The matching layer between the piezoelectric element and the tissue is designed to:

The matching layer between the piezoelectric element and the tissue is designed to:

• A. Insulate the patient from the hot element.
• B. Reduce the vibration of the transducer.
• C. Reduce the acoustic impedance mismatch between the element and tissue.
• D. Increase the reflection coefficient at the transducer-skin interface.

Answer: (C)

Efficient energy transfer from the piezoelectric element into tissue relies on impedance matching. The crystal and tissue have very different acoustic impedances, so without a matching layer much of the energy would be reflected at the interface. The matching layer provides an intermediate impedance, ideally near the geometric mean of the two, to minimize reflections at both interfaces and maximize transmission into tissue. This improves the transmitted pressure and, consequently, the received signal. The thickness is typically a quarter-wavelength at the center frequency to reinforce forward transmission. So, the matching layer is designed to reduce the acoustic impedance mismatch between the element and tissue. It isn’t meant to insulate the patient or dampen transducer vibration, and it should reduce the reflection coefficient rather than increase it.

Efficient energy transfer from the piezoelectric element into tissue relies on impedance matching. The crystal and tissue have very different acoustic impedances, so without a matching layer much of the energy would be reflected at the interface. The matching layer provides an intermediate impedance, ideally near the geometric mean of the two, to minimize reflections at both interfaces and maximize transmission into tissue. This improves the transmitted pressure and, consequently, the received signal. The thickness is typically a quarter-wavelength at the center frequency to reinforce forward transmission. So, the matching layer is designed to reduce the acoustic impedance mismatch between the element and tissue. It isn’t meant to insulate the patient or dampen transducer vibration, and it should reduce the reflection coefficient rather than increase it.