Which type of attenuation is responsible for the grainy appearance of organ tissue? Reflection Refraction Scattering Absorption

The grainy appearance of organ tissue is primarily caused by scattering. Scattering occurs when the ultrasound waves encounter small structures or irregularities in the tissue. These interactions can cause the waves to deviate from their original path, leading to a loss of clarity and resulting in a grainy or speckled visual effect on imaging studies, such as ultrasounds.

Here's a breakdown of the options:

1. Reflection - This occurs when ultrasound waves bounce back from tissue interfaces, contributing to the formation of images but not specifically to the grainy appearance.
2. Refraction - This involves the bending of ultrasound waves as they pass through tissues of different densities, which can distort the image, but it does not primarily cause a grainy look.
3. Scattering - As mentioned, this is the correct answer, as it involves the interaction of ultrasound waves with small tissue structures leading to a grainy image.
4. Absorption - This indicates that some energy is absorbed by the tissue, which can affect the intensity of the returning signal but does not directly contribute to a grainy appearance.

Therefore, the correct answer is Scattering.