Search for: computer-assisted-tomography
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    Minimization of target registration error for vertebra in image-guided spine surgery

    , Article International Journal of Computer Assisted Radiology and Surgery ; Vol. 9, issue. 1 , January , 2014 , p. 29-38 Ershad, M ; Ahmadian, A ; Dadashi Serej, N ; Saberi, H ; Amini Khoiy, K ; Sharif University of Technology
    Purpose: The accuracy of pedicle screw placement during image-guided spine surgery (IGSS) can be characterized by estimating the target registration error (TRE). The major factors that influence TRE were identified, minimized, and verified with in vitro experiments. Materials and methods: Computed-tomography- compatible markers are placed over anatomical landmarks of lumbar vertebral segments in locations that are feasible and routinely used in surgical procedures. TRE was determined directly for markers placed on the pedicles of vertebra segments. First, optimum selections of landmarks are proposed for different landmarks according to the minimum achievable TRE values in different... 

    Statistical construction of a Japanese male liver phantom for internal radionuclide dosimetry

    , Article Radiation Protection Dosimetry ; Volume 141, Issue 2 , 2010 , Pages 140-148 ; 01448420 (ISSN) Babapour Mofrad, F ; Aghaeizadeh Zoroofi, R ; Abbaspour Tehrani Fard, A ; Akhlaghpoor, S ; Hori, M ; Chen, Y. W ; Sato, Y ; Sharif University of Technology
    A computational framework is presented, based on statistical shape modelling, for construction of race-specific organ models for internal radionuclide dosimetry and other nuclear-medicine applications. This approach was applied to the construction of a Japanese liver phantom, using the liver of the digital Zubal phantom as the template and 35 liver computed tomography (CT) scans of male Japanese individuals as a training set. The first step was the automated object-space registration (to align all the liver surfaces in one orientation), using a coherent-point-drift maximum-likelihood alignment algorithm, of each CT scan-derived manually contoured liver surface and the template Zubal liver... 

    Individual virtual phantom reconstruction for organ dosimetry based on standard available phantoms

    , Article Iranian Journal of Radiation Research ; Volume 7, Issue 4 , 2010 , Pages 201-206 ; 23223243 (ISSN) Babapour Mofrad, F ; Aghaeizadeh Zoroofi, R ; Tehrani Fard, A. A ; Akhlaghpoor, S ; Chen, Y. W ; Sato, Y ; Sharif University of Technology
    Novim Medical Radiation Institute  2010
    Background: In nuclear medicine application often it is required to use computational methods for evaluation of organ absorbed dose. Monte Carlo simulation and phantoms have been used in many works before. The shape, size and volume in organs are varied, and this variation will produce error in dose calculation if no correction is applied. Materials and Methods: A computational framework for constructing individual phantom for dosimetry was performed on five liver CT scan data sets of Japanese normal individuals. The Zubal phantom was used as an original phantom to be adjusted by each individual data set. This registration was done by Spherical Harmonics (SH) and Thin-Plate Spline methods.... 

    Intensity based image registration by minimizing the complexity of weighted subtraction under illumination changes

    , Article Biomedical Signal Processing and Control ; Volume 25 , 2016 , Pages 35-45 ; 17468094 (ISSN) Aghajani, K ; Yousefpour, R ; Shirpour, M ; Manzuri, M. T ; Sharif University of Technology
    Elsevier Ltd  2016
    One crucial part of an image registration algorithm is utilization of an appropriate similarity metric. For common similarity metrics such as CC or MI, it is assumed that the intensities of image pixels are independent from each other and stationary. Accepting these assumptions, one will have difficulty doing image registration in the presence of spatially varying intensity distortion. In Myronenko et al. [5] a solution based on minimization of residual complexity is introduced to solve this problem. In this work, the weakness of RC method is investigated for more complex spatially varying intensity distortions and a modification of this method is presented to improve its performance in such... 

