Distal Acoustic shadow is caused by which of the following?
Distal Acoustic shadow is caused by substances such as bone, stones and air which have an acoustic impedence very different from that of adjacent tissue. Because of the large impedence mismatch, much of the ultrasound energy is reflected back toward the transducer. If the reflector is insonated at an approximate right angle, it produces a very bright echo.
Air
Calculi
Bone
All of the above