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Fast adapted delay and sum reconstruction algorithm in circular photoacoustic tomography
, Article 30th International Conference on Electrical Engineering, ICEE 2022, 17 May 2022 through 19 May 2022 ; 2022 , Pages 49-54 ; 9781665480871 (ISBN) ; Mostafavi, S. M ; Kavehvash, Z ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Circular photoacoustic tomography (C-PAT) arrangements are widely used in PAT systems. Many algorithms are proposed for PAT to reconstruct images such as delay and sum (DAS), universal back-projection (UBP), etc., all suffering from their own disadvantages. In this paper, to overcome these limitations, we proposed a fast uniform adapted delay and sum (ADAS) and filtered adapted delay and sum (F-ADAS) for detectors with finite and infinite bandwidth, respectively. Moreover, the edge uniformity index (EUI) metric was proposed for quantitative evaluation. Two cases 1) infinite bandwidth and 25 dB SNR level and 2) 2.25 MHz, 80% bandwidth with the same SNR level were considered for numerical...
Blind angle and angular range detection in planar and limited-view geometries for photoacoustic tomography
, Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 922-926 ; 9781665433655 (ISBN) ; Kavehvash, Z ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this paper, the relationship between the position of ultrasound transducers from the photoacoustic source and the reconstructed image is investigated. Our studies have shown that the distance of the transducer and its location from the photoacoustic source specifically affects and is closely related to the quality of the reconstructed image of the source. Also, we introduce a concept called blind angle for photoacoustic computed tomography (PACT) that have planar or circular limited-view geometry. Complete and accurate equations of this relationship are presented in this paper for all different 2D photoacoustic geometries. The main source of these equations is the spherically of the...
Image quality equations for focused transducer in circular photoacoustic computed tomography
, Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 917-921 ; 9781665433655 (ISBN) ; Kavehvash, Z ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this paper, we divide the imaging geometry of a photoacoustic computed tomography (PACT) structure that have a circular geometry and have focused transducers of positive or negative focus, into different zones of varying resolution. With using the presented analysis, it is possible to find the maximum range in which the system resolution is at its best value, according to the device specifications. The following equations are used to find the blind spot angles of the system for each source point inside the chamber. These are important for two reasons: the first is that the user can calculate the range in which the imaging system has the best quality by entering the specifications of his...
A strategy for structured illumination in synthetic aperture ultrasound imaging
, Article IEEE International Ultrasonics Symposium, IUS ; 2023 ; 19485719 (ISSN); 979-835034645-9 (ISBN) ; Yan, Y ; Hakakzadeh, S ; Kavehvash, Z ; Mehrmohammadi, M ; Sharif University of Technology
IEEE Computer Society
2023
Abstract
For many years synthetic aperture ultrasound imaging has been developed for its quality and high-resolution images, but it would be desirable to exceed its resolution limit. Structured illumination by transmitting a series of known grating patterns helps to obtain higher resolution information of the sample in optical microscopy. However, there are many challenges to realize this idea in the ultrasound imaging, regarding the acoustic field manipulation difficulties in synthetic aperture transmissions. This paper presents a method to resolve structures with sub-diffraction scales in ultrasound imaging with the aid of structured illumination. Simulation results show 48 percent resolution...
Coherent compounding for photoacoustic tomography
, Article IEEE International Ultrasonics Symposium, IUS ; 2023 ; 19485719 (ISSN); 979-835034645-9 (ISBN) ; Mostafavi, M ; Kavehvash, Z ; Sharif University of Technology
IEEE Computer Society
2023
Abstract
Circular-view detector configurations provide higher image quality in a photoacoustic (PA) imaging system than other configurations. The image quality degrades, and streak artifacts appear in the reconstructed image as the number of detectors decreases. Here, we present a coherent compounding strategy for suppressing streak artifacts. Parts of the reconstructed image that refer to the excited PA absorbers and the artifact are separable by reconstructing several sub-images and combining the reconstructed images. The numerical results showed that the presented method suppresses artifacts and improves the quality of reconstructed images than the conventional method. The peak signal-to-noise...
