stroke is amongthe leading causes of death worldwide and requires immediate care to prevent death or permanent disability. Unfortunately, the current stateof stroke diagnosis is limited to fixed neuroimaging facilities that do not allow rapid stroke diagnosis. Hence, a portable stroke-diagnosis device could assist in the pre-hospital triage of patients. Moreover, such a portable device could also be useful for bedside stroke monitoring of patients in the Neuro Intensive Care Unit (Neuro-ICU) to avoid unnecessary neuroimaging. Recent animal studies and numerical simulations have supported the idea of implementing Electrical Bioimpedance (EBI) in a portable device, allowing non-invasive assessment as a useful tool for the pre-hospital triage of stroke and Traumatic Brain Injury (TBI) patients. Unfortunately, these studies have not reported any results from human subjects in the acute phase of the stroke. The numerical simulations are also based on simple models that sometimes lack necessary details.

    Finite Element Method (FEM) simulations on a realistic numerical head model as well as experimental Bioimpedance Spectroscopy (BIS) measurements from human subjectsin the acute, subacute and chronic phasesof stroke were used to answer the following research questions: (i) Does stroke modify the electrical properties of brain tissue in a way that is detectable via EBI? (ii) Would it be possible to detect stroke via EBI as early as in the acute and sub-acute phase?(iii) Is EBI sensitive enough to monitor changes caused by stroke pathogenesis?

    Using FEM to simulate electrical current injection on the head and study the resulting distribution of electrical potential on the scalp, it was shown that Intra-Cranial Hemorrhage (ICH) affects the quasi-symmetric scalp potential distribution,creating larger left-right potential asymmetry when compared to the healthy head model. Proof-of-concept FEM simulations were also tested in a small cohort of 6ICH patients and 10 healthy controls, showing that the left-right potential difference in the patients is significantly (p<0.05) larger than in the controls. Using bioimpedance measurements in the acute,  subacute and chronic phasesof stroke and examining simple features, it was also shown that the head EBI measurements of patients suffering stroke are different from controls, enabling the discrimination of healthy controls and stroke patients at any stage of the stroke. The absolute change in test-retest resistance measurements of the control group (~5.33%) was also found to be significantly (p<0.05) smaller than the EBI measurements of patients obtained 24 hours and 72 hours after stroke onset (20.44%). These results suggested that scalp EBI is sensitive to stroke pathogenesis changesand thususeful for bedside monitoring in the Neuro-ICU. These results suggested that EBI is a potentially useful tool for stroke diagnosis and monitoring.

    Finally, the initial observations based on a small number of patients, addressing the proposed future work of this thesis, suggested that the average head resistance amplitude of hemorrhagic stroke patients is smaller than in healthy controls, while ischemic stroke patients show a larger resistance amplitude than the controls. Scalp potential asymmetry analysis of healthy, hemorrhagic and ischemic stroke subjects also suggests that these three groups can be separated. However, these results are based on a small number of patients and need to be validated using a larger cohort. Initial observations also showed that the resistance of the EBI measurements of controls is robust between test and retest measurements, showing no significant difference (less than 2% and p>0.05). Subject position during EBI recording (supine or sitting) did not seem to affect the resistance of the EBI measurements (p>0.05). However, age, sex and head size showed significant effects on the resistance measurements. These initial observations are encouraging for further research on EBI for cerebral monitoring and stroke diagnosis. However, at this stage, considering the uncertainties in stroke type differentiation, EBI cannot replace CT but has the potential to be used as a consultation tool.

