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  • 1.
    Aare, Magnus
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Evaluation of head response to ballistic helmet impacts, using FEM2003Conference paper (Refereed)
  • 2.
    Aare, Magnus
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Proposed global injury thresholds for oblique helmet impacts2003Conference paper (Refereed)
  • 3.
    Abtahi, Farhad
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Ji, Guangchao
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Lu, Ke
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Rodby, Kristian
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    A knitted garment using intarsia technique for Heart Rate Variability biofeedback: Evaluation of initial prototype2015In: Engineering in Medicine and Biology Society (EMBC), 2015 37th Annual International Conference of the IEEE, IEEE , 2015, Vol. 2015, 3121-3124 p.Conference paper (Refereed)
    Abstract [en]

    Heart rate variability (HRV) biofeedback is a method based on paced breathing at specific rate called resonance frequency by giving online feedbacks from user respiration and its effect on HRV. Since the HRV is also influence by different factors like stress and emotions, stress related to an unfamiliar measurement device, cables and skin electrodes may cover the underling effect of such kind of intervention. Wearable systems are usually considered as intuitive solutions which are more familiar to the end-user and can help to improve usability and hence reducing the stress. In this work, a prototype of a knitted garment using intarsia technique is developed and evaluated. Results show the satisfactory level of quality for Electrocardiogram and thoracic electrical bioimpedance i.e. for respiration monitoring as a part of HRV biofeedback system. Using intarsia technique and conductive yarn for making the connection instead of cables will reduce the complexity of fabrication in textile production and hence reduce the final costs in a final commercial product. Further development of garment and Android application is ongoing and usability and efficiency of final prototype will be evaluated in detail.

  • 4.
    Abtahi, Farhad
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Aslamy, Benjamin
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Boujabir, Imaneh
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    An Affordable ECG and Respiration Monitoring System Based on Raspberry PI and ADAS1000: First Step towards Homecare Applications2015In: 16th Nordic-Baltic Conference on Biomedical Engineering: 16. NBC & 10. MTD 2014 joint conferences. October 14-16, 2014, Gothenburg, Sweden, Springer, 2015, 5-8 p.Conference paper (Refereed)
    Abstract [en]

    Homecare is a potential solution for problems associated with an aging population. This may involve several physiological measurements, and hence a flexible but affordable measurement device is needed. In this work, we have designed an ADAS1000-based four-lead electrocardiogram (ECG) and respiration monitoring system. It has been implemented using Raspberry PI as a platform for homecare applications. ADuM chips based on iCoupler technology have been used to achieve electrical isolation as required by IEC 60601 and IEC 60950 for patient safety. The result proved the potential of Raspberry PI for the design of a compact, affordable, and medically safe measurement device. Further work involves developing a more flexible software for collecting measurements from different devices (measuring, e.g., blood pressure, weight, impedance spectroscopy, blood glucose) through Bluetooth or user input and integrating them into a cloud-based homecare system.

  • 5.
    Abtahi, Farhad
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Lu, Ke
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Dizon, M
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Johansson, M
    KTH-School of Technology and Health.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems. Högskolan i Borås.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering. Högskolan i Borås, Akademin för vård, arbetsliv och välfärd.
    Evaluating Atrial Fibrillation Detection Algorithm based on Heart Rate Variability analysis2015In: Medicinteknikdagarna, Uppsala: Svensk förening för medicinsk teknik och fysik , 2015Conference paper (Refereed)
  • 6.
    Abtahi, Farhad
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Electrical bioimpedance spectroscopy in time-variant systems: Is undersampling always a problem?2014In: Journal of Electrical Bioimpedance, ISSN 1891-5469, Vol. 5, no 1, 28-33 p.Article in journal (Refereed)
    Abstract [en]

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

  • 7.
    Abtahi, Farhad
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Löfgren, Nils
    Elimination of ECG Artefacts in Foetal EEG Using Ensemble Average Subtraction and Wavelet Denoising Methods: A Simulation2014In: XIII Mediterranean Conference on Medical and Biological Engineering and Computing 2013, Springer, 2014, 551-554 p.Conference paper (Refereed)
    Abstract [en]

    Biological signals recorded from surface electrodes contain interference from other signals which are not desired and should be considered as noise. Heart activity is especially present in EEG and EMG recordings as a noise. In this work, two ECG elimination methods are implemented; ensemble average subtraction (EAS) and wavelet denoising methods. Comparison of these methods has been done by use of simulated signals achieved by adding ECG to neonates EEG. The result shows successful elimination of ECG artifacts by using both methods. In general EAS method which remove estimate of all ECG components from signal is more trustable but it is also harder for implementation due to sensitivity to noise. It is also concluded that EAS behaves like a high-pass filter while wavelet denoising method acts as low-pass filter and hence the choice of one method depends on application.

