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  • 1.
    Banaem, Hossein Yousefi
    et al.
    Tehran University of Medical Science, Tehran, Iran.
    Ahmadian, Alireza
    Tehran University of Medical Science, Tehran, Iran.
    Saberi, Hooshangh
    Tehran University of Medical Science, Tehran, Iran.
    Daneshmehr, Alireza
    University of Tehran, Tehran, Iran.
    Khodadad, Davood
    Tehran University of Medical Science, Tehran, Iran.
    Brain tumor modeling: glioma growth and interaction with chemotherapy2011In: International Conference on Graphic and Image Processing (ICGIP) / [ed] Yi Xie & Yanjun Zheng, SPIE - International Society for Optical Engineering, 2011, Vol. 8285, article id 82851MConference paper (Refereed)
    Abstract [en]

    In last decade increasingly mathematical models of tumor growths have been studied, particularly on solid tumors which growth mainly caused by cellular proliferation. In this paper we propose a modified model to simulate the growth of gliomas in different stages. Glioma growth is modeled by a reaction-advection-diffusion. We begin with a model of untreated gliomas and continue with models of polyclonal glioma following chemotherapy. From relatively simple assumptions involving homogeneous brain tissue bounded by a few gross anatomical landmarks (ventricles and skull) the models have been expanded to include heterogeneous brain tissue with different motilities of glioma cells in grey and white matter. Tumor growth is characterized by a dangerous change in the control mechanisms, which normally maintain a balance between the rate of proliferation and the rate of apoptosis (controlled cell death). Result shows that this model closes to clinical finding and can simulate brain tumor behavior properly.

  • 2.
    Bergström, Per
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Khodadad, Davood
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner Dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Dual-wavelength digital holography: single-shot shape evaluation using speckle displacements and regularization2014In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 53, no 1, p. 123-131Article in journal (Refereed)
    Abstract [en]

    This paper discusses the possibility of evaluating the shape of a free-form object in comparison with its shape prescribed by a CAD model. Measurements are made based on a single-shot recording using dual-wavelength holography with a synthetic wavelength of 1.4 mm. Each hologram is numerically propagated to different focus planes and correlated. The result is a vector field of speckle displacements that is linearly dependent on the local distance between the measured surface and the focus plane. From these speckle displacements, a gradient field of the measured surface is extracted through a proportional relationship. The gradient field obtained from the measurement is then aligned to the shape of the CAD model using the iterative closest point (ICP) algorithm and regularization. Deviations between the measured shape and the CAD model are found from the phase difference field, giving a high precision shape evaluation. The phase differences and the CAD model are also used to find a representation of the measured shape. The standard deviation of the measured shape relative the CAD model varies between 7 and 19 μm, depending on the slope.

  • 3.
    Bergström, Per
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Khodadad, Davood
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Single Shot Shape Evaluation Using Dual-Wavelength Holographic Reconstructions and Regularization2014In: Fringe 2013: 7th International Workshop on Advanced Optical Imaging and Metrology / [ed] Wolfgang Osten, Springer Berlin/Heidelberg, 2014, p. 103-108Conference paper (Refereed)
    Abstract [en]

    The aim of this work is to evaluate the shape of a free form object using single shot digital holography. The digital holography results in a gradient field and wrapped phase maps representing the shape of the object. The task is then to find a surface representation from this data which is an inverse problem. To solve this inverse problem we are using regularization with additional shape information from the CAD-model of the measured object.

  • 4.
    Khodadad, Davood
    Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics, Luleå University of Technology, Luleå, Sweden.
    Combined Digital Holography and Speckle Correlation for Rapid Shape Evaluation2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In manufacturing industry there is a high demand for on line quality control to minimize the risk of incorrectly produced objects. Conventional contact measurement methods are usually slow and invasive, meaning that they cannot be used for soft materials and for complex shapes without influencing thecontrolled parts. In contrast, interferometry and digital holography in combination with computers become faster, more reliable and highly accurate as an alternative non-contact technique for industrial shape evaluation. In digital holography, access to the complex wave field and the possibility tonumerically reconstruct holograms in different planes introduce a new degree of flexibility to optical metrology. With digital holography high resolution and precise three dimensional (3D) images of the manufactured parts can be generated. This technique can also be used to capture data in a single exposure,which is important when doing measurements in a disturbed environment.The aim of this thesis is to perform online process control of free-form manufactured objects by measuring the shape and compare it to the CAD-model. To do this, a new technique to measure surface gradients and shape based on single-shot dual wavelength digital holography and image correlation of speckle displacements is demonstrated. Based on an analytical relation between phase gradients and speckle displacements it is shown that an object is retrieved uniquely to shape and position without the unwrapping problems that usually appear in dual wavelength holography. The method is firstdemonstrated using continues wave laser light from two temperature controlled laser diodes operating at 640 nm. Further a specially designed dual core diode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm is used. One significant problem when using the dual wavelength single-shot approach is that phase ambiguities are built in to the system that needs to be corrected. An automatic calibration scheme is therefore required. The intrinsic flexibility of digital holography gives a possibility to compensate these aberrations and to remove errors, fully numerically without mechanical movements. In this thesis I present a calibration method which allows single-shot online shape evaluation in a disturbed environment. It is shown that phase maps and speckle displacements can be recovered free of chromatic aberrations. This is the first time that a single-shot dual wavelength calibration is reported by defining a criteria to make an automatic procedure.By the results of the presented work, it is experimentally verified that the single-shot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. The proposed method is also robust to large phasegradients and large movements within the intensity patterns. The advantage of the approach is that, using speckle displacements, the shape measurement can be done even though the synthetic wavelength is out of the dynamic range of the height variation of the object.

