What phenomenon occurs when an ultrasound pulse encounters an interface between tissues with different acoustic impedances?

When an ultrasound pulse encounters an interface between tissues with different acoustic impedances, reflection occurs. Acoustic impedance is a property that reflects how much sound resistance a material offers, and when the ultrasound wave meets an interface where there is a significant difference in these impedances, a portion of the wave is reflected back into the original medium. This reflection is crucial for creating images in ultrasound, as the returning signals are processed to form a visual representation of the internal structures.

Reflection plays a significant role in diagnostic imaging because it allows for the differentiation of various tissues, such as muscle, fat, and fluid, based on how they reflect the ultrasound waves. The amount of reflection depends on the degree of mismatch in impedance; greater differences result in a higher percentage of reflected sound.

Transmission, on the other hand, refers to the portion of the ultrasound wave that continues through the interface and becomes useful for imaging deeper structures. Refraction involves bending of the ultrasound wave due to a change in speed as it enters a new medium at an angle, which can affect the path of the ultrasound beam but is not the primary phenomenon at the interface. Scattering occurs when the ultrasound wave encounters small irregularities in tissues, causing the waves to deviate in multiple directions, but does not specifically