What is a disadvantage of a water-path scanner?

• A. It reduces axial resolution
• B. The beam width perpendicular to the image plane is increased, resulting in poor Elevational resolution
• C. Bubbles in fluid can inhibit sound transmission into the body
• D. The fluid path increases the mechanical index

Answer: (C)

Water-path coupling relies on a fluid to transmit ultrasound from the transducer into the body. If there are gas bubbles in that fluid, they create a strong impedance mismatch and scatter or reflect most of the sound energy. That interference prevents the waves from entering the body efficiently, leading to poor transmission, weaker signals, and image artifacts. This disruption of energy delivery is the fundamental disadvantage of a water-path scanner in the presence of bubbles.

The other factors listed aren’t inherent drawbacks of the water path: axial resolution depends on pulse length and frequency, elevational resolution on beam thickness and focusing, and the mechanical index is about exposure conditions, not the coupling medium itself.