Biomedical Applications of Vibration and Acoustics in Imaging and Characterizations
3 Strain Induced by Dual Acoustic Radiation Force and Its Ultrasonic Measurement
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There are many studies on measurement of tissue mechanical properties by applying an acoustic radiation force induced by ultrasound to an object. However, one acoustic radiation force along a direction (e.g., vertical direction) does not generate the strain of an object effectively because it also causes change in the object position, which has zero spatial gradient in displacement (= no strain). Especially, when the elastic modulus of the object is much larger than that of the surrounding tissue (such like a tumor in the breast tissue), one acoustic radiation force might generate only the change in position of the object and the strain of the object is hardly generated. In such cases, mechanical properties of the object cannot be evaluated. In this study, two cyclic acoustic radiation forces are simultaneously applied to an object along two different directions (e.g., two opposite horizontal directions) to effectively generate the strain inside the object even when the object is much harder than the surrounding tissue.