Which term describes the overall image detail including axial, elevational, and lateral resolution, and is related to the number of scan lines?

• A. Spatial
• B. Contrast
• C. Temporal
• D. Dynamic range

Answer: (A)

Spatial resolution describes the image’s ability to show fine details in all three dimensions: along the beam (axial), across the image (lateral), and through the slice thickness (elevational). The number of scan lines affects how densely the image is sampled in the lateral direction, so more scan lines lead to higher lateral sampling density and sharper separation of closely spaced structures. Axial resolution depends mainly on the pulse length and frequency (shorter pulses and higher frequencies provide better depth discrimination), while elevational resolution relates to the beam thickness in the out‑of‑plane direction and improves with a thinner slice or 3D techniques. The other terms—temporal resolution (frame rate and motion timing), dynamic range (range of echo amplitudes the system can display), and contrast (brightness differences between tissues)—describe different aspects and do not capture the overall spatial detail described here.