What happens if the transducer is angled more than 15 degrees relative to the skin during ultrasound?

• A. Scattering/decreased propagation of energy
• B. Increased energy propagation
• C. No effect
• D. Decreased tissue heating

Answer: (A)

The playing field here is how incidence angle affects energy transfer into tissue. Ultrasound energy is delivered most effectively when the beam hits the skin perpendicularly. If you angle the transducer more than a small amount, the wave meets the boundary at an oblique angle, and a larger portion of the energy is reflected back or scattered rather than entering the tissue. That reduces the amount of energy that propagates through the tissue, which in turn lowers the heating effect. So the option describing scattering and decreased propagation of energy best fits what's happening. Keeping the transducer perpendicular with good coupling minimizes these losses.