Search for: image-reconstruction
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    Medical image magnification based on original and estimated pixel selection models

    , Article Journal of Biomedical Physics and Engineering ; Volume 10, Issue 3 , 2020 , Pages 357-366 Akbarzadeh, O ; Khosravi, M. R ; Khosravi, B ; Halvaee, P ; Sharif University of Technology
    Shiraz University of Medical Sciences  2020
    Background: The issue of medial image resolution enhancement is one of the most important topics for medical imaging that helps improve the performance of many post-processing aspects like classification and segmentation towards medical diagnosis. Objective: Our aim in this paper is to evaluate different types of pixel selection models in terms of pixel originality in medical image reconstruction problems. A previous investigation showed that selecting far original pixels has highly better performance than using near unoriginal/estimated pixels while magnifying some benchmarks in digital image processing. Material and Methods: In our technical study, we apply two classical inter-polators,... 

    Image reconstruction of impenetrable cylinders using cubic B-splines and genetic algorithms

    , Article IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) ; Volume 2 , 2001 , Pages 686-689 ; 15223965 (ISSN) Barkeshli, K ; Mokhtari, M ; Mahdavi Amiri, N ; Sharif University of Technology
    A new method for the shape reconstruction of conducting cylinders from the measured data based on the cubic uniform B-splines was discussed. B-Spline was defined by an ordered set of control points which determined the shape of the curve. A direct problem was formulated using standard integral equations that were solved using method of moments. Principal polarization were treated separately. The method was found less sensitive to noise than those using Fourier expansions  

    Dose Reduction Via Development of a Novel Image Reconstruction Method for Few-View Computed Tomography

    , Ph.D. Dissertation Sharif University of Technology Khodajou Chokami, Hamid Reza (Author) ; Hosseini, Abolfazl (Supervisor) ; Ay, Mohammad Reza (Supervisor)
    Sparse-view computed tomography (CT) is recently proposed as a promising method to speed up data acquisition and alleviate the issue of CT high-dose delivery to patients. However, traditional reconstruction algorithms are time-consuming and suffer from image degradation when faced with sparse-view data. To address this problem, we propose two new frameworks based on deep learning (DL) that can quickly produce high-quality CT images from sparsely sampled projections and is able for clinical use. Our first DL-based proposed model is based on the convolution, and residual neural networks in a parallel manner, named the parallel residual neural network (PARS-Net). Besides, our proposed PARS-Net... 

    Tomographical medical image reconstruction using Kalman filter technique

    , Article Proceedings - 9th IEEE International Symposium on Parallel and Distributed Processing with Applications Workshops, ISPAW 2011 - ICASE 2011, SGH 2011, GSDP 2011, 26 May 2011 through 28 May 2011 ; May , 2011 , Pages 61-65 ; 9780769544298 (ISBN) Goliaei, S ; Ghorshi, S ; Sharif University of Technology
    In this paper, a Kalman filter technique which is operated in time is introduced for noise reduction on CT set of projections to reconstruct medical images. The experiments were done on medical image of kidneys and the simulated projections are captured by CT scanner. Evaluation results indicated that as the number of projections increase in the collected ray sums corrupted by noise the quality of reconstructed image becomes better in terms of contrast and transparency. However, for the comparison issue, the same conditions are applied for reconstruction of medical image in frequency domain using filter back projection technique. It observes that filter back projection technique does not... 

    Structure and texture image inpainting

    , Article Proceedings of the 2010 International Conference on Signal and Image Processing, ICSIP 2010, 15 December 2010 through 17 December 2010 ; 2010 , Pages 119-124 ; 9781424485949 (ISBN) Hesabi, S ; Jamzad, M ; Mahdavi Amiri, N ; Sharif University of Technology
    Inpainting refers to the task of filling in the missing or damaged regions of an image in an undetectable manner. We have an image to be reconstructed in a user-defined region. We use a fast decomposition method to obtain two components of the image, namely structure and texture. Reconstruction of each component is performed separately. The missing information in the structure component is reconstructed using a structure inpainting algorithm, while the texture component is repaired by a texture synthesis technique. To obtain the inpainted image, the two reconstructed components are composed together. Taking advantage of both the structure inpainting methods and texture synthesis techniques,... 

