Open-ended coaxial probe for the quantification of edema in human brain tissue

The major task in most autopsies is the evaluation of circumstances and cause of a person's death. The quantification of edema, primarily in certain brain regions, is a promising marker to distinguish between certain causes of death. This is especially important if there is no visible reason, for example, in the case of distinguishing Sudden Infant Death Syndrome from Shaken Impact Syndrome. However, until now there is no standardized procedure in forensic medicine for the quantification of edema in parenchymatous organs. Therefore, the aim of our work is to develop a fast low-cost measuring system that fits into the procedure of an autopsy. One approach for an exact quantification of edema is to determine the humidity content in the tissue with the so-called oven dry method, which we used as a reference. The approach presented here is the determination of the humidity content via a measurement of the relative permittivity of the tissue. We use two different setups: a transmission and a reflection measurement. Thereby a linear regression between the humidity content and the relative permittivity was found with excellent regression coefficients of R = 0.98 for the transmission measurement and R = 0.97 for the reflection measurement. We compare the results of the used methods regarding accuracy and measuring time.