The path toward and away from a reflector being different describes which phenomenon?

• A. Multipath
• B. Refraction
• C. Attenuation
• D. Scatter

Answer: (A)

Multipath occurs when ultrasound energy reaches a reflector via more than one trajectory. Because tissue interfaces and structures can bend or redirect the beam, the energy can hit the same reflector along one route and return along a different route. In a simple, single-path reflection, the inbound and outbound paths would be along the same line (approximately mirror-imaged about the boundary). When multiple routes exist, the path toward the reflector and the path away from it can differ, which is the hallmark of multipath. The other options describe different phenomena—refraction is bending at a boundary when crossing into another medium, attenuation is loss of signal strength, and scatter is diffuse, multi-directional reflection—so they don’t capture the idea of multiple distinct paths to and from a reflector as accurately.