Distal Acoustic shadow is seen in?: (A) Air, (B) Calculi, (C) Bone, (D) All of the above
Answer is D. All of the above REF: Ultrasound Teaching Manual by Matthias Hofer page - 15 In simple terms when sound waves strike an interface which reflects it back, it shows on USG as a hypoechoic or anechoic shadow beyond the structure. It is seen with gas and at interface like bone, calculi and stones.