Appl. Phys. Lab., Ctr. for Industrial and Medical Ultrasound, Univ. of Washington, 1013 NE 40th St., Seattle, WA 98105.
Radiation force imparted on an elastic scatterer by a narrow ultrasound beam is different from that imparted by a plane wave, especially when the beam waist is comparable or smaller than the scatterer's diameter. Such a situation exists when a kidney stone is pushed by an acoustic wave emitted by a megahertz frequency ultrasound array. A spherical stone of several millimeters in diameter with elastic properties similar to calcium oxalate monohydrate kidney stones is considered. An acoustic wave is taken in a form of a continuous-wave 2.5 MHz focused ultrasound beam emitted by Philips HDI C4-2 imaging array. To study radiation force, the transducer field is created as a sum of plane waves of various inclinations, and scattering of each plane waves is modeled based on a known solution. Numerical calculations show that within some frequency range both the backscattering from and the radiation force on a kidney stone exceeds the values for absolutely soft or rigid spheres of the same diameter. A vector component of the radiation force can be created in a direction other than the ultrasound propagation by targeting off the stone center.
Written by:
Sapozhnikov O, Bailey M. Are you the author?
Reference: J Acoust Soc Am. 2011 Oct;130(4):2423.
PubMed Abstract
PMID: 21973887
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