Which defect is most associated with degraded beam shape and potential artifacts in ultrasound transducers?

• A. Metallurgical defects in the casing
• B. Poor electrical shielding
• C. Temperature variation
• D. Cracks or delaminations in the active element

Answer: (D)

The key idea is that beam quality depends on the integrity of the active element, the piezoelectric crystal that both emits and receives ultrasound. If there are cracks or delaminations in this active element, portions of the crystal no longer vibrate uniformly or at the correct phase. That breaks up the uniform aperture, distorts the emitted wavefront, and shifts or broadens the beam. The result is degraded beam shape and the kinds of image artifacts you can see with a faulty transducer, such as loss of resolution, irregular beam width, and ghosting.

Other defects can cause problems, but not as directly with beam shape. Metallurgical defects in the casing don’t typically alter how the emitted wavefront is formed. Poor electrical shielding mainly introduces electrical noise and interference, not a distorted beam from the element itself. Temperature variation can affect speed of sound and material properties, but the most direct and impactful cause of beam distortion is cracks or delaminations in the active element.