  • 8.
    Abtahi, Farhad
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Snäll, Jonatan
    KTH, School of Technology and Health (STH).
    Aslamy, Benjamin
    KTH, School of Technology and Health (STH).
    Abtahi, Shirin
    KTH, School of Technology and Health (STH).
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems. University of Boras, Sweden.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems. Karolinska Institute, Sweden.
    Biosignal PI, an Affordable Open-Source ECG and Respiration Measurement System2014In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 15, no 1, 93-109 p.Article in journal (Refereed)
    Abstract [en]

    Bioimedical pilot projects e.g., telemedicine, homecare, animal and human trials usually involve several physiological measurements. Technical development of these projects is time consuming and in particular costly. A versatile but affordable biosignal measurement platform can help to reduce time and risk while keeping the focus on the important goal and making an efficient use of resources. In this work, an affordable and open source platform for development of physiological signals is proposed. As a first step an 8–12 leads electrocardiogram (ECG) and respiration monitoring system is developed. Chips based on iCoupler technology have been used to achieve electrical isolation as required by IEC 60601 for patient safety. The result shows the potential of this platform as a base for prototyping compact, affordable, and medically safe measurement systems. Further work involves both hardware and software development to develop modules. These modules may require development of front-ends for other biosignals or just collect data wirelessly from different devices e.g., blood pressure, weight, bioimpedance spectrum, blood glucose, e.g., through Bluetooth. All design and development documents, files and source codes will be available for non-commercial use through project website, BiosignalPI.org.

  • 9.
    Alvarez, Victor S
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Importance of Windscreen Modelling Approach for Head Injury Prediction2016In: 2016 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury, 2016Conference paper (Refereed)
    Abstract [en]

    The objective of this study is to evaluate the capability of two modelling approaches in capturing  both accelerations and deformations from head impacts, and to evaluate the effect of modelling approach on  brain injury prediction. The first approach is a so‐called smeared technique, in which the properties of the two  glass  sheets and  the intermediate  polyvinyl  butyral  (PVB) are  combined and  divided into  two  coinciding  shell layers, of which one can fracture. The second approach consists of three shell layers, representing the glass and  PVB,  separated by  the  distance of  their  thickness, using a non‐local  failure criterion  to initiate  fracture in  the  glass.  The  two  modelling  approaches  are  compared  to  impact  experiments  of  flat  circular  windscreens,  measuring  deformations  and  accelerations  as  well  as  accelerations  from  impacts  against  full  vehicle  windscreens.  They  are  also  used  to  study  head‐to‐windscreen  impacts  using  a  detailed  Finite  Element  (FE)  model,  varying  velocity,  impact  direction  and  impact  point.  Only  the  non‐local  failure  model  is  able  to  adequately  capture  both  the accelerations and  deformations  of an  impactor. The FE  head model  simulations  also reveal that the choice of modelling approach has a large effect on the both localisation of the strain in the  brain and the characteristics of the strain‐time curve, with a difference in peak strain between 8% and 40%.  

  • 10.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hamedi, Mahiar
    Inganäs, Olle
    Forchheimer, Robert
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Neural microcontacts with wire electrodes and woven logic2007Conference paper (Refereed)
  • 11.
    Atefi, Seyed Reza
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701).
    Buendia, Ruben
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701).
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701).
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701).
    Cole Function and Conductance-Based Parasitic Capacitance Compensation for Cerebral Electrical Bioimpedance Measurements2012In: Engineering in Medicine and Biology Society (EMBC), 2012 Annual International Conference of the IEEE, San Diego: IEEE press , 2012, 3368-3371 p.Conference paper (Refereed)
    Abstract [en]

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

  • 12.
    Atefi, Seyed Reza
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Kamalian, Shervin
    Rosenthal, Eric
    Lev, Michael
    Bonmassar, Giorgio
    Intracranial haemorrhage alters scalp potential distributions in bioimpedance cerebral monitoring applications: preliminary results from FEM simulation on a realistic head model and human subjects2016In: Medical Physics, ISSN 2473-4209, Vol. 43, no 2, 675-686 p.Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    Atefi, Seyed Reza
    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).
    Electrical Bioimpedance cerebral monitoring. Preliminary results from measurements on stroke patients2012In: Engineering in Medicine and Biology Society (EMBC), 2012 Annual International Conference of the IEEE, IEEE , 2012, 126-129 p.Conference paper (Refereed)
    Abstract [en]

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

  • 14.
    Atefi, Seyed Reza
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Study of the dynamics of transcephalic cerebral impedance data during cardio-vascular surgery2013In: XV International Conference on Electrical Bio-Impedance (ICEBI) & XIV Conference on Electrical Impedance Tomography (EIT), Institute of Physics (IOP), 2013, Vol. 434, no 1, 012045- p.Conference paper (Refereed)
    Abstract [en]

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

  • 15.
    Atefi, Seyed Reza
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Thorlin, Thorleif
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Stroke Damage Detection Using Classification Trees on Electrical Bioimpedance Cerebral Spectroscopy Measurements2013In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 13, no 8, 10074-10086 p.Article in journal (Refereed)
    Abstract [en]

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

  • 16. Ayllnon, David
    et al.
    Gil-Pita, Roberto
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Detection and Classification of Measurement Errors in Bioimpedance Spectroscopy2016In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 6, e0156522Article in journal (Refereed)
    Abstract [en]

    Bioimpedance spectroscopy (BIS) measurement errors may be caused by parasitic stray capacitance, impedance mismatch, cross-talking or their very likely combination. An accurate detection and identification is of extreme importance for further analysis because in some cases and for some applications, certain measurement artifacts can be corrected, minimized or even avoided. In this paper we present a robust method to detect the presence of measurement artifacts and identify what kind of measurement error is present in BIS measurements. The method is based on supervised machine learning and uses a novel set of generalist features for measurement characterization in different immittance planes. Experimental validation has been carried out using a database of complex spectra BIS measurements obtained from different BIS applications and containing six different types of errors, as well as error-free measurements. The method obtained a low classification error (0.33%) and has shown good generalization. Since both the features and the classification schema are relatively simple, the implementation of this pre-processing task in the current hardware of bioimpedance spectrometers is possible.

