title: Simulation of sound field in a tissue medium generated by a concave spherically annular transducer.
abstract: The concave spherically annular transducer is regarded as a negative and a positive concave spherical transducer, and the spheroidal beam equation is used to simulate the linear and nonlinear sound field in a tissue medium generated by this transducer. It is found that the acoustic focus of the ring does not coincide with the acoustic focus of its central part. If the width of the ring increases, its acoustic focus will move toward the geometric focus and the amplitudes of nonlinear harmonics will increase obviously. If there are several coaxial rings placed on the concave spherical surface, more than one peak will appear along the axial direction for the fundamental, and high harmonics focus better. The distribution of sound field will change with the number and the excited signals of rings, so it maybe is a potential approach to treat locally big tumors.
authors.affiliation: College of Physics and Information Science, Hunan Normal University, Changsha 410081, China. shyqian@hunnu.edu.cn <shyqian@hunnu.edu.cn>
authors.forename: Shengyou
authors.initials: S
authors.lastname: Qian
authors.forename: Tomoo
authors.initials: T
authors.lastname: Kamakura
authors.forename: Masahiko
authors.initials: M
authors.lastname: Akiyama
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008954:Models, Biological; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D012542:Scattering, Radiation; D014464:Ultrasonic Therapy / Q000295:instrumentation* / Q000379:methods*; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods*