| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic scattering material which generates sub- harmonic echoes in high certainty. SOLUTION: This ultrasonic scattering material comprising gas-containing fine particles having an average particle diameter of 0.01 to 10μm is characterized in that the gas-containing fine particles having a distance of 0.01 to 10μm between the center of the nearest particle and the center of the second near particle are contained in an amount of 20 to 100% based on the total number of the particles.
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