Improvement of Image Quality in Photoacoustic Imaging Based on Synthetic Aperture Techniques
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
Photoacoustic imaging is one of the nascent imaging methods that has received a lot of attention in the last two decades. There are two major imaging challenges with this method, including the finite size of the transducer element and the limited view angles of the photoacoustic tomography arrangement. To compensate for the effects of finite transducer size, we have proposed a multi-angle detection method for circular photoacoustic imaging systems based on the synthetic aperture techniques, in the proposed method, each transducer, in addition to rotating around the scan center, also has a rotation in the around its center. This rotation depends on the cut-off frequency, the diameter of the...
Improving Resolution and Reducing Artifacts in Ultrasound and Optics Imaging for Computed Tomography Structures
, Ph.D. Dissertation Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
The hybrid imaging technique combining ultrasound and optical tomography, based on computed tomography, has gained significant attention in the past two decades due to its non-invasive and non-ionizing advantages in medical imaging. By integrating optical and ultrasound imaging, it enables high-resolution imaging and diagnosis based on optical absorption properties of various tissues. However, challenges such as large transducer size, limited bandwidth, and unwanted artifacts in the imaging process limit the quality of reconstructed images and prevent achieving optimal resolution and contrast. This study focuses on developing processing and structural methods to overcome these challenges and...
Signal restoration algorithm for photoacoustic imaging systems
, Article Biomedical Optics Express ; Volume 14, Issue 2 , 2023 , Pages 651-666 ; 21567085 (ISSN) ; Amjadian, M ; Zhang, Y ; Mostafavi, S. M ; Kavehvash, Z ; Wang, L ; Sharif University of Technology
Optica Publishing Group (formerly OSA)
2023
Abstract
In a photoacoustic (PA) imaging system, the detectors are bandwidth-limited. Therefore, they capture PA signals with some unwanted ripples. This limitation degrades the resolution/contrast and induces sidelobes and artifacts in the reconstructed images along the axial direction. To compensate for the limited bandwidth effect, we present a PA signal restoration algorithm, where a mask is designed to extract the signals at the absorber positions and remove the unwanted ripples. This restoration improves the axial resolution and contrast in the reconstructed image. The restored PA signals can be considered as the input of the conventional reconstruction algorithms (e.g., Delay-and-sum (DAS) and...
A spatial-domain factor for sparse-sampling circular-view photoacoustic tomography
, Article IEEE Journal of Selected Topics in Quantum Electronics ; Volume 29, Issue 4 , 2023 ; 1077260X (ISSN) ; Rajendran, P ; Nili, V.A ; Kavehvash, Z ; Pramanik, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
Circular full-view configuration of photoacoustic imaging systems (C-PAI) has many applications in biomedicine (e.g., breast and brain imaging). To obtain a high-quality reconstructed image, dense spatial sampling (a large number of acoustic detectors) is needed, which makes the system expensive and challenging. Unfortunately, by reducing the number of spatial samples, streak artifacts appear, which degrade the quality of the reconstructed image. In this article, we propose a spatial-domain factor to suppress the streak artifacts and enhance the reconstructed image quality in a sparse sampling C-PAI system. Numerical and experimental studies are conducted to evaluate the proposed method. The...
Multi-angle data acquisition to compensate transducer finite size in photoacoustic tomography
, Article Photoacoustics ; Volume 27 , 2022 ; 22135979 (ISSN) ; Mozaffarzadeh, M ; Mostafavi, S. M ; Kavehvash, Z ; Rajendran, P ; Verweij, M ; de Jong, N ; Pramanik, M ; Sharif University of Technology
Elsevier GmbH
2022
Abstract
In photoacoustic tomography (PAT) systems, the tangential resolution decreases due to the finite size of the transducer as the off-center distance increases. To address this problem, we propose a multi-angle detection approach in which the transducer used for data acquisition rotates around its center (with specific angles) as well as around the scanning center. The angles are calculated based on the central frequency and diameter of the transducer and the radius of the region-of-interest (ROI). Simulations with point-like absorbers (for point-spread-function evaluation) and a vasculature phantom (for quality assessment), and experiments with ten 0.5 mm-diameter pencil leads and a leaf...
