Change search
Refine search result
12 1 - 50 of 70
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Ayllon, David
    et al.
    Department of Signal Theory and Communications.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Gil-Pita, Roberto
    Department of Signal Theory and Communications.
    Cole equation and parameter estimation from electrical bioimpedance spectroscopy measurements: A comparative study2009In: EMBC: 2009 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-20, Buenos Aires: IEEE Engineering in Medicine and Biology , 2009, 3779-3782 p.Conference paper (Refereed)
    Abstract [en]

    Since there are several applications of Electrical Bioimpedance (EBI) that use the Cole parameters as base of the analysis, to fit EBI measured data onto the Cole equation is a very common practice within Multifrequency-EBI and spectroscopy. The aim of this paper is to compare different fitting methods for EBI data in order to evaluate their suitability to fit the Cole equation and estimate the Cole parameters. Three of the studied fittings are based on the use of Non-Linear Least Squares on the Cole model, one using the real part only, a second using the imaginary part and the third using the complex impedance. Furthermore, a novel fitting method done on the impedance plane, without using any frequency information has been implemented and included in the comparison. Results show that the four methods perform relatively well but the best fitting in terms of standard error of estimate is the fitting obtained from the resistance only. The results support the possibility of measuring only the resistive part of the bioimpedance to accurately fit Cole equation and estimate the Cole parameters, with entailed advantages.

  • 2.
    Bjällmark, Anna
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, Jacek
    Lind, Britta
    KTH, School of Technology and Health (STH), Medical Engineering.
    Hayashi, Shirley
    Mazza do Nascimento, Marcelo
    Riella, Miquel
    Seeberger, Astrid
    Effects of hemodialysis on the cardiovascular system: Quantitative analysis using wave intensity wall analysis and tissue velocity imaging2010In: Heart and Vessels, ISSN 0910-8327, E-ISSN 1615-2573Article in journal (Refereed)
    Abstract [en]

    Cardiovascular disease is the leading cause of death in patients with end stage renal disease (ESRD). The aim of this study was to investigate the changes in cardiovascular function induced by a single session of hemodialysis (HD) by the analysis of cardiovascular dynamics using wave intensity wall analysis (WIWA) and of systolic and diastolic myocardial function using tissue velocity imaging (TVI). Grey-scale cine loops of the left common carotid artery, conventional echocardiography and TVI images of the left ventricle were acquired before and after HD in 45 patients (17 women, mean age 54) with ESRD. The WIWA indexes, W1 preload-adjusted W1, W2 and preload-adjusted W2, and the TVI variables, isovolumic contraction velocity (IVCV), isovolumic contraction time (IVCT), peak systolic velocity (PSV), displacement, isovolumic relaxation velocity (IVRV), isovolumic relaxation time (IVRT), peak early diastolic velocity (E’) and peak late diastolic velocity (A’), were compared before and after HD. The WIWA measurements showed significant increases in W1 (p < 0.05) and preload-adjusted W1 (p < 0.01) after HD. W2 was significantly decreased (p < 0.05) after HD, whereas the change in preload-adjusted W2 was not significant. Systolic velocities, IVCV (p < 0.001) and PSV (p < 0.01), were increased after HD, whereas the AV-plane displacement were decreased (p < 0.01). For the measured diastolic variables, E’ was significantly decreased (p < 0.01) and IVRT was significantly prolonged (p < 0.05), after HD. A few correlations were found between WIWA and TVI variables. The WIWA and TVI measurements indicate that a single session of HD improves systolic function. The load dependency of the diastolic variables seems to be more pronounced than for the systolic variables. Preload-adjusted wave intensity indexes may contribute in the assessment of true LV contractility and relaxation.

  • 3.
    Bjällmark, Anna
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Shahgaldi, Kambiz
    Lind, Britta
    KTH, School of Technology and Health (STH).
    Winter, Reidar
    Brodin, Lars-Ake
    KTH, School of Technology and Health (STH), Medical Engineering.
    Differences in myocardial velocities during supine and upright exercise stress echocardiography in healthy adults2009In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 29, no 3, 216-223 p.Article in journal (Refereed)
    Abstract [en]

    Tissue Velocity Imaging (TVI) is a method for quantitative analysis of longitudinal myocardial velocities, which can be used during exercise and pharmacological stress echocardiography. It is of interest to evaluate cardiac response to different types of stress tests and the differences between upright and supine bicycle exercise tests have not been fully investigated. Therefore, the aim of this study was to compare cardiac response during supine and upright exercise stress tests. Twenty young healthy individuals underwent supine and upright stress test. The initial workload was set to 30 W and was increased every minute by a further 30 W until physical exhaustion. Tissue Doppler data from the left ventricle were acquired at the end of every workload level using a GE Vivid7 Dimension system (> 200 frames s(-1)). In the off-line processing, isovolumic contraction velocity (IVCV), peak systolic velocity (PSV), isovolumic relaxation velocity (IVRV), peak early diastolic velocity (E') and peak late diastolic velocity (A') were identified at every workload level. No significant difference between the tests was found in PSV. On the contrary, E' was shown to be significantly higher (P < 0.001) during supine exercise than during upright exercise and IVRV was significantly lower (P < 0.001) during supine exercise compared to upright exercise. Upright and supine exercise stress echocardiography give a comparable increase in measured systolic velocities and significant differences in early diastolic velocities.

  • 4.
    Bjällmark, Anna
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Lind, Britta
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Peolsson, Michael
    KTH, School of Technology and Health (STH).
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, Jacek
    Ultrasonographic strain imaging is superior to conventional non-invasive measures of vascular stiffness in the detection of age-dependent differences in the mechanical properties of the common carotid artery2010In: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 11, no 7, 630-636 p.Article in journal (Refereed)
    Abstract [en]

    Aims: Elastic properties of large arteries have been shown to deteriorate with age and in the presence of atherosclerotic vascular disease. In this study, the performance of ultrasonographic strain measurements was compared to conventional measures of vascular stiffness in the detection of age-dependent differences in the elastic properties of the common carotid artery.

    Methods and results: In 10 younger (25-28 years, 4 women) and 10 older (50-59 years, 4 women) healthy individuals, global and regional circumferential and radial strain variables were measured in the short-axis view of the right common carotid artery using ultrasonographic two-dimensional (2D) strain imaging with recently introduced speckle tracking technique. Conventional elasticity variables, elastic modulus (Ep) and β stiffness index, were calculated using M-mode sonography and non-invasive blood pressure measurements. Global and regional circumferential systolic strain and strain rate values were significantly higher (p < 0.001, p < 0.01 for regional late systolic strain rate) in the younger individuals, whereas the values of conventional elasticity variables in the same group were lower (p < 0.05). Among all strain and conventional elasticity variables, principal component analysis and its regression extension identified only circumferential systolic strain variables as contributing significantly to the observed discrimination between the younger and older age groups.

    Conclusion: Ultrasonographic 2D-strain imaging is a sensitive method for the assessment of elastic properties in the common carotid artery, being in this respect superior to conventional measures of vascular elasticity. The method has potential to become a valuable non-invasive tool in the detection of early atherosclerotic vascular changes.

  • 5. Borsbo, Bjorn
    et al.
    Gerdle, Bjorn
    Peolsson, Michael
    KTH, School of Technology and Health (STH).
    Impact of the interaction between self-efficacy, symptoms and catastrophising on disability, quality of life and health in with chronic pain patients2010In: Disability and Rehabilitation, ISSN 0963-8288, E-ISSN 1464-5165, Vol. 32, no 17, 1387-1396 p.Article in journal (Refereed)
    Abstract [en]

    Purpose. To investigate the interactions between self-efficacy - including subcomponents - and symptoms (pain, depression and anxiety), catastrophising, disability, quality of life and health in a population of patients with chronic pain. Method. The study used 433 patients with chronic pain including 47 patients with spinal cord injury-related pain, 150 patients with chronic whiplash-associated disorders and 236 patients with fibromyalgia. The participants answered a postal questionnaire that provided background data, pain intensity and duration and psychological- and health-related variables. Results. In the multivariate context, depression, anxiety, catastrophising and disability were intercorrelated. Self-efficacy correlated positively with variables of quality of life and general health. These two groups of variables were negatively correlated. The pain variables - duration of pain, pain intensity and spreading of pain - formed a third group of variables. Self-efficacy function was negatively correlated to these three pain variables. When regressing disability, quality of life and health, we found that self-efficacy had a positive impact whereas symptoms, catastrophising and pain had a negative influence on these aspects. Different patterns of influencing variables were discerned for the three different analyses, and specific patterns of the subscales of self-efficacy corresponded to specific patterns of negative factors for the outcome of disability, quality of life and health. Conclusion. There is a complex interaction of psychological factors and symptoms and their positive and negative influence on disability, quality of life and health. The results indicate that it might be important to assess and influence both enhancing and detoriating factors to ensure an effective pain management programme.