    Improved CT image reconstruction through partial Fourier sampling

    , Article Scientia Iranica ; Volume 23, Issue 6 , 2016 , Pages 2908-2916 ; 10263098 (ISSN) Abbasi, H ; Kavehvash, Z ; Shabany, M ; Sharif University of Technology
    Sharif University of Technology  2016
    A novel CT imaging structure based on Compressive Sensing (CS) is proposed. The main goal is to mitigate the CT imaging time and, thus, X-ray radiation dosage without compromising the image quality. The utilized compressive sensing approach is based on radial Fourier sampling. Thanks to the intrinsic relation between captured radon samples in a CT imaging process and the radial Fourier samples, partial Fourier sampling could be implemented systematically. This systematic compressive sampling helps in better control of required conditions such as incoherence and sparsity to guarantee adequate image quality in comparison to previous CS-based CT imaging structures. Simulation results prove the... 

    Shapes from Pixels

    , Article IEEE Transactions on Image Processing ; Volume 25, Issue 3 , 2016 , Pages 1193-1206 ; 10577149 (ISSN) Fatemi, M ; Amini, A ; Baboulaz, L ; Vetterli, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Continuous-domain visual signals are usually captured as discrete (digital) images. This operation is not invertible in general, in the sense that the continuous-domain signal cannot be exactly reconstructed based on the discrete image, unless it satisfies certain constraints (e.g., bandlimitedness). In this paper, we study the problem of recovering shape images with smooth boundaries from a set of samples. Thus, the reconstructed image is constrained to regenerate the same samples (consistency), as well as forming a shape (bilevel) image. We initially formulate the reconstruction technique by minimizing the shape perimeter over the set of consistent binary shapes. Next, we relax the... 

    Thorough approach toward cylindrical MMW image reconstruction using sparse antenna array

    , Article IET Image Processing ; Volume 12, Issue 8 , 2018 , Pages 1458-1466 ; 17519659 (ISSN) Mandi Sanam, P ; Seyyed Talebi, M. J ; Kazemi, M ; Kavehvash, Z ; Shabany, M
    Institution of Engineering and Technology  2018
    In this study, a thorough analysis of image reconstruction in an active millimetre-wave (MMW) cylindrical imaging system is performed. To improve the system's performance in terms of the total cost as well as the coupling effect, sparse multistatic arrays are desired. Nevertheless, the existing reconstruction methods fail to operate in sparse multi-static antenna-array systems. Therefore, to address these shortcomings, in this study, at first, the existing MMW mono-static cylindrical image reconstruction methods are modified in both single-frequency and wideband reconstruction platforms. Moreover, in order to further improve the image quality and the system cost, a sparse multi-static... 

    MCNP-FBSM: Development of MCNP/MCNPX Source Model for Simulation of Multi-Slice Fan-Beam X-Ray CT Scanners

    , Article 2019 IEEE International Symposium on Medical Measurements and Applications, MeMeA 2019, 26 June 2019 through 28 June 2019 ; 2019 ; 9781538684276 (ISBN) Khodajou Chokami, H ; Hosseini, S. A ; Reza Ay, M ; Zaidi, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Computed tomography (CT) is one of the most valuable diagnostic imaging tools in the clinic and is widely used worldwide. One of the main motivations driving research and development in CT is to achieve better image quality while keeping the radiation dose to the patient as low as possible. In this regard, computer simulations play a key role in the optimization of CT design. In this work, a fan-beam source model (FBSM) for the simulation of multi-slice fan-beam CT scanners using the MCNP Monte Carlo code, has been developed and implemented. The use of this model removes the need for using the collimator in the system configuration and thus to overcome the perennial problem of particle... 

    Total Variation Regularization In Medical Imaging

    , M.Sc. Thesis Sharif University of Technology Moosavi, Niloofar (Author) ; Fotouhi Firouzabad, Morteza (Supervisor)
    In this thesis, we study image restoration problems, which can be modeled as inverse problems. Our main focus is on inverse problems with Poisson noise; which are useful in many problems like positron emission tomography, fluorescence microscopy, and astronomy imaging. As a popular method in the literature, we use statistic modeling of inverse problem with Poisson noise, in the MAP-estimation framework. Then we introduce a semi-implicit minimization method, FB-EM-TV, that involves two alternate steps, including an EM step and a weighted ROF problem. Then we study well-posedness, existence and stability of the solution. This method can be interpreted as a forward-backward splitting strategy,... 