Reducing the Number of Elements in Order to Enhance the Speed of the Ultrasound Tomographic Imaging Systems
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor) ; Hakakzadeh, Soheil (Co-Supervisor)
Abstract
Transmission-mode ultrasound computed tomography (USCT) has emerged as a novel, safe, and cost-effective method for quantitative imaging of biological tissues, especially in breast screening. Despite technological advancements, challenges such as reduced accuracy in heterogeneous media, incomplete acoustic field coverage, sensitivity to initial conditions, and phenomena like cycle skipping still limit image quality and reconstruction speed in these systems. In this thesis, aiming to improve the speed and performance of USCT imaging, three reconstruction algorithms have been designed, implemented, and evaluated: a travel-time-based Gauss-Newton method, frequency-domain full waveform inversion...
The relationship between an EFL teacher's gender and students' willingness to communicate
, Article International Journal of Communication and Linguistic Studies ; Volume 10, Issue 4 , 2013 , Pages 17-29 ; 23277882 (ISSN) ; Pakzadian, S. S
Common Ground Publishing
2013
Abstract
Learning a foreign language encompasses a process of trial and error that can lead to the progression of the learner's interlanguage, meaning that the learners make use of their language knowledge that receives feedback and brings about progress through diagnosis of the problems and being corrected by the teacher. Therefore, there exists a need to analyze the underlying reasons causing the students to remain taciturn with a low willingness to communicate (WTC) during a language class. There has been much work done investigating the role of the learner's stable personal characteristics (traits) along with their situational changes at a specific time (states) that influence the student's...
An automated simple algorithm for realistic pore network extraction from micro-tomography images
, Article Journal of Petroleum Science and Engineering ; Vol. 123, issue , 2014 , pp. 164-171 ; ISSN: 09204105 ; Jamshidi, S ; Salehi, S
2014
Abstract
Using 3-D scanned data to analyze and extract pore network plays a vital role in investigation of porous media's characteristics. In this paper, a new simple method is developed to detect pores and throats for analyzing the connectivity and permeability of the network. This automated method utilizes some of the common and well-known image processing functions which are widely accessible by researchers and this has led to an easy algorithm implementation. In this method, after polishing and quality control of images, using city-block distance function and watershed segmentation algorithm, pores and throats are detected and 3-D network is produced. This method can also be applied on 2-D images...
Discrimination of heart arrhythmias using novel features in heart rate phase space
, Article Computing in Cardiology ; Volume 40 , Sept , 2013 , Pages 1035-1038 ; 23258861 (ISSN); 9781479908844 (ISBN) ; Rezaei, S ; Salavatian, S
2013
Abstract
In this paper, we try to recognize and distinguish different groups of arrhythmia using novel features which have been obtained from the heart rate's phase space in recent years. For this purpose, we used Triangular Phase Space Mapping (TPSM) and Parabolic Phase Space Mapping (PPSM). For recognition, we used three groups of 15 subjects using the Physionet database (Arrhythmia, Congestive Heart Failure (CHF), and Atrial Fibrillation (AF)) with Normal Sinus Rhythm (NSR). The obtained features discriminate arrhythmia from NSR by p
An intelligent hybrid classification algorithm integrating fuzzy rule-based extraction and harmony search optimization: Medical diagnosis applications
, Article Knowledge-Based Systems ; Volume 220 , 2021 ; 09507051 (ISSN) ; Abdullah, S ; Akhavan Niaki, S. T ; Banihashemi, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Uncertainty is a critical factor in medical datasets needed to be overcome for increasing diagnosis efficiency. This paper proposes an intelligent classification algorithm comprising a fuzzy rule-based approach, a harmony search (HS) algorithm, and a heuristic algorithm to classify medical datasets intelligently. Two fuzzy approaches, as well as orthogonal and triangular fuzzy sets, are first utilized to define the attributes of data. Then, an HS algorithm is integrated with a heuristic to generate fuzzy rules to select the best rules in the fuzzy rule-based systems. Moreover, to improve the performance of the proposed classification approach, a three-phase parameter tuning approach is...
