Concentric Ring Probe for Bioimpedance Spectroscopic Measurements: Design and Ex Vivo Feasibility Testing on Pork Oral Tissues

Abstract

Many oral diseases, such as oral leukoplakia and erythroplakia, which have a high potential for malignant transformations, cause abnormal structural changes in the oral mucosa. These changes are clinically assessed by visual inspection and palpation despite their poor accuracy and subjective nature. We hypothesized that non-invasive bioimpedance spectroscopy (BIS) might be a viable option to improve the diagnostics of potentially malignant lesions. In this study, we aimed to design and optimize the measurement setup and to conduct feasibility testing on pork oral tissues. The contact pressure between a custom-made concentric ring probe and tissue was experimentally optimized. The effects of loading time and inter-electrode spacing on BIS spectra were also clarified. Tissue differentiation testing was performed for ex vivo pork oral tissues including palatinum, buccal mucosa, fat, and muscle tissue samples. We observed that the most reproducible results were obtained by using a loading weight of 200 g and a fixed time period under press, which was necessary to allow meaningful quantitative comparison. All studied tissues showed their own unique spectra, accompanied by significant differences in both impedance magnitude and phase (p ≤ 0.014, Kruskal-Wallis test). BIS shows promise, and further studies are warranted to clarify its potential to detect specific pathological tissue alterations.

Effect of Open-Ended Coaxial Probe-to-Tissue Contact Pressure on Dielectric Measurements

“…We believe that applying different pressures changes the cellular matrix, which results in a different electromagnetic response. Moreover, the effect of pressure-dependent measurement responses is not limited to this specific domain, but similar trends are visible in other biology-related disciplines, as mentioned before [24][25][26][27][28].…”

“…Unfortunately, there is no guideline on when the operator should stop, i.e., which probe-to-tissue contact pressure is desired and how it varies over time. The literature reveals that the probe-to-tissue contact pressure in other biology-related disciplines has a significant impact on the measurements of, for instance, pressure waves in acoustic radiation force (ARF)-based ultrasound elasticity measurements [24], low-frequency electromagnetic waves for electrical bioimpedance measurements [25][26][27], and electromagnetic waves in the visible light and infrared spectrum for measurements of optical properties [28]. These results suggest that the probe-to-tissue contact pressure is significant and cannot be neglected.…”

Novel 3D printing-based probe for impedance spectroscopic examination of oral mucosa: design and preliminary testing with phantom models

“…A non-invasive method for diagnosing OPMDs would overcome these problems and would allow affordable regular chairside screening (e.g., at dental clinics) at risk patients and could make possible regular screening of at-risk patients. This would be particularly beneficial in the treatment of oral cancer where the low survival rates are attributable to late diagnosis [9]. To prevent malignant transformation of these oral premalignant lesions, new noninvasive point-of-care detection techniques are urgently needed to address this global health problem.…”

“…Overall, there is abundant research and scientific articles related to use of impedance-based methods in various biomedical applications such as in skin cancer diagnostics [11][12][13][14][15]. However, the BIS studies concerning the evaluation of oral mucosa condition and assessment of oral mucosal diseases are rare [3,9,16].…”

“…When considering in vivo BIS measurements inside the oral cavity, more standardised measurements are needed [17], and a new sensor design is required [9]. It should be cheap to fabricate with mass production techniques, patient-safe and single-use to avoid crosscontamination or need of any sterilisation steps.…”