  • 5.
    Khodadad, Davood
    Örebro University, School of Science and Technology. Experimental Mechanics, Luleå University of Technology, Luleå, Sweden.
    Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements for Shape Measurement2019In: International Journal of Optics, ISSN 1687-9384, E-ISSN 1687-9392, Vol. 2019, article id 4906109Article in journal (Refereed)
    Abstract [en]

    We present a digital holographic method to increase height range measurement with a reduced phase ambiguity using a dual-directional illumination. Small changes in the angle of incident illumination introduce phase differences between the recorded complex fields. We decrease relative phase difference between the recorded complex fields 279 and 139 times by changing the angle of incident 0.5° and 1°, respectively. A two cent Euro coin edge groove is used to measure the shape. The groove depth is measured as ≈300  . Further, numerical refocusing and analysis of speckle displacements in two different planes are used to measure the depth without a use of phase unwrapping process.

  • 6.
    Khodadad, Davood
    Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics, Luleå University of Technology, Sweden.
    Multiplexed Digital Holography incorporating Speckle Correlation2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In manufacturing industry there is a high demand for on line quality control to minimize the risk of incorrectly produced objects. Conventional contact measurement methods are usually slow and invasive, meaning that they cannot be used for soft materials and for complex shapes without influencing the controlled parts. In contrast, interferometry and digital holography in combination with computers become faster, more reliable and highly accurateas an alternative non-contact technique for industrial shape evaluation. For example in digital holography, access to the complex wave field and the possibility to numerically reconstruct holograms in different planes introduce a new degree of flexibility to optical metrology. With digital holography high resolution and precise three dimensional (3D) images of the manufactured parts can be generated. This technique can also be used to capture data in asingle exposure, which is important when doing measurements in a disturbed environment. The aim of this thesis is devoted to the theoretical and experimental development of shape and deformation measurements. To perform online process control of free-form manufactured objects, the measured shape is compared with the CAD-model to obtain deviations. To do this, a new technique to measure surface gradients and shape based onsingle-shot multiplexed dual-wavelength digital holography and image correlation of speckle displacements is demonstrated. Based on an analytical relation between phase gradients and speckle displacements it is shown that an object is retrieved uniquely to shape, position and deformation without the unwrapping problems that usually appear in dual-wavelength holography. The method is first demonstrated using continues-wave laser light from twotemperature controlled laser diodes operating at 640 nm. Then a specially designed dual core diode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm is used. In addition, a Nd:YAG laser with the wavelength of 532 nm is used for 3D deformation measurements. One significant problem when using the dual-wavelength single-shot approach is that phase ambiguities are built in to the system that needs to be corrected. An automatic calibration scheme is therefore required. The intrinsic flexibility of digital holography gives a possibility to compensate these aberrations and to remove errors, fully numerically without mechanical movements. In this thesis I present a calibration method which allows multiplexed singleshotonline shape evaluation in a disturbed environment. It is shown that phase maps and speckle displacements can be recovered free of chromatic aberrations. This is the first time that a multiplexed single-shot dual-wavelength calibration is reported by defining a criteria tomake an automatic procedure. Further, Digital Speckle Photography (DSP) is used for the full field measurement of 3D deformations. In order to do 3D deformation measurement, usually multi-cameras and intricate set-up are required. In this thesis I demonstrate the use of only one single camera torecord four sets of speckle patterns recorded by illuminating the object from four different directions. In this manner, meanwhile 3D speckle displacement is calculated and used for the measurement of the 3D deformations, wrapping problems are also avoided. Further, the same scale of speckle images of the surface for all four images is guaranteed. Furthermore, a need for calibration of the 3D deformation measurement that occurs in the multi-camera methods,is removed. By the results of the presented work, it is experimentally verified that the multiplexed singleshot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. Usingmultidirectional illumination, the 3D deformation measurements can also be obtained. The proposed method is robust to large phase gradients and large movements within the intensity patterns. The advantage of the approach is that, using speckle displacements, shape and deformation measurements can be performed even though the synthetic wavelength is out of the dynamic range of the object deformation and/or height variation.

  • 7.
    Khodadad, Davood
    Örebro University, School of Science and Technology. Experimental Mechanics, Luleå University of Technology, Luleå, Sweden .
    Phase-derivative-based estimation of a digital reference wave from a single off-axis digital hologram2016In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 7, p. 1663-1669Article in journal (Refereed)
    Abstract [en]

    This paper describes a method to obtain an estimated digital reference wave from a single off-axis digital hologram that matches the actual experimental reference wave as closely as possible. The proposed method is independent of a reference flat plate and speckles. The digital reference wave parameters are estimated directly from the recorded phase information. The parameters include both the off-axis tilt angle and the curvature of the reference wave. Phase derivatives are used to extract the digital reference wave parameters without the need for a phase unwrapping process. Thus, problems associated with phase wrapping are avoided. Experimental results for the proposed method are provided. The simulated effect of the digital reference wave parameters on the reconstructed image phase distribution is shown. The pseudo phase gradient originating from incorrect estimation of the digital reference wave parameters and its effect on object reconstruction are discussed.