  • 6.
    Buendia, Ruben
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Gil-Pita, Roberto
    Department of Theory of the Signal and Communications.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Cole Parameter Estimation from the Modulus of the Electrical Bioimpeadance for Assessment of Body Composition: A Full Spectroscopy Approach2011In: Journal of Electrical Bioimpedance, ISSN 1891-5469, E-ISSN 1891-5469, Vol. 2, 72-78 p.Article in journal (Refereed)
    Abstract [en]

    Activities around applications of Electrical Bioimpedance Spectroscopy (EBIS) have proliferated in the past decade significantly. Most of these activities have been focused in the analysis of the EBIS measurements, which eventually might enable novel applications. In Body Composition Assessment (BCA) the most common analysis approach currently used in EBIS is based on the Cole function, which most often requires curve fitting. One of the most implemented approaches for obtaining the Cole parameters is performed in the impedance plane through the geometrical properties that the Cole function exhibit in such domain as depressed semi-circle. To fit the measured impedance data to a semi-circle in the impedance plane, obtaining the Cole parameters in an indirect and sequential manner has several drawbacks. Applying a Non-Linear Least Square (NLLS) iterative fitting on the spectroscopy measurement, obtains the Cole parameters considering the frequency information contained in the measurement. In this work, from experimental total right side EBIS measurements, the BCA parameters have been obtained to assess the amount and distribution of whole body fluids. The values for the BCA parameters have been obtained using values for the Cole parameters estimated with both approaches: circular fitting on the impedance plane and NLLS impedance-only fitting. The comparison of the values obtained for the BCA parameters with both methods confirms that the NLLS impedance-only is an effective alternative as Cole parameter estimation method in BCA from EBIS measurements. Using the modulus of the Cole function as the model for the fitting would eliminate the need for performing a phase detection in the acquisition process, simplifying the hardware specifications of the measurement instrumentation when implementing a bioimpedance spectrometer.

  • 7.
    Buendia, Ruben
    et al.
    School of Engineering, University of Borås.
    Gil-Pita, Roberto
    Department of Theory of the Signal and Communications, University of Alcala, Madrid, Spain.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Cole parameter estimation from total right side electrical bioimpedance spectroscopy measurements: Influence of the number of frequencies and the upper limit2011In: 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), 2011, 1843-1846 p.Conference paper (Refereed)
    Abstract [en]

    Applications based on measurements of Electrical Bioimpedance Spectroscopy (EBIS) analysis are proliferating. The most spread and known application of EBIS is the non-invasive assessment of body composition. Fitting to the Cole function to obtain the Cole parameters, R<sub>0</sub> and R<sub>&#x221E;</sub>, is the core of the EBIS analysis to obtain the body fluid distribution. An accurate estimation of the Cole parameters is essential for the Body Composition Assessment (BCA) and the estimation process depends on several factors. One of them is the upper frequency limit used for the estimation and the other is the number of measured frequencies in the measurement frequency range. Both of them impose requirements on the measurement hardware, influencing largely in the complexity of the bioimpedance spectrometer. In this work an analysis of the error obtained when estimating the Cole parameters with several frequency ranges and different number of frequencies has been performed. The study has been done on synthetic EBIS data obtained from experimental Total Right Side (TRS) measurements. The results suggest that accurate estimations of R<sub>0</sub> and R<sub>&#x221E;</sub> for BCA measurements can be achieved using much narrower frequency ranges and quite fewer frequencies than electrical bioimpedance spectrometers commercially available nowadays do.

  • 8.
    Buendia, Ruben
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Gil-Pita, Roberto
    Department of Theory of the Signal and Communications, University of Alcala, Madrid, Spain.
    Experimental validation of a method for removing the capacitive leakage artifact from electrical bioimpedance spectroscopy measurements2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 11Article in journal (Refereed)
    Abstract [en]

    Often when performing electrical bioimpedance (EBI) spectroscopy measurements, the obtained EBI data present a hook-like deviation, which is most noticeable at high frequencies in the impedance plane. The deviation is due to a capacitive leakage effect caused by the presence of stray capacitances. In addition to the data deviation being remarkably noticeable at high frequencies in the phase and the reactance spectra, the measured EBI is also altered in the resistance and the modulus. If this EBI data deviation is not properly removed, it interferes with subsequent data analysis processes, especially with Cole model-based analyses. In other words, to perform any accurate analysis of the EBI spectroscopy data, the hook deviation must be properly removed. Td compensation is a method used to compensate the hook deviation present in EBI data; it consists of multiplying the obtained spectrum, Z meas (ω), by a complex exponential in the form of exp(–jωTd). Although the method is well known and accepted, Td compensation cannot entirely correct the hook-like deviation; moreover, it lacks solid scientific grounds. In this work, the Td compensation method is revisited, and it is shown that it should not be used to correct the effect of a capacitive leakage; furthermore, a more developed approach for correcting the hook deviation caused by the capacitive leakage is proposed. The method includes a novel correcting expression and a process for selecting the proper values of expressions that are complex and frequency dependent. The correctness of the novel method is validated with the experimental data obtained from measurements from three different EBI applications. The obtained results confirm the sufficiency and feasibility of the correcting method.

  • 9.
    Buendia, Ruben
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Harris, Matthew
    Phillips Research.
    Caffarel, Jeniffer
    Phillips Research.
    Gil-Pita, Roberto
    Department of Theory of the Signal and Communications, University of Alcala, Madrid, Spain.
    Hook Effect correction & resistance-based Cole fitting prior Cole model-based analysis: Experimental validation2010In: Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2010, IEEE Engineering in Medicine and Biology , 2010, 6563-6566 p.Conference paper (Refereed)
    Abstract [en]

    The analysis of measurements of Electrical Bioimpedance (EBI) is on the increase for performing non-invasive assessment of health status and monitoring of pathophysiological mechanisms. EBI measurements might contain measurements artefacts that must be carefully removed prior to any further analysis. Cole model-based analysis is often selected when analysing EBI data and might lead to miss-conclusion if it is applied on data contaminated with measurement artefacts. The recently proposed Correction Function to eliminate the influence of the Hook Effect from EBI data and the fitting to the real part of the Cole model to extract the Cole parameters have been validated on experimental measurements. The obtained results confirm the feasible experimental use of these promising pre-processing tools that might improve the outcome of EBI applications using Cole model-based analysis.

  • 10.
    Buendia, Ruben
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701). University of Alcala, Spain; Chalmers University of Technology, Sweden; University of Boras, Sweden.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701). University of Boras, Sweden.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701). University of Boras, Sweden; Karolinska Instituet, Sweden.
    Bosacus, I.
    University of Gothenburg.
    Gil-Pita, Roberto
    Department of Theory of the Signal and Communications, University of Alcala, Madrid, Spain.
    Johannsson, G.
    Ellegård, L.
    Ward, L.
    Estimation of body fluids with bioimpedance spectroscopy: state of the art methods and proposal of novel methods2015In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 36, no 10Article in journal (Refereed)
    Abstract [en]

    Determination of body fluids is a useful common practice in determination of disease mechanisms and treatments. Bioimpedance spectroscopy (BIS) methods are non-invasive, inexpensive and rapid alternatives to reference methods such as tracer dilution. However, they are indirect and their robustness and validity are unclear. In this article, state of the art methods are reviewed, their drawbacks identified and new methods are proposed. All methods were tested on a clinical database of patients receiving growth hormone replacement therapy. Results indicated that most BIS methods are similarly accurate (e.g. < 0.5 +/- 3.0% mean percentage difference for total body water) for estimation of body fluids. A new model for calculation is proposed that performs equally well for all fluid compartments (total body water, extra-and intracellular water). It is suggested that the main source of error in extracellular water estimation is due to anisotropy, in total body water estimation to the uncertainty associated with intracellular resistivity and in determination of intracellular water a combination of both.

  • 11. Capece, Sabrina
    et al.
    Chiessi, Ester
    Cavalli, Roberta
    Giustetto, Pierangela
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Paradossi, Gaio
    A general strategy for obtaining biodegradable polymer shelled microbubbles as theranostic devices2013In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, no 51, 5763-5765 p.Article in journal (Refereed)
    Abstract [en]

    Fabrication of multifunctional ultrasound contrast agents (UCAs) has been recently addressed by several research groups. A versatile strategy for the synthesis of UCA precursors in the form of biodegradable vesicles with a biocompatible crosslinked polymer shell is described. Upon ultrasound irradiation, acoustic droplet vaporization transforms such particles into microbubbles behaving as UCAs. This proof of concept entails the features of a potential theranostic microdevice.

