Search for: phantoms--imaging
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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... 

    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 fast numerical method for calculating the 3D proton dose profile in a single-ring wobbling spreading system

    , Article Australasian Physical and Engineering Sciences in Medicine ; Volume 34, Issue 3 , 2011 , Pages 317-325 ; 01589938 (ISSN) Riazi, Z ; Afarideh, H ; Sadighi Bonabi, R ; Sharif University of Technology
    Based on the determination of protons fluence at the phantom's surface, a 3D dose distribution is calculated inside a water phantom using a fast method. The dose contribution of secondary particles, originating from inelastic nuclear interactions, is also taken into account. This is achieved by assuming that 60% of the energy transferred to secondary particles is locally absorbed. Secondary radiation delivers approximately 16.8% of the total dose in the plateau region of the Bragg curve for monoenergetic protons of energy 190 MeV. The physical dose beyond the Bragg peak is obtained for a proton beam of 190 MeV using a Geant4 simulation. It is found that the dose beyond the Bragg peak is <... 

    Design of linear anti-scatter grid geometry with optimum performance for screen-film and digital mammography systems

    , Article Physics in Medicine and Biology ; Volume 60, Issue 15 , July , 2015 , Pages 5753-5765 ; 00319155 (ISSN) Khodajou Chokami, H ; Sohrabpour, M ; Sharif University of Technology
    Institute of Physics Publishing  2015
    A detailed 3D Monte Carlo simulation of the grid geometrical parameters in screen-film mammography (SFM) and digital mammography (DM) systems has been performed. A combination of IEC 60627:2013 international standard conditions and other more clinically relevant parameters were used for this simulation. Accuracy of our results has been benchmarked with previously published data and good agreement has been obtained. Calculations in a wide range of linear anti-scatter grid geometries have been carried out. The evaluated parameters for the SFM system were the Bucky factor (BF) and contrast improvement factor (CIF) and for the DM system it was signal differenceto- noise ratio improvement factor... 

    Evaluation of various energy windows at different radionuclides for scatter and attenuation correction in nuclear medicine

    , Article Annals of Nuclear Medicine ; Volume 29, Issue 4 , 2015 , Pages 375-383 ; 09147187 (ISSN) Asgari, A ; Ashoor, M ; Sohrabpour, M ; Shokrani, P ; Rezaei, A ; Sharif University of Technology
    Springer-Verlag Tokyo  2015
    Objective: Improving signal to noise ratio (SNR) and qualified images by the various methods is very important for detecting the abnormalities at the body organs. Scatter and attenuation of photons by the organs lead to errors in radiopharmaceutical estimation as well as degradation of images. The choice of suitable energy window and the radionuclide have a key role in nuclear medicine which appearing the lowest scatter fraction as well as having a nearly constant linear attenuation coefficient as a function of phantom thickness. Methods: The energy windows of symmetrical window (SW), asymmetric window (ASW), high window (WH) and low window (WL) using Tc-99m and Sm-153 radionuclide with... 

    Optical radiomic signatures derived from optical coherence tomography images improve identification of melanoma

    , Article Cancer Research ; Volume 79, Issue 8 , 2019 , Pages 2021-2030 ; 00085472 (ISSN) Turani, Z ; Fatemizadeh, E ; Blumetti, T ; Daveluy, S ; Moraes, A. F ; Chen, W ; Mehregan, D ; Andersen, P. E ; Nasiriavanaki, M ; Sharif University of Technology
    American Association for Cancer Research Inc  2019
    The current gold standard for clinical diagnosis of melanoma is excisional biopsy and histopathologic analysis. Approximately 15–30 benign lesions are biopsied to diagnose each melanoma. In addition, biopsies are invasive and result in pain, anxiety, scarring, and disfigurement of patients, which can add additional burden to the health care system. Among several imaging techniques developed to enhance melanoma diagnosis, optical coherence tomography (OCT), with its high-resolution and intermediate penetration depth, can potentially provide required diagnostic information noninvasively. Here, we present an image analysis algorithm, "optical properties extraction (OPE)," which improves the... 