    Implementation of an Efficient Image Reconstruction Algorithm in Multi-Static MillimBey ter Wave Imaging

    , M.Sc. Thesis Sharif University of Technology Abbasi Broujeni, Mehryar (Author) ; Shabany, Mahdi (Supervisor) ; Kavehvash, Zahra (Supervisor)
    Nowadays, electromagnetic waves with millimeter wavelengths have various usages including medical,non destructive testings, structure inspection and imaging usages. Millimeter waves go through most of common clothings, but unlike x-ray waves, these waves have no ionizing effects.Therefore, they have low health risks for humans. This characteristic makes the imaging systems based on millimeter wave suitable for security purposes, such as airport security. The inclined usage of these systems requires an increase in precision, speed, reduction of error and automatic object detection algorithms. An important way to increase precision is to change the imaging system structure, resulting in... 

    Effective Implementation of Image Reconstruction Algorithms for Millimeter-Wave Imaging Applications

    , M.Sc. Thesis Sharif University of Technology Nabigol, Sina (Author) ; Shabany, Mahdi (Supervisor) ; Kavehvash, Zahra (Co-Supervisor)
    Millimeter waves provide an effective opportunity to improve vision and imaging in addition to systems based on visible light, X-rays, and infrared, and researchers have paid special attention to the field of millimeter waves to develop imaging. The spectrum of millimeter waves is in the frequency between 30GHz and 300GHz, which is equivalent to the wavelength in free space, between 1 and 10mm. The advantage of millimeter waves is that it works well in different weather conditions. Also, these millimeter waves have the ability to pass through clothing and provide a suitable level of resolution in reconstructed images and provide a suitable ability to separate different materials from each... 

    Center of confusion estimation for out-of-focus images based on bispectrum

    , Article International Conference on Computational Intelligence and Multimedia Applications, ICCIMA 2007, Sivakasi, Tamil Nadu, 13 December 2007 through 15 December 2007 ; Volume 3 , 2008 , Pages 501-506 ; 0769530508 (ISBN); 9780769530505 (ISBN) Nargesian, F ; Darabi, A. A ; Jamzad, M ; Sharif University of Technology
    In this paper a new method for out-of-focus blur estimation and restoration in presence of Gaussian noise is proposed. This method is based on Bispectrum transformation. It has been proved that functions with Gaussian distribution are suppressed in Bispectrum domain. The image blur criterion is estimated using information in image Bispectrum transformation. Then, an inverse filter is used for blurred image restoration. Experimental results show satisfactory performance of presented method in degradation function parameter estimation in comparison with other algorithms. This superiority is especially obvious in restoration of noisy images, since most of the methods do not take into account... 

    An effective image based surface roughness estimation approach using neural network

    , Article 2006 World Automation Congress, WAC'06, Budapest, 24 June 2006 through 26 June 2006 ; 2006 ; 1889335339 (ISBN); 9781889335339 (ISBN) Akbari, A. A ; Milani Fard, A ; Goodarzvand Chegini, A ; Sharif University of Technology
    IEEE Computer Society  2006
    The accurate measurement of surface roughness is essential in ensuring the desired quality of machined parts. The most common method of measuring the surface roughness of machined parts is using a surface profile-meter with a contact stylus, which can provide direct measurements of surface profiles. This method has its own disadvantageous such as workpiece surface damage due to mechanical contact between the stylus and the surface, In this paper we proposed a eontactless method using image processing and artificial neural network as a pattern classifier. Having trained the network for any specific workpiece with 10 sample patterns, the system would learn how to approximate the actual surface... 

    Page segmentation of Persian/Arabic printed text using ink spread effect

    , Article 2006 SICE-ICASE International Joint Conference, Busan, 18 October 2006 through 21 October 2006 ; 2006 , Pages 259-262 ; 8995003855 (ISBN); 9788995003855 (ISBN) Shirali Shahreza, S ; Manzuri Shalmani, M. T ; ShiraliShahreza, M. H ; Sharif University of Technology
    Nowadays, OCR (Optical Character Recognition) is widely used for converting written documents to digital documents. One of the OCR phases is page segmentation. In page segmentation, text regions must be found in input image. In addition, text parts like text columns must be separated. In this paper, a new method for segmenting Persian/Arabic printed text is proposed. This method is based on Ink Spread Effect idea, a new idea that has particular features. Main features of Persian/Arabic scripts are considered in designing this method. This method is skew resistant and can segment text within frames and tables or regions with gray background. © 2006 ICASE  