  • 12.
    Eriksson, Martin
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Halvorsen, Kjartan A.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Gullstrand, Lennart
    Immediate effect of visual and auditory feedback to control the running mechanics of well-trained athletes2011In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 29, no 3, 253-262 p.Article in journal (Refereed)
    Abstract [en]

    The correlation between mechanical factors of running and running economy as measured by metabolic cost is a subject of much interest in the study of locomotion. However, no change in running technique has been shown to result in an immediate improvement in running economy on an intra-individual basis. To evaluate the effect of a modified running technique, it is probably necessary that the individual trains with the new technique for a longer period using a feedback system to control the new kinematics. In this study, we examine the feasibility of using visual and auditory feedback to adapt running technique according to a simplistic model of the mechanical cost of running. The model considers only the mechanical work against gravity, which is the product of the magnitude of the vertical displacement of the runner's centre of mass and the step-frequency. In the experiments reported here, 18 trained runners, running at 16km center dot h-1 on a treadmill, were given feedback on these parameters together with indicated target levels. In almost all cases, the runners were able to adjust their technique accordingly.

  • 13. Falkmer, Torbjern
    et al.
    Dahlman, Joakim
    Dukic, Tania
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Fixation identification in centroid versus start-point modes using eye-tracking data2008In: Perceptual and Motor Skills, ISSN 0031-5125, E-ISSN 1558-688X, Vol. 106, no 3, 710-724 p.Article in journal (Refereed)
    Abstract [en]

    Fixation-identification algorithms, needed for analyses of eye movements, may typically be separated into three categories, viz. (i) velocity-based algorithms, (ii) area-based algorithms, and (iii) dispersion-based algorithms. Dispersion-based algorithms are commonly used but this application introduces some difficulties, one being optimization. Basically, there are two modes to reach this goal of optimization, viz., the start-point mode and the centroid mode. The aim of the present study was to compare and evaluate these two dispersion-based algorithms. Manual inspections were made of 1,400 fixations in each mode. Odds ratios showed that by using the centroid mode for fixation detection, a valid fixation is 2.86 times more likely to be identified than by using the start-point mode. Moreover, the algorithm based on centroid mode dispersion showed a good interpretation speed, accuracy, robustness, and ease of implementation, as well as adequate parameter settings.

  • 14. Fröberg, Asa
    et al.
    Mårtensson, Mattias
    KTH, School of Technology and Health (STH), Medical Engineering.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Janerot-Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering.
    D'Hooge, Jan
    Arndt, Anton
    High variability in strain estimation errors when using a commercial ultrasound speckle tracking algorithm on tendon tissue2016In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 57, no 10, 1223-1229 p.Article in journal (Refereed)
    Abstract [en]

    Background: Ultrasound speckle tracking offers a non-invasive way of studying strain in the free Achilles tendon where no anatomical landmarks are available for tracking. This provides new possibilities for studying injury mechanisms during sport activity and the effects of shoes, orthotic devices, and rehabilitation protocols on tendon biomechanics. Purpose: To investigate the feasibility of using a commercial ultrasound speckle tracking algorithm for assessing strain in tendon tissue. Material and Methods: A polyvinyl alcohol (PVA) phantom, three porcine tendons, and a human Achilles tendon were mounted in a materials testing machine and loaded to 4% peak strain. Ultrasound long-axis cine-loops of the samples were recorded. Speckle tracking analysis of axial strain was performed using a commercial speckle tracking software. Estimated strain was then compared to reference strain known from the materials testing machine. Two frame rates and two region of interest (ROI) sizes were evaluated. Results: Best agreement between estimated strain and reference strain was found in the PVA phantom (absolute error in peak strain: 0.21 +/- 0.08%). The absolute error in peak strain varied between 0.72 +/- 0.65% and 10.64 +/- 3.40% in the different tendon samples. Strain determined with a frame rate of 39.4Hz had lower errors than 78.6Hz as was the case with a 22mm compared to an 11mm ROI. Conclusion: Errors in peak strain estimation showed high variability between tendon samples and were large in relation to strain levels previously described in the Achilles tendon.

  • 15.
    Govind, Satish C.
    et al.
    Bhagwan Mahavir Jain Heart Center, Bangalore, India.
    Roumina, S.
    Karolinska University Hospital at Huddinge, Stockholm, Sweden.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, J.
    Karolinska University Hospital at Huddinge, Stockholm, Sweden.
    Ramesh, S. S.
    Bhagwan Mahavir Jain Heart Center, Bangalore, India.
    Saha, S. K.
    Karolinska University Hospital at Huddinge, Stockholm, Sweden.
    Differing myocardial response to a single session of hemodialysis in end-stage renal disease with and without type 2 diabetes mellitus and coronary artery disease2006In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 4, no 9Article in journal (Refereed)
    Abstract [en]

    Background: Though hemodialysis (HD) acutely improves cardiac function, the impact of background diseases like coronary artery disease (CAD) and Type 2 diabetes (DM) in the setting of end-stage renal disease (ESRD) is not known. Tissue velocity echocardiography (TVE) offers a fast choice to follow changes in myocardial function after HD in ESRD with concomitant DM and/or CAD. Methods: 46 subjects (17 with ESRD, Group 1; 15 with DM, Group 2; 14 with DM+CAD, Group 3) underwent standard and TVE prior to and shortly after HD. Besides standard Doppler variables, regional myocardial systolic and diastolic velocities, as well as systolic strain rate were post processed. Results: Compared with pre-HD, post-HD body weight (kg) significantly decreased in all the three groups (51 ± 9 vs. 48 ± 8, 62 ± 10 vs.59 ± 10, and 61 ± 9 vs. 58 ± 9 respectively; all p < 0.01). Left ventricular end diastolic dimensions (mm) also decreased post- HD (46 ± 5 vs. 42 ± 7, 53 ± 7 vs. 50 ± 7, 51 ± 7 vs. 47 ± 8 respectively; all p < 0.01). Regional longitudinal peak systolic velocity in septum (cm/s) significantly increased post-HD in Group 1(5.7 ± 1.6 vs. 7.2 ± 2.3; p < 0.001) while remained unchanged in the other two groups. Similar trends were noted in other left ventricular walls. When the myocardial velocities (cm/s) were computed globally, the improvement was seen only in Group 1 (6.3 ± 1.5 vs. 7.9 ± 2.0; p < 0.001). Global early regional diastolic velocity (cm/s) improved in Group 1, remained unchanged in Group 2, while significantly decreased in Group 3(-5.9 ± 1.3 vs. -4.1 ± 1.8; p < 0.01). Global systolic strain rate (1/sec) increased in the first 2 Groups but remained unchanged (-0.87 ± 0.4 vs. -0.94 ± 0.3; p = ns) in Group 3. Conclusion: A single HD session improves LV function only in ESRD without coexistent DM and/or CAD. The present data suggest that not only dialysis-dependent changes in loading conditions but also co-existent background diseases determine the myocardial response to HD.

  • 16.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institutet (KI), CLINTEC – Division of Medical Imaging and Technology.
    Contrast agent for early diagnostics and monitoring of progression of liver cancer (hepatocellular carcinoma)2013Conference paper (Refereed)
  • 17.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering.
    Three modality contrast imaging using multi-functionalized microballoons2011Conference paper (Refereed)
    Abstract [en]

    In vivo multimodality imaging is a fast growing field in medical research and, although the achievements at clinical level of this diagnostic method are recent, it is already one of the most promising approaches in the diagnosis of diseases in many research addressed medical centres. At present in this area, the USA plays the protagonist role as a result of the amount of resources engaged in the arena in the last decade. Both government and private companies agree, when considering the potential of this approach, that it is one of the foremost medical advancements as it will lead to early diagnosis of diseases with high impact on the societies of western countries. Multimodality imaging is currently viewed as a simple and powerful integration of two or more imaging methods (e.g. PET-CT). 3MICRON is an ambitious project which gathers some of the most advanced European medical and technical institutions together to address the design of new strategies in diagnostics, and to push the potential of medical imaging beyond the state-of-the-art. The multimodality approaches are supported by a class of next-generation micro/nanodevices called microballoons. These subsystems are able to implement the function of an ultrasound contrast agent with other imaging methods (SPECT, MRI). In the future, they may act as a minimally invasive drug delivery method and hyperthermia device. In 3MICRON, this multi-functional device will be tested in vitro and in vivo in order to assess bioclearance and cytoxicity effects toward high impact diseases, e.g. cardiovascular and inflammation pathologies. Finally, selected types of microballoons will undergo pre-clinical screening for a consolidated assessment of the “bench-to-bed” pathway for these new microdevices.

