Diagnostic Ultrasound Quality Control: A Practical QC Program Guide

A well-run diagnostic ultrasound QC program is the difference between equipment that quietly degrades over months and a scanner that is verified to perform to its own baseline on every patient. Unlike ionizing-radiation modalities, ultrasound carries no stochastic dose risk from X-ray output, but it is not consequence-free: transducer element failure, sound-speed calibration drift, and display miscalibration all erode image quality in ways a sonographer focused on a clinical study will not reliably notice. In one multi-site program that performed 1,145 semi-annual transducer assessments, roughly 30% of probes had at least one detectable defect — dead elements, lens delamination, wire cuts — yet most continued in clinical service undetected until objective testing found them. ⁷ ACR and AIUM accreditation both require documented QC and a physicist-level equipment survey precisely because routine scanning does not reliably surface these degradation modes.

Introduction

Diagnostic ultrasound is the highest-volume cross-sectional imaging modality in clinical practice, used in abdominal, obstetric, gynecologic, vascular, musculoskeletal, small-parts, cardiac, and point-of-care applications. The equipment ranges from high-end shared-service scanners in radiology departments to portable handheld devices at the bedside. Across all of these contexts, image quality depends on the acoustic performance of the transducer, the processing chain inside the scanner, and the calibration of the display.

A systematic QC program serves three distinct purposes: (1) it detects equipment degradation before it can affect clinical diagnosis; (2) it satisfies the requirements of ACR ultrasound accreditation, AIUM practice accreditation, and The Joint Commission for facilities that seek or hold those credentials; and (3) it provides a documented baseline that supports equipment repair, replacement decisions, and medical-legal defensibility if image quality is later questioned.

The governing physics frameworks for routine ultrasound QC in the United States are AAPM Task Group 1 (Routine QA of Clinical Diagnostic Ultrasound Equipment, published as Goodsitt et al. in Medical Physics) and AAPM Task Group 128 (Quality Assurance Tests for Prostate Brachytherapy Ultrasound Systems). ^{1, 2} TG-1 establishes the test methods and a baseline-relative QA philosophy for the whole scanner; TG-128, though developed for the transrectal systems used in prostate brachytherapy, contributes transferable QA procedures — spatial-measurement accuracy, geometric distortion, and transducer-integrity checks — relevant to diagnostic transducer QC. Both emphasize that meaningful tolerances are defined against each device's own documented baseline rather than against a single universal number. ACR ultrasound accreditation and AIUM practice accreditation reference physicist-level equipment surveys as a program requirement. ^{3, 4}

DRPS supports diagnostic imaging facilities across Florida, Maryland, Virginia, Washington DC, California, and Nevada with medical physics consulting, accreditation support, and routine equipment surveys for diagnostic ultrasound QC programs.

Topic Explanation

Why does ultrasound need a formal QC program?

Ultrasound image quality is not self-verifying. A scanner may display images that appear clinically adequate while its transducer has accumulated significant element dropout, or while its grayscale mapping has drifted, or while its distance calibration has crept outside tolerance. A sonographer focused on a study will not reliably detect gradual sensitivity loss or subtle element-column dropouts during clinical operation.

Formal QC testing addresses this gap by establishing a documented baseline for each transducer-scanner combination, then periodically verifying that performance remains within defined action levels. When performance degrades, the QC record identifies the scope of the problem, the date of onset, and whether the degradation is within or outside the action-level threshold.

A QC program also has regulatory and accreditation value. ACR ultrasound accreditation requires submission of phantom images and documentation of QC testing as part of the application and reaccreditation cycle. ³ AIUM practice accreditation similarly requires a QC policy and a physicist's equipment survey. ⁴

What equipment is covered?

A comprehensive ultrasound QC program should cover:

• All diagnostic ultrasound scanners in the department (including portable and point-of-care units used for diagnostic purposes)
• All transducers used for diagnostic imaging, particularly high-volume or safety-critical applications
• Display monitors, particularly for grayscale fidelity
• Any ultrasound-guided intervention equipment where image quality directly affects procedural safety

Handheld portable units and point-of-care devices used solely for procedural guidance may be covered under a simplified protocol, but departments seeking ACR or AIUM accreditation should confirm which units are in scope for the application; the AIUM Practice Parameter for performing diagnostic and screening examinations sets the corresponding clinical-performance expectations. ¹⁰

Key Technical Principles

The full ultrasound QC test set

The table below summarizes the standard test set, methods, and recommended frequency. The action levels shown are representative thresholds in common practice, not universal mandates: AAPM TG-1 and TG-128 deliberately frame most tolerances against each device's documented baseline rather than against a single fixed number, and accreditation bodies require that a facility define and justify its own action levels in writing. ^{1, 2, 3, 4} Treat the values below as conventional starting points to be confirmed against your phantom, transducer type, and accreditation manual.

QC Test	Method	Frequency	Representative Action Level
Physical/mechanical inspection	Visual and tactile check of transducer cable, connector, housing, and lens	Each use or daily	Any crack, delamination, fluid ingress, or cable damage → remove from service immediately
Transducer element dropout	In-air reverberation (air-scan) image or purpose-built electronic transducer analyzer; compare element/column map to baseline	Monthly screening (physicist annually)	Any newly dead element or any cluster of adjacent failed elements relative to baseline; analyzer-based programs commonly act on roughly ≥1–2% dead elements or any contiguous dead group
Image uniformity	Phantom scan of uniform background region; inspect for banding, shadowing, or dropout columns	Monthly	Any visible banding, shadowing, or lateral asymmetry not present at baseline
Depth of penetration / maximum depth of visualization	Deepest detectable scatterer in a tissue-mimicking phantom at a fixed preset	Monthly	Decrease beyond baseline variability — commonly a drop of about 1 cm or ~10% from baseline
Distance measurement accuracy — axial	Measure known-spacing wire targets along the beam axis; compute percent error	Annually (physicist survey)	Error greater than ~2 mm or ~2% of the measured distance, whichever is larger
Distance measurement accuracy — lateral/horizontal	Measure known-separation horizontal wire targets across the image	Annually (physicist survey)	Error greater than ~3 mm or ~3% of separation (lateral tolerance is looser than axial because beam width grows with depth)
Spatial resolution (axial and lateral)	Wire-target group; measure smallest resolvable spacing at specified depths	Annually (physicist survey)	Measurable degradation from baseline at a fixed depth and preset
Contrast resolution / lesion-detection targets	Anechoic and hyperechoic targets at specified depths	Annually (physicist survey)	Failure to resolve targets that were visible at baseline
Dead zone (near-field)	Shallowest wire/target returning a clean echo near the transducer face	Annually (physicist survey)	Increase from baseline (e.g., a few mm), typically interpreted against the phantom's near-field target ladder
In-air reverberation test	Transducer face-up in air; evaluate parallel reverberation lines for uniformity	Monthly	Missing lines, irregular spacing, or asymmetric/attenuated bands versus baseline
Display monitor calibration	AAPM TG-270 8 (or legacy SMPTE) test patterns; ambient-light check	Annually	Inability to distinguish the 0%/5% or 95%/100% luminance patches; luminance response outside target range
Thermal index / mechanical index display	Verify TI and MI are displayed for each preset and respond to output changes	Annually	Missing or non-updating output display
Electrical safety	Chassis/patient leakage-current test per IEC 60601-1	Annually (biomedical engineering)	Exceeds applicable IEC 60601-1 limits

Transducer element dropout: the in-air test

Transducer element dropout — the failure of individual piezoelectric elements in an array — is the single most common and most clinically consequential transducer fault. The simplest field screen is the in-air reverberation test (air-scan or flat-field test); the most sensitive method is an electronic transducer analyzer that pulses each element independently and reports pulse-echo amplitude, capacitance, and impedance per channel. Both approaches are well established in clinical ultrasound QC practice.