    3D calculation of absorbed dose for 131I-targeted radiotherapy: A monte carlo study

    , Article Radiation Protection Dosimetry ; Volume 150, Issue 3 , October , 2012 , Pages 298-305 ; 01448420 (ISSN) Saeedzadeh, E ; Sarkar, S ; Abbaspour Tehrani Fard, A ; Ay, M. R ; Khosravi, H. R ; Loudos, G ; Sharif University of Technology
    Various methods, such as those developed by the Medical Internal Radiation Dosimetry (MIRD) Committee of the Society of Nuclear Medicine or employing dose point kernels, have been applied to the radiation dosimetry of 131I radionuclide therapy. However, studies have not shown a strong relationship between tumour absorbed dose and its overall therapeutic response, probably due in part to inaccuracies in activity and dose estimation. In the current study, the GATE Monte Carlo computer code was used to facilitate voxel-level radiation dosimetry for organ activities measured in an . 131I-treated thyroid cancer patient. This approach allows incorporation of the size, shape and composition of... 

    A computer model for evaluating the osteotomy parameters of Chiari pelvic osteotomy

    , Article International Orthopaedics ; Volume 34, Issue 3 , 2010 , Pages 329-333 ; 03412695 (ISSN) Karami, M ; Gouran Savadkoohi, D ; Ghadirpoor, A ; Rahimpoor, S ; Azghani, M ; Farahmand, F ; Sharif University of Technology
    This study was conducted to evaluate the effect of the various osteotomy parameters on the biomechanical aspects of the hip joint on a computerised model. The data of the radiographs and a three-dimensional (3D) CT scan of six patients with coverage deficient hip joint were used to construct a 3D computer model. Then Chiari type osteotomies were simulated using various heights, angles and fibrocartilage thicknesses. A new angle called the mid acetabular center edge (MACE) angle was defined in a mid coronal CT cut. The optimum displacement for obtaining the maximum coverage averaged 73%. The angle and height of the osteotomy had a significant effect on the MACE angle (P value∈<∈0. 01). Our... 

    Dynamic simulation of biomechanical behaviour of the pelvis in the lateral impact loads

    , Article Journal of Healthcare Engineering ; Volume 2018 , 2018 ; 20402295 (ISSN) Hatami, M ; Wang, D ; Qu, A ; Xiangsen, Z ; Wang, Q ; Baradaran Kazemian, B ; Sharif University of Technology
    The objective of this study was to develop and validate a novel 3D dynamic model of a pelvic side-impactor system. The biomechanical responses of a pelvic flexible model (having.mnf file suffix) under the lateral impact load for predicting the bone fracture mechanism are investigated as well. The 3D solid model of the side-impactor system was imported into MSC/ADAMS software for analyzing the dynamic model, and the pelvic flexible model was extracted from the CT images of a Chinese female volunteer. The flexible model of the pelvis system was developed considering a wide range of mechanical properties in the bone complex and soft tissue to achieve a realistic biomechanical response during a... 

    Accuracy Quantification of the Reverse Engineering and High-Order Finite Element Analysis of Equine MC3 Forelimb

    , Article Journal of Equine Veterinary Science ; Volume 78 , 2019 , Pages 94-106 ; 07370806 (ISSN) Mouloodi, S ; Rahmanpanah, H ; Burvill, C ; Davies, H. M. S ; Sharif University of Technology
    W.B. Saunders  2019
    Shape is a key factor in influencing mechanical responses of bones. Considered to be smart viscoelastic and inhomogeneous materials, bones are stimulated to change shape (model and remodel) when they experience changes in the compressive strain distribution. Using reverse engineering techniques via computer-aided design (CAD) is crucial to create a virtual environment to investigate the significance of shape in biomechanical engineering. Nonetheless, data are lacking to quantify the accuracy of generated models and to address errors in finite element analysis (FEA). In the present study, reverse engineering through extrapolating cross-sectional slices was used to reconstruct the diaphysis of... 

