If focusing is achieved by a physical lens, this belongs to which category?

• A. Dynamic focusing
• B. External focusing
• C. Phased array focusing
• D. Internal focusing

Answer: (B)

Focusing achieved by a physical lens is external focusing. A lens placed outside the transducer shapes and directs the ultrasound beam by refraction, creating a focal point inside the tissue without relying on the transducer’s electronic controls.

In contrast, dynamic focusing uses time delays and electronic adjustments to change the focus depth during transmission or reception, not a physical lens. Phased array focusing relies on electronically steering and focusing the beam across many small elements, again without a physical lens. Internal focusing, if used, involves a lens built into the transducer itself to shape the beam, rather than an external optic.