Proficiency Testing for Complex Permittivity Measurements of Tissue Equivalent Liquid Used in SAR Assessment

Tissue equivalent liquid plays an important role in specific absorption rate (SAR) assessment. Proficiency tests (PTs) through interlaboratory comparison of dielectric parameters (i.e., dielectric constant and the electrical conductivity of the tissue equivalent liquid) were conducted in 2017 and 2019. We coordinated the PTs performed with traveling samples circulating among the participating laboratories. As one of the most crucial issues in the PT schemes, these samples are described comprehensively, including the realization, the assignment of reference values, and the verification of homogeneity and stability. Fifteen and eleven laboratories participated in the PTs in 2017 and 2019, respectively. In total, 74 measurement results were provided in terms of best estimate and uncertainty. This paper presents and evaluates the performance of all the participating laboratories. Additionally, the measurement results are grouped in terms of the types of measurement probes. The analysis indicates that the measurement results obtained from two most widely used types of probes are compatible.