  • 8.
    Khodadad, Davood
    et al.
    Tehran University of Medical Science, Tehran, Islamic Republic of Iran.
    Ahmadian, Alireza
    Tehran University of Medical Science, Tehran, Islamic Republic of Iran.
    Ay, Mohammadreza
    Tehran University of Medical Science, Tehran, Islamic Republic of Iran.
    Esfahani, Armaghan Fard
    Tehran University of Medical Science, Tehran, Islamic Republic of Iran.
    Banaem, Hossein Yousefi
    Tehran University of Medical Science, Tehran, Islamic Republic of Iran.
    Zaidi, Habib
    Geneva University Hospital, Geneva, Switzerland.
    B-spline based free form deformation thoracic non-rigid registration of CT and PET images2011In: International Conference on Graphic and Image Processing (ICGIP 2011) / [ed] Yi Xie & Yanjun Zheng, SPIE - International Society for Optical Engineering, 2011, Vol. 8285, article id 82851KConference paper (Refereed)
    Abstract [en]

    Accurate attenuation correction of emission data is mandatory for quantitative analysis of PET images. One of the main concerns in CT-based attenuation correction(CTAC) of PET data in multimodality PET/CT imaging is misalignment between PET and CT images. The aim of this study, is to proposed a hybrid method which is simple, fast and accurate, for registration of PET and CT data which affected from respiratory motion in order to improve the quality of CTAC. The algorithm is composed of three methods: First, using B-spline Free Form Deformation to describe both images and deformation field. Then applying a pre-filtering on both PET and CT images before segmentation of structures in order to reduce the respiratory related attenuation correction artifacts of PET emission data. In this approach, B-spline using FFD provide more accurate adaptive transformation to align the images, and structure constraints obtained from prefiltering applied to guide the algorithm to be more fast and accurate. Also it helps to reduce the radiation dose in PET/CT by avoiding repetition of CT imaging. These advances increase the potential of the method for routine clinical application.

  • 9.
    Khodadad, Davood
    et al.
    Experimental Mechanics, Luleå University of Technology, Luleå, Sweden.
    Ahmadian, Alireza
    Institute for Advanced Medical Technologies (IAMT), Tehran University of Medical Science, Tehran, Iran.
    Banaem, Hossein Yousefi
    Department of Medical Physics and Medical Engineering, Isfahan University of Medical Sciences, Isfahan, Iran.
    Ay, Mohammad Reza
    Research Institute for Nuclear Medicine, Tehran University of Medical Science, Tehran, Iran .
    Fard-Esfahani, Armaghan
    Research Institute for Nuclear Medicine, Tehran University of Medical Science, Tehran, Iran .
    CT and PET Image Registration: Application to Thorax Area2013In: Journal of Image and Graphics, ISSN 2301-3699, Vol. 1, no 4, p. 171-175Article in journal (Refereed)
    Abstract [en]

    Accurate attenuation correction of emission data is mandatory for quantitative analysis of PET images. One of the main concerns in CT-based attenuation correction (CTAC) of PET data in multimodality PET/CT imaging is misalignment occurred due to respiratory artifact between PET and CT images. In this paper a combined method which is simple and fast is proposed for registration of PET and CT data to correct the effect of this artifact. The algorithm is composed of two step: First step is meant to reduce the noise by applying an adaptive gradient anistropic diffusion filter then using Iterative closest point (ICP) registration method in order to obtain initial estimation to ensure fast and accurate convergence of the algorithm. At the second step, the respiratory related artifact of PET images is greatly reduced by employing Free Form Deformation algorithm based on B-spline which provides more accurate adaptive transformation to align the images.

  • 10.
    Khodadad, Davood
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Amer, Eynas
    Luleå University of Technology, Luleå, Sweden.
    Gren, Per
    Luleå University of Technology, Luleå, Sweden.
    Melander, Emil
    Uppsala University, Uppsala, Sweden.
    Hällstig, Emil
    Fotonic, Stockholm, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Luleå, Sweden.
    Single-shot dual-polarization holography: measurement of the polarization state of a magnetic sample2015In: VI International Conference on Speckle Metrology, SPIE - International Society for Optical Engineering, 2015, Vol. 9660, article id 96601EConference paper (Refereed)
    Abstract [en]

    In this paper a single-shot digital holographic set-up with two orthogonally polarized reference beams is proposed to achieve rapid acquisition of Magneto-Optical Kerr Effect images. Principles of the method and the background theory for dynamic state of polarization measurement by use of digital holography are presented. This system has no mechanically moving elements or active elements for polarization control and modulation. An object beam is combined with two reference beams at different off-axis angles and is guided to a detector. Then two complex fields (interference terms) representing two orthogonal polarizations are recorded in a single frame simultaneously. Thereafter the complex fields are numerically reconstructed and carrier frequency calibration is done to remove aberrations introduced in multiplexed digital holographic recordings. From the numerical values of amplitude and phase, a real time quantitative analysis of the polarization state is possible by use of Jones vectors. The technique is demonstrated on a magnetic sample that is a lithographically patterned magnetic microstructure consisting of thin permalloy parallel stripes.