To perform the in-air test:

1. Place the transducer face-up in air with no coupling gel and wipe the lens clean.
2. Select a fixed preset and gain for the transducer type, and record those settings so the test is reproducible.
3. Freeze a still image and evaluate the shallow reverberation field (typically 0–3 cm).
4. A healthy array shows bright, uniform, evenly spaced horizontal reverberation lines spanning the full image width.

Dead, attenuated, or anomalously bright vertical columns in this pattern correspond to non-functioning, weak, or shorted elements. The captured pattern is compared to the device's baseline image; because the test is qualitative, baseline comparison — not an absolute appearance — is what makes a finding actionable. The in-air test reliably catches contiguous dead-element groups and gross dropout but is relatively insensitive to scattered single-element failures and to gradual sensitivity loss; an analyzer is needed to quantify those. Published programs report that a meaningful fraction of in-service probes carry at least one defect, which is why element mapping belongs in every transducer's QC record. ^{2, 7}

For phased-array and sector probes, element loss tends to produce wedge-shaped or sector-asymmetric artifacts rather than simple vertical columns, because the beamformer steers and apodizes across a small aperture — making baseline comparison even more important for these probes.

Depth of penetration

Depth of penetration (maximum depth of visualization) is the deepest point at which the speckle pattern of a uniform tissue-mimicking phantom remains distinguishable from electronic noise at a fixed preset and output. It is the most sensitive single-number indicator of overall transducer-plus-scanner sensitivity, because it integrates transmit power, element health, and receiver gain into one reproducible reading. ¹

Standard phantoms from CIRS (e.g., Model 040GSE) or ATS Laboratories (e.g., Model 539) embed wire and nylon monofilament targets and anechoic/hyperechoic structures at known depths in a background with calibrated speed of sound (nominally 1,540 m/s) and attenuation (commonly 0.5 or 0.7 dB/cm/MHz). The deepest confidently detectable depth is recorded at each evaluation, always at the same preset, focal configuration, and output used for the baseline.

A loss of roughly 1 cm or about 10% from baseline is a widely used action level, because a change of that magnitude typically signals transducer aging, element failure, lens or matching-layer degradation, internal crystal cracking, or connector corrosion. The number is a practice convention anchored to baseline, not a regulatory limit; a sudden or large drop warrants investigation before the probe returns to clinical use regardless of the nominal percentage.

Distance measurement accuracy

Distance accuracy underwrites every clinical measurement made with ultrasound — fetal biometry, organ size, vessel diameter, lesion dimensions, and biopsy-target localization. Axial errors (along the beam axis) arise from the scanner's assumed speed of sound deviating from the true tissue value: the system converts echo time-of-flight to depth using a fixed 1,540 m/s assumption, so any real-tissue mismatch scales the displayed depth. Lateral errors (across the image) arise from beam-steering geometry and pixel-to-distance mapping, and grow with depth as the beam widens.

Axial distance accuracy is tested by measuring the displayed distance between wire targets of known separation along the beam axis in a tissue-mimicking phantom. The percent error is:

$$\text{Error}(\%)=\frac{|d_{\text{measured}}-d_{\text{true}}|}{d_{\text{true}}}\times 100\%$$

where $d_{\text{measured}}$ is the on-screen caliper distance and $d_{\text{true}}$ is the known phantom target separation. A common axial action level is an error greater than about 2 mm or 2% of the measured distance, whichever is larger — a representative practice convention rather than a fixed standard, and one that should be confirmed against the phantom's certified target spacing.

Lateral distance accuracy uses horizontally separated targets and the same formula, but is conventionally held to a looser tolerance (on the order of 3 mm or 3%) because lateral resolution and pixel mapping degrade with depth as the beam widens. Measure at several depths and report each separately; a lateral error that grows with depth points to beamforming or focusing degradation rather than a global calibration offset.

