What is the IEC 60601-2-77 Testing Standard?

IEC 60601-2-77 is a dedicated international safety standard issued by the International Electrotechnical Commission (IEC) specifically for extracorporeal shock wave lithotripters. It outlines comprehensive requirements in three key areas: electrical safety, mechanical performance, and clinical efficacy. Below is a detailed summary of critical parameters and their specifications, based on the standard text and industry practices.

Electrical Safety Parameters

Leakage Current Limits:

Patient leakage current: ≤ 0.1 mA (normal condition), ≤ 0.5 mA (single fault condition)

Enclosure leakage current: ≤ 0.1 mA (normal), ≤ 0.5 mA (fault condition)

The voltage drop across the grounding path must ensure fault current is safely diverted to ground.

Dielectric Strength:

Between power input and ground: 4000 V RMS for 1 minute with no breakdown

Between applied parts and ground: 2500 V RMS for 1 minute with no breakdown

Purpose: Ensures electrical isolation between high-voltage components (e.g., shock wave driver modules) and patient-contacting parts.

Mechanical Performance Parameters

Focusing Accuracy:

Focal spot diameter: ≤ 3 mm (radial), ≤ 10 mm (axial)

Positional repeatability: ±1 mm in 3D space

Test Method: Measured via hydrophone arrays to map pressure fields and confirm energy is focused on the target zone.

Shock Wave Energy Stability:

Energy output deviation: ≤ ±20% over 100 consecutive pulses

Voltage stability: ≤ ±5% deviation at treatment setting (e.g., 15 kV setting yields 14.25–15.75 kV output)

Purpose: Prevents incomplete stone fragmentation or unintended tissue damage due to energy fluctuation.

Shock Wave Source Lifespan:

Discharge cycles: ≥ 100,000 (electromagnetic type), ≥ 50,000 (electrohydraulic type)

Maintenance: Performance check every 5000 discharges (e.g., electrode wear, capacitor degradation)

Clinical Efficacy Parameters

Peak Pressure Range:

Treatment range: 50–100 MPa for lithotripsy, 1.5–4 MPa for tissue regeneration

Safety threshold: ≤ 0.3 mJ/mm² (for ESWT applications)

Test Method: PVDF piezoelectric sensors measure pressure waveforms to ensure peak pressure matches target energy density.

Waveform Characteristics:

Pressure rise time: ≤ 10 ns (from 10% to 90% of peak pressure)

Pulse width: 1–2 µs (full width at half maximum)

Repetition rate: Adjustable between 1–15 Hz

Purpose: Sharp rise time enhances stone fragmentation, while lower frequencies help minimize thermal injury to tissues.

Imaging & Targeting Precision:

Ultrasound (B-mode) targeting error: ≤ 2 mm (lateral), ≤ 3 mm (axial)

X-ray targeting error: ≤ 1 mm in 3D

Purpose: Ensures precise overlap of the focal zone and the stone, reducing the risk of collateral tissue damage.

Environmental and Operational Parameters

Operating Conditions:

Temperature: 10–40°C

Relative Humidity: 30–75% (non-condensing)

Altitude: ≤ 2000 meters

Power supply: AC 220V ±10%, 50/60 Hz, Max power ≤ 1000 VA

Human-Machine Interface:

Touchscreen response time: ≤ 0.5 seconds

Interface language: Supports multiple languages, including English and Chinese

Alarm system: Audible and visual alerts for over-voltage, under-voltage, and abnormal temperature

Key Testing and Verification Requirements

Energy Density Measurement:

Method: Hydrophone-based pressure waveform capture combined with integration algorithms to calculate energy density (unit: mJ/mm²)

Calibration: Performed every 6 months using a standard pressure sensor

Cavitation Control:

Negative pressure threshold: ≤ -10 MPa (to prevent excessive cavitation and tissue damage)

Test Method: High-speed imaging to observe bubble dynamics and ensure cavitation is confined to the target area

Electromagnetic Compatibility (EMC):

Immunity: Meets IEC 60601-1-2 standards; stable operation under electromagnetic fields of 1 V/m (80 MHz–2.5 GHz)

Emissions: ≤ 30 dBμV/m (30 MHz–1 GHz)

Typical Parameter Comparison (Electromagnetic Lithotripter Example)

Treatment Voltage Range:

Standard: 10–18 kV (continuously adjustable)

Clinical Devices: 10–17 kV

Focal Peak Pressure:

Standard: 6–30 MPa

Clinical Devices: 8–25 MPa

Focal Zone Size (Radial / Axial):

Standard: ±7 mm / 45–50 mm

Clinical Devices: ±7 mm / 45–50 mm

Energy Density (for therapy):

Standard: 0.1–0.3 mJ/mm²

Clinical Devices: 0.15–0.25 mJ/mm²

Treatment Depth:

Standard: ≥110 mm

Clinical Devices: 120–150 mm

Technical Challenges in Implementation

Precision Energy Control

Requires a closed-loop feedback system (e.g., real-time shock wave pressure monitoring) to maintain energy output error below 5%.

Multimodal Targeting Integration

Combining ultrasound and X-ray imaging necessitates image fusion technologies to improve localization accuracy (error ≤ 1 mm).

Intelligent Safety Design

AI algorithms can automatically identify patient body shape and stone location, dynamically adjusting energy parameters (e.g., peak pressure based on BMI).

IEC 60601-2-77 establishes rigorous specifications for electrical safety, mechanical performance, and clinical efficacy to ensure the safety and reliability of extracorporeal shock wave lithotripters. These parameters are not only vital design guidelines but also serve as critical benchmarks for clinical risk management. As non-linear acoustics and intelligent control technologies evolve, the standard is expected to expand its scope—refining waveform optimization and tissue safety monitoring—to advance precision and minimally invasive stone treatment.

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