  • 11.
    Khodadad, Davood
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Bergström, Per
    Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic, Skellefteå, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Luleå, Sweden.
    Dual-wavelength digital holography: single shot calibration2014In: Interferometry XVII: Techniques and Analysis / [ed] Katherine Creath, Jan Burke & Joanna Schmit, SPIE - International Society for Optical Engineering, 2014, Vol. 9203, article id 920305Conference paper (Refereed)
    Abstract [en]

    In an on line shape measurement in disturbed environment, use of many wavelengths in order to avoid phase ambiguity may become a problem as it is necessary to acquire all holograms simultaneously due to environmental disturbances. Therefore to make the shape data available the different holograms have to be extracted from a single recorded image in spectral domain. Appropriate cut areas in the Fourier method are therefore of great importance for decoding information carried by different wavelengths. Furthermore using different laser sources, induces aberration and pseudo phase changes which must be compensated. To insure any phase change is only because of the object shape, calibration is therefore indispensable. For this purpose, effects of uncontrolled carrier frequency filtering are discussed. A registration procedure is applied using minimum speckle displacements to find the best cut area to extract and match the interference terms. Both holograms are numerically propagated to a focus plane to avoid any unknown errors. Deviations between a reference known plate and its measurement are found and used for calibration. We demonstrate that phase maps and speckle displacements can be recovered free of chromatic aberrations. To our knowledge, this is the first time that a single shot dual wavelength calibration is reported by defining a criteria to make the spatial filtering automatic avoiding the problems of manual methods. The procedure is shown to give shape accuracy of 35ÎŒm with negligible systematic errors using a synthetic wavelength of 1.1 mm.

  • 12.
    Khodadad, Davood
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Bergström, Per
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Fast and robust automatic calibration for single-shot dual-wavelength digital holography based on speckle displacements2015In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, no 16, p. 5003-5010Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to describe a fast and robust automatic single-shot dual-wavelength holographic calibration method that can be used for online shape measurement applications. We present a model of the correction in two terms for each lobe, one to compensate the systematic errors caused by off-axis angles and the other for the curvature of the reference waves, respectively. Each hologram is calibrated independently without a need for an iterative procedure or information of the experimental set-up. The calibration parameters are extracted directly from speckle displacements between different reconstruction planes. The parameters can be defined as any fraction of a pixel to avoid the effect of quantization. Using the speckle displacements, problems associated with phase wrapping is avoided. The procedure is shown to give a shape accuracy of 34 μm using a synthetic wavelength of 1.1 mm for a measurement on a cylindrical test object with a trace over a field of view of 18  mm×18  mm.

  • 13.
    Khodadad, Davood
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Bergström, Per
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Single Shot Dual-Wavelength Digital Holography: Calibration Based on Speckle Displacements2014In: International Journal of Optomechatronics, ISSN 1559-9612, Vol. 8, no 4, p. 326-339Article in journal (Refereed)
    Abstract [en]

    We present a calibration method which allows single shot dual wavelength online shape measurement in a disturbed environment. Effects of uncontrolled carrier frequency filtering are discussed as well. We demonstrate that phase maps and speckle displacements can be recovered free of chromatic aberrations. To our knowledge, this is the first time that a single shot dual wavelength calibration is reported by defining a criteria to make the spatial filtering automatic avoiding the problems of manual methods. The procedure is shown to give shape accuracy of 35 µm with negligible systematic errors using a synthetic wavelength of 1.1 mm.

  • 14.
    Khodadad, Davood
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Hallstig, Emil J.
    Optronic, Skellefteå, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Luleå, Sweden.
    Dual-wavelength digital holographic shape measurement using speckle movements and phase gradients2013In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 52, no 10, article id 101912Article in journal (Refereed)
    Abstract [en]

    A new method to measure shape by analyzing the speckle movements in images generated by numerical propagation from dual-wavelength holograms is presented. The relationship of the speckle movements at different focal distances is formulated, and it is shown how this carries information about the surface position as well as the local slope of the object. It is experimentally verified that dual-wavelength holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve the object shape. From a measurement on a cylindrical test object, the method is demonstrated to have a random error in the order of a few micrometers.

  • 15.
    Khodadad, Davood
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Luleå, Sweden.
    Shape reconstruction using dual wavelength digital holography and speckle movements2013In: Optical Measurement Systems for Industrial Inspection VIII / [ed] Peter H. Lemann, Wolfgang Osten & Armando Albertazzi, SPIE - International Society for Optical Engineering, 2013, Vol. 8788, article id 878801Conference paper (Refereed)
    Abstract [en]

    A new technique to measure depth based on dual wavelength digital holography and image correlation of speckle movements is demonstrated. By numerical refocusing of the complex optical field to different focus planes and by measuring the speckle movements caused by a wavelength shift both the object surface position and its local slope can be determined. It is shown how the speckle movement varies linearly with the surface slope, the wavelength shift and the distance of the numerical propagation. This gives a possibility to measure the slope with approximately the same precision as from the interferometric phase maps. In addition, when the object surface is in focus there is no speckle movement so by estimating in what plane the speckle movement is zero the absolute surface position can be measured.