Performance evaluation of shared hosting security methods
, Article Proc. of the 11th IEEE Int. Conference on Trust, Security and Privacy in Computing and Communications, TrustCom-2012 - 11th IEEE Int. Conference on Ubiquitous Computing and Communications ; 2012 , Pages 1310-1315 ; 9780769547459 (ISBN) ; Arshad, S ; Khoshkdahan, S ; Sharif University of Technology
2012
Abstract
Shared hosting is a kind of web hosting in which multiple websites reside on one webserver. It is cost-effective and makes the administration easier for websites' owners. However, shared hosting has some performance and security issues. In default shared hosting configuration, all websites' scripts are executed under the webserver's user account regardless of their owners. Therefore, a website is able to access other websites' resources. This security problem arises from lack of proper isolation between different websites hosted on the same webserver. In this survey, we have examined different methods for handling mentioned security issue. Also we evaluated the performance of mentioned...
The behaviour of an artificially cemented sandy gravel
, Article Geotechnical and Geological Engineering ; Volume 23, Issue 5 , 2005 , Pages 537-560 ; 09603182 (ISSN) ; Hosseini, S. M ; Toll, D. G ; Yasrebi, S. S ; Sharif University of Technology
2005
Abstract
The major section of the city of Tehran, Iran has been developed on cemented coarse-grained alluvium. This deposit consists of gravely sand to sandy gravel with some cobbles and is dominantly cemented by carbonaceous materials. In order to understand the mechanical behaviour of this soil, a series of undrained triaxial compression tests and unconfined compression tests were performed on uncemented and artificially cemented samples. Portland cement type I was used as the cementation agent for preparing artificially cemented samples. Uncemented samples and lightly cemented samples (1.5% cement) tested at high confining pressure showed contractive behaviour accompanied with positive excess pore...
An imperialist competitive algorithm approach for multi-objective optimization of direct coupling photovoltaic-electrolyzer systems
, Article International Journal of Hydrogen Energy ; Vol. 39, Issue 33 , 11 November , 2014 , pp. 18743-18757 ; ISSN: 03603199 ; Sayedin, F ; Khavas, S. S
2014
Abstract
In the context of sustainable clean hydrogen production pathways, photovoltaic-electrolyzer systems are one of the most promising alternatives for acquiring hydrogen from renewable energy sources. In fact, determining the optimal set of design and operating variables are always a key issue while coupling directly renewable electricity sources to PEM electrolyzers. Few previous studies have attempted to find the optimal size and operational condition of directly coupled photovoltaic-electrolyzer (PV/El) systems in order to maximize the hydrogen production or to minimize energy transfer loss between photovoltaic devices and the electrolyzer. Nevertheless an easy and efficient approach still...
Kalman filter based packet loss replacement in presence of additive noise
, Article 2012 25th IEEE Canadian Conference on Electrical and Computer Engineering: Vision for a Greener Future, CCECE 2012 ; 2012 ; 9781467314336 (ISBN) ; Ghorshi, S ; Tahaei, A
2012
Abstract
A major problem in real-time packet-based communication systems, is misrouted or delayed packets which results in degraded perceived voice quality. If packets are not available on time, the packets are considered as lost. The easiest solution in a network terminal receiver is to replace silence for the duration of lost speech segments. In a high quality communication system, to avoid degradation in speech quality due to packet loss, a suitable method or algorithm is needed to replace the missing segments of speech. In this paper, we introduce an adaptive filter for replacement of lost speech segment. In this method Kalman filter as a state-space based method will be used to predict the...
Investigation of Mesh Sensitivity Influence to Determine Crack Characteristic by Finite Element Methods
, Article Journal of Failure Analysis and Prevention ; Volume 16, Issue 3 , 2016 , Pages 506-512 ; 15477029 (ISSN) ; Mirjavadi, S. S ; Asli, S. A ; Sharif University of Technology
Springer New York LLC
2016
Abstract
In this research, an extended finite element model has been investigated. Investigation of opening and closure stress always has been one of the difficult parameters to analysis of results; therefore, the utilization of finite element methods would be a good and logical alternative for this purpose. In addition, linear elastic fracture criteria are used for validation of numerical results from the simulation. In this work, a detailed analysis of the influence of different parameters in the results of a specific specimen with a semi-elliptical tooling groove in terms of closure and opening stress is presented, and the impact of optimum element size in fracture characteristic in various load...