Transducers used for diagnostic ultrasound are _____ transducers.

• A. Medium-Q
• B. Ultra-wideband
• C. Low-Q
• D. High-Q

Answer: (C)

In diagnostic ultrasound, axial (along the beam) resolution improves when the emitted pulse is short, which requires a broad range of frequencies. The Q factor describes how narrow or broad a transducer’s bandwidth is: a low-Q transducer has a wide bandwidth, producing a short pulse with many frequencies. This short impulse lets the system sample structures quickly and resolves closely spaced interfaces. A high-Q transducer, with its narrow bandwidth and longer ringing, would blur fine details along the axis, which is undesirable for imaging. Therefore, transducers used for diagnostic ultrasound are designed to be low-Q to achieve the necessary short pulses and broad bandwidth.