  • 16.
    Khodadad, Davood
    et al.
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Nordebo, Sven
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Müller, Beat
    Swisstom AG, Landquart, Switzerland.
    Waldmann, Andreas
    Swisstom AG, Landquart, Switzerland.
    Yerworth, Rebecca
    Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom.
    Becher, Tobias
    Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Kiel, Germany.
    Frerichs, Inez
    Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Kiel, Germany.
    Sophocleous, Louiza
    KIOS Research Centre, Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, Cyprus.
    Van Kaam, Anton
    Department of Neonatology, Emma Children's Hospital, Academic Medical Center, Amsterdam, Netherlands; Department of Neonatologu, VU Medical Center, Amsterdam, Netherlands.
    Miedema, Martijn
    Department of Neonatology, Emma Children's Hospital, Academic Medical Center, Amsterdam, Netherlands.
    Seifnaraghi, N
    Department of Natural Sciences, Middlesex University, Hendon campus, The Burroughs, London, United Kingdom.
    Bayford, R
    Department of Natural Sciences, Middlesex University, Hendon campus, The Burroughs, London, United Kingdom.
    Optimized breath detection algorithm in electrical impedance tomography2018In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 39, no 9, article id 094001Article in journal (Refereed)
    Abstract [en]

    Objective: This paper defines a method for optimizing the breath delineation algorithms used in electrical impedance tomography (EIT). In lung EIT the identification of the breath phases is central for generating tidal impedance variation images, subsequent data analysis and clinical evaluation. The optimisation of these algorithms is particularly important in neonatal care since the existing breath detectors developed for adults may give insufficient reliability in neonates due to their very irregular breathing pattern.

    Approach: Our approach is generic in the sense that it relies on the definition of a gold standard and the associated definition of detector sensitivity and specificity, an optimisation criterion and a set of detector parameters to be investigated. The gold standard has been defined by 11 clinicians with previous experience with EIT and the performance of our approach is described and validated using a neonatal EIT dataset acquired within the EU-funded CRADL project.

    Main results: Three different algorithms are proposed that improve the breath detector performance by adding conditions on (1) maximum tidal breath rate obtained from zero-crossings of the EIT breathing signal, (2) minimum tidal impedance amplitude and (3) minimum tidal breath rate obtained from time-frequency analysis. As a baseline a zero-crossing algorithm has been used with some default parameters based on the Swisstom EIT device.

    Significance: Based on the gold standard, the most crucial parameters of the proposed algorithms are optimised by using a simple exhaustive search and a weighted metric defined in connection with the receiver operating characterics. This provides a practical way to achieve any desirable trade-off between the sensitivity and the specificity of the detectors.

  • 17.
    Khodadad, Davood
    et al.
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Nordebo, Sven
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Seifnaraghi, Nima
    Faculty of science and technology, Middlesex University, Hendon campus, The Burroughs, London, United Kingdom.
    Waldmann, Andreas D.
    Swisstom AG, Landquart, Switzerland.
    Müller, Beat
    Swisstom AG, Landquart, Switzerland.
    Bayford, Richard
    Faculty of science and technology, Middlesex University, Hendon campus, The Burroughs, London, United Kingdom.
    Breath detection using short-time Fourier transform analysis in electrical impedance tomography2017In: 2017 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS), IEEE, 2017, p. 1-3Conference paper (Refereed)
    Abstract [en]

    Spectral analysis based on short-time Fourier transform (STFT) using Kaiser window is proposed to examine the frequency components of neonates EIT data. In this way, a simultaneous spatial-time-frequency analysis is achieved.

  • 18.
    Khodadad, Davood
    et al.
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Nordebo, Sven
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Seifnaraghi, Nima
    Department of Natural Sciences, Middlesex University, Hendon Campus, The Burroughs, London, United Kingdom.
    Yerworth, Rebecca
    Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom.
    Waldmann, Andreas D.
    Swisstom AG, Landquart, Switzerland.
    Müller, Beat
    Swisstom AG, Landquart, Switzerland.
    Frerichs, Inéz
    Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Kiel, Germany.
    van Kaam, Anton
    Emma Children's Hospital, Academic Medical Center, Department of Neonatology, Amsterdam, The Netherlands.
    Miedema, Martijn
    Emma Children's Hospital, Academic Medical Center, Department of Neonatology, Amsterdam, The Netherlands.
    Bayford, Richard
    Department of Natural Sciences, Middlesex University, Hendon Campus, The Burroughs, London, United Kingdom.
    The Value of Phase Angle in Electrical Impedance Tomography Breath Detection2018In: 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Electromagnetics Academy , 2018, p. 1040-1043Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is to report our investigation demonstrating that the phase angle information of complex impedance could be a simple indicator of a breath cycle in chest Electrical Impedance Tomography (EIT). The study used clinical neonatal EIT data. The results show that measurement of the phase angle from complex EIT data can be used as a complementary information for improving the conventional breath detection algorithms.

