Quality assurance, protocols, and new technologies
a device that plots the reflection amplitudes received by the transducer.
distance closest to the transducer in which imaging cannot be performed.
testing device that measures acoustic output.
the routine, periodic evaluation of data collected on the performance of the ultrasound system and transducers.
testing used to collect data on the operation and acoustic output of the ultrasound system.
tissue-equivalent testing device with characteristics that are representative of tissues.
preventive maintenance (PM) service
periodic internal cleaning and overall evaluation of the ultrasound system function; generally performed by the system manufacturer.
ability to place echoes in proper position when imaging from different orientations.
measure of how weak a reflection the system can display.
devices without tissuelike properties designed to measure some characteristics of the imaging system.
Methods of evaluation
Operation testing
Acoustic output testing
• Considers only the pulser and transducer.
• Evaluates the safety and biological effects of ultrasound and Doppler imaging.
• Requires specialized equipment and is generally performed by the manufacturer.
Methods for Evaluating Operation
TESTING DEVICE | DESCRIPTION | PARAMETERS EVALUATED |
AIUM 100 test object | A device without tissue properties designed to measure some system characteristicsProvides measurement of system performanceUses 0.75-mm stainless steel rods placed in a mixture with a propagation speed of 1540 m/s | |
Beam profiler | A device that plots 3-D reflection amplitudes received by the transducer | Reflected amplitudes received by the transducerA device with properties representative of different tissue types |
Tissue-mimicking phantom | Tissue properties include soft tissue, cystic, and solid structuresSmall fibers are used to evaluate axial and lateral resolution | Dead zonePenetrationCompressionCompensationAxial resolutionLateral resolutionContrast resolutionSlice thickness resolutionVertical and horizontal calibrationSystem sensitivityRegistration accuracy |
Doppler phantom | A device using a blood-mimicking fluidSimulates clinical conditionsVelocity, pulse rates, and durations are knownSome may contain a stenosis, or moving string scatters the sound beamEasy to calibrateCan produce pulsatile and retrograde motion | Penetration of the Doppler beamFlow directionAccuracy of gate locationAccuracy of measured flow velocityImage congruency |
Methods for Evaluating Acoustic Output
TESTING DEVICE | DESCRIPTION | PARAMETERS EVALUATED |
Force-balance system | A device that measures the force (pressure) of the sound beam | Measures the intensity or power of the sound beam |
Hydrophone | A small transducer element mounted on the end of a hollow needle or a large piezoelectric membrane with small metallic electrodes centered on each sideMembrane is made of polyvinylidene fluoride (PVDF) | Relationship between the amount of acoustic pressure and the voltage producedMeasures acoustic outputMeasures pressure and intensities across the sound beamMeasures period, pulse repetition period, and pulse duration |
Record keeping
Statistical indices
• Positive means the test predicted disease.
• Negative means the test predicted the absence of disease.
• True positive (TP) means test matches gold standard—both are positive for disease.
• True negative (TN) means test matches gold standard—both are negative for disease.
• False positive (FP) means test does not match gold standard—the test says there is disease when there isn’t.
• False negative (FN) means test does not match gold standard—the test says there is no disease when there is.
Sensitivity: ability of a test to detect disease.
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Specificity: ability of a test to detect the absence of disease.
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Positive Predictive Value: measures how often the test is correct when positive for disease.
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Negative Predictive Value: measures how often the test is correct when negative for disease.
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Accuracy: measures the percentage of examinations that agree with the gold standard.
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Protocols
• American Institute of Ultrasound Medicine (AIUM) and American College of Radiology (ACR) have adapted universal scanning protocols for medical sonography examinations.
• Extension of these protocols may be necessary when anomalies, abnormalities, and pathologies are discovered.
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