The advantage you obtain with a wide-bandwidth transducer compared to a narrow-band transducer is:

• A. Decreased acoustic power output
• B. Improved axial resolution
• C. Improved lateral resolution
• D. Improved focusing

Answer: (B)

A wide bandwidth means the transducer emits a shorter pulse because it covers a broader range of frequencies. Axial resolution is how well we can separate two reflectors that lie along the beam—i.e., along the direction the ultrasound is traveling. This resolution depends on the spatial pulse length, which is the physical length of the pulse in tissue. Shorter pulses have shorter spatial extents, so two closely spaced echoes along the beam arrive separately and are easier to distinguish. That’s why wider bandwidth directly improves axial resolution.

Power output isn’t inherently reduced by bandwidth; the energy delivery depends on drive and impedance, not bandwidth alone. Lateral resolution relies on beam width and focusing across the image plane, which are more about aperture and focusing than bandwidth. Focusing itself is determined by the transducer’s geometry and electronic focusing, not simply by having a wider bandwidth.