In phantom-based resolution testing, which resolution is evaluated by using parallel rod targets?

In phantom-based resolution testing, which resolution is evaluated by using parallel rod targets?

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

Answer: (D)

The key idea is how finely the system can separate structures that lie side by side in the image. In phantom-based resolution testing, parallel rod targets are used because they present multiple reflectors arranged across the image plane. To distinguish two rods that are next to each other, the ultrasound beam must have a narrow lateral width at that depth. The ability to resolve those side-by-side rods directly measures lateral resolution, which is governed by the beamwidth in the direction perpendicular to the beam’s travel. Axial resolution, by contrast, depends on the pulse length and is tested with reflectors arranged along the beam path. Elevational resolution relates to slice thickness and is evaluated with targets arranged in the elevation direction. So parallel rod targets specifically probe how well the system resolves detail across the image, i.e., lateral resolution.

The key idea is how finely the system can separate structures that lie side by side in the image. In phantom-based resolution testing, parallel rod targets are used because they present multiple reflectors arranged across the image plane. To distinguish two rods that are next to each other, the ultrasound beam must have a narrow lateral width at that depth. The ability to resolve those side-by-side rods directly measures lateral resolution, which is governed by the beamwidth in the direction perpendicular to the beam’s travel.

Axial resolution, by contrast, depends on the pulse length and is tested with reflectors arranged along the beam path. Elevational resolution relates to slice thickness and is evaluated with targets arranged in the elevation direction. So parallel rod targets specifically probe how well the system resolves detail across the image, i.e., lateral resolution.