  • 224.
    Atefi, Seyed Reza
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Electrical Bioimpedance Cerebral Monitoring: From Hypothesis and Simulation to First Experimental Evidence in Stroke Patients2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Stroke is amongthe leading causes of death worldwide and requires immediate care to prevent death or permanent disability. Unfortunately, the current stateof stroke diagnosis is limited to fixed neuroimaging facilities that do not allow rapid stroke diagnosis. Hence, a portable stroke-diagnosis device could assist in the pre-hospital triage of patients. Moreover, such a portable device could also be useful for bedside stroke monitoring of patients in the Neuro Intensive Care Unit (Neuro-ICU) to avoid unnecessary neuroimaging. Recent animal studies and numerical simulations have supported the idea of implementing Electrical Bioimpedance (EBI) in a portable device, allowing non-invasive assessment as a useful tool for the pre-hospital triage of stroke and Traumatic Brain Injury (TBI) patients. Unfortunately, these studies have not reported any results from human subjects in the acute phase of the stroke. The numerical simulations are also based on simple models that sometimes lack necessary details.

    Finite Element Method (FEM) simulations on a realistic numerical head model as well as experimental Bioimpedance Spectroscopy (BIS) measurements from human subjectsin the acute, subacute and chronic phasesof stroke were used to answer the following research questions: (i) Does stroke modify the electrical properties of brain tissue in a way that is detectable via EBI? (ii) Would it be possible to detect stroke via EBI as early as in the acute and sub-acute phase?(iii) Is EBI sensitive enough to monitor changes caused by stroke pathogenesis?

    Using FEM to simulate electrical current injection on the head and study the resulting distribution of electrical potential on the scalp, it was shown that Intra-Cranial Hemorrhage (ICH) affects the quasi-symmetric scalp potential distribution,creating larger left-right potential asymmetry when compared to the healthy head model. Proof-of-concept FEM simulations were also tested in a small cohort of 6ICH patients and 10 healthy controls, showing that the left-right potential difference in the patients is significantly (p<0.05) larger than in the controls. Using bioimpedance measurements in the acute,  subacute and chronic phasesof stroke and examining simple features, it was also shown that the head EBI measurements of patients suffering stroke are different from controls, enabling the discrimination of healthy controls and stroke patients at any stage of the stroke. The absolute change in test-retest resistance measurements of the control group (~5.33%) was also found to be significantly (p<0.05) smaller than the EBI measurements of patients obtained 24 hours and 72 hours after stroke onset (20.44%). These results suggested that scalp EBI is sensitive to stroke pathogenesis changesand thususeful for bedside monitoring in the Neuro-ICU. These results suggested that EBI is a potentially useful tool for stroke diagnosis and monitoring.

    Finally, the initial observations based on a small number of patients, addressing the proposed future work of this thesis, suggested that the average head resistance amplitude of hemorrhagic stroke patients is smaller than in healthy controls, while ischemic stroke patients show a larger resistance amplitude than the controls. Scalp potential asymmetry analysis of healthy, hemorrhagic and ischemic stroke subjects also suggests that these three groups can be separated. However, these results are based on a small number of patients and need to be validated using a larger cohort. Initial observations also showed that the resistance of the EBI measurements of controls is robust between test and retest measurements, showing no significant difference (less than 2% and p>0.05). Subject position during EBI recording (supine or sitting) did not seem to affect the resistance of the EBI measurements (p>0.05). However, age, sex and head size showed significant effects on the resistance measurements. These initial observations are encouraging for further research on EBI for cerebral monitoring and stroke diagnosis. However, at this stage, considering the uncertainties in stroke type differentiation, EBI cannot replace CT but has the potential to be used as a consultation tool.

  • 225.
    Atefi, Seyed Reza
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinska sensorer, signaler och system (MSSS) (Stängd 20130701).
    Buendia, Ruben
    KTH, Skolan för teknik och hälsa (STH), Medicinska sensorer, signaler och system (MSSS) (Stängd 20130701).
    Lindecrantz, Kaj
    KTH, Skolan för teknik och hälsa (STH), Medicinska sensorer, signaler och system (MSSS) (Stängd 20130701).
    Seoane, Fernando
    KTH, Skolan för teknik och hälsa (STH), Medicinska sensorer, signaler och system (MSSS) (Stängd 20130701).
    Cole Function and Conductance-Based Parasitic Capacitance Compensation for Cerebral Electrical Bioimpedance Measurements2012Inngår i: Engineering in Medicine and Biology Society (EMBC), 2012 Annual International Conference of the IEEE, San Diego: IEEE press , 2012, s. 3368-3371Konferansepaper (Fagfellevurdert)
    Abstract [en]

