What term describes the ability to separate closely spaced objects?

• A. Resolution
• B. Penetration
• C. Duty factor
• D. Interference

Answer: (A)

Resolution is the ability to separate closely spaced objects. In ultrasound imaging, two reflectors will be seen as distinct only if the system’s resolution is high enough to distinguish them along the beam path (axial) or across the beam (lateral). Axial resolution depends on the spatial pulse length—shorter pulses and higher frequencies improve it, letting two interfaces that are close together along the beam be displayed separately. Lateral resolution depends on beam width and focusing—narrow, well-focused beams give better separation across the beam. If the objects are closer than the system can resolve, they merge and appear as one.

Penetration describes how deep the ultrasound can image, not how well two nearby objects can be separated. Duty factor is the fraction of time the transducer emits, which affects imaging dynamics and heating risk, not resolution. Interference refers to the interaction of overlapping waves, which can affect image patterns but does not define the ability to distinguish two objects.