In relation to ultrasound and implanted materials, which statement is listed?

• A. Plastic evenly transmits ultrasound
• B. Metal reflects 90% of ultrasound
• C. Ultrasound has no interaction with implanted materials
• D. Implanted materials are safe with continuous ultrasound

Answer: (B)

When ultrasound meets a metal implant, there’s a large acoustic impedance mismatch between metal and soft tissue. This causes most of the incident sound energy to reflect back rather than transmit into the implant or beyond it. The reflection can be very high—in the ballpark of about 90% for typical metal-tissue interfaces—so the implant appears as a bright echo with strong shadowing behind it and little acoustic energy passes through. That’s why implants are described as strongly reflective rather than transparent to ultrasound. The other statements don’t fit because plastics don’t guarantee even transmission, ultrasound clearly interacts with implants (producing artifacts and potential heating), and safety with continuous ultrasound isn’t universally assured.