Real-Time Electrical Bioimpedance Characterization of Neointimal Tissue for Stent Applications

Abstract

To follow up the restenosis in arteries stented during an angioplasty is an important current clinical problem. A new approach to monitor the growth of neointimal tissue inside the stent is proposed on the basis of electrical impedance spectroscopy (EIS) sensors and the oscillation-based test (OBT) circuit technique. A mathematical model was developed to analytically describe the histological composition of the neointima, employing its conductivity and permittivity data. The bioimpedance model was validated against a finite element analysis (FEA) using COMSOL Multiphysics software. A satisfactory correlation between the analytical model and FEA simulation was achieved in most cases, detecting some deviations introduced by the thin “double layer” that separates the neointima and the blood. It is hereby shown how to apply conformal transformations to obtain bioimpedance electrical models for stack-layered tissues over coplanar electrodes. Particularly, this can be applied to characterize the neointima in real-time. This technique is either suitable as a main mechanism for restenosis follow-up or it can be combined with proposed intelligent stents for blood pressure measurements to auto-calibrate the sensibility loss caused by the adherence of the tissue on the micro-electro-mechanical sensors (MEMSs).

Towards non-invasive characterisation of coronary stent re-endothelialisation – An in-vitro, electrical impedance study

“…Such a model may also be useful in enabling clinicians to interpret impedance data. The translation of this in-vitro experimentation towards a self-reporting stent for use in a clinical environment as previously proposed [ 18 , 19 ] is however a considerable technological challenge. The electrical circuitry miniaturisation needed to fit inside an artery without occluding blood flow and non-contact transmission of data without the need for percutaneous leads represents a step change in current implanted electrical device design.…”

“…A self-reporting stent, capable of providing temporal data on the vascular response to stent injury has been proposed, whereby the conductive properties of a metallic stent are exploited to carry out electrical impedance spectroscopic measurements to monitor cellular regrowth [ 18 ]. The concept of remotely monitoring neointimal growth in this way has been explored using mathematical modelling [ 19 ], an ex-vivo model [ 18 ], in-vivo balloon mounted electrodes [ 20 ], and patent activity in this area indicating possible future commercial developments [ 21 , 22 ]. The closest technological embodiment to this concept has been achieved by Oxley et al with an impedance-based stent, termed Stentrode.…”

Evaluation of Implanted Stent Occlusion Status Based on Neointimal Tissue Bioimpedance Simulations

“…Each one has its own electrical properties, derived from its electrical parameters, that is, conductivity (σ) and permittivity (ε) [23], which depend on frequency. The geometry of each layer as well as the assignment of the corresponding conductivity and permittivity at each operation frequency must be incorporated into the FEA [18,19,24]. Thus, the analysis is carried out for several types and sizes of tissues, reproducing the restenosis phenomenon for a given setup test.…”

“…There exist methods to monitor cell cultures in vivo based on their BI [17][18][19][20]. In [17], a cell-culture was transformed into a "biological oscillator" whose characteristic parameters (i.e., frequency, amplitude, phase, etc.)…”

AFM-Based Characterization Method of Capacitive MEMS Pressure Sensors for Cardiological Applications

“…Finally, the third stage involves the sensor layout description in the corresponding technology layers being sent to the manufacturer. CardioMEMS Design (CMD) is a Matlab-based computer aided design (CAD) tool developed with the aim of automating the aforementioned design steps, as well as providing a friendly interface to guide the user through the sensor design process [ 14 , 15 ]. Thus, as exposed in Figure 9 b, CMD provides as outputs the set of files required to export the designed sensor to ANSYS and Cadence Virtuoso working environments, to perform different FE analyses and build the sensor layer description, respectively.…”