What is the purpose of curving the transducer elements or applying a lens over the elements?

• A. To provide focusing in the out-of-plane (elevation) direction
• B. To reduce acoustic impedance mismatch
• C. To reduce crystal ringing and improve axial resolution
• D. To help reduce electronic interference

Answer: (A)

Focusing the beam in the elevation (out-of-plane) direction is achieved by curving the transducer elements or by placing a lens over them. This physical shaping of the aperture creates a converging wavefront in the elevation plane, which narrows the beam vertically and improves the slice thickness and elevational resolution. In contrast, impedance matching, reducing crystal ringing for axial resolution, or minimizing electronic interference are addressed by other design features (such as matching layers, dampening, or shielding) and do not rely on the curvature or lensing of the elements.