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.

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.

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.

Measurement of electrical impedance in different ex-vivo tissues.

Bioimpedance allows living tissues characterization and detection of pathological states. Although in previous years several methods have been proposed to assess bioimpedance, many instruments used in studies of living tissues characterization are commercial devices designed for the measurement of components or electronic circuits and therefore the measurement of biological tissues can be affected by electrical polarization. In order to test if electrical impedance spectroscopy may be helpful in providing further information about the structure and the properties of tissues, an impedance meter for living-tissues, able to avoid polarization, was developed. Subsequently, ex-vivo impedance measurements were performed by placing a needle-probe into 6 tissues (heart, kidney, lung, muscle, liver and fat) of 3 rabbits. Impedance was analyzed in terms of modulus and phase. In the range 2-10 kHz, considering both modulus and phase, it was possible to discriminate each tissue with statistical significance. In the lower considered range of frequencies (i.e., 10-100 Hz and 200-1000 Hz) this was not always the case. We conclude that the detailed analysis of modulus and phase in the frequency range of 2-10 kHz, by using an ad-hoc device able to avoid electrical polarization, allows to discriminate between several healthy living tissues.