    One of the most common measurement artifacts present in Electrical Bioimpedance Spectroscopy measurements (EBIS) comes from the capacitive leakage effect resulting from parasitic stray capacitances. This artifact produces a deviation in the measured impedance spectrum that is most noticeable at higher frequencies. The artifact taints the spectroscopy measurement increasing the difficulty of producing reliable EBIS measurements at high frequencies. In this work, an approach for removing such capacitive influence from the spectral measurement is presented making use of a novel method to estimate the value of the parasitic capacitance equivalent that causes the measurement artifact. The proposed method has been tested and validated theoretically and experimentally and it gives a more accurate estimation of the value of the parasitic capacitance than the previous methods. Once a reliable value of parasitic capacitance has been estimated the capacitive influence can be easily compensated in the EBIS measured data. Thus enabling analysis of EBIS data at higher frequencies, i.e. in the range of 300-500 kHz like measurements intended for cerebral monitoring, where the characteristic frequency is remarkably higher than EBIS measurements i.e. within the range 30 to 50 kHz, intended for body composition assessment.

  • 226.
    Atefi, Seyed Reza
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Seoane, Fernando
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Kamalian, Shervin
    Rosenthal, Eric
    Lev, Michael
    Bonmassar, Giorgio
    Intracranial haemorrhage alters scalp potential distributions in bioimpedance cerebral monitoring applications: preliminary results from FEM simulation on a realistic head model and human subjects2016Inngår i: Medical Physics, ISSN 2473-4209, Vol. 43, nr 2, s. 675-686Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: Current diagnostic neuroimaging for detection of intracranial hemorrhage (ICH) is limited to fixed scanners requiring patient transport and extensive infrastructure support. ICH diagnosis would therefore benefit from a portable diagnostic technology, such as electrical bioimpedance (EBI). Through simulations and patient observation, the authors assessed the influence of unilateral ICH hematomas on quasisymmetric scalp potential distributions in order to establish the feasibility of EBI technology as a potential tool for early diagnosis. Methods: Finite element method (FEM) simulations and experimental leftright hemispheric scalp potential differences of healthy and damaged brains were compared with respect to the asymmetry caused by ICH lesions on quasisymmetric scalp potential distributions. In numerical simulations, this asymmetry was measured at 25 kHz and visualized on the scalp as the normalized potential difference between the healthy and ICH damaged models. Proof-of-concept simulations were extended in a pilot study of experimental scalp potential measurements recorded between 0 and 50 kHz with the authors custom-made bioimpedance spectrometer. Mean leftright scalp potential differences recorded from the frontal, central, and parietal brain regions of ten healthy control and six patients suffering from acute/subacute ICH were compared. The observed differences were measured at the 5% level of significance using the two-sample Welch ttest. Results: The 3D-anatomically accurate FEM simulations showed that the normalized scalp potential difference between the damaged and healthy brain models is zero everywhere on the head surface, except in the vicinity of the lesion, where it can vary up to 5%. The authors preliminary experimental results also confirmed that the leftright scalp potential difference in patients with ICH (e.g., 64 mV) is significantly larger than in healthy subjects (e.g., 20.8 mV; P < 0.05). Conclusions: Realistic, proof-of-concept simulations confirmed that ICH affects quasisymmetric scalp potential distributions. Pilot clinical observations with the authors custom-made bioimpedance spectrometer also showed higher leftright potential differences in the presence of ICH, similar to those of their simulations, that may help to distinguish healthy subjects from ICH patients. Although these pilot clinical observations are in agreement with the computer simulations, the small sample size of this study lacks statistical power to exclude the influence of other possible confounders such as age, ex, and electrode positioning. The agreement with previously published simulation-based and clinical results, however, suggests that EBI technology may be potentially useful for ICH detection. © 2016 American Association of Physicists in Medicine.

