Which resolution corresponds to beam width perpendicular to the imaging plane?

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

Answer: (C)

The concept being tested is how the ultrasound beam’s shape in three dimensions determines resolution. In an ultrasound image, there are two directions in the imaging plane (along the beam direction is axial, and across the image is lateral). The beam also has width in the direction perpendicular to that plane—the elevational direction. Elevational resolution measures how well you can distinguish structures that lie at different heights out of the imaging plane, and it is directly set by the thickness of the beam in that out-of-plane dimension. A thinner beam gives better elevational resolution, reducing partial-volume artifacts where separate structures appear as one. In contrast, axial resolution concerns length along the beam, lateral resolution concerns width within the plane, and temporal resolution relates to how fast frames are captured. So the resolution corresponding to beam width perpendicular to the imaging plane is elevational resolution.