What are the two forms of reflection that occur in soft tissue?

The two forms of reflection that occur in soft tissue are specular and diffuse reflection.

Specular reflection occurs at smooth interfaces, where the angle of incidence equals the angle of reflection. This type of reflection is significant when sound waves encounter structures that have a relatively large, flat surface compared to the wavelength of the sound. For instance, the reflectivity of borders between different types of tissues, such as fat and muscle, is often due to specular reflection, allowing for a clearer image on the ultrasound.

On the other hand, diffuse reflection occurs when sound waves hit rough or irregular surfaces. In this case, the waves scatter in various directions which can still provide echoes to the ultrasound transducer, albeit with less directionality than specular reflection. This is commonly seen at interfaces where there might be a variation in tissue structures, such as within the parenchyma of organs.

Understanding the difference between these two types of reflection is essential for interpreting ultrasound images, as they both contribute to the overall echogenicity and quality of the image produced. The interaction of ultrasound waves with tissue, through both specular and diffuse reflection, plays a critical role in the sonographer's ability to assess anatomical structures and abnormalities.