  • 227.
    Atefi, Seyed Reza
    et al.
    Harvard Univsersity.
    Seoane, Fernando
    Högskolan i Borås, Akademin för vård, arbetsliv och välfärd. KTH-School of Technology and Health.
    Kamalian, Shervin
    Rosenthal, Eric
    Lev, Michael
    Massachussets University Hospital.
    Bonmassar, Giorgio
    Harvard University.
    Intracranial haemorrhage alters scalp potential distributions in bioimpedance cerebral monitoring applications: preliminary results from FEM simulation on a realistic head model and human subjects2016Inngår i: Medical Physics, ISSN 0094-2405, Vol. 43, nr 2, s. 675-686Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose:

    Current diagnostic neuroimaging for detection of intracranial hemorrhage (ICH) is limited to fixed scanners requiring patient transport and extensive infrastructure support. ICH diagnosis would therefore benefit from a portable diagnostic technology, such as electrical bioimpedance (EBI). Through simulations and patient observation, the authors assessed the influence of unilateral ICH hematomas on quasisymmetric scalp potential distributions in order to establish the feasibility of EBI technology as a potential tool for early diagnosis.

    Methods:

    Finite element method(FEM) simulations and experimental left–right hemispheric scalp potential differences of healthy and damaged brains were compared with respect to the asymmetry caused by ICH lesions on quasisymmetric scalp potential distributions. In numerical simulations, this asymmetry was measured at 25 kHz and visualized on the scalp as the normalized potential difference between the healthy and ICH damaged models. Proof-of-concept simulations were extended in a pilot study of experimental scalp potential measurements recorded between 0 and 50 kHz with the authors’ custom-made bioimpedance spectrometer. Mean left–right scalp potential differences recorded from the frontal, central, and parietal brain regions of ten healthy control and six patients suffering from acute/subacute ICH were compared. The observed differences were measured at the 5% level of significance using the two-sample Welch t-test.

    Results:

    The 3D-anatomically accurate FEM simulations showed that the normalized scalp potential difference between the damaged and healthy brainmodels is zero everywhere on the head surface, except in the vicinity of the lesion, where it can vary up to 5%. The authors’ preliminary experimental results also confirmed that the left–right scalp potential difference in patients with ICH (e.g., 64 mV) is significantly larger than in healthy subjects (e.g., 20.8 mV; P < 0.05).

    Conclusions:

    Realistic, proof-of-concept simulations confirmed that ICH affects quasisymmetric scalp potential distributions. Pilot clinical observations with the authors’ custom-made bioimpedance spectrometer also showed higher left–right potential differences in the presence of ICH, similar to those of their simulations, that may help to distinguish healthy subjects from ICH patients. Although these pilot clinical observations are in agreement with the computer simulations, the small sample size of this study lacks statistical power to exclude the influence of other possible confounders such as age, sex, and electrode positioning. The agreement with previously published simulation-based and clinical results, however, suggests that EBI technology may be potentially useful for ICH detection.

  • 228.
    Atefi, Seyed Reza
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinska sensorer, signaler och system (MSSS).
    Seoane, Fernando
    KTH, Skolan för teknik och hälsa (STH), Medicinska sensorer, signaler och system (MSSS).
    Lindecrantz, Kaj
    KTH, Skolan för teknik och hälsa (STH), Medicinska sensorer, signaler och system (MSSS).
    Electrical Bioimpedance cerebral monitoring. Preliminary results from measurements on stroke patients2012Inngår i: Engineering in Medicine and Biology Society (EMBC), 2012 Annual International Conference of the IEEE, IEEE , 2012, s. 126-129Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Electrical Bioimpedance Spectroscopy (EBIS) is currently used in different tissue characterization applications. In this work we aim to use EBIS to study changes in electrical properties of the cerebral tissues after an incident of hemorrhage/ischemic stroke. To do so a case-control study was conducted using six controls and three stroke cases. The preliminary results of this study show that by using Cole-based analysis on EBIS measurements and analyzing the Cole parameters R0 and R∞, it is possible to detect changes on electrical properties of cerebral tissue after stroke. 

