What defines the percentage of intensity that passes forward when the beam strikes an interface?

The percentage of intensity that passes forward when an ultrasound beam strikes an interface is defined by the intensity transmission coefficient. This coefficient quantifies the proportion of the incident beam's intensity that continues to propagate through the interface into the next medium. It is calculated by considering factors like the acoustic properties of the two media at the interface, such as their densities and sound speeds.

Understanding the intensity transmission coefficient is crucial in clinical practice since it impacts image quality and the amount of ultrasound energy that is absorbed by tissues. High transmission coefficients mean that more of the ultrasound energy will continue into the deeper tissues, whereas lower coefficients indicate that a significant portion may be reflected back, potentially compromising the diagnostic information available from deeper structures.

Intensity absorption coefficients, intensity reflection coefficients, and echo intensity pertain to other aspects of ultrasound physics but do not specifically address the direct measurement of transmitted intensity at an interface, making the intensity transmission coefficient the correct and relevant choice for this question.