Axial resolution equation

Axial resolution — the minimum separation along the beam axis at which two reflectors are seen as distinct — is set by the spatial pulse length (SPL), the physical length of the transmitted pulse. SPL is the number of cycles in the pulse times the wavelength, and two reflectors can be separated only if they are at least half an SPL apart:

$$\text{Axial resolution}=\frac{\text{SPL}}{2}=\frac{n\lambda }{2}$$

where $n$ is the number of cycles per pulse and $\lambda =c/f$ is the acoustic wavelength, with $c$ the speed of sound in soft tissue ($\approx 1,540$ m/s) and $f$ the transducer center frequency. ¹

For a 10 MHz transducer transmitting a 2-cycle pulse:

$$\lambda =\frac{1540\text{ m/s}}{10\times 10^6\text{ Hz}}=0.154\text{ mm}$$

$$\text{Axial resolution}=\frac{2\times 0.154}{2}=0.154\text{ mm}$$

Higher-frequency transducers improve axial resolution because shorter wavelengths yield shorter pulses — but attenuation rises with frequency, so penetration falls. This frequency-resolution-penetration trade-off is why superficial structures (thyroid, breast, tendons) are imaged with high-frequency linear arrays (8–18 MHz and higher) while deep abdominal work uses lower-frequency curved arrays (2–6 MHz). Lateral resolution, by contrast, is governed by beam width and is always coarser than axial resolution and depth-dependent, which is why QC measures both.

In QC, axial and lateral resolution are read from closely spaced wire-target groups at fixed depths. The actionable finding is degradation from the device's baseline at the same depth and preset — not a deviation from the theoretical optimum — because QC detects equipment change, not design limits.

Dead zone (near-field)

The dead zone is the shallow region immediately below the transducer face in which echoes cannot be displayed, because the receiver is still recovering from the transmit pulse and the transducer's own ring-down. Targets within the dead zone are invisible, which matters clinically for very superficial structures (skin, superficial vessels, foreign bodies) and for near-field needle visualization. In QC, the dead zone is read as the shallowest wire in the phantom's near-field target ladder that returns a clean, separable echo. An increase from baseline — typically a few millimeters before it is called actionable — can indicate transmit-pulse or damping degradation. Like the other metrics, the meaningful comparison is against the device's own baseline at a fixed preset.

In-air reverberation test for image uniformity

The in-air reverberation test serves double duty: it screens for element dropout (described above) and evaluates image uniformity across the transducer aperture. ^{1, 2}

A uniform transducer with all elements functioning will produce horizontal reverberation lines that are:

• Parallel to the transducer face
• Evenly spaced in depth
• Uniform in brightness across the full lateral extent of the image

An asymmetric brightness pattern across the image width suggests gain non-uniformity in the beamformer. Curvature of the reverberation lines may indicate coupling or array geometry issues. Irregular spacing of lines suggests errors in the time-gain compensation or processing.

Tissue-mimicking phantoms: CIRS and ATS

The two most widely used tissue-mimicking phantom families in diagnostic ultrasound QC are:

• CIRS (Computerized Imaging Reference Systems): multi-purpose phantoms such as the Model 040GSE use a background with a nominal 1,540 m/s speed of sound and a specified attenuation (commonly 0.5 or 0.7 dB/cm/MHz), with monofilament wire targets (distance and resolution), anechoic and graded-echogenicity targets (contrast and lesion detection), and a near-field ladder for dead-zone testing.
• ATS Laboratories: phantoms such as the Model 539 multi-purpose phantom provide comparable target configurations and are widely used for ACR phantom-image submissions.

Phantoms are consumable. Water-based tissue-mimicking gels can desiccate, develop air bubbles, or delaminate from the housing, while the calibrated speed of sound and attenuation drift over years and with temperature. Each phantom should carry a documented acquisition date and be inspected at every use for tears, shrinkage gaps, or bubbles; a degraded phantom will masquerade as a degraded scanner. Choose the phantom attenuation deliberately — a low-attenuation (0.5 dB/cm/MHz) phantom challenges penetration less than a 0.7 dB/cm/MHz phantom — and keep the same phantom for trending so baseline comparisons stay valid.

