Measuring the width of a target on an ultrasound phantom is most closely related to which resolution?

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

Answer: (A)

Lateral resolution defines how well two structures located side by side in the imaging plane can be distinguished. Measuring the width of a target on a phantom relies on recognizing its edges across the image, which is governed by how narrow the ultrasound beam is in the transverse direction and how well the system can focus that beam. A tighter beam and better focusing improve the ability to separate side-by-side boundaries, making the measured width more accurate. Axial resolution concerns separation along the beam direction and is determined by the spatial pulse length; elevational resolution is about the slice thickness (the dimension out of the imaging plane); and contrast resolution concerns the ability to distinguish tissues with different echogenicities rather than geometric dimensions.