Which term describes areas that produce a completely black image in ultrasound?

Anechoic refers to areas in an ultrasound image that appear completely black due to the absence of echoes returning to the transducer. This absence indicates that the tissue is fluid-filled, such as cysts or blood vessels, which do not create a significant reflection of the ultrasound waves. When the ultrasound waves pass through these fluid-filled spaces, they do not bounce back, resulting in a lack of echoes and, consequently, a dark appearance on the image.

In contrast, other terms describe different characteristics of tissue. Hypoechoic areas may reflect some sound waves but not as strongly as surrounding tissues, causing them to appear darker than the adjacent structures rather than completely black. Hyperechoic areas reflect sound waves very well, appearing bright on the ultrasound image. Echoic generally refers to tissues that produce echoes but is less frequently used than the more specific terms. Thus, anechoic is the most accurate term to describe regions that yield a black image on an ultrasound.