ACR ultrasound accreditation requires specific phantom images as part of the application package. The phantom and image submission requirements should be confirmed against the current ACR ultrasound accreditation manual before submitting. ³

Thermal index, mechanical index, and the ALARA principle

Unlike ionizing radiation, ultrasound does not carry a stochastic carcinogenic risk in the accepted dose-response framework. However, two biophysical interaction mechanisms are clinically relevant, and both are addressed by the FDA Output Display Standard (originally Track 3, 1992; updated 2019), NEMA UD 3, and IEC 60601-2-37, with acoustic-output reporting standardized in IEC 61157. ^{5, 6, 9, 12}

Thermal index (TI) is the ratio of the acoustic power produced to the power estimated to raise tissue temperature by 1 °C under defined model assumptions — so a TI of 2 corresponds to a worst-case modeled rise of about 2 °C. It is displayed in real time on FDA-compliant systems when output exceeds defined thresholds. Three variants tailor the bone-heating model to the anatomy in the beam:

• TIS (soft tissue): homogeneous soft-tissue paths with no bone in the field
• TIB (bone at focus): bone near the focal zone, e.g., second- and third-trimester fetal imaging where ossified bone lies at depth
• TIC (cranial bone): bone at or near the surface, e.g., transcranial and neonatal-head imaging

Mechanical index (MI) estimates the likelihood of inertial cavitation (bubble formation and violent collapse) and is defined as:

$$\text{MI}=\frac{p_{r,\alpha }}{\sqrt{f_c}}$$

where $p_{r,\alpha }$ is the derated peak-rarefactional (negative) acoustic pressure in MPa and $f_c$ is the center frequency in MHz. ^{5, 6} Higher MI means a higher probability of cavitation; lower frequencies raise MI for the same pressure, which is why the square-root term appears. The FDA caps MI at 1.9 for most diagnostic applications, with markedly stricter limits for ophthalmic imaging. The derating (typically 0.3 dB/cm/MHz) accounts for tissue attenuation between the transducer and the point of interest, so the displayed MI is a conservative in-situ estimate rather than the free-field value.

ALARA in ultrasound means using the lowest output settings — power, gain, and focus — consistent with obtaining the diagnostic information needed. ^{5, 11} This principle is particularly important for:

• Fetal scanning, especially in the first trimester (TIB limits)
• Neonatal and transcranial applications
• Ophthalmic scanning (strict output limits apply)
• Prolonged scanning sessions

QC testing should include a verification that TI and MI values are displayed on screen for each active preset and that they respond appropriately when output settings are changed. A non-updating or missing output display constitutes a reportable QC finding.

Clinical Impact

Degraded equipment often produces images that still look interpretable. That is the core clinical argument for a systematic program. A transducer with a contiguous dead-element group casts a predictable acoustic shadow that can obscure a lesion in the affected image column while leaving the rest of the field convincingly normal. Distance-calibration errors of a few percent look trivial on a single caliper but compound: a 3% error propagates cubically into a roughly 9% error in an organ-volume estimate, and shifts fetal biometry enough to nudge a gestational-age or growth assessment across a decision threshold. Crucially, only the most severe transducer defects perturb quantitative measurements such as Doppler peak velocity — meaning a probe can be measurably degraded yet still pass a velocity check, so QC cannot rely on clinical measurements alone to flag failing equipment. ⁷

QC results also have legal and accreditation weight. If an equipment problem is later identified and a QC program can demonstrate that the scanner was passing all tests on the dates in question, that record supports the clinical care provided. If there is no QC program, or if the tests were not performed at the required frequency, the absence of documentation is itself an exposure.

For facilities seeking or maintaining ACR ultrasound accreditation, the accreditation program requires:

• An annual physicist-level equipment evaluation
• Documented phantom imaging
• Documentation of routine staff QC tests
• Written QC policies and procedures

Missing documentation at reaccreditation can result in a deficiency finding even if the equipment is performing within tolerance. ³

Practical Optimization Tips

Define baselines at installation and after any major service event

Every QC metric — depth of penetration, distance accuracy, element dropout map, in-air reverberation pattern — should be documented when a transducer or scanner is new and after any service event that replaces components affecting image quality (transducer replacement, beamformer repair, software upgrade). The baseline is the reference against which all subsequent measurements are judged. A QC program that lacks documented baselines cannot meaningfully interpret trends.

