Which of the following is not typically a transducer component?

• A. active crystal
• B. A/D converter
• C. matching layer
• D. wire

Answer: (B)

Transducers are the parts that directly participate in converting energy between electrical and acoustic forms. The active crystal is the core element that turns electrical energy into mechanical vibrations to produce ultrasound and, when receiving, converts echoes back into electrical signals. The matching layer sits on the crystal to bridge the impedance gap between the crystal and tissue, improving energy transfer and bandwidth. A wire provides the electrical connection to drive the crystal and carry the received signal. These are all integral parts of the transducer itself. The A/D converter, however, belongs to the imaging system’s signal processing chain; it digitizes the analog signal after it leaves the receiver. Since it isn’t built into the transducer, it is not considered a transducer component.