A phantom with multiple rows of identical 5mm spherical fluid structures embedded in tissue-mimicking material is best used to evaluate which type of resolution?

A phantom with multiple rows of identical 5mm spherical fluid structures embedded in tissue-mimicking material is best used to evaluate which type of resolution?

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

Answer: (B)

Elevational resolution is being tested. This refers to the ability to distinguish structures that lie in directions perpendicular to the imaging plane, i.e., along the slice thickness. A phantom with rows of identical fluid spheres embedded in tissue-mimicking material creates reflectors that are stacked in the elevational direction. If the ultrasound system has good elevational resolution, the separate rows will appear as distinct features; if not, the rows blur together because the slice is too thick to separate them. Axial resolution would require structures separated along the beam’s path to be resolved, which isn’t the focus of rows in a phantom. Lateral resolution concerns separation within the imaging plane across the width, not along the slice thickness. Contrast resolution deals with differentiating echoes of different intensities, not distinguishing adjacent structures in the elevational direction.

Elevational resolution is being tested. This refers to the ability to distinguish structures that lie in directions perpendicular to the imaging plane, i.e., along the slice thickness. A phantom with rows of identical fluid spheres embedded in tissue-mimicking material creates reflectors that are stacked in the elevational direction. If the ultrasound system has good elevational resolution, the separate rows will appear as distinct features; if not, the rows blur together because the slice is too thick to separate them.

Axial resolution would require structures separated along the beam’s path to be resolved, which isn’t the focus of rows in a phantom. Lateral resolution concerns separation within the imaging plane across the width, not along the slice thickness. Contrast resolution deals with differentiating echoes of different intensities, not distinguishing adjacent structures in the elevational direction.