Healthy and tumoral tissue resistivity in wild-type and sparc-/- animal models

Electrical Impedance Spectroscopy for Ex-Vivo Breast Cancer Tissues Analysis

This paper describes a cancer detection procedure based on customised electrical impedance spectroscopy (EIS) in breast cancer surgical samples and an analysis of its outcomes. A tissue analyser was developed to inject a low-amplitude alternating current with penetrating electrodes into breast specimens along a broad spectrum of frequencies. Experimental measurements were carried out on more than one hundred excised breast cancer specimens, with the goal of discriminating between the tumour and surrounding non-neoplastic tissue. The probe was inserted in different locations immediately after surgical excision in order to measure tissue impedance (modulus and phase). Electrical impedance varied significantly between neoplastic and surrounding non-neoplastic tissues, with a low standard deviation among the different measurements, confirming good reproducibility. Tumours could be discriminated from non-neoplastic tissues according to their impedance modulus value for high frequencies and phase value for low frequencies. Impedance also varied significantly in both non-neoplastic and tumour tissues depending on the patient's age and tumour characteristics, such as size and histological sub-type. EIS is able to discriminate between healthy tissue and cancer. Future developments of this technology could be exploited for intraoperative real-time evaluation of the transition zone between cancer and normal tissues.

An electrical impedance tomography (EIT) multi-electrode needle-probe device for local assessment of heterogeneous tissue impeditivity

Electrical Impedance Tomography (EIT) is an image reconstruction technique applied in medicine for the electrical imaging of living tissues. In literature there is the evidence that a large resistivity variation related to the differences of the human tissues exists. As a result of this interest for the electrical characterization of the biological samples, recently the attention is also focused on the identification and characterization of the human tissue, by studying the homogeneity of its structure. An 8 electrodes needle-probe device has been developed with the intent of identifying the structural inhomogeneities under the surface layers. Ex-vivo impeditivity measurements, by placing the needle-probe in 5 different patterns of fat and lean porcine tissue, were performed, and impeditivity maps were obtained by EIDORS open source software for image reconstruction in electrical impedance. The values composing the maps have been analyzed, pointing out a good tissue discrimination, and the conformity with the real images. We conclude that this device is able to perform impeditivity maps matching to reality for position and orientation. In all the five patterns presented is possible to identify and replicate correctly the heterogeneous tissue under test. This new procedure can be helpful to the medical staff to completely characterize the biological sample, in different unclear situations.

In-vivo Measurements of Tissue Impeditivity by Electrical Impedance Spectroscopy

The electrical properties of biological tissues differ depending on their structural characteristics. In literature, a lot of study have been carried out with the intent of taking advantage of bioimpedance analysis. Unfortunately, many apparatuses used during these evaluations were not always designed for measurements on living tissues. As a consequence, data could be affected by electrode polarization. In 2016, we presented a new impedance meter, developed for measurements on living tissues. Initially, it was tested only on ex-vivo rabbit's tissues with promising results. As a continuation, this device has been tested on in-vivo samples by placing a needle-probe into 3 tissues (liver, spleen, ovary) of 2 female dogs. Furthermore, was evaluated also the bioimpedance signal of the ovary explanted, comparing it with the in-vivo data. Bioimpedance was analyzed in terms of modulus and phase along a broad spectrum of frequencies (10Hz - 10kHz).Data obtained confirm the possibility of discriminating among the 3 tested tissues, at high frequencies for modulus and at low for phase. Confirmation that values on in-vivo and exvivo tissues are comparable if detected within few minutes after the explant, is also reported. We conclude that this clinical evaluation confirmed, also in-vivo, the good performance of the device previously tested on ex-vivo tissues, and provide more information about the tissue properties and characteristics.

Improvement of Depth Profiling into Biotissues Using Micro Electrical Impedance Spectroscopy on a Needle with Selective Passivation

A micro electrical impedance spectroscopy (EIS)-on-a-needle for depth profiling (μEoN-DP) with a selective passivation layer (SPL) on a hypodermic needle was recently fabricated to measure the electrical impedance of biotissues along with the penetration depths. The SPL of the μEoN-DP enabled the sensing interdigitated electrodes (IDEs) to contribute predominantly to the measurement by reducing the relative influence of the connection lines on the sensor output. The discrimination capability of the μEoN-DP was verified using phosphate-buffered saline (PBS) at various concentration levels. The resistance and capacitance extracted through curve fitting were similar to those theoretically estimated based on the mixing ratio of PBS and deionized water; the maximum discrepancies were 8.02% and 1.85%, respectively. Depth profiling was conducted using four-layered porcine tissue to verify the effectiveness of the discrimination capability of the μEoN-DP. The magnitude and phase between dissimilar porcine tissues (fat and muscle) were clearly discriminated at the optimal frequency of 1 MHz. Two kinds of simulations, one with SPL and the other with complete passivation layer (CPL), were performed, and it was verified that the SPL was advantageous over CPL in the discrimination of biotissues in terms of sensor output.