  • 229.
    Atefi, Seyed Reza
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Seoane, Fernando
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Lindecrantz, Kaj
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Study of the dynamics of transcephalic cerebral impedance data during cardio-vascular surgery2013Inngår i: XV International Conference on Electrical Bio-Impedance (ICEBI) & XIV Conference on Electrical Impedance Tomography (EIT), Institute of Physics (IOP), 2013, Vol. 434, nr 1, s. 012045-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Postoperative neurological deficits are one of the risks associated with cardio vascular surgery, necessitating development of new techniques for cerebral monitoring. In this study an experimental observation regarding the dynamics of transcephalic Electrical Bioimpedance (EBI) in patients undergoing cardiac surgery with and without extracorporeal circulation (ECC) was conducted to investigate the potential use of electrical Bioimpedance for cerebral monitoring in cardio vascular surgery. Tetrapolar transcephalic EBI measurements at single frequency of 50 kHz were recorded prior to and during cardio vascular surgery. The obtained results show that the transcephalic impedance decreases in both groups of patients as operation starts, however slight differences in these two groups were also observed with the cerebral impedance reduction in patients having no ECC being less common and not as pronounced as in the ECC group. Changes in the cerebral impedance were in agreement with changes of haematocrit and temperature. The origin of EBI changes is still unexplained however these results encourage us to continue investigating the application of electrical bioimpedance cerebral monitoring clinically.

  • 230.
    Atefi, Seyed Reza
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Seoane, Fernando
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Thorlin, Thorleif
    Lindecrantz, Kaj
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Stroke Damage Detection Using Classification Trees on Electrical Bioimpedance Cerebral Spectroscopy Measurements2013Inngår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 13, nr 8, s. 10074-10086Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    After cancer and cardio-vascular disease, stroke is the third greatest cause of death worldwide. Given the limitations of the current imaging technologies used for stroke diagnosis, the need for portable non-invasive and less expensive diagnostic tools is crucial. Previous studies have suggested that electrical bioimpedance (EBI) measurements from the head might contain useful clinical information related to changes produced in the cerebral tissue after the onset of stroke. In this study, we recorded 720 EBI Spectroscopy (EBIS) measurements from two different head regions of 18 hemispheres of nine subjects. Three of these subjects had suffered a unilateral haemorrhagic stroke. A number of features based on structural and intrinsic frequency-dependent properties of the cerebral tissue were extracted. These features were then fed into a classification tree. The results show that a full classification of damaged and undamaged cerebral tissue was achieved after three hierarchical classification steps. Lastly, the performance of the classification tree was assessed using Leave-One-Out Cross Validation (LOO-CV). Despite the fact that the results of this study are limited to a small database, and the observations obtained must be verified further with a larger cohort of patients, these findings confirm that EBI measurements contain useful information for assessing on the health of brain tissue after stroke and supports the hypothesis that classification features based on Cole parameters, spectral information and the geometry of EBIS measurements are useful to differentiate between healthy and stroke damaged brain tissue.

  • 231.
    Atefi, Seyed Reza
    et al.
    Harvard University.
    Seoane, Fernando
    Högskolan i Borås, Akademin för vård, arbetsliv och välfärd. KTH-School of Technology and Health.
    Thorlin, Thorleif
    salhgrenska Hospital.
    Lindecrantz, Kaj
    KTH-School of Technology and Health.
    Stroke Damage Detection Using Classification Trees on Electrical Bioimpedance Cerebral Spectroscopy Measurements2013Inngår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 13, nr 8, s. 10074-10086Artikkel i tidsskrift (Fagfellevurdert)
  • 232.
    Athanasiou, Vasileios
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet.
    Estimation and modelling of fMRI BOLD response2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    One of the current topics of research in neuroimaging techniques is related to explaining and modelling the Blood Oxygen Level Dependent (BOLD) responses. BOLD responses are estimated by processing functional Magnetic Resonance Imaging (fMRI) data. BOLD responses are caused by hemodynamic responses to neural activity which alter the levels of blood oxygenation at local brain regions. The main aims of the current thesis were to i) develop and examine methods regarding BOLD response estimation from the visual cortex and the frontal cortex of human brain and to ii) develop a model in order to explain the physiological mechanisms which cause the estimated BOLD responses.

