New electrical impedance methods for the in situ measurement of the complex permittivity of anisotropic skeletal muscle using multipolar needles

Abstract

This paper provides a rigorous analysis on the measurement of the permittivity of two-dimensional anisotropic biological tissues such as skeletal muscle using the four-electrode impedance technique. The state-of-the-art technique requires individual electrodes placed at the same depth in contact with the anisotropic material, e.g. using monopolar needles. In this case, the minimum of measurements in different directions needed to estimate the complex permittivity and its anisotropy direction is 3, which translates into 12 monopolar needle insertions (i.e. 3 directions × 4 electrodes in each direction). Here, we extend our previous work and equip the reader with 8 new methods for multipolar needles, where 2 or more electrodes are spaced along the needle’s shaft in contact with the tissue at different depths. Using multipolar needles, the new methods presented reduce the number of needle insertions by a factor of 2 with respect to the available methods. We illustrate the methods with numerical simulations and new experiments on ex vivo ovine skeletal muscle (n = 3). Multi-frequency longitudinal and transverse permittivity data from 30 kHz to 1 MHz is made publicly available in the supplementary material. The methods presented here for multipolar needles bring closer the application of needle electrical impedance to patients with neuromuscular diseases.

Parameterization of physical properties of layered body structure into equivalent circuit model

“…For the practical application of the developed TPB-ECM, one maybe obtain the physcial tissue properties with the minimally invasive and pain free needles for electrical properties and the noninvasive medical imaging such as ultrasound for geometrical properties [33]. We believe, TPB-ECM has the potential to become a commonly used platform to analyze the response to TENS and could provide impactful guidance in the standardization of TENS parameter design.…”

Fundamentals, Recent Advances, and Future Challenges in Bioimpedance Devices for Healthcare Applications

“…In both cases, current injection and voltage measurement were carried out sequentially in different electrodes following a preconfigured pattern [37]. In [98,99], new methods for measuring the anisotropy of tissues using bioimpedance have been proposed by modeling the anisotropy in both the resistivity and reactivity in three or more different directions. The anisotropy measurement has the potential to provide new insights in medical evaluation and diagnosis.…”

“…The anisotropic properties of the skin and tissues must be taken into account, since the flow of the electric current inside the human body is modified by the composition and orientation of the cells in the tissues [88,359]. Since the tetrapolar configuration of electrodes, which is commonly used in bioimpedance measurements, is affected by the anisotropic properties of blood vessels, muscle and nerve fibers [98], new electrode configurations and methods must be investigated to mitigate their effects [38] or allow their measurement as a diagnostic parameter of diseases [98,99,360]. Moreover, the anisotropy is of special relevance in EIT and its incorporation to image reconstruction models using tensors of anisotropic conductivity can provide a higher resolution [361].…”

Freezing resistance evaluation of rose stems during frost dehardening using electrical impedance tomography

“…Plant cells are composed of intracellular uids, cell membranes, and a cell wall and are suspended in extracellular uids [24]. EIT has the potential to visualize tissue physiology and pathology in terms of tomographic images of the electrical impedance distribution, provides more information about tissue physiology and pathology, and hence has greater potential in several applications [12,[25][26]. EIT measures the resistance of a plant cross-section, without consideration of plant length and crosssectional area.…”