    Telemedicine and computer-based technologies during coronavirus disease 2019 infection; a chance to educate and diagnose

    , Article Archives of Iranian Medicine ; Volume 23, Issue 8 , 2020 , Pages 561-563 Jafarzadeh Esfehani, R ; Mirzaei Fard, M ; Habibi Hatam Ghale, F ; Rezaei Kalat, A ; Fathi, A ; Shariati, M ; Sadr Nabavi, A ; Miri, R ; Bidkhori, H. R ; Aelami, M. H ; Sharif University of Technology
    Academy of Medical Sciences of I.R. Iran  2020
    Coronavirus disease 2019 (COVID-19) is now of global concern due to its rapid dissemination across the globe. The rapid spread of this viral infection, along with many of its unknown aspects, has posed new challenges to the health care systems. The main challenging effects of COVID-19 are rapid dissemination through close contact and varying clinical severity among different individuals. Furthermore, the medical staff in endemic areas are becoming exhausted and deal with a considerable level of job burnout, which can negatively affect their medical decision making. Also, due to the variable pulmonary manifestations of COVID-19, some physicians may misdiagnose patients. To overcome these... 

    Computational simulation of temperature and velocity distribution in human upper respiratory airway during inhalation of hot air

    , Article Respiratory Physiology and Neurobiology ; Volume 223 , 2016 , Pages 49-58 ; 15699048 (ISSN) Goodarzi Ardakani, V ; Taeibi Rahni, M ; Salimi, M. R ; Ahmadi, G ; Sharif University of Technology
    Elsevier  2016
    The present study provides an accurate simulation of velocity and temperature distributions of inhalation thermal injury in a human upper airway, including vestibule, nasal cavity, paranasal sinuses, nasopharynx, oropharynx, larynx, and upper part of main bronchus. To this end, a series of CT scan images, taken from an adult woman, was used to construct a three dimensional model. The airway walls temperature was adjusted according to existing in vivo temperature measurements. Also, in order to cover all breathing activities, five different breathing flow rates (10, 15, 20, 30, and 40. l/min) and different ambient air temperatures (100, 200, 300, 400, and 500. °C) were studied. Different flow... 

    Subject-specific 2D/3D image registration and kinematics-driven musculoskeletal model of the spine

    , Article Journal of Biomechanics ; Volume 57 , 2017 , Pages 18-26 ; 00219290 (ISSN) Eskandari, A. H ; Arjmand, N ; Shirazi Adl, A ; Farahmand, F ; Sharif University of Technology
    An essential input to the musculoskeletal (MS) trunk models that estimate muscle and spine forces is kinematics of the thorax, pelvis, and lumbar vertebrae. While thorax and pelvis kinematics are usually measured via skin motion capture devices (with inherent errors on the proper identification of the underlying bony landmarks and the relative skin-sensor-bone movements), those of the intervening lumbar vertebrae are commonly approximated at fixed proportions based on the thorax-pelvis kinematics. This study proposes an image-based kinematics measurement approach to drive subject-specific (musculature, geometry, mass, and center of masses) MS models. Kinematics of the thorax, pelvis, and... 

    A patient specific finite element simulation of intramedullary nailing to predict the displacement of the distal locking hole

    , Article Medical Engineering and Physics ; Volume 55 , May , 2018 , Pages 34-42 ; 13504533 (ISSN) Mortazavi, J ; Farahmand, F ; Behzadipour, S ; Yeganeh, A ; Aghighi, M ; Sharif University of Technology
    Elsevier Ltd  2018
    Distal locking is a challenging subtask of intramedullary nailing fracture fixation due to the nail deformation that makes the proximally mounted targeting systems ineffective. A patient specific finite element model was developed, based on the QCT data of a cadaveric femur, to predict the position of the distal hole of the nail postoperatively. The mechanical interactions of femur and nail (of two sizes) during nail insertion was simulated using ABAQUS in two steps of dynamic pushing and static equilibrium, for the intact and distally fractured bone. Experiments were also performed on the same specimen to validate the simulation results. A good agreement was found between the model... 