  • 19.
    Khodadad, Davood
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden; Institute of Applied Optics, University of Stuttgart, Stuttgart, Germany; Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden .
    Singh, Alok Kumar
    Institute of Applied Optics, University of Stuttgart, Stuttgart. Germany .
    Pedrini, Giancarlo
    Institute of Applied Optics, University of Stuttgart, Stuttgart. Germany .
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå Sweden.
    Full-field 3D deformation measurement: comparison between speckle phase and displacement evaluation2016In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 27, p. 7735-7743Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to describe a full-field deformation measurement method based on 3D speckle displacements. The deformation is evaluated from the slope of the speckle displacement function that connects the different reconstruction planes. For our experiment, a symmetrical arrangement with four illuminations parallel to the planes (x,z) and (y,z) was used. Four sets of speckle patterns were sequentially recorded by illuminating an object from the four directions, respectively. A single camera is used to record the holograms before and after deformations. Digital speckle photography is then used to calculate relative speckle displacements in each direction between two numerically propagated planes. The 3D speckle displacements vector is calculated as a combination of the speckle displacements from the holograms recorded in each illumination direction. Using the speckle displacements, problems associated with rigid body movements and phase wrapping are avoided. In our experiment, the procedure is shown to give the theoretical accuracy of 0.17 pixels yielding the accuracy of 2 x 10(-3) in the measurement of deformation gradients.

  • 20.
    Khodadad, Davood
    et al.
    Experimental Mechanics, Luleå University of Technology, Sweden.
    Sjöberg, T.
    Division of Mechanics of Solid Materials, Luleå University of Technology, Sweden.
    A nondestructive validation of reverse impact experiment based on shape measurement using high speed photographs2013In: 2013 International Conference on Advanced Optoelectronics and Lasers (CAOL 2013), IEEE, 2013, p. 322-324Conference paper (Refereed)
    Abstract [en]

    High speed photography of a reverse impact scenario was taken in order to make shape measurement. The results from the shape measurements were then compared with results from numerical simulations in order to evaluate the possibility to use noncontact shape measurement as a validation tool in future simulations.

  • 21.
    Khodadad, Davood
    et al.
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Tayebi, Behnam
    Department of Brain and Cognitive Engineering, Korea University, Seoul, South Korea.
    Shape Measurement Based on Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements2018In: 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Electromagnetics Academy , 2018, p. 184-189Conference paper (Refereed)
    Abstract [en]

    We present a dual-directional illumination digital holographic method to increase height range measurement with a reduced phase ambiguity. Small change in the illumination angle of incident introduce phase difference between the recorded complex fields. We decrease relative phase difference between the recorded complex field 279 and 139 times by changing the angle of incident 0.5° and 1°, respectively. A two cent Euro coin edge groove is used to measure the shape. The groove depth is measured as ≈ 300μm. Further, numerical re-focusing and analysis of speckle displacements in two different planes are used to measure the depth without a use of phase unwrapping process.

  • 22.
    Nordebo, Sven
    et al.
    Department of Physics and Electrical Engineering, Linnæus University, Växjö, Sweden.
    Dalarsson, Mariana
    Department of Physics and Electrical Engineering, Linnæus University, Växjö, Sweden.
    Khodadad, Davood
    Department of Physics and Electrical Engineering, Linnæus University, Växjö, Sweden.
    Müller, Beat
    Swisstom AG, Landquart, Switzerland.
    Waldman, Andreas D
    Swisstom AG, Landquart, Switzerland.
    Becher, Tobias
    Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Kiel, Germany.
    Frerichs, Inez
    Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Kiel, Germany.
    Sophocleous, Louiza
    The KIOS Research Center, Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, Cyprus.
    Sjöberg, Daniel
    Department of Electrical and Information Technology, Lund University, Lund, Sweden.
    Seifnaraghi, Nima
    Department of Natural Sciences, Middlesex University, Hendon campus, The Burroughs, London, United Kingdom.
    A parametric model for the changes in the complex valued conductivity of a lung during tidal breathing2018In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, no 20, article id 205401Article in journal (Refereed)
    Abstract [en]

    Classical homogenization theory based on the Hashin-Shtrikman coated ellipsoids is used to model the changes in the complex valued conductivity (or admittivity) of a lung during tidal breathing. Here, the lung is modeled as a two-phase composite material where the alveolar air-filling corresponds to the inclusion phase. The theory predicts a linear relationship between the real and the imaginary parts of the change in the complex valued conductivity of a lung during tidal breathing, and where the loss cotangent of the change is approximately the same as of the effective background conductivity and hence easy to estimate. The theory is illustrated with numerical examples based on realistic parameter values and frequency ranges used with electrical impedance tomography (EIT). The theory may be potentially useful for imaging and clinical evaluations in connection with lung EIT for respiratory management and control.

