Ultrasound Coupling Layers: Verify Contrast and Near-Field Artifacts Separately

By ALEVA · California, USA

Engineering question: When an ultrasound OEM changes the coupling material between a probe and its target, what evidence should support acceptance?

A clearer image in one region is not a complete coupling assessment. A 2026 peer-reviewed study compared gel and pad-type coupling materials in ex vivo tissue imaging. Its contrast and near-field artifact measurements did not produce an identical material ranking. The practical lesson is to define separate criteria for target visibility and unwanted echoes near the interface. [1]

Separate the measurements

For an OEM evaluation, we propose three records: target-to-background contrast, near-field artifact extent, and repeatability after removing and reapplying the couplant. These answer different questions. Repeated frames from one unchanged placement should not substitute for independent contact setups.

Fix the probe, acquisition sequence, receiver settings, reconstruction and display processing before comparing materials. Record coupling-layer thickness, applied pressure, temperature and placement method. If any condition cannot be controlled, document it as a limitation. Define regions of interest before reviewing the candidate results.

Keep the trade-offs visible

A pad may help define a contact geometry, while introducing another material and interface into the acoustic path. Gel and pads should therefore be evaluated in the intended configuration; convenience during placement is not an acoustic acceptance criterion.

The cited experiment used ex vivo specimens and specific acquisition conditions. Its near-field metric depended on image intensity and region selection, and repeated acquisitions did not establish independent placement variability. Its results are useful for designing a test, but do not establish a universal best couplant or clinical performance for another system. [1]

Define the OEM handover

We propose retaining the material identity and revision, fixture description, acquisition configuration, region definitions, repeated-placement results and acceptance decision together. Set separate limits for contrast, interface artifacts and repeatability before testing. Preserve the underlying data and processing settings so the comparison can be repeated after a material or probe revision.

Acoustic testing also leaves compatibility and handling questions unresolved. AIUM's 2025 guidance emphasizes following manufacturer instructions for transducer preparation and coupling-gel use. Review those instructions separately from image-quality acceptance. [2]

This is a proposed engineering evaluation framework, not an ALEVA measurement report, material endorsement or claim of clinical validation.

References

1. Jeon, K.-S. “Quantitative evaluation of acoustic coupling characteristics and near field high echo artifacts in pad type ultrasound coupling materials.” Journal of the Acoustical Society of Korea 45(3), 240–246, May 31, 2026. Peer-reviewed journal article. DOI: 10.7776/ASK.2026.45.3.240.

2. AIUM. “Guidelines for Cleaning and Preparing External- and Internal-Use Ultrasound Transducers and Equipment Between Patients as well as Safe Handling and Use of Ultrasound Coupling Gel.” Official statement, revised July 2, 2025. Official guidance.