Designate a staff QC lead per scanner

Assigning ownership of QC records to a specific sonographer or technologist for each scanner creates accountability and ensures tests are not skipped. Staff-level QC tests — visual inspection, in-air reverberation check, phantom depth check, and image uniformity check — should be performed at least monthly and results logged in a standard form. The physicist's annual survey builds on these records.

Test transducers for your highest-acuity applications first

Not all transducers carry equal clinical stakes. The linear-array transducer used for breast imaging, the endovaginal transducer used in first-trimester obstetric scanning, and the transducer used for ultrasound-guided vascular access are high-stakes probes where image-quality degradation directly affects diagnosis and safety. Prioritize these for more frequent testing and earlier action-level review.

Log phantom temperature at each test

Acoustic speed in tissue-mimicking phantom material is temperature-dependent. Speed changes with temperature will shift apparent distance measurements in a predictable way. Phantom temperature should be recorded at each test (ideally allowed to equilibrate to room temperature for at least 30 minutes). This allows temperature-induced variation to be distinguished from genuine equipment calibration drift.

Maintain a transducer log

A transducer log tracking the serial number, purchase date, clinical assignment, any reported performance complaints, service history, QC test dates, and retirement date allows the department to identify aging equipment, correlate clinical complaints with QC findings, and support equipment replacement planning.

Regulatory Considerations

Diagnostic ultrasound QC requirements come primarily from accreditation programs rather than from federal or state radiation-control regulations, because ultrasound is not a radiation-producing machine in the ionizing sense and does not fall under state X-ray machine registration programs or NRC materials regulation.

The primary regulatory and accreditation drivers are:

• ACR Ultrasound Accreditation Program — requires annual physicist equipment survey, phantom imaging, and documented QC policies. ³
• AIUM Ultrasound Practice Accreditation — similarly requires a QC program with physicist oversight and documented testing. ⁴
• The Joint Commission — for accredited hospitals, imaging equipment performance and maintenance standards apply to ultrasound.
• FDA Output Display Standard (Track 3, 1992) — governs the display of TI and MI on FDA-cleared diagnostic ultrasound systems, establishing the requirement for real-time output display. ⁵
• IEC 60601-2-37 — international standard addressing safety requirements for ultrasonic medical diagnostic equipment, including output measurement and acoustic labeling. ⁶
• State biomedical equipment regulations — some states have requirements for equipment maintenance and safety testing (electrical leakage) that apply to ultrasound equipment regardless of its classification as a non-ionizing device. Facilities in Florida, Maryland, Virginia, California, and Nevada should confirm applicable requirements with their state health authority.

DRPS provides accreditation support and medical physicist consulting services to facilities seeking or maintaining ACR and AIUM ultrasound accreditation across all six states we serve. Annual physicist surveys are documented to meet the accreditation standard and can be coordinated with the facility's existing accreditation cycle.

Frequently Asked Questions (FAQs)

Is ultrasound QC required even though ultrasound uses no ionizing radiation?

Yes. Ultrasound image quality degrades from transducer element failure, misalignment, and equipment drift — problems that may not be visible during clinical scanning without systematic testing. ACR and AIUM accreditation programs both require documented QC testing and a physicist's equipment survey.

What is the difference between AAPM TG-1 and TG-128?

AAPM TG-1 addresses routine quality assurance of the entire clinical ultrasound system — scanner, transducer, and display — including image quality tests performed on tissue-mimicking phantoms. AAPM TG-128 provides quality-assurance test procedures for the transrectal ultrasound systems used in prostate brachytherapy; several of its geometric-accuracy and transducer-integrity methods transfer to routine diagnostic transducer QC.

