Which statement describes a major limitation of using ultrasound to evaluate bone tumors?

• A. It is highly operator-dependent.
• B. It cannot evaluate soft tissue involvement.
• C. Shadowing precludes evaluation of deeper structures within the bone unless there is significant lysis.
• D. It provides comprehensive assessment of deep bone marrow.

Answer: (C)

Ultrasound is limited for bone tumors because dense cortical bone reflects most of the sound waves and creates strong shadowing, which prevents visualization of structures inside the bone. If the cortex is intact, the ultrasound cannot access the medullary cavity or intramedullary tumor extent. Only when there is significant bone destruction (cortical lysis) does the barrier break down enough to let the ultrasound reveal deeper structures within the bone. So, while ultrasound can help assess surrounding soft tissue and any extraosseous extension, it cannot reliably evaluate intraosseous tumor extent unless there is cortical breach.