HYDROACOUSTICS
ANNUAL JOURNAL
START NEW VOL 20 SEARCH STATISTICS PAS - GDANSK DIVISION

Estimation and measurements of resonance scattering on the gas filled polymer microspheres

pp. 201-208, vol. 12, 2009

Wojciech Secomski
Department of Ultrasound Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland

Ziemowit Klimonda
Department of Ultrasound Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland

Key words: power spectrum; ultrasound; backscatter; histogram; inversed mcroscope

Abstract: The gas filled polymer spheres are used either as an ultrasonic contrast agents or controlled drug delivery microcapsules. The power spectrum of the ultrasonic backscattered signal was calculated from the resonance scattering theory for the gas bubbles surrounded by elastic shield. The size distribution of the measured microspheres was included in the calculations. In experiment, the backscattered power spectrum of measured sample was recorded by Siemens Antares ultrasonic scanner. Radio frequency (RF) data was recorded for 2.5 – 6.7 MHz transmitted ultrasonic frequencies. The backscattered spectra were calculated by Matlab software and subtracted from the transmitter spectrum, recorded as an echo from the perfect reflector. The particle size in measured sample was 12 μm mean ± 8 μm sd. The resonance frequency, measured under the microscope, was 0.60 MHz for 45 μm diameter microsphere which corresponds to 2.25 MHz for 12 μm sphere. The sample volume was 10cm³ and the mean quantity of scatterers was 6·103/cm³. In conclusion, measured spectra matched those calculated from theory. The use of ultrasonic scanner with RF data output and the high sensitivity, wide bandwidth ultrasonic transducer allows to measure backscattered signal from the very small quantity of resonance scatterers with satisfactory results at 40 dB signal to noise ratio.

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© Polish Acoustical Society - Gdansk Department, Polish Academy of Sciences. This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported. (CC BY-NC-SA 3.0)