Which tissues absorb the most energy?

• A. Superficial bones and nerves
• B. Deep muscles
• C. Cartilage
• D. Fat

Answer: (A)

Energy absorption depends on tissue properties like density and acoustic/thermal impedance. Bone is very dense and mineral-rich, so it presents a high impedance mismatch with surrounding soft tissues. When energy from a modality like ultrasound encounters bone, it is rapidly attenuated and converted into heat. If the bone is near the surface, this heating effect happens right at the skin surface, making superficial bone the tissue that absorbs the most energy compared with deep muscles, cartilage, or fat. Nerve tissue may experience effects if energy reaches it, but the dominant factor for overall absorption is the bone’s high density and impedance.