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Analysis of Acoustic Wave Interaction in Soft Tissues (Penetration, Reflection and Dispersion)

Hashemi, Saeed | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46879 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Ahmadiyan, Mohammad Taghi; Firoozbakhsh, Keikhosrow
  7. Abstract:
  8. The application of acoustic waves as a diagnostic tool in medicine is highly regarded. Because of the mechanical and Noninvasive nature of this waves when penetrate in the body will not have any adverse effects on the body. Thus development and operation of these waves is growing every day. If abnormal changes in soft tissues (such as tumors inside the body) is created, by the reflected sound waves easily recognizable although it is experimental, and a little scientific studies have been conducted on the contrast of soft tissue and acoustic waves. Soft tissues of the human body Because of the asymmetric structure has a non-uniform physical and mechanical properties in different directions, therefore, Because of the complexity of careful analysis, the reaction with acoustic waves has been less studied. Penetration and also reflection of the waves can provide good indication of the soft tissues. Methods of measurement of the value of reflection are measured through micro-sensors that are sensitive to acoustic waves. In this thesis a cylindrical structure as an approximate model of muscle tissue and another cylindrical structure inside it as an tumor is considered and incidence of acoustic waves is studied. Once again spherical structure as an an approximate model of the breast tissue and another spherical structure inside it as an tumor is considered and incidence of acoustic waves is studied. In this thesis for modeling the soft tissue viscoelastic medium we use Havriliak-Negami model that consider the viscoelastic properties of soft tissue as a function of frequency. For the constants used in the this model we used the Maxwell model, then we have studied the effect of tumor size.By increasing frequency, the influence of acoustic waves in the soft tissue and the scattered farfield pressure amplitude increases. Numerical results show that the scattered farfield pressure amplitude pattern, particularly in small and medium frequencies are highly dependent on tumor size. By increasing tumor diameter scattering pressure patterns are also changing and at high frequencies with increasing tumor diameter the pressure field amplitude also increases. By increasing the the stiffness of tumor, the scattering of wave increases and type of benign and malignant tumors can be detected
  9. Keywords:
  10. Permeability ; Echo Sounding ; Scattering ; Soft Tissues ; Sound Waves

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