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    An Investigation of Nonlinear Ultrasound Propagation in Soft-tissues and Transferred Energy

    , M.Sc. Thesis Sharif University of Technology Omidvar Pashesar, Amir Hossein (Author) ; Ahmadian, Mohammad Taghi (Supervisor)
    Abstract
    In clinical applications of high intensity focused ultrasound, high amplitude acoustic waves are used to heat and ablate tumors and kidney stones. The high amplitude of ultrasonic waves leads to nonlinear effects within the acoustic filed. Heating stems from the acoustic power absorbed by tissues. The more the acoustic power is absorbed, the more the tissue temperature increases. On the other hand, more absorption means less penetration. Since the wave frequency is one of the important factors in power absorption, a compromise should be reached between the transferred energy and desired penetration depth. In this thesis, first, a problem with common HIFU-therapy conditions is simulated;... 

    Simulation of Ultrasound Waves Propagation in Soft Tissue in Cancer Treating by HIFU

    , M.Sc. Thesis Sharif University of Technology Molayi, Hanif (Author) ; Ahmadiyan, Mohammad Taghi (Supervisor) ; Firoozbakhsh, Keikhosrow (Supervisor)
    Abstract
    Nowadays cancer has become one of the main and prevailing worldwide challenges in medical field, and many attempts have been made for treatment of this disease. The common methods for cancer treatment, have had significant side effects and even resulted death. The method of “High Intensity Focused Ultrasound” (HIFU) as a non-invasive method, has been welcomed by engineers and doctors and is using in some tumor based cancers. For predicting the level of temperature increasing in tissue, it’s necessary to model the ultrasound waves propagates from HIFU source precisely. The main object of this thesis is modeling and simulation of the behavior of ultrasound wave propagation and investigating... 

    Analysis of Appearance of Bone Barrier in HIFU Treatment Method

    , M.Sc. Thesis Sharif University of Technology Torkinejad Ziarati, Pouriya (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Firoozbakhsh, Keykhosrow (Supervisor)
    Abstract
    Currently, the HIFU (High Intensity Focused Ultrasound) therapy method is known as one of the most advanced surgical techniques in tumor ablation therapy. Simulation of the HIFU therapy in the case of appearance of bon barrier is essential in HIFU planning to improve the usefulness and efficiency of treatment in brain tumor cases. In this work, linear, thermoviscous equations are applied for simulation of phase correction array and steering method, after analysis of performance, these methods are used in a 3D human brain and skull model to estimate thermal ablation in case of using these methods. Results indicate that the maximum focal pressure of 1.42 and 1.65 MPa can be achieved for... 

    Propagation Modeling of High Intensity Focused Ultrasound Wave through Multi Layer Tissue along with Experimental Validation

    , Ph.D. Dissertation Sharif University of Technology Haddadi, Samaneh (Author) ; Ahmadian, Mohammad Taghi (Supervisor)
    Abstract
    One of the main problems in human health, both in advanced societies and in growing societies, is a variety of cancers, one of which is brain tumor. One of the non-invasive methods of treating tumors is the use of ultrasound.HIFU (High Intensity Focused Ultrasound) therapy method is known as one of the most advanced surgical techniques in tumor ablation therapy. HIFU are produced and concentrated by powerful transducers. The two main mechanisms in HIFU are mechanical and thermal mechanisms, and the effects of these two mechanisms appear as thermal effects and cavitation. The fundamental mechanism in the HIFU is to absorb ultrasonic waves and to convert them into heat.The purpose of this... 

    Numerical Modeling of Treatment of Liver Tissue Cancer by Using High Intensity Focused Ultrasound (Hifu)

    , Ph.D. Dissertation Sharif University of Technology Mohammadpour Ghadikolaie, Maryam (Author) ; Firoozabadi, Bahar (Supervisor)
    Abstract
    In recent years, the incidence rate of liver cancer has increased sharply and nowadays liver cancer is known as the second leading cause of cancer death in the world. Surgical resection is usually used to treat malignant hepatic tumors. However, in some cases, surgical resection is not possible because of some reasons, such as tumor size and location. In these cases, other minimally invasive ablation methods such as radio-frequency ablation, microwave ablation, and high intensity focused ultrasound (HIFU) can be used. HIFU has some advantages such as noninvasiveness, high penetration depth, and low cost in comparison to the other ablation techniques such as radiofrequency ablation. In HIFU... 

    High intensity focused ultrasound (HIFU) ablation of porous liver: numerical analysis of heat transfer and hemodynamics

    , Article Applied Thermal Engineering ; Volume 170 , April , 2020 Mohammadpour, M ; Firoozabadi, B ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    In the present study, the influence of the liver vascular bed on heat transfer in a tumor located close to the hepatic artery and exposed to high intensity focused ultrasound (HIFU), is studied numerically. For this purpose, an acoustics-thermal-fluid coupling model based on the porous media theory under the local thermal non-equilibrium assumption is used to calculate the temperature field in the tumor, porous liver, and the hepatic artery. Different generations of the liver vasculature including arterial branches, terminal arterial branches, terminal veins and venous branches are examined at different porosities (the volume fraction of the vasculature). It is found that the liver... 

