Structures that exhibit lower amplitude echoes than surrounding tissues are termed:

Structures that exhibit lower amplitude echoes than surrounding tissues are termed hypoechoic. Hypoechoic areas appear darker on ultrasound images compared to the surrounding tissues because they return fewer echoes to the transducer. This characteristic is significant in sonography as it helps in differentiating various types of tissues and identifying pathological conditions. For instance, a hypoechoic mass may indicate the presence of a cyst, tumor, or other lesions that are less dense than their surroundings, which is critical for diagnosis.

In contrast, anechoic structures do not reflect any ultrasound waves, resulting in a completely dark appearance on the image, typically seen in fluid-filled structures like cysts. Isoechoic structures have echo amplitudes similar to their surrounding tissues, making them harder to distinguish. Echogenic structures reflect more sound waves, leading to brighter areas on an ultrasound image, which can represent solid or calcified tissues. Understanding these terms is essential for interpreting ultrasound images correctly and making accurate clinical decisions.