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  • 1.
    Banaem, Hossein Y.
    et al.
    Tehran University of Medical Sciences, Iran.
    Ahmadian, Alireza
    Tehran University of Medical Sciences, Iran.
    Saberi, Hooshangh
    Tehran University of Medical Sciences, Iran.
    Daneshmehr, Alireza
    Univiversity of Tehran, Iran.
    Khodadad, Davood
    Tehran University of Medical Sciences, Iran.
    Brain tumor modeling: glioma growth and interaction with chemotherapy2011Ingår i: Proc. SPIE 8285, International Conference on Graphic and Image Processing (ICGIP 2011), SPIE - International Society for Optical Engineering, 2011, artikel-id 82851MKonferensbidrag (Refereegranskat)
    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.
    Luleå University of Technology.
    Khodadad, Davood
    Luleå University of Technology.
    Hällstig, Emil
    Optronic Partner dp AB.
    Sjödahl, Mikael
    Luleå University of Technology.
    Single Shot Shape Evaluation Using Dual-Wavelength Holographic Reconstructions and Regularization2013Ingår i: Fringe 2013: 7th International Workshop on Advanced Optical Imaging and Metrology / [ed] Wolfgang Osten, Springer, 2013, s. 103-108Konferensbidrag (Refereegranskat)
    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.

  • 3.
    Khodadad, Davood
    et al.
    Luleå University of Technology.
    Bergström, Per
    Luleå University of Technology.
    Hällstig, Emil
    Optronic Partner dp AB.
    Sjödahl, Mikael
    Luleå University of Technology.
    Dual-wavelength digital holography: single shot calibration2014Ingår i: Proc. SPIE9203: Interferometry XVII: Techniques and Analysis / [ed] Katherine Creath; Jan Burke; Joanna Schmit, SPIE - International Society for Optical Engineering, 2014, artikel-id 920305Konferensbidrag (Refereegranskat)
    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 35μm with negligible systematic errors using a synthetic wavelength of 1.1 mm.

  • 4.
    Khodadad, Davood
    et al.
    Luleå University of Technology.
    Bergström, Per
    Luleå University of Technology.
    Hällstig, Emil
    Optronic Partner dp AB.
    Sjödahl, Mikael
    Luleå University of Technology.
    Fast and robust automatic calibration for single-shot dual-wavelength digital holography based on speckle displacements2015Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, nr 16, s. 5003-5010Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Khodadad, Davood
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Nordebo, Sven
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Seifnaraghi, Nima
    The Burroughs, UK.
    Waldmann, Andreas D.
    Swisstom AG, Switzerland.
    Müller, Beat
    Swisstom AG, Switzerland.
    Bayford, Richard
    The Burroughs, UK.
    Breath detection using short-time Fourier transform analysis in electrical impedance tomography2017Ingår i: 2017 32nd General Assembly and Scientific Symposium of the International Union of Radio Science, URSI GASS 2017, IEEE, 2017, , s. 3s. 1-3Konferensbidrag (Refereegranskat)
    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.

  • 6.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Dalarsson, Mariana
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Khodadad, Davood
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Müller, Beat
    Swisstom AG, Switzerland.
    Waldermann, Andreas D.
    Swisstom AG, Switzerland.
    Becher, Tobias
    University Medical Centre Schleswig-Holstein, Germany.
    Frerichs, Inez
    University Medical Centre Schleswig-Holstein, Germany.
    Sophocleous, Louiza
    University of Cyprus, Cyprus.
    Sjöberg, Daniel
    Lund University.
    Seifnaraghi, Nima
    Middlesex University, UK.
    Bayford, Richard
    Middlesex University, UK.
    A parametric model for the changes in the complex valued conductivity of a lung during tidal breathing2018Ingår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, nr 20, artikel-id 205401Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    Yousefi, Hossein
    et al.
    Tehran University of Medical Sciences (TUMS), Iran.
    Ahmadian, Alireza
    Tehran University of Medical Sciences (TUMS), Iran.
    Khodadad, Davood
    Luleå University of Technology ; Exceptional Talents Development Centre, Iran.
    Saberi, Hooshangh
    Tehran University of Medical Sciences (TUMS), Iran ; Spinal Injuries Repair Research Centre, Iran.
    Daneshmehr, Alireza
    University of Tehran, Iran.
    An Optimised Linear Mechanical Model for Estimating Brain Shift Caused by Meningioma Tumours2013Ingår i: International Journal of Biomedical Science and Engineering, ISSN 2376-7227, Vol. 1, nr 1, s. 1-9Artikel i tidskrift (Refereegranskat)
    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%.

  • 8.
    Yousefi-Banaem, Hossein
    et al.
    Isfahan University of Med. Sci., Iran.
    Kermani, Saeed
    Isfahan University of Med. Sci., Iran.
    Sarrafzadeh, Omid
    Isfahan University of Med. Sci., Iran.
    Khodadad, Davood
    Luleå University of Technology.
    An improved spatial FCM algorithm for cardiac image segmentation2013Ingår i: 13th Iranian Conference on Fuzzy Systems (IFSC), 2013, IEEE Press, 2013Konferensbidrag (Refereegranskat)
    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 - 8 av 8
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