Electrical Impedance Spectroscopy of the Human Prostate

Abstract

Tissue electrical impedance is a function of its architecture and has been used to differentiate normal and cancer tissues in a variety of organs including breast, cervix, skin, and bladder. This paper investigates the possibility of differentiating normal and malignant prostate tissue using bioimpedance spectra. A probe was designed to measure impedance spectra over the range of 10 kHz to 1 MHz. The probe was fully characterized using discrete loads and saline solutions of different concentrations. Impedance spectra of five ex vivo prostates were measured in the operating room immediately following radical prostatectomy. Wilcoxon signed-rank tests were used to compare the normal and malignant findings. The impedance probe had a signal-to-noise ratio (SNR) > 84 dB across the entire spectrum and measured a tissue volume of approximately 46 mm(3). At 10 kHz, prostate conductivity (or) ranged from 0.232 S/m to 0.310 S/m for tumor and from 0.238 S/m to 0.901 S/m for normal tissue. At 1 MHz the ranges were 0.301 S/m to 0.488 S/m for tumor and 0.337 S/m to 1.149 S/m for normal. Prostate permittivity (epsilonr) ranged from 6.64 x10(4) to 1.25 x 10(5) for tumor and from 9.08 x 10(4) to 4.49 x 10(5) for normal tissues at 10 kHz. And, at 1 MHz the er ranges were 9.23 x 10(2) to 1.88 x 10(3) for tumor and 1.16 x 10(3) to 2.18 x 10(3) for normal tissue. Both sigma and epsilonr of tumor tissue were found to be significantly lower than that of normal tissue (P < 0.0001). Conductivity and permittivity are both higher in normal prostate tissues than they are in malignant tissue making them suitable parameters for tissue differentiation. This is in agreement with trends observed in other tissues reported in much of the literature. Expanded studies are needed to further validate this finding and to explore the biological mechanism responsible for generating the results.

Electrical impedance spectroscopy study of biological tissues

“…The permittivity is related to the extent to which the bound charges can be displaced or polarized under the influence of the electric field. Each polarizable entity within the tissue will exhibit its own characteristic response and thus a distribution of relative permittivities will give rise to a complex function of frequency of the form [16]: (1) where ε ∞ is the high frequency permittivity at which the polarizable entities are unable to respond, ε s is the low frequency permittivity where polarization is maximal, ω is the angular frequency, and τ is the characteristic relaxation time of the tissue under study. A dielectric dispersion is therefore associated with biological tissues [17] in which the relative permittivity decreases with increasing frequency.…”

“…Tissue electrical impedance is a function of its structure and it can be used to differentiate normal and cancerous tissues in a variety of organs, including breast, cervix, skin, bladder and prostate [1]. Electrical Impedance Spectroscopy (EIS) has been widely used to assess the condition of animal tissues, both in vivo, in vitro and ex vivo and for various other applications [2][3][4][5][6][7][8][9][10][11][12][13].…”

“…In general EIS provides impedance information with respect to a wide range of frequency, which is not available via other non-invasive diagnostic techniques and which can be used for treatment purposes [2,12]. For example, impedance spectroscopy was used to differentiate normal and malignant prostate tissue by Halter et al [1]. It was used to study the malignant and normal breast tissues of 26 patients by Kerner et al [2].…”

Electrotherapy on Cancer: Experiment and Mathematical Modeling

“…Among these techniques may be mentioned the Electric Current Density Imaging [Halter et al, 2007;Serša et al, 1997], Electrical Impedance Tomography [Saulnier et al, 2001], Magnetic Resonance Electrical Impedance Tomography [Seo et al, 2005], Magnetic Induction Tomography, Magnetoacoustic Tomography and Magnetoacoustic Tomography with Magnetic induction . These imaging techniques are useful to map spatial distribution of electric currents generated for any electrodes array in the tumor and its surrounding healthy tissue and to visualize the changes on electric current density patterns when the electrodes array parameters above mentioned are modified.…”

Micro electrical impedance spectroscopy on a needle for ex vivo discrimination between human normal and cancer renal tissues

“…Many studies have reported significant differences in electrical impedance, using the EIS devices, between dissimilar cells or tissues from various organs. [12][13][14][15][16][17] Despite the availability of EIS probes in tumor detection, it is inappropriate for detecting completely buried endophytic tumors and estimating tumor depth from the surface of the organ. On the other hand, the lEoN is a needle with EIS incorporated on its tip, which enables the device to penetrate through the tissues and reach the tumor, as well as the deepest margin between the tumor and normal tissues.…”