Nonlinear Effects in Ultrasound Fields of Diagnostic-type Transducers Used for Kidney Stone Propulsion: Characterization in Water

• Published in: AIP conference proceedings 2015-10, Vol.1685 (1)
• Main Authors: Karzova, M, Cunitz, B, Yuldashev, P, Andriyakhina, Y, Kreider, W, Sapozhnikov, O, Bailey, M, Khokhlova, V
• Format: Article
• Language: English
• Subjects: Acoustic propagation; Acoustics; BIOMEDICAL RADIOGRAPHY; BOUNDARY CONDITIONS; CALCULI; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COMPARATIVE EVALUATIONS; Computer simulation; CYLINDRICAL CONFIGURATION; Diagnostic software; Diagnostic systems; Fiber optics; FIBERS; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Kidney stones; KIDNEYS; MHZ RANGE 01-100; Nonlinear analysis; NONLINEAR PROBLEMS; Optical fibers; PROBES; PROPULSION; PULSES; Pushing; Radius of curvature; SATURATION; SIMULATION; THREE-DIMENSIONAL CALCULATIONS; TRANSDUCERS; Ultrasonic imaging; Ultrasonic radiation; ULTRASONIC WAVES; ULTRASONOGRAPHY; WATER; Waveforms
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.4934397

Newer imaging and therapeutic ultrasound technologies require higher pressure levels compared to conventional diagnostic values. One example is the recently developed use of focused ultrasonic radiation force to move kidney stones and residual fragments out of the urinary collecting system. A commercial diagnostic 2.3 MHz C5-2 array probe is used to deliver the acoustic pushing pulses. The probe comprises 128 elements equally spaced at the 55 mm long convex cylindrical surface with 38 mm radius of curvature. The efficacy of the treatment can be increased by using higher transducer output to provide stronger pushing force; however, nonlinear acoustic saturation effect can be a limiting factor. In this work nonlinear propagation effects were analyzed for the C5-2 transducer using a combined measurement and modeling approach. Simulations were based on the 3D Westervelt equation; the boundary condition was set to match low power pressure beam scans. Focal waveforms simulated for increased output power levels were compared with the fiber-optic hydrophone measurements and were found in good agreement. It was shown that saturation effects do limit the acoustic pressure in the focal region of the transducer. This work has application to standard diagnostic probes and imaging.