Characterization of high intensity focused ultrasound transducers using acoustic streaming
(Color online) Flow chart summarizing the inverse methodology used to determine acoustic power and intensity.
(a) Schematic of the acoustic streaming generation system. (b) Block diagram of the DPIV measurement system.
Unprocessed DPIV image and streaming velocity contour, for HIFU-2 in water. Acoustic power: . Streaming velocity contour is obtained from the average of 50 image pairs captured in a duration. The standard deviation for 50 images at the point of maximum velocity is .
(Color online) Validation of computational model with streaming-velocity data from Fig. 2 of Kamakura et al. (1995). Gaussian shaded transducer with diameter , focal length , and central frequency , driven at a maximum source pressure of .
(a) Radial plot of streaming velocity in water. Transducer is HIFU-2; power=. (b) Photograph of the experimental apparatus showing the thickness of the laser sheet.
(Color online) Velocity magnitude vs radial distance for (i) water, (ii) 1.4% Natrosol solution, (iii) 2.4% Natrosol solution, and (iv) 3.4% Natrosol solution.
Speed contours obtained in 2.4% Natrosol solution for (i) HIFU-1, (ii) HIFU-2, and (iii) HIFU-3 transducers. Transducer input voltage=.
(Color online) Velocity profiles obtained from computations and experiments in 2.4% Natrosol solution; (a) velocity profile along axial direction and (b) velocity profile along radial direction. Transducer is HIFU-3; input voltage=35 . For the experimental data, standard deviation error bars for five trials are also shown. The maximum standard deviation for five trials is .
Comparison of source pressure for HIFU-2 in water, obtained via the streaming method and by radiation force balance. Results based upon the streaming technique are shown with and without averaging over the laser sheet thickness. Standard deviation error bars for three trials are also shown. For RFB measurements, the maximum standard deviation for three trials is less than 1% of the mean value. For the streaming measurements, the maximum standard deviation for three trials is 3% of the mean.
(Color online) Acoustic intensity profiles as a function of (a) axial and (b) radial distances (cm), obtained from backcalculation and hydrophone scanning in water for HIFU-2 transducer. Transducer input voltage=10 .
(Color online) (a) Flow chart of the inverse problem to estimate acoustic absorption coefficient, (Np/cm), of the 2.4% Natrosol fluid medium. (b) Absorption coefficient of 2.4% Natrosol fluid obtained using the inverse method, for different powers using HIFU-2 transducer. Standard deviation error bars for three trials are also shown. The maximum standard deviation for three trials is less than 1% of the mean.
(Color online) Comparison of acoustic power obtained from backcalculation and RFB in 2.4% Natrosol medium, for transducers HIFU-1 and HIFU-3.
(Color online) Acoustic intensity as a function of (a) axial and (b) radial distances obtained using HIFU-3 transducer in 2.4% Natrosol solution. Acoustic power=.
Physical characteristics of HIFU transducers used in the experiments.
Focusing characteristics of HIFU transducers used in the experiments.
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