In ultrasound array transducers, what does pitch refer to?

• A. The frequency of the transmitted pulse
• B. The spacing between element centers
• C. The depth of the imaging plane
• D. The width of each element

Answer: (B)

Pitch is the spacing between the centers of adjacent transducer elements. In an array, each element has a width and there may be a small gap between elements; the pitch is the distance from one element’s center to the next element’s center, effectively element width plus any kerf. This distance sets how tightly the elements are packed and, together with the element width, defines the aperture of the array and how the beam is formed and steered. A smaller pitch (relative to the tissue wavelength) helps avoid grating lobes when steering the beam and can improve lateral resolution, while a larger pitch increases the risk of unwanted grating lobes and alters beam characteristics. The other options refer to the transmitted frequency, imaging depth, or the physical width of a single element, which are different concepts from pitch.