How often should a physicist perform an ultrasound equipment survey?

ACR and AIUM accreditation programs generally expect an annual physicist-level equipment survey. Routine staff QC tests — visual inspection, image uniformity checks, and basic phantom imaging — are typically performed at least monthly, and more frequently for high-volume or critical-application equipment.

What is transducer element dropout and why does it matter?

Transducer element dropout refers to non-functioning piezoelectric elements in an array transducer. Failed elements degrade lateral resolution, image uniformity, and sensitivity in a spatially predictable pattern. Dropout that exceeds allowable thresholds can cause missed findings and must be identified by systematic QC testing, not by scanning patients.

What tissue-mimicking phantom is used for ultrasound QC?

Tissue-mimicking phantoms from manufacturers such as CIRS and ATS Laboratories contain materials with acoustic properties simulating soft tissue, along with wire targets for distance measurements, point targets for resolution, and anechoic or hyperechoic contrast targets. Phantoms should be tracked over time for material degradation.

What are the thermal index and mechanical index, and what is ALARA in ultrasound?

The thermal index (TI) estimates the maximum temperature rise in insonated tissue. The mechanical index (MI) estimates the likelihood of inertial cavitation. Both are displayed in real time under the FDA Output Display Standard. ALARA in ultrasound means using the minimum output settings needed for the diagnostic task, particularly for fetal, neonatal, and ophthalmic applications.

What action level should trigger a service call for ultrasound QC?

Action levels are defined against each device's baseline and written into the facility's QC policy before testing begins. Representative thresholds in common practice include: a drop of about 1 cm or 10% in depth of penetration from baseline; any new contiguous group of dead elements (or, on an electronic analyzer, roughly 1–2% dead elements); axial distance error greater than about 2 mm or 2% (lateral about 3 mm or 3%); or any image-uniformity artifact in the diagnostic field that was not present at baseline. These are conventions to confirm against your phantom and accreditation manual, not fixed regulatory limits.

Key Takeaways

• Ultrasound QC is required for ACR and AIUM accreditation and is good clinical practice regardless of accreditation status. Equipment degrades silently — about a third of in-service probes in one large program carried at least one detectable defect. ⁷
• AAPM TG-1 and TG-128 are the foundational U.S. physicist references. TG-1 covers the full system with a baseline-relative QA philosophy; TG-128 (developed for prostate-brachytherapy ultrasound) contributes transferable QA test methods. ^{1, 2}
• Action levels are baseline-relative, not universal numbers. The thresholds quoted in practice (≈10% depth-of-penetration loss, ≈2 mm/2% axial distance error) are conventions to confirm against your phantom and accreditation manual, and accreditation requires you to define and justify your own.
• Transducer element dropout is screened by the in-air reverberation test and quantified by an electronic analyzer. Evaluate monthly; act on any new contiguous dead-element group before clinical use.
• Depth of penetration is the most sensitive single-number indicator of transducer-plus-scanner sensitivity; trend it monthly at a fixed preset.
• Distance accuracy propagates: small caliper errors compound into volume and biometry errors. The metric is $\frac{|d_{\text{measured}}-d_{\text{true}}|}{d_{\text{true}}}\times 100\%$, with axial held tighter than lateral.
• TI and MI display is required under the FDA Output Display Standard; verify each preset shows them and that they track output changes. ALARA applies hardest to fetal, neonatal, and ophthalmic scanning.
• Baseline documentation, phantom selection, and phantom temperature are the most commonly neglected details — and all three are prerequisites for meaningful trending.

Conclusion

A diagnostic ultrasound QC program is not bureaucratic overhead — it is the mechanism by which a clinical department verifies that its equipment is actually performing at the level assumed during image interpretation. Transducers age, elements fail, calibration drifts, and displays shift. None of these changes announce themselves during clinical scanning; all of them are detectable with systematic QC.

