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Title: Enhanced focus steering abilities of multi-element therapeutic arrays operating in nonlinear regimes

Steering abilities of a typical HIFU therapeutic array operated in linear and nonlinear regimes were compared using numerical simulation with the 3D Westervelt equation. The array included 256 elements of 1.2 MHz frequency and 6.6 mm diameter distributed in a quasi-random pattern over a spherical shell with a 130 mm aperture and a focal length of 120 mm. In the case of linear focusing, thermal effects are proportional to the intensity level and the criterion for safe array operation is that the intensity in the grating lobes should be less than 10% of the intensity in the main focus. In the case of nonlinear focusing, the heating effect is no longer proportional to intensity; therefore the heat deposition rate was chosen as the relevant metric, using the same 10% threshold for the secondary lobe in comparison with the focal maximum. When steering the focus, the same linearly predicted intensity level at the main focus was maintained by increasing the array power. Numerical simulations of the acoustic field were performed for nonlinear propagation both in water and in tissue. It was shown that for shock-forming conditions in the main focus, the steering range of safe electronic focusing is larger than thatmore » for linear propagation conditions. Nonlinear sonication regimes therefore can be used to enlarge tissue volumes that can be sonicated using electronic steering of the focus of HIFU arrays.« less
Authors:
;  [1] ;  [2] ; ;  [1] ;  [3] ;  [4]
  1. Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation)
  2. Andreyev Acoustics Institute, 4 Schvernik Str., 117036 Moscow (Russian Federation)
  3. (United States)
  4. Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40"t"h, Street, Seattle, WA 98105 (United States)
Publication Date:
OSTI Identifier:
22492629
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1685; Journal Issue: 1; Conference: 20. international symposium on nonlinear acoustics, Ecully (France), 29 Jun - 3 Jul 2015, 2. international sonic boom forum, Ecully (France), 29 Jun - 3 Jul 2015; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 42 ENGINEERING; ACOUSTICS; ANIMAL TISSUES; APERTURES; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; FOCUSING; HEAT; HEATING; LENGTH; MHZ RANGE 01-100; NONLINEAR PROBLEMS; SPHERICAL CONFIGURATION; TEMPERATURE DEPENDENCE; THREE-DIMENSIONAL CALCULATIONS; ULTRASONIC WAVES; WATER