  • 18.
    Grishenkov, Dmitry
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brismar, Torkel B.
    CLINTEC, Department of Radiology, Karolinska University Hospital.
    Paradossi, Gaio
    Dipartimento di Chimica, Università di Roma Tor Vergata.
    On comparison between polymer- and phospholipid-shelled microbubbles for contrast-enhanced ultrasound measurements of capillary microcirculation.2011In: Proceedings of the 34th Scandinavian Symposium on Physical Acoustics / [ed] Rolf J. Korneliussen, 2011Conference paper (Refereed)
    Abstract [en]

    The focus of contrast-enhanced ultrasound research has developed beyond visualizing the blood circulation to new areas such as perfusion and molecular imaging, drug and gene therapy. This work compares the application of polymer- and phospholipid-shelled ultrasound contrast agents (UCAs) employed for characterization of the capillary microcirculation. To quantify microcirculation destruction/replenishment technique with varied time intervals between destructive and monitoring pulses is used. The dependence of the peak-to-peak amplitude of backscattered wave versus pulse interval is fitted with an exponential function of the time y=A(1-exp(-βt)) , where A represents capillary volume and the time constant β represents velocity of the flow. Working under assumption that backscattered signal is linearly proportional to the microbubble concentration, for both types of the UCAs it is observed that capillary volume, A, is in linearly relationship with the concentration, and the flow velocity, β, remain unchanged. Using 500 µm diameter microtube as a vessel phantom a delay of about 0.25 s in evaluation of the perfusion characteristics is found for the phospholipid-shelled UCA, while polymer-shelled UCA provide response immediately. In conclusion, these results suggest that the novel polymer-shelled microbubbles have a potential to be used for perfusion evaluation.

  • 19.
    Grishenkov, Dmitry
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brismar, Torkel B.
    CLINTEC, Department of Radiology, Karolinska Institutet.
    Paradossi, Gaio
    Dipartimento di Chimica, THE UNIVERSITY OF ROME.
    In vitro contrast-enhanced ultrasound measurements of capillary microcirculation: Comparison between polymer- and phospholipid-shelled microbubbles2011In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 51, no 1, 40-48 p.Article in journal (Refereed)
    Abstract [en]

    The focus of contrast-enhanced ultrasound research has developed beyond visualizing the blood pool and its flow to new areas such as perfusion imaging, drug and gene therapy, and targeted imaging. In this work comparison between the application of polymer- and phospholipid-shelled ultrasound contrast agents (UCAs) for characterization of the capillary microcirculation is reported. All experiments are carried out using a microtube as a vessel phantom. The first set of experiments evaluates the optimal concentration level where backscattered signal from microbubbles depends on concentration linearly. For the polymer-shelled UCAs the optimal concentration level is reached at a value of about 2 x 10(4) MB/ml, whereas for the phospholipid-shelled UCAs the optimal level is found at about 1 x 10(5) MB/ml.

    Despite the fact that the polymer shell occupies 30% of the radius of microbubble, compared to 0.2% of the phospholipid-shelled bubble, approximately 5-fold lower concentration of the polymer UCA is needed for investigation compared to phospholipid-shelled analogues. In the second set of experiments, destruction/replenishment method with varied time intervals ranging from 2 ms to 3 s between destructive and monitoring pulses is employed. The dependence of the peak-to-peak amplitude of backscattered wave versus pulse interval is fitted with an exponential function of the time gamma = A( 1 - exp(-beta t)) where A represents capillary volume and the time constant beta represents velocity of the flow. Taking into account that backscattered signal is linearly proportional to the microbubble concentration, for both types of the UCAs it is observed that capillary volume is linearly proportional to the concentration of the microbubbles, but the estimation of the flow velocity is not affected by the change of the concentration. Using the single capillary model, for the phospholipid-shelled UCA a delay of about 0.2-0.3 s in evaluation of the perfusion characteristics is found while polymer-shelled UCA provide response immediately. The latter at the concentration lower than 3.6 x 10(5) MB/ml have no statistically significant delay (p < 0.01), do not cause any attenuation of the backscattered signal or saturation of the receiving part of the system. In conclusion, these results suggest that the novel polymer-shelled microbubbles have a potential to be used for perfusion evaluation.

  • 20.
    Grishenkov, Dmitry
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Kothapalli, Veeravenkata S.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Gonon, Adrian
    Karolinska University Hospital, Huddinge, Sweden .
    Janerot Sjöberg, Birgitta
    CLINTEC, Department of Medical Imaging and Technology, Karolinska Institute.
    Ultrasound contrast agent loaded with nitric oxide as a theranostic microdevise for myocardial ischemia2013In: European Heart Journal Cardiovascular Imaging: Abstracts of EUROECHO 2013 The Seventeenth Annual Meeting of the European Association of Echocardiography, 2013Conference paper (Refereed)
    Abstract [en]

    Cardiovascular disease (CVD) accounts for 1/3 of total global deaths worldwide. The most widespread CVD is ischemic heart disease. It is the leading cause of death in both genders, equally diagnosed in developed and developing countries with mortality exponentially increasing with age. Efforts of healthcare system should be primary focused on prevention, timely detection, efficient differentiation and instant treatment of the disease.

  • 21.
    Grishenkov, Dmitry
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    Assessment of ultrasound-induced fracture of polymer-shelled ultrasound contrast agents using superharmonic technique2012Conference paper (Refereed)
    Abstract [en]

    Ultrasound imaging techniques can be greatly improved by the use of ultrasound contrast agents. Knowledge of the peak negative pressure at which contrast agents fracture is paramount for the imaging application as well as for local drug delivery. Gasholdning microbubbles encapsulated into biocompatible poly vinyl alcohol shells are of particular interest for their enhanced shelf life and demonstratedchemical versatility. A gas core allows microbubbles to efficiently scatter ultrasound waves. In vitro ultrasound tests showed a sufficient enhancement of the backscattered power (25±1 dB), comparable to the soft tissue attenuation coefficients (0.8±0.04 dB/cm MHz) and phase velocities (1519±2 m/s). At temperature values between 24 and 37 °C the monotonic increase of the attenuation and phase velocity with frequency indicates that thick-shelled microbubbles do not resonate in a typical medical ultrasound frequency range of 1-15 MHz. In fact, they work as an amplifier of the incident acoustic wave. The novel approach based on detection of superharmonics (3f and 4f) is proposed for assessment of the fracture pressure threshold, Pthr. In vitro tests suggests that fatigue, i.e. accumulation of damage within the shell, is the major physical mechanism responsible for the fracturing process. It has been observed that there is a decrease of Pthr from 1.15±0.09 MPa to 0.9±0.05 MPa when the number of cycles in the pulse, N, increases from 6 to 12. It is worth noting that the reported pressure values are within clinically approved safety limits. The main conclusion to be drawn from our study is that superharmonic approach appears to be more sensitive in Pthr assessment than traditional second harmonic imaging. This claim is supported also by images acquired with a commercially available system, where contrast pulse sequencing technique, specific to third harmonic, is required for visualization of thick-shelled microbubbles.

  • 22. Gullstrand, Lennart
    et al.
    Halvorsen, Kjartan
    Tinmark, Fredrik
    Eriksson, Martin
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nilsson, Johnny
    Measurements of vertical displacement in running, a methodological comparison2009In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 30, no 1, 71-75 p.Article in journal (Refereed)
    Abstract [en]

    The aim was (1) to evaluate measurements of vertical displacements (V-disp) of a single point on sacrum as an estimate of the whole body centre of mass (CoM) V-disp during treadmill running and (2) to compare three methods for measuring this single point. These methods were based on a position transducer(PT), accelerometers (AMs) and an optoelectronic motion capture system. Criterion method was V-disp of the whole body CoM measured with the motion capture system. Thirteen subjects ran at 10, 12, 14, 16. 18, 20 and 22 km h(-1) with synchronous recordings with the three methods. Four measurements of the (V-disp) were derived: (1) V-disp of CoM calculated from a segment model consisting of 13 segments tracked with 36 reflective markets, (2) V-disp of the sacrum recorded with the PT, (3) V-disp of the sacrum Calculated from the AM, and (4) V-disp of the sacrum calculated as the mid point of two reflective markets (sacrum marker, SM) attached at the level of the sacral bone. The systematic discrepancy between the Measurements of sacrum V-disp and CoM V-disp varied between 0 and 1.5 mm and decreased with increasing running velocity and decreasing step duration. PT and SM measurements showed strong correlation, whereas the AM showed a variability increasing with velocity. The random discrepancy within each Subject was 7 mm for all three methods. In conclusion single-point recordings of the sacrum V-disp may be used to monitor changes in V-disp of CoM during treadmill running.

