A hypodermic needle has been introduced incorporating an electrical impedance spectroscopy (EIS) sensor, called micro-EIS-on-a-needle for depth profiling (μEoN-DP). The μEoN-DP can locate endophytic renal tumors as well as determine tumor margins by detecting the impedance difference between normal and cancer tissues. To evaluate the μEoN-DP as a novel tool to determine the optimal surgical margin during partial nephrectomy (PN), the electrical impedance differences between renal parenchymal tissues and renal cell carcinoma (RCC) tumors are investigated with regard to the distance from the tumors. Optimal frequencies at which the discrimination extent is maximized are suggested based on the discrimination index. The resistance and capacitance of normal and cancer tissues are extracted using electrical equivalent circuit by excluding the influences of other electrical components on the sensor output. The extracted resistance and capacitance of cancer tissues are 37.8% larger and 25.7% smaller than that of normal tissues, respectively. Additionally, high sensitivity and specificity are obtained by using extracted resistance and capacitance, thus implying that the μEoN-DP shows promise as a supplementary tool for PN margin evaluation and decreasing the prevalence of positive surgical margins while maximizing parenchymal preservation.
Keywords: electrical impedance; hypodermic needles; optimal surgical margin; partial nephrectomy; renal cancer.
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