  • 17.
    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.

  • 18. Azar, J.C.
    et al.
    Hamid Muhammed, Hamed
    KTH, School of Technology and Health (STH), Medical Engineering.
    Automated Tracking of the Carotid Artery in Ultrasound Image Sequences Using a Self Organizing Neural Network2010In: Proceedings of 20th International Conference on Pattern Recognition (ICPR 2010), Istanbul, Turkey, Istanbul, Turkey, 2010, 2548-2551 p.Conference paper (Refereed)
    Abstract [en]

    An automated method for the segmentation and tracking of moving vessel walls in 2D ultrasound image sequences is introduced. The method was tested on simulated and real ultrasound image sequences of the carotid artery. Tracking was achieved via a self organizing neural network known as Growing Neural Gas. This topology-preserving algorithm assigns a net of nodes connected by edges that distributes itself within the vessel walls and adapts to changes in topology with time. The movement of the nodes was analyzed to uncover the dynamics of the vessel wall. By this way, radial and longitudinal strain and strain rates have been estimated. Finally, wave intensity signals were computed from these measurements. The method proposed improves upon wave intensity wall analysis, WIWA, and opens up a possibility for easy and efficient analysis and diagnosis of vascular disease through noninvasive ultrasonic examination.

  • 19. Bassan, Gioia
    et al.
    Larsson, David
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Nordenfur, Tim
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Acquisition of multiple mode shear wave propagation in transversely isotropic medium using dualprobe setup2015Conference paper (Refereed)
  • 20.
    Batool, Nazre
    KTH, School of Technology and Health (STH).
    Detection and Spatial Analysis of Hepatic Steatosis in Histopathology Images using Sparse Linear Models2016In: 2016 SIXTH INTERNATIONAL CONFERENCE ON IMAGE PROCESSING THEORY, TOOLS AND APPLICATIONS (IPTA), IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    Hepatic steatosis is a defining feature of nonalcoholic fatty liver disease, emerging with the increasing incidence of obesity and metabolic syndrome. The research in image-based analysis of hepatic steatosis mostly focuses on the quantification of fat in biopsy images. This work furthers the image-based analysis of hepatic steatosis by exploring the spatial characteristics of fat globules in whole slide biopsy images after performing fat detection. An algorithm based on morphological filtering and sparse linear models is presented for fat detection. Then the spatial properties of detected fat globules in relation to the hepatic anatomical structures of central veins and portal tracts are explored. The test dataset consists of 38 high resolution images from 21 patients. The experimental results provide an insight into the size distributions of fat globules and their location with respect to the anatomical structures.

  • 21. Beillas, P.
    et al.
    Petit, P.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kirscht, S.
    Chawla, A.
    Jolivet, E.
    Faure, F.
    Praxl, N.
    Bhaskar, A.
    Specifications of a software framework to position and personalise human body models2015In: 2015 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury, International Research Council on the Biomechanics of Injury , 2015, 594-595 p.Conference paper (Refereed)
  • 22. Bernard, Olivier
    et al.
    Bosch, J G
    Heyde, Brecht
    Alessandrini, Martino
    Barbosa, Daniel
    Camarasu-Pop, S
    Cervenansky, F
    Valette, S
    Mirea, O
    Bernier, M
    Jodoin, P M
    Domingos, J S
    Stebbing, R V
    Keraudren, K
    Oktay, O
    Caballero, J
    Shi, W
    Rueckert, D
    Milletari, F
    Ahmadi, S A
    Smistad, E
    Lindseth, F
    van Stralen, M
    Wang, Chunliang
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization.
    Smedby, Örjan
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization.
    Donal, E
    Monaghan, M
    Papachristidis, A
    Geleijnse, M L
    Galli, E
    Dhooge, Jan
    Standardized evaluation system for left ventricular segmentation algorithms in 3D echocardiography.2015In: IEEE Transactions on Medical Imaging, ISSN 0278-0062, E-ISSN 1558-254XArticle in journal (Refereed)
    Abstract [en]

    Real-time 3D Echocardiography (RT3DE) has been proven to be an accurate tool for left ventricular (LV) volume assessment. However, identification of the LV endocardium remains a challenging task, mainly because of the low tissue/blood contrast of the images combined with typical artifacts. Several semi and fully automatic algorithms have been proposed for segmenting the endocardium in RT3DE data in order to extract relevant clinical indices, but a systematic and fair comparison between such methods has so far been impossible due to the lack of a publicly available common database. Here, we introduce a standardized evaluation framework to reliably evaluate and compare the performance of the algorithms developed to segment the LV border in RT3DE. A database consisting of 45 multivendor cardiac ultrasound recordings acquired at different centers with corresponding reference measurements from 3 experts are made available. The algorithms from nine research groups were quantitatively evaluated and compared using the proposed online platform. The results showed that the best methods produce promising results with respect to the experts' measurements for the extraction of clinical indices, and that they offer good segmentation precision in terms of mean distance error in the context of the experts' variability range. The platform remains open for new submissions.

  • 23.
    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.

  • 24.
    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.

  • 25.
    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.

