Overview
ISO 20498-1:2019 defines the general requirements for a Computerized Tongue Image Analysis System (CTIS) used in Traditional Chinese Medicine (TCM). The standard focuses on the technical and safety aspects of CTIS hardware and software-covering components, image acquisition quality, colour capture, data processing, display and biocompatibility-while explicitly excluding clinical diagnosis or interpretation of tongue images.
Key topics and technical requirements
- CTIS components: lighting part, image acquisition part, data processing part, display, and optional tongue positioning.
- Tongue positioning: guidance or fixtures to ensure an undistorted image; whole exposed tongue must be included. Valid incident angle between tongue surface and sensor: 0°–30° (see Annex A).
- Lighting: requirements for luminance, colour temperature, colour rendering index (CRI) and illumination distribution. Lighting should uniformly cover the five anatomical tongue areas (tip, centre, root, left and right margins). (See ISO 20498-2 for detailed lighting environment requirements.)
- Image acquisition:
- Spatial resolution: sensor resolution of at least 1.0 megapixel.
- Colour components: capture at least one colour model or three colour components (examples: RGB, CIE Lab*, CMYK).
- Acquisition techniques: Bayer filter, three-CCD systems, or hyperspectral imaging are acceptable methods.
- Data processing: image correction, segmentation and feature extraction algorithms required to produce clear, reproducible tongue images (see Annex C for processing considerations).
- Display and storage: monitors must present the original image resolution; image data (original, corrected, segmented) shall be stored in editable/storable image formats.
- Safety and biocompatibility:
- Material safety and biological evaluation per ISO 10993-1.
- Infection prevention and cleaning routines for closed systems.
- Electrical and mechanical safety per IEC 60601-1 requirements (referenced clauses).
Practical applications and users
ISO 20498-1:2019 is used by:
- Medical device manufacturers designing CTIS hardware (cameras, lighting, positioning fixtures).
- Software developers building image-correction, segmentation and analysis pipelines for tongue imaging.
- Clinical researchers and trial designers seeking standardized acquisition for reproducible data.
- Regulatory and quality assurance teams evaluating safety, biocompatibility and conformance.
- TCM practitioners and integrative clinics implementing standardized imaging workflows for documentation and research (not clinical diagnosis guidance).
Related standards
- ISO 20498-2 - Traditional Chinese medicine - CTIS - Part 2: Light environment (detailed lighting requirements)
- ISO 10993-1 - Biological evaluation of medical devices
- IEC 60601-1 - Medical electrical equipment - Basic safety and essential performance
This standard helps ensure consistent, high-quality tongue image capture and safe device design-foundational for reproducible research, device certification and clinical-grade imaging systems in TCM applications.