Safe Use of Refurbished Ultrasound Systems and Probes

Diagnostic ultrasound is one of the most widely deployed imaging modalities in hospitals and clinics across Africa, Latin America, and Asia because it is portable, radiation-free, and relatively low-cost compared with CT or MRI. Used and refurbished ultrasound systems can extend access to safe imaging when they are properly inspected, maintained, and operated. This article summarizes internationally recognized safety practices for operating ultrasound systems and handling transducers (probes), including transesophageal echocardiography (TEE) probes, so that biomedical engineers and clinicians can get the most diagnostic value with the least risk.

Understanding Ultrasound Bioeffects and the ALARA Principle

Diagnostic ultrasound is generally considered safe when used appropriately, but it is not risk-free. Ultrasound energy can produce two categories of biological effects: thermal effects (tissue heating) and mechanical effects (cavitation-like phenomena), particularly at higher acoustic outputs or with prolonged exposure to sensitive tissues such as the fetus or eye (FDA, Marketing Clearance of Diagnostic Ultrasound Systems and Transducers).

To manage this risk, the ultrasound community follows the As Low As Reasonably Achievable (ALARA) principle. The American Institute of Ultrasound in Medicine (AIUM) states that ALARA should be applied whenever adjusting controls that affect acoustic output, and that operators should weigh clinical benefit against potential risk for every exam (AIUM Official Statement on ALARA).

Practicing ALARA requires that operators:

1. Use manufacturer examination presets built into the system whenever available, since these are optimized for the exam type (AIUM ALARA Statement).
2. Adjust power to the lowest setting that still produces a diagnostic-quality image, and reduce power at the end of an exam so the next user starts at the lowest output.
3. Monitor the Mechanical Index (MI) and Thermal Index (TI) displayed on-screen throughout the exam, especially in obstetric, transcranial, and ophthalmic scanning.
4. Limit scanning time and transducer dwell time over any one location to the minimum needed for diagnosis.
5. Avoid Doppler modes (which carry higher acoustic output than B-mode) unless clinically necessary, and minimize their duration.

MI/TI Quick Reference

For obstetric imaging in particular, keyboard presets, exam duration, and MI/TI display must be actively monitored, and non-medical "keepsake" scanning is discouraged by AIUM and FDA guidance because it exposes the fetus to ultrasound energy without medical benefit (FDA, Avoid Fetal "Keepsake" Images, Heartbeat Monitors).

Pre-Use Inspection Checklist for Refurbished Systems

Because equipment sold on the secondary market has an unknown service history unless documented, a structured acceptance inspection is essential before clinical use.

Manufacturer service/refurbishment documentation, when available, should be reviewed alongside this physical inspection, and any system without a verifiable safety test record should be electrically tested before first clinical use.

Transducer (Probe) Handling and Infection Control

Ultrasound transducers come into direct contact with patients and, in the case of endocavitary and TEE probes, with mucous membranes — making correct cleaning and disinfection a patient-safety issue, not just a maintenance one.

AIUM classifies transducers by contact type, which determines the required reprocessing level (AIUM Guidelines for Cleaning and Preparing Ultrasound Transducers):

• Noncritical (external) transducers — contact intact skin only (e.g., abdominal, cardiac surface probes). Require low-level disinfection (LLD) between patients.
• Semicritical (internal/endocavitary) transducers — contact mucous membranes (e.g., transvaginal, transrectal, and TEE probes). Require high-level disinfection (HLD) between patients, plus a single-use probe cover during every exam, even when a cover is used, because covers can fail.
• Critical transducers — used in sterile body cavities or with intraoperative contact — require sterilization.

Standard Transducer Cleaning Steps

1. Disconnect the transducer from the system per the operator manual before immersion cleaning (never immerse the connector).
2. Remove the probe cover (if used) and wipe away bulk gel/debris with a soft cloth or brush.
3. Clean with a mild, non-abrasive soap or manufacturer-approved wipe to remove residual film.
4. Rinse and dry according to the transducer's Instructions for Use (IFU).
5. For semicritical probes, follow with an EPA/FDA-cleared high-level disinfectant, immersing only to the manufacturer-specified level — never submerging the connector or strain relief (AIUM Cleaning Guidelines).

TEE Probe-Specific Care

TEE probes carry additional risk because they are inserted into the esophagus and are mechanically complex (steering mechanism, articulating tip):

• Inspect the shaft and articulating tip for cracks, delamination, or exposed wiring before every use — a compromised sheath can cause electrical leakage or patient injury.
• Perform an electrical leakage current test on the TEE probe at intervals defined by the manufacturer and facility policy, since TEE probes are semi-invasive and any leakage poses a direct risk.
• Use a bite guard for every patient to protect the probe shaft from tooth damage.
• Always high-level disinfect the entire insertable portion after each use, following exact immersion depth and contact time in the manufacturer IFU; automated endoscope reprocessors compatible with TEE probes may be used if validated by the probe manufacturer.
• Store the TEE probe in a dedicated, ventilated hanging cabinet — never coiled tightly — to avoid mechanical stress on the internal steering cables.

Probe Storage, Transport, and Cable Care

• Store transducers in a padded rack or manufacturer case, never stacked on top of each other or resting on their lens face.
• Avoid dropping, which is a leading cause of internal element and lens damage in secondary-market probes.
• Keep cables free of sharp bends and avoid running over them with equipment wheels or carts.
• Do not use tape directly on the cable or connector, as adhesive residue attracts dust and complicates repair.
• Avoid submerging the probe connector or the strain-relief joint, as this is the most common water-ingress failure point.

Daily and Periodic Operational Checks