  • 26. Blystad, Ida
    et al.
    Warntjes, J. B. Marcel
    Smedby, Örjan
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization. Linköping University, Sweden.
    Lundberg, Peter
    Larsson, Elna-Marie
    Tisell, Anders
    Quantitative MRI for analysis of peritumoral edema in malignant gliomas2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 5, e0177135Article in journal (Refereed)
    Abstract [en]

    Background and purpose Damage to the blood-brain barrier with subsequent contrast enhancement is a hallmark of glioblastoma. Non-enhancing tumor invasion into the peritumoral edema is, however, not usually visible on conventional magnetic resonance imaging. New quantitative techniques using relaxometry offer additional information about tissue properties. The aim of this study was to evaluate longitudinal relaxation R-1, transverse relaxation R-2, and proton density in the peritumoral edema in a group of patients with malignant glioma before surgery to assess whether relaxometry can detect changes not visible on conventional images. Methods In a prospective study, 24 patients with suspected malignant glioma were examined before surgery. A standard MRI protocol was used with the addition of a quantitative MR method (MAGIC), which measured R-1, R-2, and proton density. The diagnosis of malignant glioma was confirmed after biopsy/surgery. In 19 patients synthetic MR images were then created from the MAGIC scan, and ROIs were placed in the peritumoral edema to obtain the quantitative values. Dynamic susceptibility contrast perfusion was used to obtain cerebral blood volume (rCBV) data of the peritumoral edema. Voxel-based statistical analysis was performed using a mixed linear model. Results R-1, R-2, and rCBV decrease with increasing distance from the contrast-enhancing part of the tumor. There is a significant increase in R1 gradient after contrast agent injection (P<.0001). There is a heterogeneous pattern of relaxation values in the peritumoral edema adjacent to the contrast-enhancing part of the tumor. Conclusion Quantitative analysis with relaxometry of peritumoral edema in malignant gliomas detects tissue changes not visualized on conventional MR images. The finding of decreasing R-1 and R-2 means shorter relaxation times closer to the tumor, which could reflect tumor invasion into the peritumoral edema. However, these findings need to be validated in the future.

  • 27. Bora, K.
    et al.
    Chowdhury, Manish
    KTH, School of Technology and Health (STH).
    Mahanta, L. B.
    Kundu, M. K.
    Das, A. K.
    Pap smear image classification using convolutional neural network2016In: ACM International Conference Proceeding Series, Association for Computing Machinery , 2016Conference paper (Refereed)
    Abstract [en]

    This article presents the result of a comprehensive study on deep learning based Computer Aided Diagnostic techniques for classification of cervical dysplasia using Pap smear images. All the experiments are performed on a real indigenous image database containing 1611 images, generated at two diagnostic centres. Focus is given on constructing an effective feature vector which can perform multiple level of representation of the features hidden in a Pap smear image. For this purpose Deep Convolutional Neural Network is used, followed by feature selection using an unsupervised technique with Maximal Information Compression Index as similarity measure. Finally performance of two classifiers namely Least Square Support Vector Machine (LSSVM) and Softmax Regression are monitored and classifier selection is performed based on five measures along with five fold cross validation technique. Output classes reflects the established Bethesda system of classification for identifying pre-cancerous and cancerous lesion of cervix. The proposed system is also compared with two existing conventional systems and also tested on a publicly available database. Experimental results and comparison shows that proposed system performs efficiently in Pap smear classification.

  • 28. 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.

  • 29. Brismar, Torkel B.
    et al.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Gustafsson, Björn
    Härmark, Johan
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Structural Biotechnology.
    Barrefelt, Åsa
    Kothapalli, Satya V. V. N.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Margheritelli, Silvia
    Oddo, Letizia
    Caidahl, Kenneth
    Hebert, Hans
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Structural Biotechnology.
    Paradossi, Gaio
    Magnetite Nanoparticles Can Be Coupled to Microbubbles to Support Multimodal Imaging2012In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 13, no 5, 1390-1399 p.Article in journal (Refereed)
    Abstract [en]

    Microbubbles (MBs) are commonly used as injectable ultrasound contrast agent (UCA) in modern ultrasonography. Polymer-shelled UCAs present additional potentialities with respect to marketed lipid-shelled UCAs. They are more robust; that is, they have longer shelf and circulation life, and surface modifications are quite easily accomplished to obtain enhanced targeting and local drug delivery. The next generation of UCAs will be required to support not only ultrasound-based imaging methods but also other complementary diagnostic approaches such as magnetic resonance imaging or computer tomography. This work addresses the features of MBs that could function as contrast agents for both ultrasound and magnetic resonance imaging. The results indicate that the introduction of iron oxide nanoparticles (SPIONs) in the poly(vinyl alcohol) shell or on the external surface of the MBs does not greatly decrease the echogenicity of the host MBs compared with the unmodified one. The presence of SPIONs provides enough magnetic susceptibility to the MBs to accomplish good detectability both in vitro and in vivo. The distribution of SPIONs on the shell and their aggregation state seem to be key factors for the optimization of the transverse relaxation rate.

