In the ultrasound transducer, the crystal also serves as which component?

• A. Transmitter
• B. Receiver
• C. Amplifier
• D. Filter

Answer: (B)

Piezoelectric crystals in ultrasound transducers are bidirectional energy converters, meaning they can do both the emission and the detection of ultrasound. When the crystal is driven by a pulsed electrical voltage, it vibrates and emits an ultrasound pulse. Afterward, when echoes return from tissue, those mechanical pressures cause the crystal to deform and generate a small electrical voltage. This generated signal is what the receiver stage amplifies and processes. So, during reception, the crystal serves as the receiver, converting the mechanical echo into an electrical signal for the system to analyze. Amplifiers and filters exist as separate stages in the signal chain, not as the crystal itself; while the crystal can also function as a transmitter when energized, the focus here is on its role as the detector.