Establishing European traceability for medical measuring devices through optical absorbance liquid filters

There are strong demands for the international recognition of quality in medical and metrology services for which NMIs need to provide spectral transmittance and optical absorbance traceable to SI units through liquid absorbance filters.

Optical absorbance liquid filters (OALF) are used to calibrate optical absorbance equipment, but there is currently a capability gap in the manufacturing, characterisation, and use of such filters, which leads to a lack of traceability.

This project aims to bridge this gap by supporting the development of measurement capabilities for optical absorbance of liquid filters in emerging NMIs and DIs, and to enable them to provide traceability of measurement results as well as OALF as reference materials with the lowest possible measurement uncertainty. Many medical measuring devices use optical absorbance as the measurand. This project will improve the accuracy of clinical measurements and treatment outcomes for patients.

Objectives

The overall objective for this project is NMIs (see Project Partners) to develop and to upgrade their national metrological capacity in SI traceable measurements of optical absorbance of liquid absorbance filters.

The specific objectives of the project are:

1. To determine a set of minimal criteria (physical and chemical properties) for optical absorbance liquid filters as reference materials, which will include a dilution series of optical absorbance liquid filters to be characterised and calibrated.
2. To develop traceable measurement capabilities of absorbance of optical absorbance liquid filters in emerging NMIs and DIs for the minimum spectral range from 220 nm to 780 nm, and absorbance range from 0.001 up to 3.000 (corresponding to a nominal internal transmittance of 99.77 % and 0.1 %, respectively), at atmospheric pressure, within the temperature interval from 15 °C to 40 °C and with a relative standard uncertainty of 0.3 % to 1.0 %.
3. To establish equivalence in the measurement of optical absorbance liquid filters across participating European NMIs according to capabilities developed in Objective 2.
4. To produce a good practice guide on the manufacture, characterisation, and use of optical absorbance liquid filters, which will be shared with EURAMET TC-PR along with a request for its consideration to be published as a EURAMET guide.
5. To facilitate the take up and long-term operation of the capabilities, technology and measurement infrastructure for optical absorbance measurements using optical absorbance liquid filters developed in the project, by the measurement supply chain (NMIs/DIs, calibration, and testing laboratories), standards developing organisations (OIML, EURAMET TC-PR), and end users (e.g., industry, instrument manufacturers, regulators). To include preparation of strategies and roadmaps for the future development of these capabilities by all participant NMIs.