Elevational resolution is commonly evaluated with phantoms containing spherical structures embedded in tissue-mimicking material to assess resolution in which orientation?

• A. Axial
• B. Lateral
• C. Elevational
• D. Temporal

Answer: (C)

Elevational resolution refers to distinguishing structures across the thickness of the ultrasound slice, i.e., in the elevation direction out of the imaging plane. Phantoms with spherical targets are ideal for testing this because spheres look the same from any angle; if the system’s elevational resolution is limited, two spheres separated along the elevation axis will blur together or appear as a single elongated shape in the image. Using tissue-mimicking material makes the test reflect how sound interacts with real tissue, so the measured slice thickness and beam elevation width are realistic. This approach specifically probes the dimension through the slice, rather than along the beam (axial) or across the image plane (lateral), and is distinct from temporal aspects like frame rate.