  • 23.
    Seifnaraghi, Nima
    et al.
    Department of Science and Technology, Middlesex University, London, UK.
    Tizzard, Andrew
    Department of Science and Technology, Middlesex University, London, UK.
    de Gelidi, Serena
    Department of Science and Technology, Middlesex University, London, UK.
    Khodadad, Davood
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Nordebo, Sven
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Van Kaam, Anton
    Faculty of Medicine, University of Amsterdam, Amsterdam, The Netherlands.
    Frerichs, Inez
    Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Kiel, Germany.
    Waldmann, Andreas
    Swisstom AG company, Landquart, Switzerland.
    Sorantin, Erich
    Department of Radiology, Medical University of Graz, Graz, Austria.
    Tschauner, Sebastian
    Department of Radiology, Medical University of Graz, Graz, Austria.
    Demosthenous, Andreas
    Department of Electronic & Electrical Engineering, UCL, London, UK.
    Christofides, Stelios
    Department of Medical Physics, Nicosia Generel Hospital, Nicosia, Cyprus.
    Bayford, Richard
    Department of Science and Technology, Middlesex University, London, UK.
    Estimation of thorax shape for forward modelling in lungs EIT2017In: Proceedings of the 18th International Conference on Biomedical Applications of Electrical Impedance Tomography / [ed] Alistair Boyle, Ryan Halter, Ethan Murphy & Andy Adler, Hanover, New Hampshire, USA: Thayer School of Engineering at Dartmouth , 2017, p. 58-58Conference paper (Refereed)
    Abstract [en]

    The thorax models for pre-term babies are developed based on the CT scans from new-borns and their effect on image reconstruction is evaluated in comparison with other available models.

  • 24.
    Shiraz, A.
    et al.
    Department of Electronic and Electrical Engineering, University College London, London, United Kingdom.
    Khodadad, Davood
    Örebro University, School of Science and Technology.
    Nordebo, S.
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Yerworth, R.
    Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom.
    Frerichs, I.
    Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Kiel, Germany.
    van Kaam, A.
    Department of Neonatology, Emma Children’s Hospital, Academic Medical Center, Amsterdam, The Netherlands; Department of Neonatology, VU Medical Center, Amsterdam, The Netherlands.
    Kallio, M.
    PEDEGO Research Unit, Medical Research Center Oulu, University of Oulu, Oulu, Finland; Department of Children and Adolescents, Oulu University Hospital, Finland.
    Papadouri, T.
    Bayford, R.
    Department of Electronic and Electrical Engineering, University College London, London, United Kingdom.
    Demosthenous, A.
    Department of Electronic and Electrical Engineering, University College London, London, United Kingdom.
    Compressive sensing in electrical impedance tomography for breathing monitoring2019In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 40, no 3, article id 034010Article in journal (Refereed)
    Abstract [en]

    Objective: Electrical impedance tomography (EIT) is a functional imaging technique in which cross-sectional images of structures are reconstructed based on boundary trans-impedance measurements. Continuous functional thorax monitoring using EIT has been extensively researched. Increasing the number of electrodes, number of planes and frame rate may improve clinical decision making. Thus, a limiting factor in high temporal resolution, 3D and fast EIT is the handling of the volume of raw impedance data produced for transmission and its subsequent storage. Owing to the periodicity (i.e. sparsity in frequency domain) of breathing and other physiological variations that may be reflected in EIT boundary measurements, data dimensionality may be reduced efficiently at the time of sampling using compressed sensing techniques. This way, a fewer number of samples may be taken.

    Approach: Measurements using a 32-electrode, 48-frames-per-second EIT system from 30 neonates were post-processed to simulate random demodulation acquisition method on 2000 frames (each consisting of 544 measurements) for compression ratios (CRs) ranging from 2 to 100. Sparse reconstruction was performed by solving the basis pursuit problem using SPGL1 package. The global impedance data (i.e. sum of all 544 measurements in each frame) was used in the subsequent studies. The signal to noise ratio (SNR) for the entire frequency band (0 Hz–24 Hz) and three local frequency bands were analysed. A breath detection algorithm was applied to traces and the subsequent error-rates were calculated while considering the outcome of the algorithm applied to a down-sampled and linearly interpolated version of the traces as the baseline.

    Main results: SNR degradation was generally proportional with CR. The mean degradation for 0 Hz–8 Hz (of interest for the target physiological variations) was below ~15 dB for all CRs. The error-rates in the outcome of the breath detection algorithm in the case of decompressed traces were lower than those associated with the corresponding down-sampled traces for CR  ⩾  25, corresponding to sub-Nyquist rate for breathing frequency. For instance, the mean error-rate associated with CR  =  50 was ~60% lower than that of the corresponding down-sampled traces.

    Significance: To the best of our knowledge, no other study has evaluated the applicability of compressive sensing techniques on raw boundary impedance data in EIT. While further research should be directed at optimising the acquisition and decompression techniques for this application, this contribution serves as the baseline for future efforts.

  • 25.
    Sjödahl, Mikael
    et al.
    Luleå University of Technology, Lkuleå, Sweden.
    Hallstig, Emil
    Optronic, Sekellefteå, Sweden.
    Khodadad, Davood
    Luleå University of Technology, Lkuleå, Sweden.
    Multi-spectral speckles: theory and applications2012In: Speckle 2012: V International Conference on Speckle Metrology / [ed] Ángel Fernandez Doval & Cristina Trillo, SPIE - International Society for Optical Engineering, 2012, Vol. 8413, article id 841306Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is to discuss the properties and a few applications of multi-spectral speckles. The paper starts with a theoretical section where the correlation properties of multi-spectral speckles are detailed for the case of reflective imaging geometry. Both a free-space geometry and an imaging geometry are detailed. As an application example effects and possibilities provided by the theory in a measurement of surface shape of a generally shaped object from a dual-wavelength holographic recording are detailed. It is showed that the same phase profile is obtained from integration of speckle movements and phase unwrapping and they are therefore exchangeable quantities.

