Challenges of Post-measurement Histology for the Dielectric Characterisation of Heterogeneous Biological Tissues

Abstract

The dielectric properties of biological tissues are typically measured using the open-ended coaxial probe technique, which is based on the assumption that the tissue sample is homogeneous. Therefore, for heterogeneous tissue samples, additional post-measurement sample processing is conducted. Specifically, post-measurement histological analysis may be performed in order to associate the measured dielectric properties with the tissue types present in a heterogeneous sample. Accurate post-measurement histological analysis enables identification of the constituent tissue types that contributed to the measured dielectric properties, and their relative distributions. There is no standard protocol for conducting post-measurement histological analysis, which leads to high numbers of excluded tissue samples and inconsistencies in the resulting reported data for heterogeneous tissues. To this extent, this study examines the post-measurement histological process and the challenges in associating the acquired dielectric properties with the different tissue types present in heterogeneous samples. The results demonstrate that the histological process inevitably alters the morphology of samples, thus introducing errors in the interpretation of the dielectric properties acquired from heterogeneous biological samples. Notably, sample size was seen to shrink by up to 90% through the histological process, meaning that sensing volume determined from fresh tissues is not directly applicable to histology images.

The Complex Permittivity of Biological Tissues: A Practical Measurement Guideline

“…Further, using histology requires identifying a histology region (on the image of the sample slice) that contains tissues that contributed to the dielectric measurement. To achieve the most representative histology region requires knowledge of both the sensing volume of the probe and how tissue samples shrink or deform during histology [94]. Many studies have examined the sensing volume of the probe, under conditions of different tissue types present, different tissue distributions, and different frequency ranges [48,80,81,84,[95][96][97][98][99].…”

Development of MRI‐based axillary numerical models and estimation of axillary lymph node dielectric properties for microwave imaging

“…The hilum is a fatty region, in contrast to the remaining ALN composition. These two aspects of the ALN composition can hamper OECP results, as this technique has known limitations associated with measuring heterogeneous structures 23 . Second, only a very limited number of metastasized ALNs was measured, which ranged from 1 to 12 metastasized ALNs in each study 16,19,20 .…”

“…These two aspects of the ALN composition can hamper OECP results, as this technique has known limitations associated with measuring heterogeneous structures. 23 Second, only a very limited number of metastasized ALNs was measured, which ranged from 1 to 12 metastasized ALNs in each study. 16,19,20 Those numbers are not sufficient to infer a dielectric contrast between healthy and metastasized ALNs with confidence, which would have been important to evaluate the feasibility of distinguishing these structures at microwave frequencies.…”