Which component prevents electrical noise from contaminating the diagnostic signals used to create images?

• A. Case
• B. Wire
• C. PZT
• D. Electrical shield

Answer: (D)

Blocking unwanted electrical interference relies on shielding—the conductive layer surrounding the signal path that is tied to ground to intercept and divert noise away from the delicate signals. In ultrasound, the piezoelectric element (PZT) generates small electrical voltages when it receives echoes, so these signals are easily swamped by electromagnetic noise. An electrical shield surrounds the signal path and, by providing a grounded barrier, prevents external fields from coupling into the signal line. The case may help protect the transducer and can include shielding, but the function that prevents contamination is the electrical shield. Wires simply carry the signal, and the PZT is the sensing material, not a noise barrier.