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

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

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

Answer: (B)

This item focuses on acoustic impedance and how to minimize reflections at an interface. The transducer’s piezoelectric element has a much higher acoustic impedance than body tissue, so when ultrasound hits the skin, a large portion can reflect back unless an intermediary helps bridge the gap. A matching layer sits between the crystal and the skin and has an impedance between the crystal and tissue. This layer acts as an acoustic transformer, transforming the high impedance of the element toward the tissue impedance, which reduces the reflection and allows more energy to transmit into the body. For optimal performance, the matching layer is typically designed to be a quarter-wavelength thick at the operating frequency, maximizing transmission and minimizing loss due to reflection. The lens focuses the beam, not the reflection issue. The element is the active piezoelectric material that generates and receives sound, and the backing material dampens the rear of the crystal to shorten the pulse and broaden bandwidth rather than address interface reflections.

This item focuses on acoustic impedance and how to minimize reflections at an interface. The transducer’s piezoelectric element has a much higher acoustic impedance than body tissue, so when ultrasound hits the skin, a large portion can reflect back unless an intermediary helps bridge the gap.

A matching layer sits between the crystal and the skin and has an impedance between the crystal and tissue. This layer acts as an acoustic transformer, transforming the high impedance of the element toward the tissue impedance, which reduces the reflection and allows more energy to transmit into the body. For optimal performance, the matching layer is typically designed to be a quarter-wavelength thick at the operating frequency, maximizing transmission and minimizing loss due to reflection.

The lens focuses the beam, not the reflection issue. The element is the active piezoelectric material that generates and receives sound, and the backing material dampens the rear of the crystal to shorten the pulse and broaden bandwidth rather than address interface reflections.