Which type of transducer should you select to produce the narrowest slice thickness throughout the image plane?

• A. A phased array with a small footprint
• B. A 1.5D multi-row array
• C. A tightly curved curvilinear array
• D. A mechanical sector

Answer: (D)

The key idea is elevational resolution, i.e., slice thickness—the width of the ultrasound beam in the direction perpendicular to the imaging plane. The narrower that beam, the thinner the slice thickness across the image.

A mechanical sector transducer uses a single, small-height element and mechanical sweeping to form the image. That fixed, compact elevational footprint yields a very narrow beam in the elevational direction that stays consistent across the field, giving the thinnest slice thickness throughout the image plane.

Other transducer designs rely on larger or multiple elevational apertures or electronic focusing that can broaden or vary the elevational beam as you move across the image, leading to a thicker slice in places. So, for the thinnest, most uniform slice across the plane, the mechanical sector is the best choice.