    Prediction of temperature distribution and volume of lesion during HIFU therapy

    , Article ITNG 2009 - 6th International Conference on Information Technology: New Generations, 27 April 2009 through 29 April 2009, Las Vegas, NV ; 2009 , Pages 1468-1473 ; 9780769535968 (ISBN) Heydari, M ; Jahed, M ; Sharif University of Technology
    Abstract
    Ultrasound hyperthermia is used to treat tumors in human tissue by heat. It is characterized by the application of high intensity focused ultrasound (HIFU), high local temperatures and short treating time of a few seconds. HIFU is a non-invasive treatment modality for a variety of cancers, including breast, prostate, kidney, liver, bone, uterus, and pancreatic cancers. Computer models have been used to determine tissue temperatures during ultrasound hyperthermia. In this work, we consider a liver tissue with a tumor at its center. We calculated temperature distribution in the presence a large blood vessel. We studied the effect of varying the exposure time (heating duration) and the diameter... 

    Analysis of the Ultrasonic Cavitation on the Cancer Tumors

    , M.Sc. Thesis Sharif University of Technology Maleki Birjandi, Morteza (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Fallah Rajabzadeh, Famida (Supervisor)
    Abstract
    A complete understanding of high-intensity focused ultrasound-induced temperature changes in tissue requires insight into all potential mechanisms for heat deposition. Applications of therapeutic ultrasound often utilize acoustic pressures capable of producing cavitation activity. Recognizing the ability of bubbles to transfer acoustic energy into heat generation, a study of the role bubbles play in tissue hyperthermia becomes necessary. These bubbles are typically less than 50μm.
    This dissertation examines the contribution of bubbles and their motion to an enhanced eating effect observed in a tissue-mimicking phantom. A series of experiments established a lationship between bubble... 

    Pattern of the Acoustic Wave Penetration Into Soft Tissue and the Related Heat Generation

    , M.Sc. Thesis Sharif University of Technology Zeinalian Khameneh, Ali (Author) ; Assempour, Ahmad (Supervisor) ; Ahmadian, Mohamad Taghi (Supervisor)
    Abstract
    nowadays Acoustic play an important role in the treatment of various diseases, especially cancer. in 2020 cancer has been the cause of death for more than 10 million patients. High intensity focused ultrasound is a non-invasive technique that used successfully to treat Malignant cancers like liver, pancreas and prostate. One of the major problems of using acoustic waves is the absorption of high frequency waves by the tissue before reaching the target area. in this study, a finite element model used to find the relation between frequency and acoustic pressure of transducer and focal region intensity. the results show, the maximum intensity in focal region linearly proportional to frequency... 

    A new model of pressure propagation in human tissue in HIFU application

    , Article Acta Medica Mediterranea ; Volume 31, Issue 7 , 2015 , Pages 1501-1505 ; 03936384 (ISSN) Hajian, S. R ; Abbaspour Tehrani Fard, A ; Pouladian, M ; Hemmasi, G. R ; Sharif University of Technology
    A. CARBONE Editore  2015
    Abstract
    This project is a new pressure model for propagating pressure inside one or several tissues at the time of treatment with high intensity focus ultrasound (HIFU). Pressure's changes are converted to heat's changes in tissue and this is done oscillatory. When the treatment is done in deeper tissues, obtained heat can affect surficial tissues. This pressure effect also can enter surficial tissues. Amount of pressure and heat possible injury can be controlled and reduced through this mechanical modelling. In this model we have used three layers and pressure also is obtained within these three layers and is investigated averagely. Obtained tissue in this mood is kidney tissue and it is tried to... 

    Analysis of nonlinear acoustic wave propagation in HIFU treatment using westervelt equation

    , Article Scientia Iranica ; Volume 25, Issue 4 , 2018 , Pages 2087-2097 ; 10263098 (ISSN) Haddadi, S ; Ahmadian, M. T ; Sharif University of Technology
    Sharif University of Technology  2018
    Abstract
    Currently, the HIFU (High-Intensity Focused Ultrasound) therapy method is known as one of the most advanced surgical techniques of tumor ablation therapy. Simulation of the non-linear acoustic wave and tissue interaction is essential in HIFU planning to improve the usefulness and efficiency of treatment. In this paper, linear, thermoviscous, and nonlinear equations are applied using two different media: liver and water. Transducer power of 8.3-134 Watts with the frequency of 1.1 MHz is considered as the range of study to analyze the interaction of wave and tissue. Results indicate that the maximum focal pressure of about 0.5-4.3 MPa can be achieved for transducer power rates of 8.3 to 134 W.... 

    Numerical study of the effect of vascular bed on heat transfer during high intensity focused ultrasound (HIFU) ablation of the liver tumor

    , Article Journal of Thermal Biology ; Volume 86 , 2019 ; 03064565 (ISSN) Mohammadpour, M ; Firoozabadi, B ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    In this study, the influence of vascular bed comprising terminal arterial branches on heat transfer in a liver tumor exposed to high intensity focused ultrasound (HIFU) is studied numerically. Also, the effect of vascular density on temperature distribution is investigated. A coupled set of acoustics, thermal, and fluid models is used to calculate the temperature distribution in the liver. The numerical model is established based on the Westervelt and bioheat equations along with the Navier-Stokes equations. Moreover, the acoustic streaming effect is included with Newtonian and non-Newtonian flow assumptions. It is found that in a vascular bed comprising terminal arterial branches, the...