What transducer component reduces reflection at the transducer/skin interface?

What transducer component reduces reflection at the transducer/skin interface?

• A. Matching layer
• B. Lens
• C. Element
• D. Backing material

Answer: (A)

Reflection at the transducer/skin boundary comes from a mismatch in acoustic impedance between the piezoelectric element and tissue. The matching layer sits between the element and the skin and has an acoustic impedance between those two materials, chosen to bridge the gap. This creates a smoother transition for the traveling wave, so fewer waves are reflected back and more energy is transmitted into the tissue. When the layer is about a quarter of a wavelength thick at the center frequency, reflections from the two interfaces can interfere destructively, further boosting transmission. The other components have different roles: focusing the beam (lens), shortening the pulse and reducing ringing (backing material), and forming the actual vibrating element (the piezoelectric crystal).

Reflection at the transducer/skin boundary comes from a mismatch in acoustic impedance between the piezoelectric element and tissue. The matching layer sits between the element and the skin and has an acoustic impedance between those two materials, chosen to bridge the gap. This creates a smoother transition for the traveling wave, so fewer waves are reflected back and more energy is transmitted into the tissue. When the layer is about a quarter of a wavelength thick at the center frequency, reflections from the two interfaces can interfere destructively, further boosting transmission. The other components have different roles: focusing the beam (lens), shortening the pulse and reducing ringing (backing material), and forming the actual vibrating element (the piezoelectric crystal).