  • 23.
    Halvorsen, Kjartan
    KTH, School of Technology and Health (STH), Medical Engineering.
    Comments on "The equations of motion for a standing human reveal three mechanisms for balance" (A. Hof, Vol. 40, pp. 451-457)2010In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 43, no 16, 3244-3247 p.Article in journal (Refereed)
  • 24.
    Hamid Muhammed, Hamed
    et al.
    KTH, School of Technology and Health (STH), Health Systems Engineering.
    Moustafa, Ahmed M. Nasr
    KTH, School of Technology and Health (STH), Health Systems Engineering.
    Hassan, Moustapha
    Karolinska University Hospital Huddinge, Stockholm, SWEDEN.
    Skin Cancer Detection Using Temperature Variation Analysis2013In: Engineering, ISSN 1947-394X, Vol. 5, no 10BArticle in journal (Refereed)
    Abstract [en]

    In the medical field, new technologies are incorporated for the sole purpose of enhancing the quality of life for the patients and even for the normal healthy people. Infrared technology is one of the technologies that have some applications in both the medical and biological fields. In this work, the thermal infrared (IR) measurement is used to investigate the potential of skin cancer detection. IR enjoys non-invasive and non-contact advantages as well as favorable cost, apparently. It is also very well developed regarding the technological and methodological aspects. IR per se is an electro-metric radiation that all objects emit when their temperature is above the absolute zero. And the human body is not different in this regard. The IR range extends, ideally, to cover wavelengths from 800 nanometer to few hundred micrometer. Cancer, in modern life, has grown tangibly due to many factors, such as life expectancies increase, personal habits and ultraviolet radiation exposures among others. Moreover, the significant enhancement of technologies has helped identifying more types of cancers than before. The sole purpose of this work is to investigate further IR technology methods and applications not yet matured in skin cancer detection to enhance the detection ability with higher safety level.

  • 25.
    Hamid Muhammed, Hamed
    et al.
    KTH, School of Technology and Health (STH), Health Systems Engineering.
    Raghavendra, Jammalamadaka
    KTH, School of Technology and Health (STH), Health Systems Engineering, Systems Safety and Management.
    Optomyography (OMG): A Novel Technique for the Detection of Muscle Surface Displacement Using Photoelectric Sensors2015In: Measurements - Proceedings of the 10th International Conference on Bioelectromagnetism, International Society for Bioelectromagnetism, 2015, Vol. 10Conference paper (Refereed)
    Abstract [en]

    Several techniques have been introduced for detecting, measuring, processing and analyzing the signals generated during muscular activities. With the development of more advanced technical solutions, the measurement and analysis of these signals help not only to understand the medical abnormalities and characterization of muscle activities but also to develop human machine interfaces of higher efficiency. In this work, a novel technique to detect and measure the displacement caused on the surface of the skin due to muscle activities was introduced and developed using near-infrared photoelectric sensors. The new technique was coined as OptoMyoGraphy (OMG). In order to evaluate the new technique, real-time pairs of signals were registered using two photoelectric sensors measuring near-infrared rays reflected on the forearm while moving the hand to make a number of different gestures. Different pairs of signals, changing over time and showing repeated patterns while repeating the same hand gesture, were measured for different hand gesture. The signal to noise ratio (SNR) of these signals was good enough to be able to differentiate among the pairs of signals which correspond to different hand gestures using visual inspection.

  • 26. Henareh, Loghman
    et al.
    Jedefors, Camilla
    Jogestrand, Tomas
    Brodin, Lars Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Agewall, Stefan
    Intima-Media Thickness of Common Carotid and Brachial Arteries and Prothrombin Fragment 1+2 Are Associated with Left Ventricular Diastolic Dysfunction in Patients with Myocardial Infarction2010In: Echocardiography, ISSN 0742-2822, E-ISSN 1540-8175, Vol. 27, no 6, 651-658 p.Article in journal (Refereed)
    Abstract [en]

    Aims: To investigate the association between intima-media thickness of brachial and common carotid arteries and factors of the coagulation- and fibrinolysis-system with left ventricular diastolic dysfunction in patients with a previous myocardial infarction. Patients and methods: One hundred and twenty three patients, men (76%) and women (24%) aged between 32and 81 years with a history of previous acute myocardial infarction were included. B-mode ultrasound of common carotid and brachial arteries and echocardiography with tissue Doppler imaging (TDI) were evaluated. Factors of the coagulation- and fibrinolysis-system were also measured. Results: In patients with previous myocardial infarction, late diastolic filling time was significantly and positively associated with log Prothrombin fragment 1 + 2 (P < 0.001) and with calculated intima-media area (cIMa) of the both common carotid and brachial arteries (P < 0.05). Mitral early-to-late flow velocity ratio (E/A) was significantly and negatively associated with log Prothrombin fragment 1 + 2 (P < 0.001), total cholesterol and cIMa of the both common carotid and brachial arteries (P < 0.05). Moreover both late diastolic filling time and mitral E/A correlated significantly with age and systolic blood pressure. In stepwise multiple regression analysis, log Prothrombin fragment 1 + 2 remained the only variable with independent significant correlation to late diastolic filling time and mitral E/A. Conclusions: In a population sample of patients with myocardial infarction, late diastolic filling time and mitral E/A were associated with cIMa of common carotid and brachial arteries, systolic blood pressure, and prothrombin fragment 1 + 2, suggesting a relationship between diastolic dysfunction, thrombin generation and atherosclerosis. (Echocardiography 2010;27:651-658).

  • 27.
    Janerot Sjöberg, Birgitta
    et al.
    CLINTEC, Department of Medical Imaging and Technology, Karolinska Institute.
    Gonon, Adrian
    tutet (KI), Dept of Medicine.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institutet (KI), CLINTEC – Division of Medical Imaging and Technology.
    In Search of the Optimal Ultrasound Heart Perfusion Imaging Platform2013Conference paper (Refereed)
  • 28.
    Kothapalli, Veera Venkata Satya Naray
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering.
    Optimization of driving pulse envelopes in detection of harmonic response from lipid-shelled ultrasound contrast agent2012In: 19th International Congress on Sound and Vibration 2012, ICSV 2012: Volume 3, 2012, 2012, 1882-1889 p.Conference paper (Refereed)
    Abstract [en]

    The assessment of the harmonic response is commonly used in analysis of the signals from ultrasound contrast agents (UCAs). Theoretical and experimental studies report that acoustic behavior of UCAs strongly depends on insonation pressure. Other system parameters, such as the number of cycles, driving and repetition frequency and the pulse shape are equally important. The major focus of this work is to investigate the effect of the shape of driving pulse envelopes on detection of second- (2f), super- (3f, 4f, 5f), sub- (f/2), and ultra-harmonics (3f/2). In this paper, numerical simulations on thin-shelled lipidic UCA have been performed. The simulation results indicate that, high sidelobe suppression envelopes (e.g. 4-term Blackman-Harris), manage to detect second and third harmonic with harmonic-to-fundamental ratio (HFR) of 32 and 69 dB, respectively, at low acoustic pressure of 5 kPa. However, conventional low sidelobe suppression envelopes (e.g. rectangular, cos-tapered, Hanning, Gaussian) fail to identify the harmonic response. Yet the increase of the insonation pressure to 200 kPa leads to increase of the broadband noise. This negatively effects the frequency resolution when high suppression sidelobe envelopes are applied to the driving pulse. As a result, the application of conventional envelopes in harmonic response detection at intermediate acoustic pressure, is recommended. It is also worth mentioning, that at high isonation pressure of 0.9 MPa, cos-tapered envelope, having a side lobe fall-off equal to 18 dB/octave, is able to identify the sub- and ultra-harmonics. In conclusion our study demonstrates that the driving pulse envelope should be selected according to the incident pressure for the complete exploitation of the unique nonlinear signature from UCA. A compromise could be found with the application of adjustable Kaiser-Bessel envelope where by varying the β parameter from 0 to 10 one goes from low to high sidelobe suppression envelope.

  • 29.
    Kothapalli, Veera Venkata Satya Naray
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    Coded Excitation Technique in Detection of Polymeric-Shelled Ultrasound contrast Agents: in Vitro Study2011In: 8th International Conference on Nanosciences & Nanotechnologies (NN11) 12-15 July 2011, Thessaloniki, Greece.: Workshop: NANOMEDICINE, 2011Conference paper (Refereed)
    Abstract [en]

    A novel ultrasound contrast agent (UCA) based on air-filled polymer-shelled microbubbles, is prepared within 3MiCRON project for multimodality approach covering ultrasound, MRI and SPECT investigation. These bubbles have thick, about 30% of the radius, shell providing greater stability and longer half life in a pulmonary circulation compare to commercially available phospholipid UCAs. In addition, extensive storage capacity and possibility to incorporate drugs or pharmacological relevant materials are inherited to these bubbles. 

