Where is a piezoelectric crystal found?

• A. X-ray detector
• B. Ultrasound probe
• C. MRI coil
• D. Gamma camera

Answer: (B)

Piezoelectric crystals are the active element in an ultrasound transducer. They convert electrical energy into mechanical vibrations to emit ultrasound waves, and then they detect echoes by vibrating and generating electrical signals that are processed into an image. This transmitter–receiver role is the hallmark of how ultrasound probes work.

Other imaging devices use different detector technologies: X-ray detectors rely on scintillators or semiconductors to convert X-ray photons to an electrical signal; MRI coils detect signals from spinning protons in a magnetic field; gamma cameras use scintillators to detect gamma photons. That’s why a piezoelectric crystal is found in ultrasound probes.