  • 30.
    Brolin, Karin
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Leijonhufvud, I.
    The effect of muscle activation on neck response2005In: Traffic Injury Prevention, ISSN 1538-9588, E-ISSN 1538-957X, Vol. 6, no 1, 67-76 p.Article in journal (Refereed)
    Abstract [en]

    Prevention of neck injuries due to complex loading, such as occurs in traffic accidents, requires knowledge of neck injury mechanisms and tolerances. The influence of muscle activation on outcome of the injuries is not clearly understood. Numerical simulations of neck injury accidents can contribute to increase the understanding of injury tolerances. The finite element (FE) method is suitable because it gives data on stress and strain of individual tissues that can be used to predict injuries based on tissue level criteria. The aim of this study was to improve and validate an anatomically detailed FE model of the human cervical spine by implement neck musculature with passive and active material properties. Further, the effect of activation time and force on the stresses and strains in the cervical tissues were studied for dynamic loading due to frontal and lateral impacts. The FE model used includes the seven cervical vertebrae, the spinal ligaments, the facet joints with cartilage, the intervertebral disc, the skull base connected to a rigid head, and a spring element representation of the neck musculature. The passive muscle properties were defined with bilinear force-deformation curves and the active properties were defined using a material model based on the Hill equation. The FE model's responses were compared to volunteer experiments for frontal and lateral impacts of 15 and 7 g. Then, the active muscle properties where varied to study their effect on the motion of the skull, the stress level of the cortical and trabecular bone, and the strain of the ligaments. The FE model had a good correlation to the experimental motion corridors when the muscles activation was implemented. For the frontal impact a suitable peak muscle force was 40 N/cm2 whereas 20 N/cm2 was appropriate for the side impact. The stress levels in the cortical and trabecular bone were influenced by the point forces introduced by the muscle spring elements; therefore a more detailed model of muscle insertion would be preferable. The deformation of each spinal ligament was normalized with an appropriate failure deformation to predict soft tissue injury. For the frontal impact, the muscle activation turned out to mainly protect the upper cervical spine ligaments, while the musculature shielded all the ligaments disregarding spinal level for lateral impacts. It is concluded that the neck musculature does not have the same protective properties during different impacts loadings.

  • 31.
    Brolin, Karin
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Nordberg, Axel
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Stability and fibre reinforced adhesive fixation of vertebral fractures in the upper cervical spine2006In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, 151-152 p.Article in journal (Refereed)
  • 32.
    Broomé, Michael
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Frenckner, Björn
    Broman, Mikaeö
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Recirculation during veno-venous extra-corporeal membrane oxygenation: a simulation study2015In: International Journal of Artificial Organs, ISSN 0391-3988, E-ISSN 1724-6040, Vol. 38, no 1, 23-30 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE:

    Veno-venous ECMO is indicated in reversible life-threatening respiratory failure without life-threatening circulatory failure. Recirculation of oxygenated blood in the ECMO circuit decreases efficiency of patient oxygen delivery but is difficult to measure. We seek to identify and quantify some of the factors responsible for recirculation in a simulation model and compare with clinical data.

    METHODS:

    A closed-loop real-time simulation model of the cardiovascular system has been developed. ECMO is simulated with a fixed flow pump 0 to 5 l/min with various cannulation sites - 1) right atrium to inferior vena cava, 2) inferior vena cava to right atrium, and 3) superior+inferior vena cava to right atrium. Simulations are compared to data from a retrospective cohort of 11 consecutive adult veno-venous ECMO patients in our department.

    RESULTS:

    Recirculation increases with increasing ECMO-flow, decreases with increasing cardiac output, and is highly dependent on choice of cannulation sites. A more peripheral drainage site decreases recirculation substantially.

    CONCLUSIONS:

    Simulations suggest that recirculation is a significant clinical problem in veno-venous ECMO in agreement with clinical data. Due to the difficulties in measuring recirculation and interpretation of the venous oxygen saturation in the ECMO drainage blood, flow settings and cannula positioning should rather be optimized with help of arterial oxygenation parameters. Simulation may be useful in quantification and understanding of recirculation in VV-ECMO.

  • 33.
    Broomé, Michael
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Maksuti, Elira
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Frenckner, Björn
    Janerot-Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Closed-loop real-time simulation model of hemodynamics and oxygen transport in the cardiovascular system2013In: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 12, no 1, 69- p.Article in journal (Refereed)
    Abstract [en]

    Background: Computer technology enables realistic simulation of cardiovascular physiology. The increasing number of clinical surgical and medical treatment options imposes a need for better understanding of patient-specific pathology and outcome prediction. Methods: A distributed lumped parameter real-time closed-loop model with 26 vascular segments, cardiac modelling with time-varying elastance functions and gradually opening and closing valves, the pericardium, intrathoracic pressure, the atrial and ventricular septum, various pathological states and including oxygen transport has been developed. Results: Model output is pressure, volume, flow and oxygen saturation from every cardiac and vascular compartment. The model produces relevant clinical output and validation of quantitative data in normal physiology and qualitative directions in simulation of pathological states show good agreement with published data. Conclusion: The results show that it is possible to build a clinically relevant real-time computer simulation model of the normal adult cardiovascular system. It is suggested that understanding qualitative interaction between physiological parameters in health and disease may be improved by using the model, although further model development and validation is needed for quantitative patient-specific outcome prediction.

