String test objects are used to evaluate which aspect of Doppler performance?

String test objects are used to evaluate which aspect of Doppler performance?

• A. Contrast resolution
• B. Axial resolution
• C. Doppler accuracy
• D. Elevation resolution

Answer: (C)

Doppler accuracy is what string test objects assess. These phantoms use a string moved at a precisely controlled speed through a fluid so the Doppler frequency shift from the moving scatterers is predictable. The ultrasound system measures that shift and converts it to velocity, so by comparing the measured velocity (and the angle information used in the calculation) to the known value you can judge how accurately the device reports Doppler data, including how well angle correction and velocity encoding are working. This is different from image-resolved tests like contrast resolution, axial resolution, or elevation resolution, which focus on image sharpness and spatial discrimination rather than the accuracy of Doppler velocity measurements.

Doppler accuracy is what string test objects assess. These phantoms use a string moved at a precisely controlled speed through a fluid so the Doppler frequency shift from the moving scatterers is predictable. The ultrasound system measures that shift and converts it to velocity, so by comparing the measured velocity (and the angle information used in the calculation) to the known value you can judge how accurately the device reports Doppler data, including how well angle correction and velocity encoding are working. This is different from image-resolved tests like contrast resolution, axial resolution, or elevation resolution, which focus on image sharpness and spatial discrimination rather than the accuracy of Doppler velocity measurements.