    In order to satisfy the main aims, fMRI data were provided by the Center of Medical Imaging and Visualization (CMIV). The provided fMRI data consist of fMRI brain measurements of twelve healthy human subjects who were subjected to visual stimulation. By processing the fMRI data, Regions Of Interest (ROIs) were extracted at the anatomical sites of the visual cortex and the frontal cortex. Afterwards, the fMRI data were manipulated in order to extract BOLD responses from the visual cortex and the frontal cortex. Various methods were developed and compared in terms of which technique provided well representative BOLD responses.       

    Subsequently, a model was developed by using software Wolfram Mathematica 9 in order to explain the physiological mechanisms of the estimated BOLD responses at the visual and the frontal cortex. The model aimed to solve for oxygen concentration in blood plasma as blood flows from the arterial part to the venous part of the blood circulation system through a capillary. Oxygen outward diffusion through the capillary wall and oxygen concentration at the extravascular environment were modelled as well. Blood plasma oxygen concentration was turned into hemoglobin oxygen saturation (Sa ) through hemoglobin oxygen dissociation curve and Henry’s law for gases. As a result, the Sa  was estimated through modelling for oxygen concentration in blood plasma. Finally, the developed model ended to a system with input the fractional change of Cerebral Blood Flow (CBF) velocity and Cerebral Metabolic Rate of Oxygen (CMR ) and as output a proportional signal to the BOLD response. By simulating for different scenarios of fractional changes of CBF velocity and CMR  and by comparing the resulted BOLD responses to the estimated ones, it was attempted to explain for the physiological mechanisms which caused the BOLD responses at the anatomical sites of the visual and frontal cortex.

  • 233.
    Auer, Martin
    et al.
    Develoment, Vascops GmbH, Graz, Austria.
    Gasser, Thomas Christian
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Biomekanik.
    Portugaller, R.
    Automatic Displacement and Strain measuring in the Aorta from dynamic electrocardiographically-gated Computed Tomographic Angiography2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Introduction

    Image modalities like Duplex Ultrasound, Transesophageal Echocardiography, Intravascular Ultrasound, Computed Tomography and Magnetic Resonance provide vascular interventionists and surgeons with useful diagnostic information for treatment planning. Recent developments in cross-sectional imaging, including multi-modality image fusion and new contrast agents have resulted in improved spatial resolution. Specifically, dynamic Electrocardiographically-Gated Computed Tomographic Angiography (ECG-gated CTA) provides valuable information regarding motion and deformation of the normal and diseased aorta during the cardiac cycle. Extracting and presenting (visualization) of accurate quantitative information from the recorded image data, however remains a challenging task of image post processing.

    Method

    The algorithm proposed within this paper processes ECG-gated CTA data (here goes the scanner model and manufacturer) in DICOM (digital imaging and communication in medicine) format, within which the user manually defines an Eulerian Region of Interest (ROI). 2D deformable (active) contour models are used to pre-segment the luminal surfaces of the selected vessels at an arbitrary time point during the cardiac cycle. A tessellation algorithm is used to define the initial configuration of a 3D deformable (active) contour model, which in turn is used for the final segmentation of the luminal surfaces continuously during the cardiac cycle. Specifically, Finite Element (FE) formulations [1] for frames and shells, as known from structural mechanics, are used to define the deformable contour modes. This allows a direct mechanical interpretation of the applied set of reconstruction parameters and leads to an efficient FE implementation of the models [2]; parallel processor architecture is used to solve the global set of non-linear FE equations. Finally displacement and strain measures are derived from the dynamic segmentations and color coded plots are used to visualize them.