    Mechanical characterization of the ligaments in subject-specific models of the patellofemoral joint using in vivo laxity tests

    , Article Knee ; Volume 26, Issue 6 , 2019 , Pages 1220-1233 ; 09680160 (ISSN) Akbar, M ; Farahmand, F ; Arjmand, N ; Sharif University of Technology
    Elsevier B.V  2019
    Background: The purpose of this study was to propose a methodology for mechanical characterization of the ligaments in subject-specific models of the patellofemoral joint (PFJ) of living individuals. Method: PFJ laxity tests were performed on a healthy volunteer using a specially designed loading apparatus under biplane fluoroscopy. A three-dimensional (3D) parametric model of the PFJ was developed in the framework of the rigid body spring model using the geometrical data acquired from the subject's computed tomography and magnetic resonance images. The stiffness and pre-strains of the medial and lateral PFJ ligaments were characterized using a two-step optimization procedure which minimized... 

    An optimization based approach embedded in a fuzzy connectivity algorithm for airway tree segmentation

    , Article Proceedings of the 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS'08 - "Personalized Healthcare through Technology", 20 August 2008 through 25 August 2008, Vancouver, BC ; 2008 , Pages 4011-4014 ; 9781424418152 (ISBN) Yousefi Rizi, F ; Ahmadian, A. R ; Fatemizadeh, E ; Alirezaie, J ; Sharif University of Technology
    The main problem with airway segmentation methods which significantly influences their accuracy is leakage into the extra-luminal regions due to thinness of the airway wall during the process of segmentation. This phenomenon potentially makes large regions of lungparenchyma to be wrongly identified as airways. A solution to this problem in the previous methods was based on leak detection followed by reducing leakage during the segmentation process. This has been dealt with adjusting the segmentation parameters and performing the re-segmentation process on the pre-segmented area. This makes the algorithm very exhaustive and more dependent on the user interaction. The method presented here is... 

    3D Image Segmentation with Sparse Annotation by Self-Training and Internal Registration

    , Article IEEE Journal of Biomedical and Health Informatics ; Volume 25, Issue 7 , 2021 , Pages 2665-2672 ; 21682194 (ISSN) Bitarafan, A ; Nikdan, M ; Baghshah, M. S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Anatomical image segmentation is one of the foundations for medical planning. Recently, convolutional neural networks (CNN) have achieved much success in segmenting volumetric (3D) images when a large number of fully annotated 3D samples are available. However, rarely a volumetric medical image dataset containing a sufficient number of segmented 3D images is accessible since providing manual segmentation masks is monotonous and time-consuming. Thus, to alleviate the burden of manual annotation, we attempt to effectively train a 3D CNN using a sparse annotation where ground truth on just one 2D slice of the axial axis of each training 3D image is available. To tackle this problem, we propose... 

    Cardiac contraction motion compensation in gated myocardial perfusion SPECT: a comparative study

    , Article Physica Medica ; Volume 49 , 2018 , Pages 77-82 ; 11201797 (ISSN) Salehi, N ; Rahmim, A ; Fatemizadeh, E ; Akbarzadeh, A ; Farahani, M. H ; Farzanefar, S ; Ay, M. R ; Sharif University of Technology
    Associazione Italiana di Fisica Medica  2018
    Introduction: Cardiac contraction significantly degrades quality and quantitative accuracy of gated myocardial perfusion SPECT (MPS) images. In this study, we aimed to explore different techniques in motion-compensated temporal processing of MPS images and their impact on image quality and quantitative accuracy. Material and method: 50 patients without known heart condition underwent gated MPS. 3D motion compensation methods using Motion Freezing by Cedars Sinai (MF), Log-domain Diffeomorphic Demons (LDD) and Free-Form Deformation (FFD) were applied to warp all image phases to fit the end-diastolic (ED) phase. Afterwards, myocardial wall thickness, myocardial to blood pool contrast, and... 

