Principles of Image Resolution Flashcards

Which statement about dynamic receive focusing is correct?

Answer: It adjusts the receive focus continuously as echoes return from increasing depths

Dynamic receive focusing updates the receive delays in real time so the system is always focused at the depth from which echoes are currently arriving.

The quality factor (Q factor) of a transducer is defined as:

Answer: Operating frequency divided by bandwidth

Q = operating frequency / bandwidth; a lower Q factor indicates a wider bandwidth and better axial resolution.

Grating lobes degrade image quality primarily by causing:

Answer: Artifactual echoes from off-axis structures appearing in the main image

Grating lobes are secondary beams that return echoes from off-axis targets, producing artifacts in the image.

Which aperture change improves lateral resolution for a linear array?

Answer: Increasing the active aperture

A larger aperture creates a more tightly focused beam, improving lateral resolution.

At the near field (Fresnel zone) boundary, the beam diameter is approximately:

Answer: Half the transducer diameter

At the last axial maximum (near-field/far-field boundary), the beam width is approximately half the transducer diameter.

Which mode of ultrasound provides the best temporal resolution?

Answer: M-mode

M-mode interrogates a single line of sight repeatedly at very high rates, giving the best temporal resolution.

Axial resolution is most correctly defined as the minimum distance between two reflectors that can be distinguished along:

Answer: The direction of beam propagation

Axial resolution separates targets along the direction of sound travel, determined by spatial pulse length.