    Results and Conclusions

    The clinical relevance of dynamic imaging has not been fully exploited and accurate and fast image processing tools are critical to extract valuable information from ECG-gated CTA data. Such information is not only of direct clinical relevance but also critical to process our current understanding regarding normal and pathological aortic motions and deformations. The image processing concept proposed in this paper leads to efficient and clinically applicable software that facilitates an analysis of the entire aorta on a standard Personal Computer within a few minutes. Deformable (active) contour models are known to be more accurate compared to threshold based segmentation concepts [3] and the accuracy of the present approach is in the range of the in-plane image resolution. Apart from direct diagnostic information the extracted geometrical data could also be used (once enriched by accurate pressure measurements) for none invasive (minimal invasive) estimation of biomechanical aortic tissue properties.

    References

    [1] O. C. Zienkiewicz and R. L. Taylor, vol.1,2, 5th ed. Oxford: Butterworth Heinemann, 2000.

    [2] M. Auer and T. C. Gasser,

    IEEE T. Med. Imaging, 2010 (in press).

    [3] M. Sonka and J. M. Fitzpatrick, editors.,

    Bellingham: Spie press, 2000

  • 234.
    Augustine, Robin
    Uppsala University.
    A Non-invasive Skin Burn Degree Analysis Using Microwaves2015Konferansepaper (Annet vitenskapelig)
  • 235.
    Augustine, Robin
    Uppsala University.
    A Preliminary Study on Skin Burn Degree Analysis Based on Coupling Effect between Burn Area and Micro Strip Ring Resonator2016Konferansepaper (Fagfellevurdert)
  • 236.
    Augustine, Robin
    Uppsala University.
    Application of UWB Radar Techniques for Imaging cranial vaults2015Konferansepaper (Annet vitenskapelig)
  • 237. Augustine, Robin
    Arrowroot (Maranta arundinacea) is an edible starch, commercially available as powder, prepared from the roots of the plant family Marantaceae. Arrowroot is well known for its medicinal effects and use as chief ingredient in infant cookies. Arrowroot in film form is prepared and its microwave absorption characteristics, permittivity, loss factor, conductivity, skin depth, and heating coefficient are analyzed. The results are quite promising and can be concluded that arrowroot in film form is a potential candidate for several applications in medical field, when compared with well studied chitosan film2009Inngår i: Microwave and Optical Technology Letters, Vol. 51, nr 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Arrowroot (Maranta arundinacea) is an edible starch, commercially available as powder, prepared from the roots of the plant family Marantaceae. Arrowroot is well known for its medicinal effects and use as chief ingredient in infant cookies. Arrowroot in film form is prepared and its microwave absorption characteristics, permittivity, loss factor, conductivity, skin depth, and heating coefficient are analyzed. The results are quite promising and can be concluded that arrowroot in film form is a potential candidate for several applications in medical field, when compared with well studied chitosan film

  • 238. Augustine, Robin
    Biocompatibility study of beta tricalcium phosphate bioceramics and chitosan biopolymer and their use as phantoms for medical imaging applications2009Inngår i: Microwave and Optical Technology Letters, Vol. 51, nr 12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Beta tricalcium phosphate (b-TCP) bioceramics and chitosan biopolymers are used as biomedical implants because of their better biocompatibility and good bioresorption characteristics. As they are biomaterials, they have good interactions with microwave frequencies. b-TCP and chitosan powder, films, pellets, and gel are prepared and studied at the S-band microwave frequencies. Dielectric parameters such as dielectric constant, dielectric loss, conductivity, and S-parameters are evaluated. Dielectric parameters of different forms of b-TCP and chitosan show resemblance with that of human tissues. Hence, these materials can also be considered as potential phantoms for specific absorption rate measurements as well as in microwave imaging applications. V

  • 239. Augustine, Robin
    Biocompatibility study of hydroxyapatite-chitosan composite for medical applications at microwave frequencies2008Inngår i: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 50, nr 11, s. 2931-2934Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) bioceramic and chitosan (poly [(β-1-4) d-glucosamine]) biopolymer show good biocompatibility in vivo. They have biological origin and show excellent interactions with microwave. Microwave study of HAp made using different drying techniques and their composites with chitosan in the ISM band is presented. Pastes are made using HAp and chitosan with different ratios of mixing. The dielectric properties of this composites match with that of human fat, collagen tissues. Some of the compositions exhibit dielectric property close to that of natural bone. This makes them more biocompatible and better substitutes for natural bone. Thus composite bioceramics can be considered as phantom model constituents for imaging purposes.