    Understanding the behavior of the UCA under ultrasound exposure is paramount to the proper and total exploitation of all unique features that these gas-filled microdevice offers. Even though, thickness of the polymeric shell is considerably higher than of commercial UCAs, the enhancement of backscattered power of about 25 dB produced from suspension insonified at low pressure (100 kPa) was observed. It should be noted that thick polymer shell could still be disrupted by high pressure (1 MPa) ultrasonic pulse. Nevertheless, diagnostic imaging typically utilizes the intermediate pressure level, where nonlinear oscillation of the microbubbles give rise to harmonic component in the received echo. It was observed that at pressure level of 400 kPa, Pulse Inversion (PI) technique fail to distinguish between the regions filled with polymer UCA and surrounding ultrasound phantom, mimicking liver tissue. 

    In this paper, a coded excitation technique is proposed to characterize the non-linear properties of the polymer-shelled microbubbles in vitro at intermediate pressure. For a decade ago, coded excitation technique has been adopted into the ultrasound scanners in order to increase the signal-to-noise ratio (SNR) and penetration depth, while matching filters compensates the decrease in axial resolution. In the proposed method, a time domain signal is modulated by a several window functions (e.g. Blackman-Harries, Hanning, Hamming, and Kaiser-Bessel) with or without linear chirp pulses constructed for experiments in vitro. 

    Our preliminary results suggest that coded excitation technique offers an increase of approximately 15dB in contrast-to-tissue ration (CTR) compared to the result achieved from a commercially available Pulse Inversion technique. 

    In conclusion, proposed polymer-shelled microbubbles provide a viable system to be used among the next generation of UCAs, and in combination with improved signal handling is superior not only in image enhancement relevant to diagnostics but also in localized and specific drug delivery for non-invasive therapy. 

  • 30.
    Kothapalli, Veeravenkata Satya
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institutet (KI), CLINTEC – Division of Medical Imaging and Technology.
    Dynamic and Structural behavior of Magnetized PVA-shelled Microbubbles: Acoustic Characterization2013Conference paper (Refereed)
  • 31.
    Kronander, Håkan
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Elmqvist, Håkan
    KTH, School of Technology and Health (STH), Medical Engineering.
    Exercise electrocardiography for diagnosis of coronary artery disease: impact of sampling rate on the diagnostic performance of ST/HR-loop based on data from early recovery phase2007In: Clinical Physiology and Functionel Imaging, ISSN 1475-0961, Vol. 28, no 2, 96-100 p.Article in journal (Refereed)
    Abstract [en]

    Quantitative analysis of electrocardiographic ST-segment/heart rate relationship (ST/HR loop) during early recovery phase of exercise stress test provides a sensitive tool for the detection of coronary artery disease (CAD). This study evaluates the effect of data sampling frequency on the diagnostic performance of ST/HR loop in 1876 patients undergoing a routine exercise test on a bicycle ergometer. CAD was verified angiographically in 668 patients and excluded by coronary angiography (n = 119), myocardial scintigraphy (n = 250) and on clinical grounds (n = 839) in 1208 patients. The normalized ST/HR loop area was calculated in all cases by integration of ST-segment amplitude difference from the end of exercise to the end of the first 3 min of recovery period over HR and dividing the integral by the HR difference over the integration period. The effect of different sampling rates (one, two and five samples per minute) on the CAD discrimination ability of ST/HR loop area was subsequently evaluated using receiver operating characteristic (ROC) curves. Reduction in ST/HR data sampling frequency from two to one sample per minute resulted in a significantly decreased diagnostic performance of the ST/HR loop whereas no differences in CAD discrimination capacity were observed between sampling frequencies of two and five samples per minute. The choice of ST/HR data sampling frequency may have a significant impact on the CAD diagnostic ability of the ST/HR loop. The use of sampling frequency below two samples per minute results in a significantly diminished diagnostic performance, a fact that should be taken into consideration when employing ST/HR diagnostic procedures.

  • 32.
    Kronander, Håkan
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Fischer-Colbrie, Werner
    Nowak, Jacek
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Elmqvist, Håkan
    KTH, School of Technology and Health (STH), Medical Engineering.
    Diagnostic performance and partition values of exercise electrocardiographic variables in the detection of coronary artery disease - improved accuracy by using ST/HR hysteresis2010In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 30, no 2, 98-106 p.Article in journal (Refereed)
    Abstract [en]

    P>Exercise electrocardiography is widely used for initial identification of patients with coronary artery disease (CAD). This study compares the measurements of ST-segment changes during exercise and during early postexercise recovery in terms of diagnostic discrimination capacity and optimal partition values. Data from 1876 patients undergoing a routine bicycle exercise test were analysed. CAD was angiographically verified in 668 patients, and excluded by angiography (n = 119), myocardial scintigraphy (n = 250), and on clinical grounds (n = 839) in 1208 patients. Postexercise ST/HR hysteresis was calculated as normalized for heart rate (HR) ST/HR loop area during the first 3 min of recovery. ST/HR index was obtained by dividing the overall ST amplitude change during exercise by exercise-induced HR change, and ST/HR slope was calculated using linear regression analysis of ST/HR data pairs during exercise. ST-segment depression was measured during, and for 3 min after the exercise. Discriminating capacity of the methods was evaluated in terms of receiver operating characteristic areas and optimal partition values providing the combination of the best sensitivity and specificity were established. The best diagnostic discrimination was provided by ST/HR hysteresis at optimal partition value of -15 mu V, followed by postexercise ST amplitude measurements at gender-specific partition values of -10 to -90 mu V, ST/HR slope [partition value 2 center dot 4 mu V (beats/min)-1], ST/HR index [partition value 1 center dot 6 mu V (beats/min)-1], and ST-segment depression during exercise (partition value 70 mu V in men and 90 mu V in women). The results demonstrate that analysis of postexercise ST/HR hysteresis offers the most accurate and gender indifferent identification of patients with CAD.

  • 33.
    Larsson, David
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Spuhler, Jeannette H.
    Petersson, Sven
    Nordenfur, Tim
    Hoffman, Johan
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Colarieti-Tosti, Massimiliano
    Winter, Reidar
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Multimodal validation of patient-specific intraventricular flow simulations from 4D echocardiography2016In: 2016 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS), IEEE conference proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    The combination of refined medical imaging techniques and computational fluid dynamics (CFD) models has enabled the study of complex flow behavior on a highly regional level. Recently, we have developed a platform for patient-specific CFD modelling of blood flow in the left ventricle (LV), with input data and required boundary conditions acquired from 4D echocardiography. The platform robustness has been evaluated with respect to input variable variations, but for any clinical implementation model flow validation is essential. Therefore, the aim of this study is to evaluate the accuracy of the patient-specific CFD model against multimodal image-based flow measurements. For the validation, 4D echocardiography was acquired from two healthy subjects, from which LV velocity fields were simulated. In-vivo flows from the same two subjects were then acquired by pulsed wave (PW) Doppler imaging over both LV-valves, and by cine phase-contract magnetic resonance imaging (PC-MRI) at eight defined anatomical planes in the LV. By fusing PC-MRI and the ultrasound acquisitions using a three-chamber alignment algorithm, simulated and measured flows were quantitatively compared. General flow pattern correspondence was observed, with a mean error of 1.4 cm/s and root mean square deviation of 5.7 cm/s for all measured PC-MRI LV-planes. For the PW-Doppler comparison, a mean error of 3.6 cm/s was reported. Overall, the following work represents a validation of the proposed patient-specific CFD platform, and the agreement with clinical data highlight the potential for future clinical use of the models.

  • 34.
    Larsson, Tore J
    KTH, School of Technology and Health (STH), Centres, Centre for Health and Building, CHB.
    Safety Management - Technology and health: Invited keynote lecture2004In: Health and Safety at Public Works, 2004Conference paper (Refereed)
  • 35.
    Lindberg, Frida
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Öhberg, Fredrik
    Granåsen, Gabriel
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Grönlund, Christer
    Pennation angle dependency in skeletal muscle tissue doppler strain in dynamic contractions2011In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 37, no 7, 1151-1160 p.Article in journal (Refereed)
    Abstract [en]

    Tissue velocity imaging (TVI) is a Doppler based ultrasound technique that can be used to study regional deformation in skeletal muscle tissue. The aim of this study was to develop a biomechanical model to describe the TVI strain's dependency on the pennation angle. We demonstrate its impact as the subsequent strain measurement error using dynamic elbow contractions from the medial and the lateral part of biceps brachii at two different loadings; 5% and 25% of maximum voluntary contraction (MVC). The estimated pennation angles were on average about 4 degrees in extended position and increased to a maximal of 13 degrees in flexed elbow position. The corresponding relative angular error spread from around 7% up to around 40%. To accurately apply TVI on skeletal muscles, the error due to angle changes should be compensated for. As a suggestion, this could be done according to the presented model.