    Contributive representation-based reconstruction for online 3d action recognition

    , Article International Journal of Pattern Recognition and Artificial Intelligence ; Volume 35, Issue 2 , 2021 ; 02180014 (ISSN) Tabejamaat, M ; Mohammadzade, H ; Sharif University of Technology
    World Scientific  2021
    Recent years have seen an increasing trend in developing 3D action recognition methods. However, despite the advances, existing models still suffer from some major drawbacks including the lack of any provision for recognizing action sequences with some missing frames. This significantly hampers the applicability of these methods for online scenarios, where only an initial part of sequences are already provided. In this paper, we introduce a novel sequence-To-sequence representation-based algorithm in which a query sample is characterized using a collaborative frame representation of all the training sequences. This way, an optimal classifier is tailored for the existing frames of each query... 

    3D-Reconstruction Using Static and Mobile Stereo-Camera for 3D-Reconstruction

    , M.Sc. Thesis Sharif University of Technology Boomari, Hossein (Author) ; Zarei, Alireza (Supervisor)
    3D-object modeling and its representation in computers are one of the interested fields in computer science and engineering and problems like object and environment modeling, representation, storage and physical interactions are some of the important problems in this field. Increasing the applications of the technologies like localization, machine vision and virtual reality made the 3D-object modeling and its related problems, like 3D-model extraction and reconstruction, a nowadays interested challenges and a variety of solutions such as time of flight sensors,
    structured light, sonar sensors and multi-camera reconstruction are presented for it. Multi-camera solutions, just like the... 

    Ultrasound Image Reconstruction using Capacitive Micromachined Ultrasonic Transducers

    , M.Sc. Thesis Sharif University of Technology Shirazi, Sara (Author) ; Vosoughi Vahdat, Bijhan (Supervisor)
    In this thesis its considered the characterization of an ultrasound wave in a medium with some obstacles. Derivation of speed of molecules and pressure of the wave is carried out in the Cartesian coordinates system. Simulation is carried out to prove the dependency of wave speed to set up parameters such as the target point (x,y,z) at which the speed value is obtained, the location of the obstacles, the amplitude of original wave emitting from the source, and the propagation speed in different layers of the medium. From the numerical results, it is apparent that the amplitude of the speed wave gets degraded as the wave travels through the medium which is a function of reflection and... 

    Image Reconstruction in Superconducting Bolometric Detector Infra Red Imaging System Based on Physical Optics Principle

    , M.Sc. Thesis Sharif University of Technology Aghaeizadeh Ghezelghaya, Mosa (Author) ; Fardmanesh, Mehdi (Supervisor) ; Kavehvash, Zahra (Co-Supervisor) ; Mirzaei, Eiman (Co-Supervisor)
    Recently Infrared imaging has been very much considered for its applications.and because the infrared wavelengths are harmless, considered in medical and industrial applications. the imaging system examined in this thesis is passive and the object's own radiation is received by a single-pixel detector, these images are taken by two superconducting sensors and a pyroelectric Sensor. the purpose of this thesis is to improve the quality of images And reconstruction for the resulting images and if possible, optimize the system. to improve this system, various work has been proposed and done. including parabolic mirror distortion survey available in the system and compensated for it, take a... 

    Design and Implementation of Amplitude Detection Method for Millimeter Wave Imaging

    , M.Sc. Thesis Sharif University of Technology Sepehripour, Fahimeh (Author) ; Khavasi, Amin (Supervisor) ; Fakharzadeh, Mohammad (Co-Supervisor)
    Conventional imaging systems composed of two linear arrays of antennas as a transmitter and receiver. These arrays of antennas electronically scan along their antenna elements and are mechanically moved along a second orthogonal direction for scanning large two-dimensional areas quickly. In this thesis, the transmitter antenna elements are Tapered slot-line Antenna operating at 20-30GHz. A multiplexer circuit is used to transmit wideband signals to each antenna in the array. The receiver is composed of Schottky diode and pick up antenna that they are printed onto the radiating end of the antennas on the edge of the transmitter circuit board.In the available imaging systems, for achieving the...