title: Experimental validation of a nonlinear derating technique based upon Gaussian-modal representation of focused ultrasound beams.
abstract: A technique useful for performing derating at acoustic powers where significant harmonic generation occurs is illustrated and validated with experimental measurements. The technique was previously presented using data from simulations. The method is based upon a Gaussian representation of the propagation modes, resulting in simple expressions for the modal quantities, but a Gaussian source is not required. The nonlinear interaction of modes within tissue is estimated from the nonlinear interaction in water, using appropriate amounts of source reduction and focal-point reduction derived from numerical simulations. An important feature of this nonlinear derating method is that focal temperatures can be estimated with little additional effort beyond that required to determine the focal pressure waveforms. Hydrophone measurements made in water were used to inform the derating algorithm, and the resulting pressure waveforms and increases in temperature were compared with values directly measured in tissue phantoms. For a 1.05 MHz focused transducer operated at 80 W and 128 W, the derated pressures (peak positive, peak negative) agreed with the directly measured values to within 11%. Focal temperature rises determined by the derating method agreed with values measured using a remote thermocouple technique with a difference of 17%.
authors.affiliation: Department of Mechanical and Materials Engineering, College of Engineering and Applied Science, University of Cincinnati, 2600 Clifton Avenue, Cincinnati, Ohio 45221, USA.
authors.forename: Seyed Ahmad Reza
authors.initials: SA
authors.lastname: Dibaji
authors.affiliation: Department of Mechanical and Materials Engineering, College of Engineering and Applied Science, University of Cincinnati, 2600 Clifton Avenue, Cincinnati, Ohio 45221, USA.
authors.forename: Rupak K
authors.initials: RK
authors.lastname: Banerjee
authors.affiliation: Division of Applied Mechanics, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993, USA.
authors.forename: Yunbo
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Division of Applied Mechanics, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993, USA.
authors.forename: Joshua E
authors.initials: JE
authors.lastname: Soneson
authors.affiliation: Division of Applied Mechanics, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993, USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Myers
mesh_terms: D000074059:Extracorporeal Shockwave Therapy / Q000295:instrumentation / Q000379:methods*; D009038:Motion; D017711:Nonlinear Dynamics; D016011:Normal Distribution; D019047:Phantoms, Imaging; D011312:Pressure; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013696:Temperature; D013997:Time Factors; D014159:Transducers; D000069453:Ultrasonic Waves; D014465:Ultrasonics / Q000295:instrumentation / Q000379:methods*; D014867:Water
chemical_list: D014867:Water