  • 36.
    Lindh, Thomas
    et al.
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Orhan, Ibrahim
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Performance Control in Wireless Sensor Networks2009In: Pervasive Computing Technologies for Healthcare, 2009. PervasiveHealth 2009. 3rd International Conference on, IEEE , 2009Conference paper (Refereed)
    Abstract [en]

    This paper presents an implementation of a method for performance control in wireless body sensor networks based on measurement feedback, especially targeted for demanding healthcare applications.

  • 37.
    Lindh, Thomas
    et al.
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Orhan, Ibrahim
    KTH, School of Technology and Health (STH), Medical Engineering.
    Performance Measurements and Control in Contention-Based Wireless Sensor Networks2009In: 6th Swedish National Computer Networking Workshop (SNCNW 2009), 2009Conference paper (Refereed)
    Abstract [en]

    This paper presents an implementation of a method for performance control in wireless body sensor networks based on measurement feedback, especially targeted for demanding healthcare applications.

  • 38.
    Lindh, Thomas
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Orhan, Ibrahim
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Performance Monitoring and Control in Contention-Based Wireless Sensor Networks2009In: Proceedings of the 2009 6th International Symposium on Wireless Communication Systems, ISWCS'09, NEW YORK: IEEE conference proceedings, 2009, 507-511 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a method for performance monitoring and control in wireless body sensor networks based on measurement feedback. Test results using a prototype implementation of the method are also analyzed. The method has been evaluated for demanding healthcare related applications in wireless personal area networks.

  • 39.
    Lindh, Thomas
    et al.
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Orhan, Ibrahim
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Gonga, Antonio
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    A performance monitoring method for wireless sensor networks2008In: PETRA '08 Proceedings of the 1st international conference on PErvasive Technologies Related to Assistive Environments, New York: ACM , 2008Conference paper (Refereed)
    Abstract [en]

    This paper presents a monitoring method and its implementation as a light-weight end-to-end performance meter for quality-demanding applications in wireless sensor networks. The use of performance feedback information for control and management is also considered. The method is evaluated in a wireless sensor network testbed for healthcare applications.

  • 40.
    Manouras, Aristomenis
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Shala, Arben
    Nyktari, Evangelia
    Shahgaldi, Kambiz
    Winter, Reidar
    Vardas, Panagiotis
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, Jacek
    Are measurements of systolic myocardial velocities and displacement with colour and spectral Tissue Doppler compatible?2009In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 7, 29- p.Article in journal (Refereed)
    Abstract [en]

    Background: Tissue Doppler (TD) in pulsed mode (spectral TD) and colour TD are the two modalities today available in tissue velocity echocardiography (TVE). Previous studies have shown poor agreement between these two methods when measuring myocardial velocities and displacement. In this study, the concordance between the myocardial velocity and displacement measurements using colour TD and different spectral TD procedures was evaluated. Methods: Left ventricular (LV) longitudinal systolic myocardial velocities and displacement during ejection period were quantified at the basal septal and lateral wall in 24 healthy individuals (4 women and 20 men, 34 +/- 12 years) using spectral TD, colour TD and M-mode recordings. Mean, maximal and minimal spectral TD systolic velocities and the corresponding displacement values were obtained by measurements at the outer and inner borders of the spectral velocity signal. The results were then compared with those obtained with the two other modalities used. Results: Systolic myocardial velocities derived from mean spectral TD frequencies were highly concordant with corresponding colour TD measurements (mean difference 0.10 +/- 0.54 cm/sec in septal and 0.09 +/- 0.97 cm/sec in lateral wall). Similarly, the agreement between spectral and colour TD (mean difference 0.22 +/- 0.74 mm in septal and 0.02 +/- 0.86 mm in lateral wall) as well as M-mode was good when mean spectral velocities were temporally integrated and the results did not differ statistically. Conversely, displacement values from the inner or outer border of the spectral signal differed significantly from values obtained with colour TD and M-mode (p < 0.001, in both cases). Conclusion: LV systolic myocardial measurements based on mean spectral TD frequencies are highly concordant with those provided by colour TD and M-mode. Hence, in order to maintain compatibility of the results, the use of this particular spectral TD procedure should be advocated in clinical praxis.

  • 41.
    Marquez, Juan Carlos
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Ferreira, Javier
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Buendia, Ruben
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Textile electrode straps for wrist-to-ankle bioimpedance measurements for Body Composition Analysis: Initial validation & experimental results2010In: 2010 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), IEEE Engineering in Medicine and Biology Society , 2010, 6385-6388 p.Conference paper (Refereed)
    Abstract [en]

    Electrical Bioimpedance (EBI) is one of the non-invasive monitoring technologies that could benefit from the emerging textile based measurement systems. If reliable and reproducible EBI measurements could be done with textile electrodes, that would facilitate the utilization of EBI-based personalized healthcare monitoring applications. In this work the performance of a custom-made dry-textile electrode prototype is tested. Four-electrodes ankle-to-wrist EBI measurements have been taken on healthy subjects with the Impedimed spectrometer SFB7 in the frequency range 5 kHz to 1 MHz. The EBI spectroscopy measurements taken with dry electrodes were analyzed via the Cole and Body Composition Analysis (BCA) parameters, which were compared with EBI measurements obtained with standard electrolytic electrodes. The analysis of the obtained results indicate that even when dry textile electrodes may be used for EBI spectroscopy measurements, the measurements present remarkable differences that influence in the Cole parameter estimation process and in the final production of the BCA parameters. These initial results indicate that more research work must be done to in order to obtain a textile-based electrode that ensures reliable and reproducible EBI spectroscopy measurements.

  • 42.
    Marquez, Juan Carlos
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Skin-electrode contact area in electrical bioimpedance spectroscopy. Influence in total body composition assessment2011In: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS, IEEE Engineering In Medicine and Biology Society , 2011, Vol. 2011, 1867-1870 p.Conference paper (Refereed)
    Abstract [en]

    Electrical Bioimpedance Spectroscopy (EBIS) has been widely used for assessment of total body composition and fluid distribution. (EBIS) measurements are commonly performed with electrolytic electrodes placed on the wrist and the ankle with a rather small skin-electrode contact area. The use of textile garments for EBI requires the integration of textrodes with a larger contact area surrounding the limbs in order to compensate the absence of electrolytic medium commonly present in traditional Ag/AgCl gel electrodes. Recently it has been shown that mismatch between the measurements electrodes might cause alterations on the EBIS measurements. When performing EBIS measurements with textrodes certain differences have been observed, especially at high frequencies, respect the same EBIS measurements using Ag/AgCl electrodes. In this work the influence of increasing the skin-electrode area on the estimation of body composition parameters has been studied performing experimental EBIS measurement. The results indicate that an increment on the area of the skin-electrode interface produced noticeable changes in the bioimpedance spectra as well as in the body composition parameters. Moreover, the area increment showed also an apparent reduction of electrode impedance mismatch effects. This influence must be taken into consideration when designing and testing textile-enable EBIS measurement systems.

  • 43. Marquez, Juan Carlos
    et al.
    Seoane, Fernando
    Välimäki, Elina
    University of Borås.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Comparison of dry-textile electrodes for electrical bioimpedance spectroscopy measurements2010Conference paper (Refereed)
    Abstract [en]

    Textile Electrodes have been widely studied for biopotentials recordings, specially for monitoring the cardiac activity. Commercially available applications, such as Adistar T-shirt and Textronics Cardioshirt, have proved a good performance for heart rate monitoring and are available worldwide. Textile technology can also be used for Electrical Bioimpedance Spectroscopy measurements enabling home and personalized health monitoring applications however solid ground research about the measurement performance of the electrodes must be done prior to the development of any textile-enabled EBI application. In this work a comparison of the measurement performance of two different types of dry-textile electrodes and manufacturers has been performed against standardized RedDot 3M Ag/AgCl electrolytic electrodes. 4-Electrode, whole body, Ankle-to-Wrist EBI measurements have been taken with the Impedimed spectrometer SFB7 from healthy subjects in the frequency range of 3kHz to 500kHz. Measurements have been taken with dry electrodes at different times to study the influence of the interaction skin-electrode interface on the EBI measurements. The analysis of the obtained complex EBI spectra shows that the measurements performed with textile electrodes produce constant and reliable EBI spectra. Certain deviation can be observed at higher frequencies and the measurements obtained with Textronics and Ag/AgCl electrodes present a better resemblance. Textile technology, if successfully integrated it, may enable the performance of EBI measurements in new scenarios allowing the rising of novel wearable monitoring applications for home and personal care as well as car safety.