  • 34. Brown, Shannon
    et al.
    Ortiz-Catalan, Max
    Petersson, Joel
    Rodby, Kristian
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering. University of Borås, Sweden.
    Intarsia-Sensorized Band and Textrodes for Real-Time Myoelectric Pattern Recognition2016In: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS / [ed] Patton, J Barbieri, R Ji, J Jabbari, E Dokos, S Mukkamala, R Guiraud, D Jovanov, E Dhaher, Y Panescu, D Vangils, M Wheeler, B Dhawan, AP, Institute of Electrical and Electronics Engineers (IEEE), 2016, 6074-6077 p., 7592114Conference paper (Refereed)
    Abstract [en]

    Surface Electromyography (sEMG) has applications in prosthetics, diagnostics and neuromuscular rehabilitation. Self-adhesive Ag/AgCl are the electrodes preferentially used to capture sEMG in short-term studies, however their long-term application is limited. In this study we designed and evaluated a fully integrated smart textile band with electrical connecting tracks knitted with intarsia techniques and knitted textile electrodes. Real-time myoelectric pattern recognition for motor volition and signal-to-noise ratio (SNR) were used to compare its sensing performance versus the conventional Ag-AgCl electrodes. After a comprehending measurement and performance comparison of the sEMG recordings, no significant differences were found between the textile and the Ag-AgCl electrodes in SNR and prediction accuracy obtained from pattern recognition classifiers.

  • 35.
    Brown, Shannon
    et al.
    Högskolan i Borås.
    Ortiz-Catalan, Max
    Chalmers University of Technology.
    Petersson, Joel
    Högskolan i Borås.
    Rödby, Kristian
    Högskolan i Borås.
    Seoane, Fernando
    KTH, School of Technology and Health (STH). Högskolan i Borås, Akademin för vård, arbetsliv och välfärd.
    Intarsia-sensorized band and textrodes for real-time myoelectric pattern recognition2016In: Engineering in Medicine and Biology Society (EMBC), 2016 IEEE 38th Annual International Conference of the, Institute of Electrical and Electronics Engineers (IEEE), 2016, 6074-6077 p.Conference paper (Refereed)
  • 36.
    Buendia, Ruben
    et al.
    University of Borås, Sweden.
    bogonez-franco, Paco
    Technical University of Catalonia.
    Nescolarde, Lexa
    Technical University of Catalonia.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Influence of electrode mismatch on Cole parameter estimation from Total Right Side Electrical Bioimpedance Spectroscopy measurements2012In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 34, no 7, 1024-1028 p.Article in journal (Refereed)
    Abstract [en]

    Applications based on measurements of Electrical Bioimpedance (EBI) spectroscopy analysis, like assessment of body composition, have proliferated in the past years. Currently Body Composition Assessment (BCA) based in Bioimpedance Spectroscopy (BIS) analysis relays on an accurate estimation of the Cole parameters R-0 and R-infinity. A recent study by Bogonez-Franco et al. has proposed electrode mismatch as source of remarkable artefacts in BIS measurements. Using Total Right Side BIS measurements from the aforementioned study, this work has focused on the influence of electrode mismatch on the estimation of R-0 and R-infinity using the Non-Linear Least Square curve fitting technique on the modulus of the impedance. The results show that electrode mismatch on the voltage sensing electrodes produces an overestimation of the impedance spectrum leading to a wrong estimation of the parameters R-0 and R-infinity, and consequently obtaining values around 4% larger that the values obtained from BIS without electrode mismatch. The specific key factors behind electrode mismatch or its influence on the analysis of single and spectroscopy measurements have not been investigated yet, no compensation or correction technique is available to overcome the deviation produced on the EBI measurement. Since textile-enabled EBI applications using dry textrodes, i.e. textile electrodes with dry skin-electrode interfaces and potentially large values of electrode polarization impedance are more prone to produce electrode mismatch, the lack of a correction or compensation technique might hinder the proliferation of textile-enabled EBI applications for personalized healthcare monitoring.

  • 37.
    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.

  • 38.
    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.

  • 39.
    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.

  • 40.
    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.

  • 41.
    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.

  • 42. 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.

  • 43. Capese, Sabrina
    et al.
    Chiessi, E.
    Cavalli, R.
    Giustetto, P.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    A general strategy for the obtainment of biodegradable polymer shelled microbubbles as theranostic device2013Conference paper (Refereed)
    Abstract [en]

    Introduction

    Fabrication of multifunctional ultrasound contrast agents (UCAs) has been addressed by many research groups.1,2 Recently a poly(vinyl alcohol) shelled microbubble 3 has shown a remarkable chemical and physical stability and versatility for the surface functionalization, leading to a platform for multimodality imaging (ultrasounds, magnetic resonance, single photon emission computer tomography) and targeting inflammation and tumours4. In this contribution we present a new strategy for the synthesis of UCAs precursors in the form of vesicles with a biodegradable crosslinked polymer shell.

    Methods

    Deposition of methacryloyl-derivative of hydrophilic and biodegradable polymers as dextran (DexMA50) or hyaluronic acid (HAMA30) on a lipid vesicle with a liquid perfluoropentane core, 5,6 followed by a photopolymerization of the methacrylate moiety allows the obtainment of polymer shelled vesicles.

    Results

    Lipid shelled vesicles with a perfluorocarbon (PFC) core (Figure 1a) undergo an acoustic droplet vaporization (ADV),7 upon ultrasounds (US) irradiation, transforming such particles into ultrasound effective microbubbles (Fig 1b). The process is reversible as the US are switched off (Fig 1c). In the “microbubble” state, i.e. during US irradiation, the system is echogenic at low mechanical index, allowing their use as UCAs. In this contribution we show that additional functions can be implemented into the microbubbles. For example, we demonstrated the possibility to obtain shells with a thermoreversible behaviour.