  • 240. Augustine, Robin
    Chitosan Biopolymer for Microwave Tomography Applications2008Konferansepaper (Fagfellevurdert)
  • 241. Augustine, Robin
    Complex dielectric permittivity measurements of human skin and biological solution in2-67GHz range2012Konferansepaper (Fagfellevurdert)
  • 242.
    Augustine, Robin
    Uppsala University.
    COmplex Fracture Orthopedic RehabiliTation – COMFORT2016Konferansepaper (Fagfellevurdert)
  • 243.
    Augustine, Robin
    Uppsala University.
    Experimental procedure for determination of the dielectric properties of biological samples in the 2-50 GHz range2014Inngår i: IEEE Journal of Translational Engineering in Health and Medicine, E-ISSN 2168-2372Artikkel i tidsskrift (Fagfellevurdert)
  • 244. Augustine, Robin
    Human skin permittivity models for the millimeter-wave range2011Inngår i: IET Electronics Letters, Vol. 47, s. 427-428Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The complex permittivity of the human skin has been measured in vivo in the 10 –60 GHz range using a recently developed coaxial slim probe. The results are compared with the literature data at millimetre waves, and a broad-band Cole-Cole model is proposed for several locations on the arm, namely at the palm, wrist, and forearm. This reported study provides relevant data required for studying interactions between emerging body-centric wireless millimetre-wave technologies and the human body

  • 245.
    Augustine, Robin
    Uppsala University.
    Microwave antenna for analysis of mineralization in cranial vaults2015Konferansepaper (Annet vitenskapelig)
  • 246.
    Augustine, Robin
    Uppsala University.
    Microwave head phantoms for post-craniotomy and BMP based implant2015Konferansepaper (Annet vitenskapelig)
  • 247.
    Augustine, Robin
    Uppsala University.
    Microwave studies on Beta Tricalcium Phosphate Bioceramics for medical application2006Konferansepaper (Fagfellevurdert)
  • 248.
    Augustine, Robin
    Uppsala University.
    Monitoring weight bearing in an ambulant setting: the SensiStep2016Konferansepaper (Fagfellevurdert)
  • 249. Augustine, Robin
    Near-field dosimetry for the millimeter-wave exposure of human cells in vitro2012Inngår i: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, s. 55-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Due to the expected mass deployment of millimeter-wave wireless technologies, thresholds of potential millimeter-wave-induced biological and health effects should be carefully assessed. The main purpose of this study is to propose, optimize, and characterize a near-field exposure configuration allowing illumination of cells in vitro at 60 GHz with power densities up to several tens of mW/cm(2) . Positioning of a tissue culture plate containing cells has been optimized in the near-field of a standard horn antenna operating at 60 GHz. The optimal position corresponds to the maximal mean-to-peak specific absorption rate (SAR) ratio over the cell monolayer, allowing the achievement of power densities up to 50 mW/cm(2) at least. Three complementary parameters have been determined and analyzed for the exposed cells, namely the power density, SAR, and temperature dynamics. The incident power density and SAR have been computed using the finite-difference time-domain (FDTD) method. The temperature dynamics at different locations inside the culture medium are measured and analyzed for various power densities. Local SAR, determined based on the initial rate of temperature rise, is in a good agreement with the computed SAR (maximal difference of 5%). For the optimized exposure setup configuration, 73% of cells are located within the ±3 dB region with respect to the average SAR. It is shown that under the considered exposure conditions, the maximal power density, local SAR, and temperature increments equal 57 mW/cm(2) , 1.4 kW/kg, and 6 °C, respectively, for the radiated power of 425 mW.

  • 250.
    Augustine, Robin
    Uppsala University.
    Phantom models for human hip and thigh2016Konferansepaper (Fagfellevurdert)
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