    Automatic segmentation, detection, and diagnosis of abdominal aortic aneurysm (AAA) using convolutional neural networks and hough circles algorithm

    , Article Cardiovascular Engineering and Technology ; Volume 10, Issue 3 , 2019 , Pages 490-499 ; 1869408X (ISSN) Mohammadi, S ; Mohammadi, M ; Dehlaghi, V ; Ahmadi, A ; Sharif University of Technology
    Springer New York LLC  2019
    Purpose: An abdominal aortic aneurysm (AAA) is known as a cardiovascular disease involving localized deformation (swelling or enlargement) of aorta occurring between the renal and iliac arteries. AAA would jeopardize patients’ lives due to its rupturing risk, so prompt recognition and diagnosis of this disorder is vital. Although computed tomography angiography (CTA) is the preferred imaging modality used by radiologist for diagnosing AAA, computed tomography (CT) images can be used too. In the recent decade, there has been several methods suggested by experts in order to find a precise automated way to diagnose AAA without human intervention base on CT and CTA images. Despite great... 

    Hypersensitivity of trunk biomechanical model predictions to errors in image-based kinematics when using fully displacement-control techniques

    , Article Journal of Biomechanics ; Volume 84 , 2019 , Pages 161-171 ; 00219290 (ISSN) Eskandari, A. H ; Arjmand, N ; Shirazi Adl, A ; Farahmand, F ; Sharif University of Technology
    Elsevier Ltd  2019
    Recent advances in medical imaging techniques have allowed pure displacement-control trunk models to estimate spinal loads with no need to calculate muscle forces. Sensitivity of these models to the errors in post-imaging evaluation of displacements (reported to be ∼0.4–0.9° and 0.2–0.3 mm in vertebral displacements) has not yet been investigated. A Monte Carlo analysis was therefore used to assess the sensitivity of results in both musculoskeletal (MS) and passive finite element (FE) spine models to errors in measured displacements. Six static activities in upright standing, flexed, and extended postures were initially simulated using a force-control hybrid MS-FE model. Computed vertebral... 

    A stability-based model of a growing spine with adolescent idiopathic scoliosis: A combination of musculoskeletal and finite element approaches

    , Article Medical Engineering and Physics ; Volume 64 , 2019 , Pages 46-55 ; 13504533 (ISSN) Kamal, Z ; Rouhi, G ; Arjmand, N ; Adeeb, S ; Sharif University of Technology
    Elsevier Ltd  2019
    Using a combined musculoskeletal and finite element (FE) approach, this study aimed to evaluate stability-based muscle forces in a spine with adolescent idiopathic scoliosis (AIS) as compared to a normal spine; and subsequently, determine the effects of stress distribution on the growth plates (GPs) of the growing spine. For this purpose a nonlinear 3D FE model of one normal and one scoliotic thoracolumbar spine, consisting of GPs attached to rigid L1 to L4 vertebrae, were developed using computed tomography images coupled with a growth modulation using the Stokes’ model. Corresponding well with recent in-vivo and in-vitro studies, results of the models predicted intradiscal pressures at the... 

    A new deep convolutional neural network design with efficient learning capability: Application to CT image synthesis from MRI

    , Article Medical Physics ; Volume 47, Issue 10 , 2020 , Pages 5158-5171 Bahrami, A ; Karimian, A ; Fatemizadeh, E ; Arabi, H ; Zaidi, H ; Sharif University of Technology
    John Wiley and Sons Ltd  2020
    Purpose: Despite the proven utility of multiparametric magnetic resonance imaging (MRI) in radiation therapy, MRI-guided radiation treatment planning is limited by the fact that MRI does not directly provide the electron density map required for absorbed dose calculation. In this work, a new deep convolutional neural network model with efficient learning capability, suitable for applications where the number of training subjects is limited, is proposed to generate accurate synthetic computed tomography (sCT) images from MRI. Methods: This efficient convolutional neural network (eCNN) is built upon a combination of the SegNet architecture (a 13-layer encoder-decoder structure similar to the...