  • 44. Mohino-Herranz, Inma
    et al.
    Gil-Pita, Roberto
    Ferreira, Javier
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems. University of Boras, Boras, Sweden.
    Rosa-Zurera, Manuel
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems. University of Boras, Boras, Sweden.
    Assessment of Mental, Emotional and Physical Stress through Analysis of Physiological Signals Using Smartphones2015In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 15, no 10, 25607-25627 p.Article in journal (Refereed)
    Abstract [en]

    Determining the stress level of a subject in real time could be of special interest in certain professional activities to allow the monitoring of soldiers, pilots, emergency personnel and other professionals responsible for human lives. Assessment of current mental fitness for executing a task at hand might avoid unnecessary risks. To obtain this knowledge, two physiological measurements were recorded in this work using customized non-invasive wearable instrumentation that measures electrocardiogram (ECG) and thoracic electrical bioimpedance (TEB) signals. The relevant information from each measurement is extracted via evaluation of a reduced set of selected features. These features are primarily obtained from filtered and processed versions of the raw time measurements with calculations of certain statistical and descriptive parameters. Selection of the reduced set of features was performed using genetic algorithms, thus constraining the computational cost of the real-time implementation. Different classification approaches have been studied, but neural networks were chosen for this investigation because they represent a good tradeoff between the intelligence of the solution and computational complexity. Three different application scenarios were considered. In the first scenario, the proposed system is capable of distinguishing among different types of activity with a 21.2% probability error, for activities coded as neutral, emotional, mental and physical. In the second scenario, the proposed solution distinguishes among the three different emotional states of neutral, sadness and disgust, with a probability error of 4.8%. In the third scenario, the system is able to distinguish between low mental load and mental overload with a probability error of 32.3%. The computational cost was calculated, and the solution was implemented in commercially available Android-based smartphones. The results indicate that execution of such a monitoring solution is negligible compared to the nominal computational load of current smartphones.

  • 45. Molina, Daniel Martinez
    et al.
    Lundbäck, Anna-Karin
    KTH, School of Technology and Health (STH).
    Niegowski, Damian
    Eshaghi, Said
    Expression and purification of the recombinant membrane protein YidC: A case study for increased stability and solubility2008In: Protein Expression and Purification, ISSN 1046-5928, E-ISSN 1096-0279, Vol. 62, no 1, 49-52 p.Article in journal (Refereed)
    Abstract [en]

    YidC is an inner membrane protein from Escherichia coli and is an essential component in insertion, translocation and assembly of membrane proteins in the membranes. Previous purification attempts resulted in heavy aggregates and precipitated protein at later stages of purification. Here we present a rapid and straightforward stability screening strategy based on gel filtration chromatography, which requires as little as 10 mu g of protein and takes less than 15 min to perform. With this technique, we could rapidly screen several buffers in order to identify an optimum condition that stabilizes purified YidC. After optimization we could obtain several milligrams of purified YidC that could be easily prepared at high concentrations and that was stable for weeks at +4 degrees C. The isolated protein is thus well suited for structural studies.

  • 46.
    Mårtensson, Mattias
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Evaluation of tissue Doppler-based velocity and deformation imaging: a phantom study of ultrasound systems.2011In: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 12, no 6, 467-476 p.Article in journal (Refereed)
    Abstract [en]

    AIMS: The objective of this study was to test the accuracy and diagnostic interchangeability of tissue Doppler-based displacement, velocity, strain, and strain rate measurements in commercially used ultrasound (US) systems. METHODS AND RESULTS: Using an in-house made phantom, four different US scanner models were evaluated. Two different scanners of the same model were tested, and one scanner acquisition was tested twice with two generations of the same workstation giving six test results in total. The scanners were in active clinical use and are subject to regular maintenance checks. There were three displacement and four velocity results that stood out from the rest and could be regarded as accurate and interchangeable. Among the deformation measurements, three acceptable strain results were found while there were no acceptable strain rate results. Furthermore, the study showed that measurements from scanners of the same model, same acquisition post-processed on different workstations and repeated measurements from the same scanner, can yield disparate results. CONCLUSION: Measurements that are accurate and of interchangeable use can be found for displacement and velocity measurements, but are less likely to be found for strain and strain rate measurements. It is strongly recommended that the ability of each individual US scanner to measure displacement, velocity, strain, and strain rate is evaluated before it is introduced into clinical practice, and it must always be evaluated together with the workstation the scanner is intended to be used in conjunction with.

  • 47.
    Mårtensson, Mattias
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Winter, Reidar
    Cederlund, Kerstin
    Ripsweden, Jonaz
    Mir-Akbari, Habib
    Nowak, Jacek
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Assessment of left ventricular volumes using simplified 3-D echocardiography and computed tomography - a phantom and clinical study2008In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 6Article in journal (Refereed)
    Abstract [en]

    Objectives: To compare the accuracy of simplified 3-dimensional (3-D) echocardiography vs. multi-slice computed tomography (MSCT) software for the quantification of left ventricular (LV) volumes. Design: Three-D echocardiography (3-planes approach) and MSCT-CardIQ software were calibrated by measuring known volumes of 10 phantoms designed to closely mimic blood-endocardium interface. Subsequently, LV volumes were measured with both the methods in 9 patients referred routinely for coronary angiography and the agreement between the measurements was evaluated. Results: Simplified 3D-echocardiography provided higher degree of agreement between the measured and true phantom volumes (mean difference 0 +/- 1 ml, variation range + 4 to -4 ml) than MSCT software (mean difference 6 +/- 5 ml; variation range + 22 to -10 ml). The agreement between LV measurements in the patients was considerably poorer, with significantly larger volumes produced by MSCT (mean difference - 23 +/- 40 ml, variation between + 93 and -138 ml). Conclusion: Simplified 3-D echocardiography provides more accurate assessment of phantom volumes than MSCT-CardIQ software. The discrepancy between the results of LV measurements with the two methods is even greater and does not warrant their interchangeable diagnostic use.

  • 48.
    Nordberg, Axel
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Brolin, Karin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Beckman, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Vertebral fractures fixation with composite patch fibre reinforced adhesives2007In: Bio-medical materials and engineering, ISSN 0959-2989, E-ISSN 1878-3619, Vol. 17, no 5, 299-308 p.Article in journal (Refereed)
    Abstract [en]

    Purpose: The aim is to investigate fixation of cervical vertebral fractures by patching it with a composite laminate of adhesive and fibres, in comparison with use of only adhesives. Material and methods: The composite fixation was tested on bonded roe deer vertebrae. 25 specimens were sawed in two halves, creating a generic fracture, and thereafter bonded. The adhesives used were a dental system, Scotchbond XT, and a cyanoacrylate, M-bond 200. The fibres used were unidirectional carbon fibres and randomly distributed E-glass fibres. The composites were applied as a 7 mm wide patch circumferential along the induced fracture. Reference specimens for comparison were also made. The ultimate tensile strength was tested in an Instron 5567. The failure site was examined with a microscope. Strain vectors were tracked using Digital Speckle Analysis. Results: Scotchbond XT + E-glass fibres gave best results, with a tensile strength of 3.5 N/mm circumferential length (24.3% of reference). All composites had lower stiffness than cortical bone. The dental adhesive fibre composites gave better results than the cyanoacrylate fibre composites. In all cases fibre reinforced adhesive composite gave better results than adhesive without fibre reinforcement. Conclusion: Fibre-adhesive composite is a promising technique for fixating cervical vertebral fractures.

  • 49.
    Orhan, Ibrahim
    et al.
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Gonga, Antonio
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Lindh, Thomas
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    An End-to-End Performance Meter for Applications in Wireless Body Sensor Networks2008In: 2008 5th International Summer School and Symposium on Medical Devices and Biosensors, Institute of Electrical and Electronics Engineers (IEEE), 2008, 295-298 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a monitoring method and its implementation as a light-weight end-to-end performance meter for quality-demanding applications in wireless body sensor networks. The method is evaluated in a wireless sensor network testbed for healthcare applications.

  • 50.
    Orhan, Ibrahim
    et al.
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Lindh, Thomas
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Measurement-based admission control in wireless sensor networks2010In: 2010 Eleventh International Conference on Mobile Data Management (MDM), IEEE , 2010, 426-431 p.Conference paper (Refereed)
    Abstract [en]

    Wireless sensor networks have today emerged as a feasible infrastructure for healthcare applications. This paper addresses the non-trivial performance problems in contentionbased wireless networks. We present a method for admission control in contention-based networks, implemented as a component of a performance management system. The test results show that admission control can improve the predictability and level of performance in wireless sensor networks. The system can be used as a tool for dimensioning and configuration as well as for real-time admission control. The often unpredictable dynamics in contention-based access networks means that continuous performance control is needed to maintain a desired quality of service.

12 1 - 50 of 70
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf