Quality Assurance chapter 22

What is Quality Assurance (QA) in ultrasound?

A program designed to ensure consistent image quality, patient safety, and equipment performance.

What is Quality Control (QC)?

The routine testing and monitoring of equipment performance.

QA vs QC — what’s the difference?

-QA = overall program

-QC = daily/periodic tests within QA

Why is QA important in ultrasound?

-Ensures diagnostic accuracy

-Detects equipment malfunction

-Reduces patient exposure

-Maintains accreditation standards

What is the most important component of a QA program?

Regular documentation of test results.

What tool is used for most QA testing?

A tissue-mimicking phantom.

What is a phantom?

A test object that simulates human tissue acoustic properties.

What acoustic properties do phantoms mimic?

-Speed of sound

-Attenuation

-Scattering

-Backscatter

What is the assumed speed of sound used in phantoms?

1540 m/s.

What is dead zone?

The region near the transducer where accurate imaging is not possible.

What causes the dead zone?

-Ring-down

-Transducer recovery time

How is dead zone evaluated?

Using near-field targets in a phantom.

What is axial resolution?

The ability to distinguish two structures along the beam axis.

How is axial resolution tested?

With vertically aligned targets in a phantom.

What improves axial resolution?

-Higher frequency

-Shorter pulse length

-Greater bandwidth

What is lateral resolution?

Ability to distinguish objects side by side.

How is lateral resolution evaluated?

With horizontally spaced targets.

What improves lateral resolution?

-Narrow beam width

-Proper focusing

-Higher frequency

What is elevation (slice thickness) resolution?

Ability to distinguish structures perpendicular to the image plane.

Poor elevation resolution results in what artifact?

Partial volume artifact.

What is distance accuracy?

Accuracy of depth and spacing measurements.

How is distance accuracy tested?

Measuring known target separations in a phantom.

What does horizontal distance accuracy test?

Lateral measurement accuracy.

What does vertical distance accuracy test?

Axial measurement accuracy.

What is geometric accuracy?

Correct display of shape and spatial relationships.

What affects geometric accuracy?

-Speed of sound errors

-System calibration issues

What is sensitivity in QA testing?

Ability to detect low-level echoes.

How is sensitivity tested?

By determining the maximum depth of penetration.

What factors affect penetration depth?

-Output power

-Frequency

-Gain

-Attenuation

What is contrast resolution?

Ability to distinguish differences in echo intensity.

How is contrast resolution evaluated?

Using targets with different echogenicities.

What is grayscale mapping (dynamic range)?

The number of shades of gray displayed.

Increasing dynamic range will:

Increase gray shades and decrease image contrast.

What is uniformity?

Consistent brightness across the image.

What causes poor uniformity?

-Defective transducer elements

-Improper TGC settings

What is dropout?

Loss of signal due to damaged transducer elements.

What QA test checks for transducer defects?

Element sensitivity testing.

What is TGC?

Time Gain Compensation — compensates for depth-dependent attenuation.

How often should QA testing be performed?

-Daily (basic checks)

-Monthly

-Annually (comprehensive testing)

Which resolution is NOT affected by beam width?

Axial resolution.