    Conclusions

    This new class of polymer shelled vesicles/microbubbles entails features desired in a potential theranostic microdevice.

  • 44.
    Chen, Fengnong
    et al.
    KTH, School of Technology and Health (STH). College of Life Information Science & Instrument Engineering, Hangzhou Dianzi University, Hangzhou 310018, China.
    Chen, Pulan
    Muhammed, Hamed Hamid
    KTH, School of Technology and Health (STH).
    Zhang, Juan
    Intravoxel Incoherent Motion Diffusion for Identification of Breast Malignant and Benign Tumors Using Chemometrics2017In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, 3845409Article in journal (Refereed)
    Abstract [en]

    Theaim of the paper is to identify the breast malignant and benign lesions using the features of apparent diffusion coefficient (ADC), perfusion fraction f, pseudodiffusion coefficient D*, and true diffusion coefficient D from intravoxel incoherent motion (IVIM). There are 69 malignant cases (including 9 early malignant cases) and 35 benign breast cases who underwent diffusion-weighted MRI at 3.0 T with 8 b-values (0 similar to 1000 s/mm(2)). ADC and IVIM parameters were determined in lesions. The early malignant cases are used as advanced malignant and benign tumors, respectively, so as to assess the effectiveness on the result. A predictive model was constructed using Support VectorMachine Binary Classification (SVMBC, also known Support VectorMachine Discriminant Analysis (SVMDA)) and Partial Least Squares Discriminant Analysis (PLSDA) and compared the difference between them both. The.. value and ADC provide accurate identification of malignant lesions with.. = 300, if early malignant tumor was considered as advanced malignant (cancer). The classification accuracy is 93.5% for cross-validation using SVMBC with ADC and tissue diffusivity only. The sensitivity and specificity are 100% and 87.0%, respectively, r(2) (cv) = 0.8163, and root mean square error of cross-validation (RMSECV) is 0.043. ADC and IVIM provide quantitative measurement of tissue diffusivity for cellularity and are helpful with the method of SVMBC, getting comprehensive and complementary information for differentiation between benign and malignant breast lesions.

  • 45.
    Chowdhury, Manish
    et al.
    KTH, School of Technology and Health (STH).
    Jörgens, Daniel
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization.
    Wang, Chunliang
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization. KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Smedby, Örjan
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization.
    Moreno, Rodrigo
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization.
    Segmentation of Cortical Bone using Fast Level Sets2017In: MEDICAL IMAGING 2017: IMAGE PROCESSING / [ed] Styner, MA Angelini, ED, SPIE - International Society for Optical Engineering, 2017, UNSP 1013327Conference paper (Refereed)
    Abstract [en]

    Cortical bone plays a big role in the mechanical competence of bone. The analysis of cortical bone requires accurate segmentation methods. Level set methods are usually in the state-of-the-art for segmenting medical images. However, traditional implementations of this method are computationally expensive. This drawback was recently tackled through the so-called coherent propagation extension of the classical algorithm which has decreased computation times dramatically. In this study, we assess the potential of this technique for segmenting cortical bone in interactive time in 3D images acquired through High Resolution peripheral Quantitative Computed Tomography (HR-pQCT). The obtained segmentations are used to estimate cortical thickness and cortical porosity of the investigated images. Cortical thickness and Cortical porosity is computed using sphere fitting and mathematical morphological operations respectively. Qualitative comparison between the segmentations of our proposed algorithm and a previously published approach on six images volumes reveals superior smoothness properties of the level set approach. While the proposed method yields similar results to previous approaches in regions where the boundary between trabecular and cortical bone is well defined, it yields more stable segmentations in challenging regions. This results in more stable estimation of parameters of cortical bone. The proposed technique takes few seconds to compute, which makes it suitable for clinical settings.

  • 46.
    Chowdhury, Manish
    et al.
    KTH, School of Technology and Health (STH).
    Klintström, Benjamin
    KTH, School of Technology and Health (STH). Linköping University, Sweden.
    Klintström, E.
    Smedby, Örjan
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization. Linköping University, Sweden.
    Moreno, Rodrigo
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization.
    Granulometry-based trabecular bone segmentation2017In: 20th Scandinavian Conference on Image Analysis, SCIA 2017, Springer, 2017, Vol. 10270, 100-108 p.Conference paper (Refereed)
    Abstract [en]

    The accuracy of the analyses for studying the three dimensional trabecular bone microstructure rely on the quality of the segmentation between trabecular bone and bone marrow. Such segmentation is challenging for images from computed tomography modalities that can be used in vivo due to their low contrast and resolution. For this purpose, we propose in this paper a granulometry-based segmentation method. In a first step, the trabecular thickness is estimated by using the granulometry in gray scale, which is generated by applying the opening morphological operation with ball-shaped structuring elements of different diameters. This process mimics the traditional sphere-fitting method used for estimating trabecular thickness in segmented images. The residual obtained after computing the granulometry is compared to the original gray scale value in order to obtain a measurement of how likely a voxel belongs to trabecular bone. A threshold is applied to obtain the final segmentation. Six histomorphometric parameters were computed on 14 segmented bone specimens imaged with cone-beam computed tomography (CBCT), considering micro-computed tomography (micro-CT) as the ground truth. Otsu’s thresholding and Automated Region Growing (ARG) segmentation methods were used for comparison. For three parameters (Tb.N, Tb.Th and BV/TV), the proposed segmentation algorithm yielded the highest correlations with micro-CT, while for the remaining three (Tb.Nd, Tb.Tm and Tb.Sp), its performance was comparable to ARG. The method also yielded the strongest average correlation (0.89). When Tb.Th was computed directly from the gray scale images, the correlation was superior to the binary-based methods. The results suggest that the proposed algorithm can be used for studying trabecular bone in vivo through CBCT.