The practical program outlined in this guide — grounded in AAPM TG-1, TG-128, ACR accreditation requirements, and AIUM practice accreditation standards — gives physicists, sonographers, and department managers the tools to establish baselines, perform monthly staff-level checks, conduct annual physicist surveys, and act on findings before degraded equipment affects clinical care. In a department with diverse transducer types, high patient volumes, and accreditation requirements, a documented QC program is not optional — it is the standard of care.

How DRPS Can Help

Diagnostic Radiation Physics Services provides medical physicist consulting and accreditation support for diagnostic ultrasound QC programs, including annual physicist equipment surveys, transducer element dropout testing, phantom image acquisition and analysis, distance accuracy evaluation, and written QC policy development aligned with ACR and AIUM accreditation requirements.

DRPS supports facilities across Florida, Maryland, Virginia, Washington DC, California, and Nevada. Whether you are building a new QC program, preparing for accreditation, or investigating a specific equipment concern, our board-certified medical physicists can assess your equipment, document the findings, and help you establish a practical program your staff can maintain. Contact us or visit our service locations for more information.

Related Resources

• ACR Accreditation Physics Requirements
• Mammography Quality Control and MQSA
• Bone Densitometry (DEXA) QC
• Digital Breast Tomosynthesis QC
• SMPTE Monitor QC
• Medical Physicist Consulting
• Accreditation Support

References

1. Goodsitt MM, Carson PL, Witt S, Hykes DL, Kofler JM. Real-time B-mode ultrasound quality control test procedures. Report of AAPM Ultrasound Task Group No. 1. Medical Physics. 1998;25(8):1385-1406. doi:10.1118/1.598404. doi.org
2. Pfeiffer D, Sutlief S, Feng W, Pierce HM, Kofler J. AAPM Task Group 128: quality assurance tests for prostate brachytherapy ultrasound systems. Medical Physics. 2008;35(12):5471-5489. doi:10.1118/1.3006337. doi.org
3. American College of Radiology. ACR Ultrasound Accreditation Program Requirements. Reston, VA: ACR. acraccreditation.org
4. American Institute of Ultrasound in Medicine. AIUM Ultrasound Practice Accreditation. Laurel, MD: AIUM. aium.org
5. U.S. Food and Drug Administration. Marketing Clearance of Diagnostic Ultrasound Systems and Transducers: Guidance for Industry and FDA Staff (Output Display Standard, Track 3). Silver Spring, MD: FDA; 2019 (originally 1992). fda.gov
6. International Electrotechnical Commission. IEC 60601-2-37: Medical Electrical Equipment — Part 2-37: Particular Requirements for the Basic Safety and Essential Performance of Ultrasonic Medical Diagnostic and Monitoring Equipment. Geneva: IEC; 2015 (and amendments). iec.ch
7. Kruger R, Wolf K, Bloms N, Accola I. Clinical ultrasound transducer degradation effects on the accuracy of spectral Doppler velocity measurements. Medical Physics. 2012;39(6Part5):3651. doi:10.1118/1.4734831. doi.org
8. American Association of Physicists in Medicine. AAPM Report No. 270: Display Quality Assurance (Report of Task Group 270). College Park, MD: AAPM; 2019. aapm.org
9. National Electrical Manufacturers Association. NEMA UD 3: Standard for Real-Time Display of Thermal and Mechanical Acoustic Output Indices on Diagnostic Ultrasound Equipment. Rosslyn, VA: NEMA. nema.org
10. American Institute of Ultrasound in Medicine. AIUM Practice Parameter for the Performance of Diagnostic and Screening Ultrasound Examinations. Laurel, MD: AIUM; 2022. aium.org
11. American Institute of Ultrasound in Medicine. AIUM Official Statement: Prudent Use and Safety of Diagnostic Ultrasound (As Low As Reasonably Achievable / ALARA). Laurel, MD: AIUM. aium.org
12. International Electrotechnical Commission. IEC 61157: Standard Means for the Reporting of the Acoustic Output of Medical Diagnostic Ultrasonic Equipment. Geneva: IEC; 2007 (and amendments). iec.ch