    Images of finite sized spherical particles in confocal and conventional microscopes when illuminated with arbitrary polarization

    , Article Applied Optics ; Volume 47, Issue 3 , 2008 , Pages 453-458 ; 1559128X (ISSN) Alali, S ; Massoumian, F ; Sharif University of Technology
    OSA - The Optical Society  2008
    We investigate the form of the image of a finite sized spherical particle in confocal and conventional microscopes when the illuminating light has an arbitrary polarization. In particular, we take the cases of radial and azimuthal polarizations and use the Mie theory to find the scattered field from differently sized particles for these cases. We present numerical results for the changes in the detected intensity when subresolution and resolvable spherical particles are illuminated with particular wavelengths and polarizations. Further, we find the limiting size of a particle for which it can be considered a point scatterer for a particular wavelength. © 2008 Optical Society of America  

    Nonlinear ultrasound propagation through layered liquid and tissue-equivalent media: Computational and experimental results at high frequency

    , Article Physics in Medicine and Biology ; Volume 51, Issue 22 , 2006 , Pages 5809-5824 ; 00319155 (ISSN) Williams, R ; Cherin, E ; Lam, T. Y. J ; Tavakkoli, J ; Zemp, R. J ; Foster, F. S ; Sharif University of Technology
    Nonlinear propagation has been demonstrated to have a significant impact on ultrasound imaging. An efficient computational algorithm is presented to simulate nonlinear ultrasound propagation through layered liquid and tissue-equivalent media. Results are compared with hydrophone measurements. This study was undertaken to investigate the role of nonlinear propagation in high frequency ultrasound micro-imaging. The acoustic field of a focused transducer (20 MHz centre frequency, f-number 2.5) was simulated for layered media consisting of water and tissue-mimicking phantom, for several wide-bandwidth source pulses. The simulation model accounted for the effects of diffraction, attenuation and... 

    A validation study of a virtual-based haptic system for endoscopic sinus surgery training

    , Article International Journal of Medical Robotics and Computer Assisted Surgery ; Volume 15, Issue 6 , 2019 ; 14785951 (ISSN) Sadeghnejad, S ; Khadivar, F ; Abdollahi, E ; Moradi, H ; Farahmand, F ; Sadr Hosseini, S. M ; Vossoughi, G ; Sharif University of Technology
    John Wiley and Sons Ltd  2019
    Background: The development of endoscopic sinus surgery (ESS) training simulators for clinical environment applications has reduced the existing shortcomings in conventional teaching methods, creating a standard environment for trainers and trainees in a more accurate and repeatable fashion. Materials and methods: In this research, the validation study of an ESS training simulator has been addressed. It is important to consider components that guide trainees to improve their hand movements control in the orbital floor removal in an ESS operation. Therefore, we defined three tasks to perform: pre-experiment learning, training, and evaluation. In these tasks, the critical regions introduced in... 

    Microwave medical imaging based on sparsity and an iterative method with adaptive thresholding

    , Article IEEE Transactions on Medical Imaging ; Volume 34, Issue 2 , September , 2015 , Pages 357-365 ; 02780062 (ISSN) Azghani, M ; Kosmas, P ; Marvasti, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    We propose a new image recovery method to improve the resolution in microwave imaging applications. Scattered field data obtained from a simplified breast model with closely located targets is used to formulate an electromagnetic inverse scattering problem, which is then solved using the Distorted Born Iterative Method (DBIM). At each iteration of the DBIM method, an underdetermined set of linear equations is solved using our proposed sparse recovery algorithm, IMATCS. Our results demonstrate the ability of the proposed method to recover small targets in cases where traditional DBIM approaches fail. Furthermore, in order to regularize the sparse recovery algorithm, we propose a novel...