  • 47.
    Chowdhury, Manish
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization.
    Rota Bulò, S.
    Moreno, Rodrigo
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization.
    Kundu, M.K.
    Smedby, Örjan
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization.
    An Efficient Radiographic Image Retrieval System Using Convolutional Neural Network2016In: 2016 23rd International Conference on Pattern Recognition (ICPR), Institute of Electrical and Electronics Engineers (IEEE), 2016, 3134-3139 p., 7900116Conference paper (Refereed)
    Abstract [en]

    Content-Based Medical Image Retrieval (CBMIR) is an important research field in the context of medical data management. In this paper we propose a novel CBMIR system for the automatic retrieval of radiographic images. Our approach employs a Convolutional Neural Network (CNN) to obtain high- level image representations that enable a coarse retrieval of images that are in correspondence to a query image. The retrieved set of images is refined via a non-parametric estimation of putative classes for the query image, which are used to filter out potential outliers in favour of more relevant images belonging to those classes. The refined set of images is finally re-ranked using Edge Histogram Descriptor, i.e. a low-level edge-based image descriptor that allows to capture finer similarities between the retrieved set of images and the query image. To improve the computational efficiency of the system, we employ dimensionality reduction via Principal Component Analysis (PCA). Experiments were carried out to evaluate the effectiveness of the proposed system on medical data from the “Image Retrieval in Medical Applications” (IRMA) benchmark database. The obtained results show the effectiveness of the proposed CBMIR system in the field of medical image retrieval.

  • 48. Cinti, M. N.
    et al.
    Scafe, R.
    Bennati, Paolo
    KTH, School of Technology and Health (STH), Medical Engineering.
    Lo Meo, S.
    Frantellizzi, V.
    Pellegrini, R.
    De Vincentis, G.
    Sacco, D.
    Fabbri, A.
    Pani, R.
    Innovative LuYAP:Ce array for PET imaging2017In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 12, no 3, C03069Article in journal (Refereed)
    Abstract [en]

    We present an imaging characterization of a 10 x 10 LuYAP array (2 x 2 x 10 mm3 pixels) with an innovative dielectric coating insulation (0.015 mm thick), in view of its possible use in a gamma camera for imaging positron emission tomography (PET) or in similar applications, e.g. as γ-prompt detector in hadron therapy. The particular assembly of this array was realized in order to obtain a packing fraction of 98%, improving detection efficiency and light collection. For imaging purpose, the array has been coupled with a selected Hamamatsu H10966-100 Multi Anode Photomultiplier read out by a customized 64 independent channels electronics. This tube presents a superbialkali photocathode with 38% of quantum efficiency, permitting to enhance energy resolution and consequently image quality. A pixel identification of about 0.5 mm at 662 keV was obtained, highlighting the potentiality of this detector in PET applications.

  • 49.
    Cloots, Rudy J.H.
    et al.
    Eindhoven University of Technology, Department of Mechanical Engineering.
    van Dommelen, J.A.W.
    Eindhoven University of Technology, Department of Mechanical Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Geers, Marc
    Eindhoven University of Technology, Department of Mechanical Engineering.
    Multi-scale mechanics of traumatic brain injury: predicting axonal strains from head loads2013In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 12, no 1, 137-150 p.Article in journal (Refereed)
    Abstract [en]

    The length scales involved in the development of diffuse axonal injury typically range from the head level (i.e., mechanical loading) to the cellular level. The parts of the brain that are vulnerable to this type of injury are mainly the brainstem and the corpus callosum, which are regions with highly anisotropically oriented axons. Within these parts, discrete axonal injuries occur mainly where the axons have to deviate from their main course due to the presence of an inclusion. The aim of this study is to predict axonal strains as a result of a mechanical load at the macroscopic head level. For this, a multi-scale finite element approach is adopted, in which a macro-level head model and a micro-level critical volume element are coupled. The results show that the axonal strains cannot be trivially correlated to the tissue strain without taking into account the axonal orientations, which indicates that the heterogeneities at the cellular level play an important role in brain injury and reliable predictions thereof. In addition to the multi-scale approach, it is shown that a novel anisotropic equivalent strain measure can be used to assess these micro-scale effects from head-level simulations only.

  • 50.
    Cloots, Rudy J.H.
    et al.
    Eindhoven University of Technology, Department of Mechanical Engineering.
    van Dommelen, JAW
    Eindhoven University of Technology, Department of Mechanical Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Geers, Marc
    Eindhoven University of Technology, Department of Mechanical Engineering.
    Traumatic Brain Injury at Multiple Length Scales: Relating Diffuse Axonal Injury to Discrete Axonal Impairment2010In: 2010 INTERNATIONAL IRCOBI CONFERENCE ON THE BIOMECHANICS OF INJURY PROCEEDINGS, 2010, 119-130 p.Conference paper (Refereed)
1234567 1 - 50 of 308
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