  • 26.
    Tjörnhammar, Staffan
    et al.
    Department of Applied Physics, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Eklöf, Finn Klemming
    Department of Applied Physics, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Yu, Zhangwei
    Department of Applied Physics, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Khodadad, Davood
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden .
    Hällstig, Emil
    Fotonic, Stockholm, Sweden .
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden .
    Laurell, Fredrik
    Department of Applied Physics, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Multiwavelength laser designed for single-frame digital holography2016In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 27, p. 7517-7521Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a tailored multiwavelength Yb-fiber laser source in the 1.03 μm spectral region for spatially multiplexed digital holographic acquisitions. The wavelengths with bandwidths below 0.1 nm were spectrally separated by approximately 1 nm by employing fiber Bragg gratings for spectral control. As a proof of concept, the shape of a cylindrically shaped object with a diameter of 48 mm was measured. The holographic acquisition was performed in single-shot dual-wavelength mode with a synthetic wavelength of 1.1 mm, and the accuracy was estimated to be 3% of the synthetic wavelength.

  • 27.
    Yousefi, Hossein
    et al.
    Research Centre for Biomedical Technology and Robotics, RCBTR, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences (TUMS), Tehran, Iran.
    Ahmadian, Alireza
    Research Centre for Biomedical Technology and Robotics, RCBTR, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences (TUMS), Tehran, Iran.
    Khodadad, Davood
    Experimental Mechanics, Luleå University of Technology, Luleå, Sweden; Exceptional Talents Development Centre,Tehran, Iran .
    Saberi, Hooshangh
    Brain and Spinal Injuries Repair Research Centre, Department of Neurosurgery, Tehran University of Medical Sciences (TUMS), Tehran, Iran.
    Daneshmehr, Alireza
    Department of Mechanical Engineering, University of Tehran, Tehran, Iran .
    An optimised linear mechanical model for estimating brain shift caused by meningioma tumours2013In: International Journal of Biomedical Science and Engineering, ISSN 2376-7227, Vol. 1, no 1, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Estimation of brain deformation plays an important role in computer-aided therapy and image-guided neurosurgery systems. Tumour growth can cause brain deformation and change stress distribution in the brain. Biomechanical models exist that use a finite element method to estimate brain shift caused by tumour growth. Such models can be categorised as linear and non-linear models, both of which assume finite deformation of the brain after tumour growth. Linear models are easy to implement and fast enough to for applications such as IGS where the time is a great of concern. However their accuracy highly dependent on the parameters of the models in this paper, we proposed an optimisation approach to improve a naive linear model to achieve more precise estimation of brain displacements caused by tumour growth. The optimisation process has improved the accuracy of the model by adapting the brain model parameters according to different tomour sizes.We used patient-based tetrahedron finite element mesh with proper material properties for brain tissue and appropriate boundary conditions in the tumour region. Anatomical landmarks were determined by an expert and were divided into two different sets for evaluation and optimisation. Tetrahedral finite element meshes were used and the model parameters were optimised by minimising the mean square distance between the predicted locations of the anatomical landmarks derived from Brain Atlas images and their actual locations on the tumour images. Our results demonstrate great improvement in the accuracy of an optimised linear mechanical model that achieved an accuracy rate of approximately 92%.

  • 28.
    Yousefi-Banaem, Hossein
    et al.
    Department of Biomedical Engineering, Faculty of Advance Medical Technology, Isfahan University of Medical Science, Isfahan Iran.
    Kermani, Saeed
    Department of Biomedical Engineering, Faculty of Advance Medical Technology, Isfahan University of Medical Science, Isfahan Iran.
    Sarrafzadeh, Omid
    Department of Biomedical Engineering, Faculty of Advance Medical Technology, Isfahan University of Medical Science, Isfahan Iran.
    Khodadad, Davood
    Experimental Mechanics, Luleå University of Technology, Luleå, Sweden.
    An improved spatial FCM algorithm for cardiac image segmentation2013In: 2013 13th Iranian Conference on Fuzzy Systems (IFSC), IEEE, 2013, p. 1-4Conference paper (Refereed)
    Abstract [en]

    Image segmentation is one of challenging field in medical image processing. Segmentation of cardiac wall is one of challenging work and it is very important step in evaluation of heart functionality by existing methods. For cardiac image analysis, Fuzzy C- Means (FCM) algorithm proved to be superior over the other clustering approaches in segmentation field. However, the nave FCM algorithm is sensitive to noise because of not considering the spatial information in the image. In this paper an improved FCM algorithm is formulated by incorporating the spatial domain neighborhood information into the membership function for clustering (ISFCM). In this paper we applied improved Fuzzy c-Means with spatial information for left ventricular wall segmentation. Obtained results showed that the proposed method can segment cardiac wall automatically with acceptable accuracy. The comparison of proposed method with nave FCM proved that ISFCM can segment with more accuracy than nave FCM.

1 - 28 of 28
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