Overview
IEC TR 62799:2013 - Models for evaluation of thermal hazard in medical diagnostic ultrasonic fields is a technical report that provides background and modelling guidance to support users of IEC 62359 in evaluating thermal effects from diagnostic ultrasound. The report reviews the limitations of the current Thermal Index (TI) as used in IEC 60601-2-37 and describes methods and exposure parameters for estimating temperature rise in theoretical tissue‑equivalent models due to acoustic absorption. It compares several potential replacements or refinements to the TI to improve ultrasound thermal hazard assessment.
Key topics covered
- Purpose and scope: Background information for standards developers, manufacturers and regulators on thermal exposure parameters and models.
- Thermal modelling fundamentals: Discussion of acoustic parameters such as acoustic absorption and attenuation, and how these affect tissue heating.
- Limitations of the existing TI: Identifies issues including linear display assumptions, equilibrium temperature concepts, variability of tissue parameters, transducer self‑heating and current safety limits.
- Alternative exposure metrics: Evaluation of candidate replacements or enhancements to TI, including but not limited to:
- Exponential display of TI
- Thermally Equivalent Time Index (TETI)
- Time to Threshold (TT)
- Safe Use Time (SUT)
- Thermally Equivalent Time Display (TETD)
- Methods for determination: Procedures to determine exposure parameters relating to temperature rise using theoretical tissue‑equivalent models and illustrative results for each option.
- Recommendations: Guidance for applying models in standards development and device risk assessment.
Practical applications and users
IEC TR 62799 is intended for:
- Standards committees and developers (for maintenance and evolution of IEC 62359)
- Medical device manufacturers (for thermal risk assessment, design decisions, and labelling)
- Regulatory authorities and test houses (for implementing test methods and compliance checks)
- Clinical engineers and safety assessors (to interpret TI and alternative indices in context of patient exposure)
Typical uses:
- Selecting or justifying an exposure metric for device safety documentation
- Implementing test procedures that estimate temperature rise in tissue models
- Informing software/display choices for thermal indices on ultrasound equipment
- Supporting regulatory submissions and conformity assessment for medical electrical equipment
Related standards
- IEC 62359: Field characterization - Test methods for determination of thermal and mechanical indices
- IEC 60601‑2‑37: Particular requirements for ultrasonic medical diagnostic equipment
- IEC 62127‑1 / IEC 62127‑2: Hydrophone measurements and calibration (relevant to field characterization)
Keywords: IEC TR 62799, thermal hazard, diagnostic ultrasound, thermal index, TETI, temperature rise, IEC 62359, IEC 60601‑2‑37, ultrasound safety, exposure parameter.