Accuratein vivodielectric properties of liver from 500 MHz to 40 GHz and their correlation toex vivomeasurements

Abstract

In this article, we report on the characterization of the dielectric properties of in vivo rat liver at 36.4°C from 500 MHz up to 40 GHz with less than 5% uncertainty. The measured data were fitted to a Cole-Cole model and dielectric parameters are presented together with their respective 95% confidence interval. The root mean square error is 0.42. Moreover, ex vivo measurements were conducted in situ at 1, 2, 4 and 6 min after animal death and are compared to in vivo measurements. The results show that immediate changes in [Formula: see text]and [Formula: see text] are within experimental uncertainty, and therefore changes between in vivo and published ex vivo dielectric properties can be attributed to tissue hydration.

Investigation of the effect of dehydration on tissue dielectric properties in ex vivo measurements

“…Farrugia et al studied the correlation between in vivo and ex vivo dielectric properties and reported no significant difference immediately after animal expiry (if the temperature is kept constant). A decrease in both the dielectric constant and conductivity in this study compared to in vivo data from (Farrugia et al 2016) can be seen in figures 7 and 8. This difference can be attributed to tissue temperature differences in the studies (Farrugia et al 37°C,this study 22°C).…”

“…No significant difference has been found between the data from the interior group and first measurement taken at the surface of tissue at time T0, which was performed on freshly excised tissue. In order to understand the relevance of the data from this study in terms of tissue moisture, a comparison has been made with dielectric data of rat liver from in vivo measurements (Farrugia et al 2016) and ex vivo measurements (Peyman et al 2001). The graphs shown are based on the data derived from Cole-Cole models presented in (Farrugia et al 2016) and (Peyman et al 2001) at body temperature (37°C).…”

“…In order to understand the relevance of the data from this study in terms of tissue moisture, a comparison has been made with dielectric data of rat liver from in vivo measurements (Farrugia et al 2016) and ex vivo measurements (Peyman et al 2001). The graphs shown are based on the data derived from Cole-Cole models presented in (Farrugia et al 2016) and (Peyman et al 2001) at body temperature (37°C). Farrugia et al studied the correlation between in vivo and ex vivo dielectric properties and reported no significant difference immediately after animal expiry (if the temperature is kept constant).…”

“…A decrease of 50% of the baseline value in conductivity was observed 1 h after animal death. In the most recent study on rat liver by Farrugia et al (2016), the dielectric properties of rat liver over the microwave range of frequencies (0.5-40 GHz) were measured in situ before and after animal death. In this carefully designed experiment, no statistically significant difference was observed in the dielectric properties of liver before and immediately after animal expiry (within the first 6 min).…”

“…The data from the surface group are compared with those from the interior group. A comparison with ex vivo data on rat liver from Peyman et al (2001) and in vivo data from Farrugia et al (2016) is also presented.…”